New member from the STL. 1981 CB750C

Posted: Tue Jun 28, 2016 11:11 am

The manual says 8.0 ounces of fork oil. Is this the correct amount when using progressive springs?

I took the forks apart and it was just sludge so I'm beyond due apparently.

Waiting on the springs to come in the mail next.

PJ

Posted: Tue Jun 28, 2016 11:50 am

Quote:

The manual says 8.0 ounces of fork oil. Is this the correct amount when using progressive springs?

Yes. This is a good time to do the fork seals and dust covers too then, and clean them out. Be sure to read pd750s fork document, in the Tips and Tricks area:

http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=244

Here's another :

http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=23136

And another for a 900C

http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&t=12937

Posted: Tue Jun 28, 2016 12:58 pm

Thanks Gene. I have the All Balls forks seals and dust seals ready to be put on. I'm going to do a fair amount of cleaning too while they are apart. Those links will help.

PJ

Posted: Sat Jul 02, 2016 11:03 pm

Update:

Forks are done!

I purchased from Amazon
All Balls dust cap + fork seal kit. Part number: 56-115
Progressive Springs. Part number: 11-1106

I followed the directions posted by Gene as well as a youtube video:
https://www.youtube.com/watch?v=reQ6qLQgvx0
I didn't follow the video on a few parts. Namely the use of motor oil in the forks and I believe they cut off the old fork seal while it was still on the upper fork (horrible idea).

I basically kept the upper fork in the mount until the fork was in two pieces then took it all out of the triple trees. I also ran some metal polish on the fork upper where the fork seal would glide then cleaned off the polish with some alcohol.
http://imgur.com/tRkFRwf
http://imgur.com/T8aVGEW
http://imgur.com/2FG4wIb

Then I cleaned all the parts inside and out. I used a little brake cleaner and high pressure washer. That got all the sludge out of the little spots.
http://imgur.com/ImwBfns

After I got the parts clean, I put the two halves back together as per the directions. I used the old fork seal to help drive in the new one. Then I put them back into the triple. Easy if you put them back together in the right order and remember to put the drain plug in (lost a cup of oil in that mistake).

Time to compare the new vs old springs.
New on top and old on bottom.
http://imgur.com/lX4dOte

For a spacer I used 1/2" pvc. I bought the 3/4" as the springs are 1" but I guess pvc is measured ID and I measured the springs OD. The 1/2" pvc worked well.
http://imgur.com/v0netrU

Measuring time!
Old springs - 22.75"
New springs - 19"
So spacers were cut to 3.75" and sanded the edges and cleaned them of any loose debris.
http://imgur.com/d5tsl0F

I put in fresh 8 oz of fork oil, then placed in the progressive springs with the tighter coils up top near the cap.
Tip for putting on the fork cap. Try screwing them on without the spacer in to determine where the threads lock in, remember this position. Next remove the cap and put the spacer back in. Now push the cap back on with the handle of a hammer, smallest one you got. You should now have enough room to put the 17mm wrench on the fork cap and twist that sucker until the threads are fully seated. Now you can take off that hammer and twist the cap fully on.

Reassemble and it is done.
http://imgur.com/iz9HKf4

Thanks for everyones help with this. It was way easier than I anticipated.

PJ

Posted: Sun Jul 03, 2016 8:02 am

djpj wrote:

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'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.

PJ

I am not experienced in this area. Did you pour MMO directly into the cylinders through the spark plug hole? If so, how much and how did you remove afterwards?

I've only used SeaFoam in the past in the fuel and oil. I am thinking of doing a MMO or Auto-Rx treatment.

Posted: Sun Jul 03, 2016 8:28 am

djpj wrote:

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

I really shy away from putting additives of any sort in the crankcase oil. Our wet clutches can be very picky about what's in there and the wrong thing can cause them to slip.

