Free bike! (but you know the deal)

Posted: Sat Apr 25, 2020 2:31 am

Much of that oil and carbon is from the bad valve stem seals you mentioned. All that carbon should be removed too, from the pistons, combustion chamber, ports and talves. That builds up and then flakes and gets stuck in a valve, so contributes to the valve leaking and eventually burning. Get some Viton valve stem seals.

Hard to see in the pic, but the cylinder bore I can see looks a bit worn.

Be sure the ring landings on the pistons are all perfect too. If the landings are screwed up, the rings don't get adequate pressure to seal.

Posted: Sat Apr 25, 2020 8:32 am

There sure is a lot of meat in those stock cylinders, I see an overbore in that engine's future.

Posted: Sat Apr 25, 2020 10:08 am

genesound wrote:

Much of that oil and carbon is from the bad valve stem seals you mentioned. All that carbon should be removed too, from the pistons, combustion chamber, ports and talves. That builds up and then flakes and gets stuck in a valve, so contributes to the valve leaking and eventually burning. Get some Viton valve stem seals.

Hard to see in the pic, but the cylinder bore I can see looks a bit worn.

Be sure the ring landings on the pistons are all perfect too. If the landings are screwed up, the rings don't get adequate pressure to seal.

Cleaned the piston tops after the pics. Was one smallish scuff on one piston; probably an over heat. Had to work the stuck oil rings out of their grooves. Rings are all soaking now but need to spend more time on cleaning the piston ring grooves.

Using a different head that came with the bike. But your comment about worn seals leading to carbon buildup is well taken.

Will take some better pictures of the cylinder bores next time. They all appeared fairly straight and without distortion but will try and get some measurements to confirm. Certainly don't want to waste this effort by using out of spec cylinders.

Posted: Sat Apr 25, 2020 10:24 am

Fitz wrote:

There sure is a lot of meat in those stock cylinders, I see an overbore in that engine's future.

Have limited experience but reasonably good evidence that this is the first time the engine has been apart. Agreed, stock/standard cylinders.

Will do some measuring to confirm piston and bore dimensions. Bike ran well until it didn't with a dead cylinder from burnt valve. Rings have good tension and appear in serviceable condition.

An over bore with new pistons and rings is very much an option especially with the engine torn down this far. But if the clearances are within spec I'm leaning toward using the cylinder, pistons and rings as is. Well, with a hone. Will check and report back.

Would very much regret wasting this effort so if an over bore is the smart play you may be right about what you see for the future of the cylinders.

(took almost as long to get the old base gasket removed as it did to get the head off.)

Posted: Sat Apr 25, 2020 12:09 pm

If you hone the cylinders, you must replace the rings; and if you replace the rings, you must hone the cylinders.

With 63K miles the rings are probably close to 75% worn if the bike was well maintained all it's life.

If the rings were difficult to remove, pay extra attention to ring landings, after a careful cleaning. They need to be unharmed or it might not seal well. The ring seal has less to do with "tension" and more to do with the ring landing condition.
https://www.google.com/search?q=motorcycle+piston+ring+landings

Check cylinder bore for taper, out-of-round, banana shape wear, and scratches.
https://www.google.com/search?q=how+to+check+cylinder+bore+wear

When it comes to machine shop work, be sure to use someone that has experience with these old motors. A V-twin or automotive guy might not have the skill set necessary for the best results with these old air cooled high performance motors.

Posted: Sat Apr 25, 2020 1:12 pm

genesound wrote:

If you hone the cylinders, you must replace the rings; and if you replace the rings, you must hone the cylinders.

With 63K miles the rings are probably close to 75% worn if the bike was well maintained all it's life.

If the rings were difficult to remove, pay extra attention to ring landings, after a careful cleaning. They need to be unharmed or it might not seal well. The ring seal has less to do with "tension" and more to do with the ring landing condition.
https://www.google.com/search?q=motorcycle+piston+ring+landings

Check cylinder bore for taper, out-of-round, banana shape wear, and scratches.
https://www.google.com/search?q=how+to+check+cylinder+bore+wear

When it comes to machine shop work, be sure to use someone that has experience with these old motors. A V-twin or automotive guy might not have the skill set necessary for the best results with these old air cooled high performance motors.

75% huh? Hmm... And the bike was not well maintained. No valve adjustment probably lead/contributed to burnt valve. No particles in oil but certainly black. Fork seals shot. Very dirty and rusty. Not well maintained.

The only rings that were 'stuck' were the oil rings. They came out reasonably easy and cleaned up well along with the other rings. Inspected the piston grooves but will take a closer look at the grooves and lands.

May I ask for a bit more on the hone/new ring topic. Have ball honed car engine cylinders with used rings for a reseal and had good results.

If the bores are decent and I reuse the rings should I simply reinstall the cylinder without the ball hone? There was no evidence of a poor ring seal before the bike was stopped due to the burnt valve.

As the top end is disassembled and intend on lapping the valves and installing new valve seals I wouldn't want to make an obvious mistake with the rings/cylinders.

Posted: Sat Apr 25, 2020 1:44 pm

Quote:

... Have ball honed car engine cylinders with used rings for a reseal and had good results ...

Well, it's generally a bad idea, unless some special circumstances like very low mileage warrant it. And comparing procedures for a 10,000 rpm air cooled motor to automotive maintenance is not advisable.

When you honed, it ruins the seal that was made when the pistons/rings/cylinders were broken in. When the hone job is fresh, it's rough, and that is smoothed by the rings breaking in. It causes them to seal well together. Old rings are already have the original edge filed away by the old cylinder wall surface. The freshly honed cylinder wall may never really get properly dressed by the old rings.

In airplane maintenance, where all work is certified, rehoning and using old rings is forbidden by law, so it's not just a good idea...

Posted: Sat Apr 25, 2020 1:51 pm

genesound wrote:

Quote:

... Have ball honed car engine cylinders with used rings for a reseal and had good results ...

Well, it's generally a bad idea, unless some special circumstances like very low mileage warrant it. And comparing procedures for a 10,000 rpm air cooled motor to automotive maintenance is not advisable.

When you honed, it ruins the seal that was made when the pistons/rings/cylinders were broken in. When the hone job is fresh, it's rough, and that is smoothed by the rings breaking in. It causes them to seal well together. Old rings are already have the original edge filed away by the old cylinder wall surface. The freshly honed cylinder wall may never really get properly dressed by the old rings.

In airplane maintenance, where all work is certified, rehoning and using old rings is forbidden by law, so it's not just a good idea...

Understood and thanks.

If old rings are reused would you recommend simply reinstalling them as is and reinstalling the cylinder without the hone?

Posted: Sat Apr 25, 2020 2:16 pm

Yes, but make sure everything goes back together in exactly same places as it came apart.

Posted: Sat Apr 25, 2020 2:30 pm

Also if you do buy rings, I suggest getting "Made in Japan" rings, can find for under $25 per piston.

https://www.vintagecb750.com/products/4/engine/75/piston-ring-sets

Posted: Sat Apr 25, 2020 4:00 pm

There is also the option option of Total Seal piston rings, they are exclusively who I use for rings no matter the application. They are made in Arizona and are extremely accommodating.
I send the Cruisinimage pistons I have my customers buy from eBay to have Total Seal rings fit to the pistons. You have a choice between standard rings or gapless rings.
Standard compression pistons get standard rings for my applications, higher compression pistons get gapless rings and really pump up the compression

Posted: Sat Apr 25, 2020 4:19 pm

Total Seal makes very good products, and I assume somewhat expensive.

What's it cost to do all that Ray?

I'm just guessing about $40-$50 a hole for just standard rings without additional work.

Posted: Tue Apr 28, 2020 6:43 pm

Picked up a bunch of new to me used parts for the CB900C.

Great stock recovered seat, exhaust system in much better condition, needed rear turn signal lights etc.

Even have a headlight and ears if I want to dump the Vetter.

And a battery which is now on trickle charge.

Still need tires but may be an actual runner soon.

https://postimg.cc/gallery/HxFJXxG

Posted: Tue Apr 28, 2020 10:42 pm

There's some good stuff in those pics!

Posted: Tue Apr 28, 2020 11:12 pm

genesound wrote:

There's some good stuff in those pics!

It was a good score.

Hoping the engine comes together over the next couple of weekends.

Seller was asking $400 for the lot but gave a C19 discount and accepted $100.

The headlight and ears give me the option to dump the Vetter fairing. Thing is pretty worn but makes the bike much more useful on higher speed, longer runs. Probably put it back for now.

The current shocks are very rusty even though the rod is clean. The upper mounts appear damaged or degraded. The stock air shocks that came in the parts lot appear in better condition than anything on ebay. If they hold air may install them for now as they cost nothing extra and may be better than the current ones.

Besides engine assembly the next priority is front brake pads, they are missing for some reason, and tires.

Posted: Tue Apr 28, 2020 11:28 pm

I like the air shocks for touring. Very handy to be able to pump them up for a passenger and maybe camping load and stuff.

Posted: Tue Apr 28, 2020 11:47 pm

genesound wrote:

I like the air shocks for touring. Very handy to be able to pump them up for a passenger and maybe camping load and stuff.

Sounds right.

Leave the Vetter on and install the air shocks; assuming they work.

Will be making the trip between Glendale, Santa Clarita, Santa Barbara and back often and the Vetter will be nice to have.

The rubber mounted engine and tall gearing will work well in this regard too.

After a whole lot more cleaning, the thing is a rolling infection, the cosmetics deserve a bit of attention too. Been watching U toob videos on tank dents and painting.

Posted: Wed Apr 29, 2020 12:06 am

If I were you, I'd put new seals in them (unless they were just done) and look them over good. Also the accordion rubbers (gaiters) need to be untorn and basically perfect. As soon as one splits, dirt starts getting in and then the stanchion starts to wear. If wear goes through the finish on the stanchion then they'll never hold air and will rip up seals quickly.

Posted: Wed Apr 29, 2020 2:00 pm

genesound wrote:

If I were you, I'd put new seals in them (unless they were just done) and look them over good. Also the accordion rubbers (gaiters) need to be untorn and basically perfect. As soon as one splits, dirt starts getting in and then the stanchion starts to wear. If wear goes through the finish on the stanchion then they'll never hold air and will rip up seals quickly.

Thanks for the input. Will do.

Not a real fan of the airshocks but these appear to be a better choice than the ones currently on the bike. But this is only true if the airshocks actually function; hold air.

Will also convert the forks to non-air function with new springs at some point, probably when the bike gets updated with new shocks, but for now they also need to hold air.

Trying to get this bike on the road with a limited budget but of course some items are simply a necessity. Also would like to avoid having to re-do things simply because they were missed/ignored when there was a chance to address them.

Posted: Wed Apr 29, 2020 4:14 pm

If you keep the fairing, you might want the air forks.

If not look at RaceTech springs and cartridge emulators. Just progressives without air won't be firm enough.

https://www.racetech.com/

Posted: Mon May 04, 2020 1:25 am

https://postimg.cc/tZTSw3Rq

Cylinders are on! Again.

Based on forum advice reused the rings without hone. Makes sense, there was apparently a decent ring/cylinder seal just before the bike stopped running.

Had to remove and clean the oil ring as they were stuck and not moving.

As the Vetter will need attention before it can be utilized will likely just use the 'new' headlight and fork ears instead.

Also as the shocks are pretty poor and the 'new' air shocks look quite good, will likely install the air shocks. At least for now.

Significant oil has leaked out of the air hose while the air shocks have been stored in plastic bags. Advice/suggestion on if it should be put back. How much, what type oil...?

The 'new' exhaust is a clear step up from the current system.

And the 'new' seat is really very nice too.

Still no fluid getting to the rear caliper. Looks like the rear master will need to come out.

Posted: Mon May 04, 2020 3:48 am

There isn't any way to add fluid and check the level. The specs are in the book, but I remember that the rear shock oil spec is wrong. It should be more like 10 oz. The seal replacement stuff is good. Only way to really know the level, is to disassemble the shocks, empty them, clean em up, change the seals and fill them, put them together.

Posted: Mon May 04, 2020 9:48 am

Regular Cars Youtube channel just did a review on an '82 CB900C.

His take on society through the lens of our vehicles is interesting.

https://www.youtube.com/watch?v=1J973Ekyjh0

Posted: Mon May 04, 2020 12:53 pm

Yeah, he's mostly right.

They're a fun bike when everything works right.

Posted: Mon May 04, 2020 1:39 pm

genesound wrote:

There isn't any way to add fluid and check the level. The specs are in the book, but I remember that the rear shock oil spec is wrong. It should be more like 10 oz. The seal replacement stuff is good. Only way to really know the level, is to disassemble the shocks, empty them, clean em up, change the seals and fill them, put them together.

Got it. Appreciated.

Probably just install them and then swap them out for a set of Progressive when they become annoying. The current shocks are a back up but they are worn, very rusted and have degraded mount sleeves.

Change out the fork springs, add an emulator and a brace when I get to the new shocks.