Free bike! (but you know the deal)

Posted: Tue Apr 14, 2020 7:37 pm

Hello all,

new member here.

Just was given a 'free' 1980 CB900 Custom. As many of you know there is rarely a true 'free' bike.

The bike has been stored outdoors for a number of years and needs substantial repair.

One cylinder is dead and probably has a bad valve. The upside is the bike came with a replacement complete head.

Needs tires, battery and complete review of brake and induction systems.

Pretty horrible cosmetics too. Tank and side panels will need paint and the Vetter fairing has a significant crack that will need to be addressed.

Of course there is a king/queen seat that is badly worn and is well taped.

I have some limited experience with older bikes. Would like to ask if there is any particular item that should be addressed while the head is off the engine.

Will probably take a run at starting this Friday the 17th.

Thanks

Posted: Wed Apr 15, 2020 7:47 am

Welcome to the site Ecklund ... Smile

If you haven't read the following page , now is the time .

http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&p=80601#80601

If you run into problems with any of that , Please let us know . Thanks . Smile

How many miles on the bike ?
And , do you know any of it's maintenance history ?

Posted: Wed Apr 15, 2020 1:10 pm

pd750 wrote:

Welcome to the site Ecklund ... Smile

If you haven't read the following page , now is the time .

http://www.cb750c.com/modules.php?name=Forums&file=viewtopic&p=80601#80601

If you run into problems with any of that , Please let us know . Thanks . Smile

How many miles on the bike ?
And , do you know any of it's maintenance history ?

Thanks.

bike has about 63K.

PO was known to owner that gave me the bike. The fact that bike was likely ridden without valve adjustment until it burned a valve indicates low level of maintenance.

A bit of a time piece as it has a Vetter fairing, a king/queen seat and a whitewall rear tire. Needs new tires but will keep and repair the faring and recover the seat.

Not looking to mod this bike. Just bring it back to good solid function.

Will replace the valve seals in the replacement head and check the valves to see if they need lapping.

Really considering replacing the piston rings while I have the head off too.

Was interested in asking if there is some specific or unique item to the 900 engine that may/would require attention if the head were pulled. Timing chain guide/s or...?

Thanks

Posted: Wed Apr 15, 2020 1:30 pm

I am your local DOHC Honda authority and can help with any aspect of your engine rebuild.
Unless you are going overbore, leave the rings alone because they are not the problem.
The burnt valve is the problem and maybe the valve seats all need to be cut, I do this and am quite good at it.
If you want or need help, 818-259-8690
I am in Granada Hills only 20 minutes away, do not hesitate to ask for help, DOHC Hondas are what I do

Posted: Thu Apr 16, 2020 3:44 pm

Fitz wrote:

I am your local DOHC Honda authority and can help with any aspect of your engine rebuild.
Unless you are going overbore, leave the rings alone because they are not the problem.
The burnt valve is the problem and maybe the valve seats all need to be cut, I do this and am quite good at it.
If you want or need help, 818-259-8690
I am in Granada Hills only 20 minutes away, do not hesitate to ask for help, DOHC Hondas are what I do

Hello,

thanks very much for the advice/info.

Did not necessarily want to change out the piston rings but the bike has 63K I thought it would be reasonable as the head needs to come off anyway.

But based on your suggestion if the pistons and cylinders look OK I'll leave the rings as is.

If the replacement head doesn't work out for some reason I'll bring you both heads and see what you think is the best way forward.

Besides valve seals and possibly lapping any particular items that should be addressed with the head off on these engines?

Thanks again.

Posted: Thu Apr 16, 2020 4:13 pm

That kind of mileage, you're probably in for cam chains, guides, and tension adjusters, unless they were changed already, maybe even if they were.

Posted: Thu Apr 16, 2020 5:36 pm

Fitz wrote:

I am your local DOHC Honda authority and can help with any aspect of your engine rebuild.
Unless you are going overbore, leave the rings alone because they are not the problem.
The burnt valve is the problem and maybe the valve seats all need to be cut, I do this and am quite good at it.
If you want or need help, 818-259-8690
I am in Granada Hills only 20 minutes away, do not hesitate to ask for help, DOHC Hondas are what I do

This is out of topic of the thread so I apologize; but the current aftermarket conventional rear shocks appear quite old with substantially rusted springs.

Was actually thinking of finding a set of stock air shocks and going back to stock configuration. is there a place/person that sells rebuilt stock air shocks or is the rebuild straightforward enough that I could buy a set of used air shocks and rebuild them myself?

Posted: Thu Apr 16, 2020 5:39 pm

genesound wrote:

That kind of mileage, you're probably in for cam chains, guides, and tension adjusters, unless they were changed already, maybe even if they were.

Well taken.

Just hate to pull the thing apart and not do something that is needed and then have to do it anyway six months from now.

Advice/info appreciated.