Posted: Sun Jul 03, 2016 8:07 pm

Aero,

I took all the spark plugs out and put MMO in the cylinders using a oil can: https://www.google.com/?ion=1&espv=2#q=oil+can

I added about 5 pumps or whatever I thought would thoroughly coat the bottom of the cylinder. When I would store cars for extended periods of time I would add enough fluid until it would pour out of the spark plug hole. I don't believe that much is necessary for what I was doing.

To remove the fluid after letting it sit I would place a few layers of paper towels on top of the spark plug holes. Then cover the paper towels with some heavy sockets to keep them in place. And then proceed to turn the engine over for a few seconds, multiple times. Without the paper towels the MMO will shoot everywhere out of the holes and without the sockets the paper towels will get blown all over by the compressed air being forced out of the cylinder.

PJ

Posted: Sun Jul 03, 2016 8:17 pm

Whozaa,

I have noticed that adding Seafoam/MMO being added to the crankcase oil is a very polarizing subject. I believe that as long as I'm not running it for an extensive amount of time and not under any load then it'll be fine. I also do a full oil change after that and I've done it a few times before on other bikes with no ill effects. I hope it continues to work will for me.

PJ

Posted: Sun Jul 03, 2016 8:31 pm

Running something like MMO or even kerosene in the oil for a minute during the oil change process was something that was done in the way back old days when non detergent oil left a thick disgusting waxy buildup of sludge inside motors.

It's easy enough to see what the sludge story is on one of these by looking under the valve cover, which should be done every 4000 miles because the valve are supposed have their clearances checked and adjusted then anyway. And I've torn down these motors numerous times and see no good reason to put anything other than decent detergent motorcycle oil in them and change it on a regular basis, about twice as often as the book says. They are always clean as a houndstooth inside.

I think there is more potential of doing more harm than good by screwing around running a super high performance motor with funky thinned out oil in it for even 1/2 minute. If the crank and rod bearings seize from lack of viscosity, that's the end of the road until it's fixed. And there's no guarantee that the chems might not have a long term hardening or deleterious affect on the wet clutch plates either.

I just wouldn't even consider it unless I knew for certain that the motor was gunked up with sludge, and then I'd say with one of these, it should be taken apart to really fix it. Really, one of these motors full of waxy sludge from non detergent oil like I remember seeing in the 50s or 60s would probably already have nuked anyway. They're just a completely different animal, so to speak.

Posted: Mon Jul 04, 2016 9:18 am

djpj wrote:

Aero,

I took all the spark plugs out and put MMO in the cylinders using a oil can: https://www.google.com/?ion=1&espv=2#q=oil+can

I added about 5 pumps or whatever I thought would thoroughly coat the bottom of the cylinder. When I would store cars for extended periods of time I would add enough fluid until it would pour out of the spark plug hole. I don't believe that much is necessary for what I was doing.

To remove the fluid after letting it sit I would place a few layers of paper towels on top of the spark plug holes. Then cover the paper towels with some heavy sockets to keep them in place. And then proceed to turn the engine over for a few seconds, multiple times. Without the paper towels the MMO will shoot everywhere out of the holes and without the sockets the paper towels will get blown all over by the compressed air being forced out of the cylinder.

PJ

Kewl, I'll do that. Thanks.

Posted: Mon Jul 04, 2016 1:58 pm

The thing about MMO is it should help free up sticky rings if that's what's happened. Problem is to actually get it past the top ring.

First test compression for a "before" reading. Then inject a few squirts in the plug hole, then put old spark plugs in and turn it over just a couple times with the kill switch to off so it doesn't spark, then maybe do it all again, then let it sit for a couple days. Then clean out the remainder of the oil left in the holes, and try to start it. After it cleans up, put in fresh plugs, run it for a ride, then see how "after" compression is.

Posted: Mon Aug 22, 2016 11:28 am

So I'M BACK. I've been gone for military duty and busy at work but I did get some stuff done.

I attended my first Vintage Bike Night at Schlafly Bottleworks. Some people really loved that front fairing.
http://imgur.com/yqc9q4y

On the trip home I noticed two things:
1. Part of the front fairing flew off on the highway and landed in the bushes. So that thing's got to go.
2. A creep to a high idle when it's really hot. Went home and tested for a vacuum leak to discover carb insulators 2&3 were cracked but didn't show until it was really hot. So I ordered new aftermarket ones.

