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djpj
Getting up steam
Getting up steam



Joined: May 15, 2016
Posts: 34
Location: STL, MO

PostPosted: Sat May 21, 2016 1:10 pm Reply with quote Back to top

Hello everyone. Just bought a new to me 1981 CB750C. It's not my first carb bike (I mostly ride newer sport bikes) but this is my first old carb bike. I found the bike on craigslist and after a thorough inspection and test ride I brought it home.

Problems at pick up:
Carbs leak out the overflow (Needle and seat probably)
Front tire is cracked (cracked a bunch more on the way home... Shocked )
Runs a little rough
Horn barely works
Lever brake light switch not working
And a huge front fairing!

So far I've completed a compression check. Dry 125, 120, 125, 140. Wet 160, 150, 170, 170. After soaking the cylinders in Marvel's Mystery Oil overnight and then running the engine back up to temperature I got some better numbers. Dry 155, 150, 160, 150. I think some previous owner did a valve check because it has dried gasket maker leaking out the valve cover. I believe that's some good numbers so I'll stick with it for now.

I've also done an oil and filter change with the Shell Rotella after adding a bunch of Seafoam and MMO to the crankcase oil and running it for a good fifteen minutes, spark plug swap (looked dark and dry), added some Seafoam and MMO to the gas tank, and swapped the air filter.

My main goal is to remain nearly stock-ish looking and still be able to ride two-up next year. My wife is currently preggo with our first so no riding this year for her. It'll also be a good transportation for me when I go off to military duty all the time on the other side of the state.

To do list:
Brake fluid change
Replace front tire and put balance beads in all the tires. I love this in my sport bike
Rebuild the carbs
Running new lighting after removing the fairing
Swap the cracked coils for some F3 coils and wires
Fix brake lever switch
Reseal the gas tank
Clean up the chain and adjust
Change out the fork oil and adjust the overall height as needed.

Here she is: http://imgur.com/RZoheqX

PJ

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1981 CB750C

Last edited by djpj on Sat May 21, 2016 1:14 pm; edited 1 time in total
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djpj
Getting up steam
Getting up steam



Joined: May 15, 2016
Posts: 34
Location: STL, MO

PostPosted: Sat May 21, 2016 1:13 pm Reply with quote Back to top

I have some mechanical knowledge but know little about carbs. I need to buy a carb for dummies book.

Any good suggestions for a carb kit to fix the needle valve and seat?
Also, where do I find some spark plug wires for the F3 coil swap?

I appreciate the help.

PJ

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1981 CB750C
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djpj
Getting up steam
Getting up steam



Joined: May 15, 2016
Posts: 34
Location: STL, MO

PostPosted: Sat May 21, 2016 1:29 pm Reply with quote Back to top

http://imgur.com/a/bRVRx

More pictures.

PJ

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pd750
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Joined: Aug 01, 2007
Posts: 23189
Location: Las Cruces , New Mexico

PostPosted: Sat May 21, 2016 1:31 pm Reply with quote Back to top

Welcome to the site PJ ... Smile

You might want that fairing if you'll be traveling across state regularly . They make road time MUCH more pleasurable .

SeanG wrote an excellent guide for cleaning these carbs . Look in the Tech Docs section .

You may not need a carb kit . The seats can usually be polished with Brasso and Q tips . The jets and passages usually clean up nicely with brake cleaner and compressed air .

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New Members Read This Thread :
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"The only thing that you have which can never be replaced or recovered is your time. Use it well." Author Unknown .
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1982 CB750C - Sold > Looking for my next one .
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pd750
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Joined: Aug 01, 2007
Posts: 23189
Location: Las Cruces , New Mexico

PostPosted: Sat May 21, 2016 1:34 pm Reply with quote Back to top

One other thing : you would be wise to pull the oil pan and clean it and the pick up screen .
Even if they aren't dirty , it's the only way you can be sure .

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sunshine New members , Please read and understand :

Please put the year and model of your bike in the signature section on your profile page and set "Always attach signature " to YES .
NOTE : In order for your signature to show up in posts you also have to check the box that's labeled "Attach signature (signatures can be changed in profile)" , just below the Quick Reply box at the bottom of threads , when making your next post . This only has to be done once . Thanks

New Members Read This Thread :
http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&p=98405#98405

Picture Posting :
http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=11546

Checklist :
http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&p=68384
* *
Every man makes his own chains .
* *
A candle loses nothing by lighting another candle ...