Posted: Thu Apr 16, 2020 6:31 pm

Ecklund wrote:

Fitz wrote:

I am your local DOHC Honda authority and can help with any aspect of your engine rebuild.
Unless you are going overbore, leave the rings alone because they are not the problem.
The burnt valve is the problem and maybe the valve seats all need to be cut, I do this and am quite good at it.
If you want or need help, 818-259-8690
I am in Granada Hills only 20 minutes away, do not hesitate to ask for help, DOHC Hondas are what I do

This is out of topic of the thread so I apologize; but the current aftermarket conventional rear shocks appear quite old with substantially rusted springs.

Was actually thinking of finding a set of stock air shocks and going back to stock configuration. is there a place/person that sells rebuilt stock air shocks or is the rebuild straightforward enough that I could buy a set of used air shocks and rebuild them myself?

There is someone that rebuilds stock shocks but, it ain't me and I really do not remember who it was either. Buy Progressive brand shocks, stock suck.
Buy Progressive fork springs too.

Posted: Thu Apr 16, 2020 6:44 pm

Fitz wrote:

Ecklund wrote:

Fitz wrote:

I am your local DOHC Honda authority and can help with any aspect of your engine rebuild.
Unless you are going overbore, leave the rings alone because they are not the problem.
The burnt valve is the problem and maybe the valve seats all need to be cut, I do this and am quite good at it.
If you want or need help, 818-259-8690
I am in Granada Hills only 20 minutes away, do not hesitate to ask for help, DOHC Hondas are what I do

This is out of topic of the thread so I apologize; but the current aftermarket conventional rear shocks appear quite old with substantially rusted springs.

Was actually thinking of finding a set of stock air shocks and going back to stock configuration. is there a place/person that sells rebuilt stock air shocks or is the rebuild straightforward enough that I could buy a set of used air shocks and rebuild them myself?

There is someone that rebuilds stock shocks but, it ain't me and I really do not remember who it was either. Buy Progressive brand shocks, stock suck.
Buy Progressive fork springs too.

Again, thanks for the input.

I updated my last bike, '81 GS1100e, with progressives and they worked great. Will do on this bike. And the fork springs too.

Much appreciated.

Posted: Sat Apr 18, 2020 12:42 pm

Seeing my CB900 in person for the first time this morning.
Ouch! And pea yoo!
This is the poster child bike for looking past the corrosion to see a potential decent motorcycle.
Wish pics could be posted here. Words are in are inadequate.
Pulling the engine today. Hopefully the head too.
What can done for a completely rusted header?
At least the four mufflers are there; and in decent shape too.

Posted: Sat Apr 18, 2020 2:17 pm

Pics ... Try using https://postimgs.org .
Free and easy .

Posted: Sun Apr 19, 2020 12:38 am

pd750 wrote:

Pics ... Try using https://postimgs.org .
Free and easy .

Thanks, will try it. Can see how to pull in pics to the app, just not sure how to get them on the forum posts.

Pulled the head with the engine in place today. Was able to take out the studs once the head was loose and grab them by their base. Probably too late to ask but what is the risk of removing the head this way?

Yep, burnt valve. Rest of head looks good. Replacement head also looks good.
Engine oil was black but it was in decent supply. What I can see the cylinder walls looks pretty good with little or no ridge.

Can't be sure but appears first time engine was disassembled.

Will try and use link to post pics ASAP.

Posted: Sun Apr 19, 2020 1:03 am

https://postimg.cc/gallery/9wHw8dc

Mmm, rusty...

Posted: Sun Apr 19, 2020 1:09 am

https://postimg.cc/gallery/5HZnL54

Head off and burnt valve.

Need to de-rust and paint headers.

Posted: Sun Apr 19, 2020 1:37 am

Yep, that's a burnt valve. Others may be leaky too, even on the other head. Kind of a thing with these bikes unless the maintenance is kept up well. One look at that bike and it's obvious that hasn't happened. Sad

click for larger

Posted: Sun Apr 19, 2020 1:53 am

genesound wrote:

Yep, that's a burnt valve. Others may be leaky too, even on the other head. Kind of a thing with these bikes unless the maintenance is kept up well. One look at that bike and it's obvious that hasn't happened. Sad

click for larger

Aint that the truth. Not sure if C19 or the organisms living on this bike are worse.

I do have to say the coils and wiring looked OK; well under a lot of dirt/dust.

Other head appears good. However, will check out valves and probably swap out valve seals.

Was a bit apprehensive about taking out the entire engine so loosened the head and removed the studs with a vice grip. Any obvious risk of damage with this method? Seems better/easier/quicker than pulling the entire engine. But?

Decided to take the leap and since the head is off replace the piston rings and hone the cylinders. With some lapped valves and new rings would be nice to have some good compression.

Posted: Sun Apr 19, 2020 1:58 am

"Was a bit apprehensive about taking out the entire engine so loosened the head and removed the studs with a vice grip. Any obvious risk of damage with this method? Seems better/easier/quicker than pulling the entire engine. But?"

Yeah, the but is you'll never get it back together right without removing the motor. There's a guy goes by "headless" on here and other fora that got his moniker just like that.

There's another guy here that sells the good Viton valve stem seals for cheap to forum members. Same guy also has cheap grade 12.9 cam holder bolts, the stock ones break... OK, it's me. Look in the stickies in the for sale area:
http://www.cb750c.com/modules.php?name=Forums&file=viewforum&f=6

Posted: Sun Apr 19, 2020 9:26 am

genesound wrote:

There's another guy here that sells the good Viton valve stem seals for cheap to forum members. Same guy also has cheap grade 12.9 cam holder bolts, the stock ones break... OK, it's me. Look in the stickies in the for sale area:
http://www.cb750c.com/modules.php?name=Forums&file=viewforum&f=6

Hey, I know that guy and his bolts & seals have been working in my rebuilds for more than 10 years but, he is a silly fucker in person. Oh wait, that's you Gene. Giggity

Posted: Sun Apr 19, 2020 10:45 am

genesound wrote:

"Was a bit apprehensive about taking out the entire engine so loosened the head and removed the studs with a vice grip. Any obvious risk of damage with this method? Seems better/easier/quicker than pulling the entire engine. But?"

Yeah, the but is you'll never get it back together right without removing the motor. There's a guy goes by "headless" on here and other fora that got his moniker just like that.

There's another guy here that sells the good Viton valve stem seals for cheap to forum members. Same guy also has cheap grade 12.9 cam holder bolts, the stock ones break... OK, it's me. Look in the stickies in the for sale area:
http://www.cb750c.com/modules.php?name=Forums&file=viewforum&f=6

Thanks for the feedback. Don't want to disregard what is clear experience and screw things up. May I ask how not removing the engine would prevent it from going back together 'right'? The dowels appear to locate the cylinder and head so the studs can be dropped in.

Of course that sounds good but having never done it before is another matter.

Also thanks for the heads up on the seals. May I ask, do the stock cam saddle bolts typically break on reinstallation?

Certainly going to be learning a lot about rust removal and fairing repair with this project.

Posted: Sun Apr 19, 2020 2:42 pm

When you pull the head off, it releases the tension on the base gasket, which usually causes it to leak after. Only way to prevent that is to remove the cylinders and change the base gasket. It's easier to pull the motor than try to get that all back right without breaking rings and such. Also, removing the cylinders is not always all that easy, and I don't think there is room to get the cylinder block off of the pistons in the frame.

I also wonder how you removed the studs with vise grips without damaging the threads.

If you work on these bikes much, you will break cam holder bolts. It happens a lot. I've had 3 different issues over the years on my 900C. I had 1 break during installation (piece came out easy), another one stretch and I was lucky and it didn't break, and another one that installed OK, but when I did a valve adjustment, I discovered one that must have broken while it was together, as it didn't look right and when I touched it, it was loose. It took me 3 days to get the broken off piece out. Of course I was working with the fairing on too.

Posted: Sun Apr 19, 2020 3:05 pm

genesound wrote:

When you pull the head off, it releases the tension on the base gasket, which usually causes it to leak after. Only way to prevent that is to remove the cylinders and change the base gasket. It's easier to pull the motor than try to get that all back right without breaking rings and such. Also, removing the cylinders is not always all that easy, and I don't think there is room to get the cylinder block off of the pistons in the frame.

I also wonder how you removed the studs with vise grips without damaging the threads.

If you work on these bikes much, you will break cam holder bolts. It happens a lot.

Understood and thanks again for the info.

The studs have a 'blank' space above the thread that can be 'grabbed'.

But all your comments are well taken. Not looking to make this any more difficult or to be breaking parts.

Thanks

Posted: Sun Apr 19, 2020 3:36 pm

You should use the search, there's a lot of info and stories on the site.

Posted: Sun Apr 19, 2020 4:17 pm

genesound wrote:

You should use the search, there's a lot of info and stories on the site.

Must not be using it properly as I looked a number of times for removing head with engine in frame.

Will try again.

Posted: Sat Apr 25, 2020 1:28 am

Cylinders came off with a bit of persuasion on a sticky down pin.

Center left piston had minor scuff. Appears at least one overheat condition in bike's 63K.

Oils rings on all pistons were stuck in their grooves. Removed and cleaned but appear to be serviceable.

All other rings appear serviceable. Will reuse per Fitz.

Bores appear in good shape. Took a fair bit of colorful language and time to clean off the base gasket.

Removed four decades of crud on the top of the cases.

May be picking up a few used but far better condition than current parts/pieces this Sunday. Will report.

https://postimg.cc/gallery/92qM8HL