The front fairing pretty much fell apart as I took screws out.
http://imgur.com/JwRNXex

I then replaced the insulators on the carbs and no more leak. While the carbs were off the bike I discovered an issue with the accel pump circuit. The fuel would drip out of the accel injectors and not spray, and carb 4 wasn't getting any at all. So I replaced the diaphragm, spring, boot and all. Then I stuck a needle in the accel injector of carb 4 and got some air flowing through it. All good now.

Someone on another forum convinced me I was being lazy with the carb sync so I bought some real gauges. I connected all four gauges together and then connected that to cylinder 2 to adjust them to be equal. Then I connected them to the individual cylinders and set my idle at 1000 and sync'd them. The idle could still probably come up a hair. The idle also still has a slight rumble to it but it's more smooth and accelerates quick and smooth now. The accel pump really made a difference.
http://imgur.com/MPOJDAp

While I was there I replaced my old horn for a new Wolo type. I'm considering running a dual (hi/lo) setup in the future.
http://imgur.com/VqRTfLo

Next, it's onto the front lights.

Posted: Mon Aug 22, 2016 11:28 am

I had to completely disconnect the front wiring to get the fairing off.
http://imgur.com/a/bRVRx

The original harness was all chewed up with splicing tools. Worthless crap destroys the old wiring so I had to replace portions of the wiring.
http://imgur.com/BNQfMvG

Pulled the wiring up an through the brake bracket and labeled all the wires.
http://imgur.com/UGx2ivj
http://imgur.com/iNQ5Sz9

Removed unused wires and cleaned up the area making sure not to leave any exposed wires or un-soldered joints. I also added a new headlight plug and extended the headlight wire to make it easier to stuff into the bucket.
http://imgur.com/f14kKXR
http://imgur.com/4ZLvUwH

Now it is time for the aftermarket fork mounts and turn signals. I thoroughly sealed the turn signals with some silicone. Slight overkill.
http://imgur.com/M9JFXzp

Then I mounted the turn signals to the headlight mount and clamped them to the forks.
http://imgur.com/hdlY73u
http://imgur.com/PMa4VPX
http://imgur.com/rxwbhJr

I used part of an old military rubber boot for a washer between the headlight and the mount. This should keep it from wiggling and won't be too unisightly.
http://imgur.com/tDdSB4K

All ready to go (or so I thought).
http://imgur.com/JtiHaO3

New headlight from Amazon. Looks great.
http://imgur.com/KxPEwsZ

Connected and tested.
http://imgur.com/yP2GRyI

Then I went to mount the headlight and found the mounts were too far apart. So I flipped the mount and got them closer together. Crisis averted. I'm going to buy some acorn nuts later to cover the threads of the bolts. I then opened up the headlight bucket, wound the wires in, and put it all back together. Beautiful.
http://imgur.com/KDFplnK
http://imgur.com/c0L76fV (Here you can see the mounts flipped and threads sticking out. I also did get more of the wiring hidden in the bucket after this photo)

Posted: Mon Aug 22, 2016 11:29 am

Next I needed to replace some of the dash lighting. While I was replacing two bulbs I figured I might as well go ahead and replace them all with LEDs. The gauge lighting is good but the idiot lights were INTENSE.
http://imgur.com/Bxb5EIH

I figured this would be a problem riding at night so I decided to diffuse them with some paper. I took the cover off and taped paper up behind the colored lens. This did the trick.
http://imgur.com/9jrVYMf

Posted: Mon Aug 22, 2016 11:29 am

Now is the time to go ahead and mount the tank and finish up the front and middle of the bike. I had left the tank on a drip pan in case the petcock leaked a little and I guess it had tipped over at some point. This cause fuel to slowly leak out the cap and down the side of the tank. What I was not prepared for was the fuel to slowly get under the base coat and peel it away..... Damnit!!!
http://imgur.com/b9u6CoL
http://imgur.com/GNCTn9D

Luckly I was planning on painting the bike. I wasn't planning on painting it so SOON....