"The only thing that you have which can never be replaced or recovered is your time. Use it well." Author Unknown .
* *
1982 CB750C - Sold > Looking for my next one .
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Whozaa
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Joined: May 09, 2010
Posts: 5698
Location: St Louis, Missouri USA

PostPosted: Sat May 21, 2016 1:36 pm Reply with quote Back to top

Welcome

PD750 covered everything I was going to say. Except that you can use bulk 7mm spark wire and NGK caps for the coils. Or buy the full assys from Honda.

I'm right across the river in IL. Give me a holler if you need help with anything.

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79 CB750F
68 CT90

Hey new guy! Please read the New Members Thread behind this link. http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=7149
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Duke
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Joined: Sep 27, 2009
Posts: 13086
Location: ABQ, NM, USA

PostPosted: Sat May 21, 2016 2:10 pm Reply with quote Back to top

Welcome to the site djpj. That is a nice looking bike you have there.

All the manuals you most likely will need are available for download here like pd750 says.

Enjoy the site.

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Duke

1981 CB900 Custom

New Members Thread. Learn how to use the search engine, post proper sized pictures and get answers to very common questions that have been asked numerous times: Click Here

Find the FSM (factory service manual) and other tech docs here: Click Here

Have problems with your charging system?: Click Here

SeanG´s new to you bike Checklist (make your 30+ year old bike tip top before you ride it): Click Here

SeanG´s Excellent Carb Manual And Rebuild Guide: Click Here

Find out what Petcock fits your tank!! Just because you have a 1981 bike doesn't always mean it has a 1981 tank: Click Here

Buy Procom Ignitors directly from Procom´s website: Click Here

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seanathon
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Joined: Aug 08, 2014
Posts: 518
Location: Rochester, NY

PostPosted: Sat May 21, 2016 2:29 pm Reply with quote Back to top

Welcome! Nice looking bike - you'll love working on old stuff Laughing

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Seanathon
1981 CB750c (Felicia)
1963 BSA B40 (project)
1974 Triumph Trident T150v (future project)

New members, read the NMT (New Member's Thread) HERE
Find the FSM (Factory Service Manual) and other technical documents HERE
"They're not clean until they're 'Sean G.' Clean" - Sean's (not mine - better Sean) Carb Cleaning Manual HERE
USE THE SEARCH FEATURE FIRST before asking questions

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genesound
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Joined: Jul 24, 2007
Posts: 41226
Location: Studio City, CA

PostPosted: Sat May 21, 2016 5:04 pm Reply with quote Back to top

Welcome to here wave

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NMT - New Member's Thread, a Must Read, click here!!! - Information For New and Veteran Members.
Contains SITE RULES, how to enter required bike information in your signature, thread and picture posting...
Also some important DOHC wrenching tips, and some other information.
Kindly read this linked thread with the rules before posting
pictures or asking lots of questions that are already answered in it.

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For Honda Shop Manuals (FSM), Click Here.
Click here to go fiche at Parts Pit Stop.
Click here to go fiche at Partzilla.
Sean's Bike Maintenance Checklist Click!
MacGregor Carb Rebuilding Manual, Click Here.
⊳⊳⊳⊳Learn to use the Search Engine Click Here.⊲⊲⊲⊲
Be sure to use Copper Anti-Seize on your Spark Plug Threads!
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djpj
Getting up steam
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Joined: May 15, 2016
Posts: 34
Location: STL, MO

PostPosted: Sat May 21, 2016 5:59 pm Reply with quote Back to top

Thanks everyone!

I would keep the fairing except the headlight sucks, the stereo sucks, I can't use the highway pegs because of it, and I don't like the additional weight over the front wheel. I might try and find a regular windscreen later.

I'll look into that carb cleaning. That sounds way easier. I forgot to mention the bike has 24,000 miles on it. And I will wait till next oil change to look into the pan. Does the exhaust need to be removed for that?

Any suggestions where to buy this bulk spark plug wire? I'm excited to build my own wires. Never tried that before.

Thanks again for all the suggestions and help. I have worked on a few old cars in my day and so far this bike seems way easier.

For swapping out the fork oil do you all recommend using syringes to get the right amount or what? I would prefer a little more resistance to what I'm experiencing now also. I know it's not like my typical sport bike but I don't want it to be a boat either.

Thanks again.

PJ

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Duke
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Location: ABQ, NM, USA

PostPosted: Sat May 21, 2016 6:42 pm Reply with quote Back to top

djpj wrote:


For swapping out the fork oil do you all recommend using syringes to get the right amount or what? I would prefer a little more resistance to what I'm experiencing now also. I know it's not like my typical sport bike but I don't want it to be a boat either.

Thanks again.

PJ


If your front fork springs are original it wouldn't hurt to replace them with Progressive springs as your originals are likely sacked and are contributing to poor suspension performance. Replacing the old with new will add a lot of life back into your suspension.

_________________
Duke

1981 CB900 Custom

New Members Thread. Learn how to use the search engine, post proper sized pictures and get answers to very common questions that have been asked numerous times: Click Here

Find the FSM (factory service manual) and other tech docs here: Click Here

Have problems with your charging system?: Click Here

SeanG´s new to you bike Checklist (make your 30+ year old bike tip top before you ride it): Click Here

SeanG´s Excellent Carb Manual And Rebuild Guide: Click Here

Find out what Petcock fits your tank!! Just because you have a 1981 bike doesn't always mean it has a 1981 tank: Click Here

Buy Procom Ignitors directly from Procom´s website: Click Here

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flogger
Now you're talking
Now you're talking



Joined: Feb 14, 2016
Posts: 97
Location: Indiana

PostPosted: Sun May 22, 2016 1:07 am Reply with quote Back to top

Hello... Answered you on the other site... One note, if you are not a good mech on Carbs and Valves, seek out an expert to learn from... Most carbs problems are the POs mistakes (stupidity)... and a real mech fixes their mistakes... I am fortunate in that I have a great local shop that is trustworthy and welcomes older bikes AND is priced fairly. They DID tell me (and SHOWED me) I was missing some internal carb parts when mine were cleaned n rebuilt... Mine were done ONCE and they run like a dream... But carbs can run you 100 to 150 a barrel for good work...

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1981 CB750 Custom
1983 GL650i SilverWing
1996 GL1500 Goldwing SE
1981 CM400 (Newest Project)

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djpj
Getting up steam
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Joined: May 15, 2016
Posts: 34
Location: STL, MO

PostPosted: Sun May 22, 2016 10:31 am Reply with quote Back to top

Flogger,

Thanks. I think the carbs work alright for now besides the leak. I am going to find someone near me to look at them still.

PJ

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RDIII
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Joined: Jul 26, 2011
Posts: 246
Location: Peru, IN

PostPosted: Mon May 23, 2016 7:52 pm Reply with quote Back to top

Welcome!

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1979 CB750 Limited (Lisa)
1981 CB900 Custom (Celine)
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flogger
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Joined: Feb 14, 2016
Posts: 97
Location: Indiana

PostPosted: Mon May 23, 2016 7:58 pm Reply with quote Back to top

djpj wrote:
Flogger,

Thanks. I think the carbs work alright for now besides the leak. I am going to find someone near me to look at them still.

PJ


Prob need rebuilt to stop the leak, see what the others here think...

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1981 CB750 Custom
1983 GL650i SilverWing
1996 GL1500 Goldwing SE
1981 CM400 (Newest Project)

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seanathon
Feel the Power
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Joined: Aug 08, 2014
Posts: 518
Location: Rochester, NY

PostPosted: Mon May 23, 2016 8:23 pm Reply with quote Back to top

Quote:
Prob need rebuilt to stop the leak, see what the others here think...


If you're leaking, do a rebuild. Sean G has the software and hardware (allen heads) that are very reasonably priced, and his manual is a step-by-step guide (I've NEVER touched a carburetor before my rebuild, and even I couldn't screw it up too bad). Other than some pine-sol and your time, a re-build is well worth it. If you can get a manometer to sync up once you're done, you'll be golden for a few years.

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Seanathon
1981 CB750c (Felicia)
1963 BSA B40 (project)
1974 Triumph Trident T150v (future project)

New members, read the NMT (New Member's Thread) HERE
Find the FSM (Factory Service Manual) and other technical documents HERE
"They're not clean until they're 'Sean G.' Clean" - Sean's (not mine - better Sean) Carb Cleaning Manual HERE
USE THE SEARCH FEATURE FIRST before asking questions

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Whozaa
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Joined: May 09, 2010
Posts: 5698
Location: St Louis, Missouri USA

PostPosted: Tue May 24, 2016 7:59 am Reply with quote Back to top

The big question is where are they leaking from? If it's out of the drain nipples, you might get away with only polishing up the float valves.

I helped a guy out in Troy MO clean up the carbs on his 900C. His were royally messed up too. Mismatched parts from different models and what not.

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79 CB750F
68 CT90

Hey new guy! Please read the New Members Thread behind this link. http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=7149
It contains the rules for forum posting and other valuable info you need to know.
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djpj
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Joined: May 15, 2016
Posts: 34
Location: STL, MO

PostPosted: Tue May 24, 2016 8:07 am Reply with quote Back to top

I'm going to take the carbs off soon and I'll get working on that rebuild. I downloaded that PDF on the carbs. I've never touched the inside of a carburetor either but I'm meticulous. Thanks for your ideas.

PJ

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djpj
Getting up steam
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Joined: May 15, 2016
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PostPosted: Tue May 24, 2016 8:07 am Reply with quote Back to top

Update:

Lever brake light switch fixed. Checked it with a multimeter and it showed no connectivity. Threw it on the ground, rechecked and now it's working. I went ahead and filled it up through the two small holes with some contact cleaner and then some dielectric grease since it's 35 years old and been in a bunch of weather. All lights work now.

Inspected the horn and I believe it had to be removed to put the front fairing braces on, so I started to wonder if they connected it back correctly. I took the horn off the bike and connected it directly to the battery but it was still quiet. I decided to flip the connection and now I have a loud horn and some ringing in my ears..... It's a go for inspection now at least.

I have ordered the F3 coils, plug wires, relay, and inline fuse. Waiting on delivery and with the bad weather this week I think I'll find time to complete that.

PJ

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holysmokes
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PostPosted: Wed May 25, 2016 8:21 am Reply with quote Back to top

hello

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On a steel horse i ride
.mm to inch conversion chart
http://www.carolynrelei.com/inchchart.htm
picture posting
http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=127
link to manuals + tech threads>
http://www.cb750c.com/modules.php?name=Forums&file=viewforum&f=5
valve adjust thread>
http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=12173&highlight=shim
check charging video
https://www.youtube.com/watch?v=YvRe9g_2gyM
carb cleaning thread>
http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=13611&highlight=carb
verifying ground
https://www.youtube.com/watch?v=SyNYlaoInUE
checking stator
https://www.youtube.com/watch?v=5v2LtHlvcqI
checking r/r
https://www.youtube.com/watch?v=kDx3zgOLShY
checking rotor ohms thread>
http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=1477&highlight=ohms
torque values thread >
http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&p=81382#81382

http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=52
http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=6935&highlight=shadow
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djpj
Getting up steam
Getting up steam



Joined: May 15, 2016
Posts: 34
Location: STL, MO

PostPosted: Thu May 26, 2016 7:28 am Reply with quote Back to top

Update:

New front tire - Dunlop Metric Cruiser
http://imgur.com/yfa5JXa
Balance beads in both tires. I made a tool to help the beads into the valve stem. Pretty ingenious.
http://imgur.com/BU12IyY

So the front is all torqued up and greased. Now I'm waiting on the F3 coils and I should get those today and completed before the weekend.

Next week: Carburetors


PJ

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seanathon
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Joined: Aug 08, 2014
Posts: 518
Location: Rochester, NY

PostPosted: Thu May 26, 2016 7:55 am Reply with quote Back to top

You're doing great! These bikes are a ton of fun once you get them dialed in.

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Seanathon
1981 CB750c (Felicia)
1963 BSA B40 (project)
1974 Triumph Trident T150v (future project)

New members, read the NMT (New Member's Thread) HERE
Find the FSM (Factory Service Manual) and other technical documents HERE
"They're not clean until they're 'Sean G.' Clean" - Sean's (not mine - better Sean) Carb Cleaning Manual HERE
USE THE SEARCH FEATURE FIRST before asking questions

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djpj
Getting up steam
Getting up steam



Joined: May 15, 2016
Posts: 34
Location: STL, MO

PostPosted: Fri May 27, 2016 7:50 am Reply with quote Back to top

Update:

Coil swap completed. Bought some 1997 CBR600 F3 coils from FleaBay and a coil kit from Z1 Enterprises: https://www.z1enterprises.com/product/DYDW600

Ten layers of wrap and tape keeps coils safe I guess. Here they are after unwrapping: http://imgur.com/LiZS7um

Measured the different length between the coils and it came out to be 15/16" shorter. So I grabbed the old license plate thaat came with the bike, cut out two strips, folded them in half, drilled out some holes, and Robert's your mother's brother.
http://imgur.com/mhHGGlt
http://imgur.com/PoGbSA8

Then I plugged them up to the bike and tested it out. It started very quick for having sat for a week and didn't require a lot of throttle or choke to keep running.
http://imgur.com/RZtlpNY
http://imgur.com/hMsptKc

After that test it was time to cut my own spark plugs. I've never tried it before so I figured it was going to be complicated. Turns out it was easier than I thought.
I took the coil cap off the red plugs to use for the new wires. Measured the old black wires and added 4 inches to the new black wires (in case I muff it up). Then I cut the new wire and put on the old black wire heat shielding and wire labels. I don't know if these wire labels are stock but they are SUPER helpful. If you don't have some, get some. The new plug wires came with a cap to put on the spark plugs so the wires attach properly, so I did that. Then I put the coil caps from the red plugs on the new wires. That had three pieces: the big screw-on cap, small plastic washer, and the grommet. How I imagine it works is the grommet gets squished onto the wire when you tighten down the screw-on cap with the plastic washer inbetween them. I should have taken pictures of these things, I might have the old ones still sitting in my trash. Then I took a small nail and inserted it into the coil end of the new black wires about an 1/8" to split the wiring evenly. then I add some grease to the outer sleeve and slid it into the coil. The inside of the coil has a sharp point inside that pushes into the wire. then I tightened up the screw-on cap. I did all four like this with the coil off the bike. After they were all measured, cut, and assembled on the coil I reinstalled the coil on the bike. Then connect the wires to the plugs with some more grease.
http://imgur.com/gP9w4gm
http://imgur.com/j7FeqGd
http://imgur.com/GayIVhQ
If I thought it ran good before this swap, then it ran great after putting on the new coils. And then after adding the new wires it's still even better. Smooth idle, instant start on cranking, quick acceleration in the revs.

I think the extra length in the wires is too much but I liked having the ability to move the coils under the frame easier. Plus they tuck up nicely. I think the black wires keep the older look.

Wires: 17+ shipping = $26.15
Coils: 34 + Free shipping
Use the screw-on coil connectors, grommets, and washers. Don't forget some grease. Easy upgrade.

I'm going out of town this weekend so the relay will have to wait. In the mean time, I need to find a suitable place to mount it.
Location options:
Under the tank with the coils - hot, high voltage, gross engine fluids
Under the seat - no room, and too jammed with other wires
Side cover - no mounting spot, tight fitting, but could be organized well
Above the airbox - no mounting spot, could be in the way later on

I just want a clean spot that I don't have to unplug the relay everytime I want to do simple maintenance. Is under the tank, next to the coils really the worst idea? I'm up for suggestions.

Here's all the pictures I took so far: http://imgur.com/a/bRVRx
I'll try and get the pictures of the grommets and screw-on caps.
Let me know if you can think of the best place for this relay.

PJ

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Whozaa
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Joined: May 09, 2010
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Location: St Louis, Missouri USA

PostPosted: Fri May 27, 2016 8:29 am Reply with quote Back to top

I haven't done the mod myself. But if it were me, I'd stick the relay close to the coils. Make yourself another little bracket and hang it off one of the coil mounting bolts.

If you mount it by the battery, you'll have to lengthen the trigger wire (black/white) and run it all the way back to the battery area.

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79 CB750F
68 CT90

Hey new guy! Please read the New Members Thread behind this link. http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=7149
It contains the rules for forum posting and other valuable info you need to know.
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djpj
Getting up steam
Getting up steam



Joined: May 15, 2016
Posts: 34
Location: STL, MO

PostPosted: Sun May 29, 2016 4:59 pm Reply with quote Back to top

Here is the order of the screw-on caps with the wiring.
http://imgur.com/Gkyvh4H

Here is the nail I used to start a pilot hole in the wires.
http://imgur.com/6We5GkL

And here are the spikes that are inside the coils themselves that the wires get pressed onto.
http://imgur.com/MZjgokG
http://imgur.com/jfsQR56
http://imgur.com/GFTBVhC

I hope these pictures help someone else who decides to do this coil swap.

PJ

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genesound
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Joined: Jul 24, 2007
Posts: 41226
Location: Studio City, CA

PostPosted: Sun May 29, 2016 10:10 pm Reply with quote Back to top

Yep, good work. Smile

The power wire length to/from the relay isn't a really big deal, because the overall distance of maybe 2-3 feet is relatively short. If you're using 14 - 16 Ga wire for the wire to the coils and from the battery, there won't be appreciable voltage drop from the wire. You should be able to locate the relay where it fits and looks best, or is easiest to access and run wires. The other wires to the relay can be smaller if you like. The green wire by the signal flasher that normally goes nowhere can be used for the field coil ground side.

I do recommend using a waterproof relay, and try to locate it to keep it from getting soaked in rain or washing water. If you can't get a waterproof one, you might want to seal it with silicone caulk. Air pressure release shouldn't be a big deal for it.

Here's the link to the relay page in case you hadn't found it:

http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=2740

_________________
NMT - New Member's Thread, a Must Read, click here!!! - Information For New and Veteran Members.
Contains SITE RULES, how to enter required bike information in your signature, thread and picture posting...
Also some important DOHC wrenching tips, and some other information.
Kindly read this linked thread with the rules before posting
pictures or asking lots of questions that are already answered in it.

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For Honda Shop Manuals (FSM), Click Here.
Click here to go fiche at Parts Pit Stop.
Click here to go fiche at Partzilla.
Sean's Bike Maintenance Checklist Click!
MacGregor Carb Rebuilding Manual, Click Here.
⊳⊳⊳⊳Learn to use the Search Engine Click Here.⊲⊲⊲⊲
Be sure to use Copper Anti-Seize on your Spark Plug Threads!
To Fix and Better Understand Your DOHC Honda Charging System, Click Here.

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djpj
Getting up steam
Getting up steam



Joined: May 15, 2016
Posts: 34
Location: STL, MO

PostPosted: Tue May 31, 2016 5:16 pm Reply with quote Back to top

Update:

Wiring all made up for the coil relay. I determined that the best position is going to be by the battery. Under the tank would let the relay get too hot and it might short out. I found the operating temp range for these things is around 185*F so above the air-cooled engine is a no-go.

Wires:
Black = negative from relay, 10 gauge
Red with fuse = power to relay, 10 gauge
Brown = From one of the blk/whte trigger wires on the coil, 14 gauge
Green = From relay to coils, split to go to both coils, 14 gauge
http://imgur.com/8iC2o5F
http://imgur.com/lejepCS
http://imgur.com/w0Rpn3o

Ran the wires alongside the original wiring harness and shrink wrapped like a doomsday prepper. (Excessive? I'm the one riding the bike so I'll be the one stuck somewhere if it's not perfect)

http://imgur.com/u6RoKlH
http://imgur.com/LqPKNyD
http://imgur.com/sLecgfh
http://imgur.com/9MmcxLH
http://imgur.com/rYaLqNF
http://imgur.com/RvkOeYz

Grounded at the airbox to frame mount. Received a strong ground there so I'm happy with it. I can still loosen it a little and move the airbox to get at the carbs.

Next I connected all the wiring to my relay and the battery.. POOF. Blew the inline fuse. Then, I checked and rechecked all the connections but I was still getting a current running through the inline fuse without the bike running. I pulled the relay and tested the ohms from the power to the ground without any other wires connected. Got a positive connection reading so I guess my Amazon relay is trash. I then went up to the local auto store and got another, tested it, and we are good to go again.

http://imgur.com/ZqeII2u
http://imgur.com/9JQaKYy

Test fire was a great success. It fired up quicker than my sport bike. Tested all the plugs and they are firing evenly. Then I proceeded to shrink wrap every connection and grease up any spots that could be susceptible to some water. Once again three layers of varying sizes of shrink wrap will hold it together until Skynet comes for us all. I might even add some more to the green wires connected to the coils.

Out of focus: http://imgur.com/zez0Pas

Test fire again and it's all good. I like to test after every little stage so I don't get too far along and realize that after 5 steps my bike won't run. Now it's onto the carbs:

http://imgur.com/iKCozGW
http://imgur.com/6uKMB3T
http://imgur.com/cVN00nr

Labeled every connection and took some pictures. I broke one vent hose and I'll replace both when I reassemble. Next step is to clean those dirty dirty carbs. I'll also use this time to get some degreaser on that engine and rinse it off, after I close up all the holes of course.

Gene,

Thanks for your help. I couldn't find a waterproof one but I'm going to build a tomb of silicone caulking on it before I put the carbs back on.

PJ

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genesound
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Joined: Jul 24, 2007
Posts: 41226
Location: Studio City, CA

PostPosted: Tue May 31, 2016 5:44 pm Reply with quote Back to top

Good job!

Jeeberz! Your wire is much larger than necessary, but it won't hurt anything other than a little extra weight.

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NMT - New Member's Thread, a Must Read, click here!!! - Information For New and Veteran Members.
Contains SITE RULES, how to enter required bike information in your signature, thread and picture posting...
Also some important DOHC wrenching tips, and some other information.
Kindly read this linked thread with the rules before posting
pictures or asking lots of questions that are already answered in it.

ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ
For Honda Shop Manuals (FSM), Click Here.
Click here to go fiche at Parts Pit Stop.
Click here to go fiche at Partzilla.
Sean's Bike Maintenance Checklist Click!
MacGregor Carb Rebuilding Manual, Click Here.
⊳⊳⊳⊳Learn to use the Search Engine Click Here.⊲⊲⊲⊲
Be sure to use Copper Anti-Seize on your Spark Plug Threads!
To Fix and Better Understand Your DOHC Honda Charging System, Click Here.

ŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻŻ
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___ImageCB1000C __ Image ___ CB1100FImage__
View user's profile Send private message Visit poster's website
djpj
Getting up steam
Getting up steam



Joined: May 15, 2016
Posts: 34
Location: STL, MO

PostPosted: Wed Jun 01, 2016 7:01 am Reply with quote Back to top

Ya I wanted to use 14 gauge wire only but when it came time to start wiring I only had 16 or 10 gauge for the red and black wires. At least they are only8 inches each!

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djpj
Getting up steam
Getting up steam



Joined: May 15, 2016
Posts: 34
Location: STL, MO

PostPosted: Sun Jun 05, 2016 10:28 pm Reply with quote Back to top

Update

It's been a weekend of failures.

I tried the lemon juice boiling trick and either I didn't get the real lemon juice (said 0% daily amount of vitamin C) or I didn't cook it long enough (30 mins and moving it every 5 min) but it barely did a thing.

So, I polished the valve seat for carbs 1 & 2 with some metal polish and it came out like a mirror. Then I clean up all the float bowls with some carb cleaner. Put it all back together and then the number 1 carb wasn't getting any fuel into the cylinder so I opened the drain and nothing came out. And I noticed 3 & 4 were now overflowing.... I know, I know, I should have polished those seat valves while I had it out.

So I took the carbs back out of the bike and opened up number 1 and it had no fuel and the float was way higher than the other. I guess I got a bunch of carb cleaner on the float needle and the rubber part swelled up so it was blocking the passage. And the passage plug got soaked and just fell apart. I think this is a case of "too much of a good thing". Then the bowl gaskets fell apart.

So I ordered 4 new gaskets, a pack of passage plugs, and a new float needle from vintagecb750.com. Hopefully it gets here soon. Otherwise they are pretty clean, maybe that lemon juice did something after all.

http://imgur.com/OhD72LD
I added those tubes to the overflow to help me recognize problems more accurately and drain them more cleanly as needed.

While I am waiting on that I decided to flush out the front brake lines. The fluid was black as night. I proceeded to open the bleed valve and squeezed lever and I got a little bit out but right before the master cylinder was drained the lever went rock solid. I poured the remainder of the fluid out of the cylinder and the bottom was filled with sediment. Couldn't even make out the holes in the bottom. Spent 20 minutes working on it and it looked like this
http://imgur.com/Z8ez801

I pulled the lever and cylinder off the bike and cleaned it all and got some fluid flowing through it but the main brake line is clogged solid. I can't even get brake cleaner through the line and I'm not about to ram a wire through it all.

So I'm left without front brakes and no carbs... Better to find out now than on the road I guess......

PJ

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flogger
Now you're talking
Now you're talking



Joined: Feb 14, 2016
Posts: 97
Location: Indiana

PostPosted: Sun Jun 05, 2016 11:15 pm Reply with quote Back to top

You are making progress and doing a great job detailing your work... Did you get carb kits?

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1981 CB750 Custom
1983 GL650i SilverWing
1996 GL1500 Goldwing SE
1981 CM400 (Newest Project)

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pd750
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Joined: Aug 01, 2007
Posts: 23189
Location: Las Cruces , New Mexico

PostPosted: Mon Jun 06, 2016 7:01 am Reply with quote Back to top

djpj wrote:
Update



So I took the carbs back out of the bike and opened up number 1 and it had no fuel and the float was way higher than the other. I guess I got a bunch of carb cleaner on the float needle and the rubber part swelled up so it was blocking the passage. And the passage plug got soaked and just fell apart. I think this is a case of "too much of a good thing". Then the bowl gaskets fell apart.



PJ


Exactly why we recommend using brake cleaner and NOT carb cleaner .

Carb cleaner eats rubber . If that's a good thing ...

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"The only thing that you have which can never be replaced or recovered is your time. Use it well." Author Unknown .
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djpj
Getting up steam
Getting up steam



Joined: May 15, 2016
Posts: 34
Location: STL, MO

PostPosted: Mon Jun 06, 2016 1:38 pm Reply with quote Back to top

Flogger: I did buy a carb kit this time.

pd750: Brake cleaner? Brilliant. I had no idea.

I am going to go find some place to make me some new brake lines for the front. I can't believe they are clogged. I figured the pressure from squeezing the lever would push anything through. I'm going to test the master cylinder on another brake hose also.
Any advice on how to get the master cylinder apart to clean it better?

PJ

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Whozaa
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Joined: May 09, 2010
Posts: 5698
Location: St Louis, Missouri USA

PostPosted: Mon Jun 06, 2016 4:10 pm Reply with quote Back to top

djpj wrote:
Any advice on how to get the master cylinder apart to clean it better?


The service manual shows how to disassemble it for cleaning and inspection.

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79 CB750F
68 CT90

Hey new guy! Please read the New Members Thread behind this link. http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=7149
It contains the rules for forum posting and other valuable info you need to know.
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djpj
Getting up steam
Getting up steam



Joined: May 15, 2016
Posts: 34
Location: STL, MO

PostPosted: Fri Jun 10, 2016 6:58 am Reply with quote Back to top

Update:

Master cylinder clean and flushed with new fluid. I'm having a local shop build some new brake lines for me.

Replaced the faulty float valve and all the gaskets and the carburetors don't leak any more. But now I think I have a dead cylinder number 2. I felt the exhaust and they were all super hot except number 2. It was slightly warm but I think that was just from the radiant heat of the other exhaust pipes.

I checked the drain on the float bowl and there's fuel in the bowl. I checked the spark with an inline spark tester and it flashed thoroughly. So I took some extra gas in a pipette and squirted it into the number 2 carb with the airbox removed and the engine smoothed out and the exhaust pipe got hotter. So maybe somehow the fuel isn't getting from the float bowl to the cylinder.

I know the jets are clear and the needle slides easily. The only thing I really changed on the that carburetor was it was missing the accel pump gasket and I replaced the float bowl gasket. Last time I had the carbs together the float needle in the number one carb wasn't letting in any fuel but the number two carb was working fine. Now the number one is working fine and the number two isn't.

Would anything with the accel pump (diaphram, gasket, etc) keep the fuel from flowing out of the float bowl? I don't think I did anything else to that carb from last time. This is frustrating.


PJ

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djpj
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PostPosted: Fri Jun 10, 2016 7:56 am Reply with quote Back to top

I also replaced the passage plugs too because they were all old and hard. I wonder if I need to blow out the passage under the plug with some compressed air.

I don't think it's the float or needle valve because after I found the number two not working I swapped the float and needle valve with number one and I had the same problem.

PJ

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pd750
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PostPosted: Fri Jun 10, 2016 8:25 am Reply with quote Back to top

Sounds like a plugged idle circuit .

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sunshine New members , Please read and understand :

Please put the year and model of your bike in the signature section on your profile page and set "Always attach signature " to YES .
NOTE : In order for your signature to show up in posts you also have to check the box that's labeled "Attach signature (signatures can be changed in profile)" , just below the Quick Reply box at the bottom of threads , when making your next post . This only has to be done once . Thanks

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Every man makes his own chains .
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A candle loses nothing by lighting another candle ...

"The only thing that you have which can never be replaced or recovered is your time. Use it well." Author Unknown .
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Whozaa
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PostPosted: Fri Jun 10, 2016 8:30 am Reply with quote Back to top

It's hard to effectively spot-clean these carbs. You almost always have to break them completely down and do a complete thorough cleaning. I see that you found Sean's manual, but I don't know how much of it you did?

That, and you really need to have the airbox installed. These carbs run like crap without it. I know its a big pain to work with, but that's another reason to do a thorough carb cleaning the first time. So you don't have to keep messing with the airbox. Very Happy

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79 CB750F
68 CT90

Hey new guy! Please read the New Members Thread behind this link. http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=7149
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djpj
Getting up steam
Getting up steam



Joined: May 15, 2016
Posts: 34
Location: STL, MO

PostPosted: Fri Jun 10, 2016 9:08 am Reply with quote Back to top

I didn't break the carbs completely down because I felt that was over my head for a first timer.
However, I did split the bank into pairs, soaked them in boiling lemon juice, cleaned the slides, cleaned the float bowl, cleaned the needle valves and seats, cleaned the jets.

The carbs were running just fine before but a few were overflowing. That's why I even wanted to tear them down.

I agree on keeping the airbox. I have no dreams of tossing it. I'm just trying to get the fuel into the number 2 cylinder first then I can reassemble everything. It didn't work with the airbox attached after the first try and it hasn't changed since I removed it. Also, the other cylinders are still getting fuel.

PJ

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pd750
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PostPosted: Fri Jun 10, 2016 9:20 am Reply with quote Back to top

pd750 wrote:
Sounds like a plugged idle circuit .

_________________
sunshine New members , Please read and understand :

Please put the year and model of your bike in the signature section on your profile page and set "Always attach signature " to YES .
NOTE : In order for your signature to show up in posts you also have to check the box that's labeled "Attach signature (signatures can be changed in profile)" , just below the Quick Reply box at the bottom of threads , when making your next post . This only has to be done once . Thanks

New Members Read This Thread :
http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&p=98405#98405

Picture Posting :
http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=11546

Checklist :
http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&p=68384
* *
Every man makes his own chains .
* *
A candle loses nothing by lighting another candle ...

"The only thing that you have which can never be replaced or recovered is your time. Use it well." Author Unknown .
* *
1982 CB750C - Sold > Looking for my next one .
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