Posted: Mon Aug 22, 2016 11:29 am

Next I replaced the flasher relay with an electronic one so fix the LED flash rate. Cylinder style from NAPA, ziptied in. Perfect fit and function.
http://imgur.com/9ogzLOg
http://imgur.com/vCBYtiw

Then I started working on the tail light. Silicone EVERYWHERE!
http://imgur.com/Bc7Gr0o
http://imgur.com/1DchYLh

I then plugged it in to realize it has something like 8 yellow LEDs for integrated turn signals (which I do not want) and only 2 red running light LEDs and 4 red brake light LEDs. So I'm going to take it apart and replace the yellows with reds and increase my running lights for safety. Hopefully I don't screw this up too bad. I ordered my dashboard LEDs and these new red LEDs through superbrightleds.com. They have an impressive selection, especially since they had those old type for the dashboard.

I also grabbed a few strips of bright red LEDs to mount later for an additional brake light. Safety first.
http://imgur.com/YTNCi4x

I think this will turn out like I hope. The tail light is currently small but these additional LEDs will make a big difference.

PJ

Posted: Mon Aug 22, 2016 2:12 pm

Looks like it's coming along nicely .

The boots at the carbs you're referring to are called insulators .

Please use proper terminology . It makes any search more productive and it leaves no question as to what you're trying to say . Thanks .

One more thing : keep an eye on those aftermarket insulators . They seem to have a rather short life span and might crack long before you'd expect .
I know that from first hand experience . Since , I recommend none other than OEM insulators .

Posted: Mon Aug 22, 2016 2:34 pm

pd750, corrected. Thanks.

Do you recommend any specific place to attain OEM insulators? I have used bike bandit before.

Thanks again.

PJ

Posted: Mon Aug 22, 2016 4:38 pm

djpj wrote:

pd750, corrected. Thanks.

Do you recommend any specific place to attain OEM insulators? I have used bike bandit before.

Thanks again.

PJ

Thanks for the correction .

I have done a bit of biz with these folks and had good results . Both in their store and on line :

http://www.hondapartspitstop.com/oemparts/#/l/hon/50541774f870021c54bef632/1981-cb750c-a-parts

Posted: Mon Aug 22, 2016 9:03 pm

Bike Bandit's prices are typically about 20% higher than other online Honda dealers, like Parts Pit Stop, Partzilla, or Service Honda.

Posted: Tue Aug 23, 2016 1:10 pm

Gene, thanks. Noted.

PJ

Posted: Thu Sep 08, 2016 1:38 pm

Update:

All the lights are working well (don't get LED headlights), idles and runs good. I "accidentally" logged 50 miles on a test ride.

Next problem is a leaky valve cover. List as follows:

1. Cylinder Head Cover gasket
2. 8 Cover bolt gaskets
3. Tach Drive O Ring

Do I need to apply any sealant to the gasket around the four chrome pieces on the sides of the cover?

I'll be checking the valve clearances also while the valve cover is off. Is the shop manual sufficient for this? I have done it before on my crotch rocket and I hope this goes as easy.

I'm starting to plan on the paint scheme next and while the cover is off it might go out to powder coating.

PJ

Posted: Thu Sep 08, 2016 4:49 pm

The FSM indicates where to apply Honda Bond or it's equivalent and the valve clearance measuring procedure . Set the clearances at .005" +/- .001" . NOT THE .002" STATED IN THE MANUAL ..

Posted: Thu Sep 08, 2016 6:58 pm

I don't use any sticky stuff on the VC gasket, just a light coat of grease all the way around. You can use rubber bands to hold the gasket in the cover while positioning it, then clip and pull out the bands. Examine the gasket edge carefully all the way around to make sure it's settled into the groove properly and not folded over or slipped out. The whole top of the head fills up like a lake when running, so if there is an error it will leak, and maybe profusely.

However, this is what the manual says: