Important engine rebuilt questions.

[Totaled108]

So after months of sitting in a garage across town and not having the time to work on these bikes, I've got my own garage and got to work the first free day I had.
This is a 1980 CB650 engine with 34,000mile on the clock.

So far I'm at this point...



I've have never stripped down an engine this far, so I'm a bit nervous but am having fun and being very careful with everything.

So one question is, are the head bolt supposed to be thoroughly cleaned and reused, or are new ones required?



Reason I removed the head is because the left side of the head would be spitting hot oil onto my leg, any speed over 20 mph. When I got to that silly left o-ring, it was severely discolored and as soon as I removed it from the block gently, it sort of disintegrated as I held it. The reason for removing the cylinders was due to how so gritty the fins at the front of it are, i really want the fins to be very clean after this build, and as I was removing the head, it slid up a little, so I figured I'd replace the gasket and o-rings down there while I'm this far along..



I believe this engine has never been rebuilt from the look of the bolts, threads and fins still being fully intact.

Other then that it ran great! I was going to send the head and cylinders off to a motorcycle machine shop so they can check all the specs and clean it up perfectly. I lack the equipment to do this, and want to have all the valve seals replaced by professionals.

The engine still has great looking cross hatches in all the cylinder bores, and before taking everything apart, it all moves very easily by hand via pulsar generator bolt.

The question here is, how imperative is it at this point to replace the rings? I'm guessing just like the lower cylinder gasket, I'm here, it's times to replace. When I do get new rings, how much modifying the the gaps should I expect to do? Just scared of messing them up is all.

I'll have more questions as this comes along. Any advice from experienced folks that I may not have thought of, please throw it my way.

Thanks for anything.

[MiGhost]

So one question is, are the head bolt supposed to be thoroughly cleaned and reused, or are new ones required?

As long as the bolts/studs are undamaged (good clean threads, no excessive rust) they should be fine to reuse. You may want to consider replacing the acorn nuts with stainless steel to dress up the engine a bit.

The question here is, how imperative is it at this point to replace the rings? I'm guessing just like the lower cylinder gasket, I'm here, it's times to replace. When I do get new rings, how much modifying the the gaps should I expect to do? Just scared of messing them up is all.

As the engine was running good prior to tear down. I would consider that the rings would still be in good shape. It would have been better to have gotten a compression test done before disassembling the engine to be able to determine the condition of the rings. Lacking a compress test. Carefully check the rings for any damage, or excessive/unusual wear. Any nicks/scratches will require the ring to be replaced.

One other thing to consider while you are rebuilding the top end. Volker had an idea about shimming the o-rings for the oil passage to help prevent future oil leaks.

Ghost

[Totaled108]

Cool, the threads on the headbolts are in great shape with regards to rust or pitting. I'll wire wheel them up when get a chance..

Before I parked it last fall I had done a compression test. All 4 were about 120psi in only a few revolutions, I think that means they are in good shape. I didn't add oil or anything to the cylinders, so it should be the true reading.

I just saw yesterday, that thread about shoring up the o-rings on the head gasket. How easy is it to find an off the shelf version, or do I need to fab them up?

Thanks for the help

Tom

[MiGhost]

With 120 psi on the cylinders for compression. Those rings should be in good shape to reuse. Just be careful not to damage them before they are safely back in the cylinders.

The oil seal shimming is strictly a fab job. No off the shelf option exsists to my knowledge.

Ghost

[Volker_P]

I've have never stripped down an engine this far, so I'm a bit nervous but am having fun and being very careful with everything.

Sure you had fun as your bottom gasket obviously came off easily.
I remember my stock one did not and I had no fun at all.

Rings is no issue as long as compression is still fine. But consider to replace the valve stem seals.
The cam chain may stay in there another 15000mls, so no need to replace it now.

The O-ring supports are so far just my idea and I still don't have them installed.
But someone should try that.
I will replace my cam chain at Easter but again the head will stay in place. Not worth it, I want to go riding.

Be careful to reinstall the cam chain tensioner correctly.

[Totaled108]

I forgot to update a bit.

Honed cylinders, new rings, lapped valves and valve seal, done.

So I thoroughly cleaned the head bolts and female side for them with brake cleaner and Q-tips, being very careful about keeping rocks and crap out of the other holes and the engine itself.

Anyways, since I forgot to keep the head bolts in the correct pattern as when removed, I threaded them all in moving some around till they all moved fully into the hole with just finger pressure. In the end it worked out great, then all seemed to thread in smoothly and torque with same feel all around.




Maybe I shouldn't have done this, but added a very small amount of oil resistant high temp black RTV around the leak prone o-ring, just to take up a small amount of space around it and the head gasket. Crossing my fingers it doesn't bite me in the butt. Used less then what would fit in a single pea for both sides.



Custom ring compressors, using hand strength to hold them closed.





Feeding in the head bolts...



Torquing the bolts down in crisscross pattern.



Put '1-4 T' at TDC and installed cam chain and gear, cam at correct index point.



No pix of cylinder head cover installed, but that was installed just before leaving for bed. All adjusting screws fully backed off, ready for adjustment.

Woohoo, what fun!

[Volker_P]

Thanks for the update and the pictures.
Obviously taking care for the threads and careful handle of bolts is the way to avoid stripped threads.
Good work!

[lakebluewater]

could you post the sequence for how the cam cover bolts need to torqued?

[Volker_P]

Here you are:

[lakebluewater]

thanks I had seen the manual but could not make ot the numbers yours is much better but still cant make out all the numbers in the middle can make out 1,2,6 and everything from 9 on I think I can get by being the middle are close to each other as long as i crisscross them would rtv silicon gasket maker work for the cam cover gasket or should I find the oem gasket.

[Volker_P]

In fact the inner numbers are 1-2-3-3 which is irritating.
You start at the center valve cover, do crisscross for the 4 inner bolts, then criscross for the 4 outer bolts.
Then continue out to both sides, but there the numbers are better readable.

I reuse the rubber gasket (something like an 1240x3.5mm O-ring) with a bit of Hylomar.
I once got a OEM gasket with a poor surface from a Honda dealer which made me give it back and use a 3.5mm rubber rope cut at the required length instead.

[lakebluewater]

In fact the inner numbers are 1-2-3-3 which is irritating.
You start at the center valve cover, do crisscross for the 4 inner bolts, then criscross for the 4 outer bolts.
Then continue out to both sides, but there the numbers are better readable.

I reuse the rubber gasket (something like an 1240x3.5mm O-ring) with a bit of Hylomar.
I once got a OEM gasket with a poor surface from a Honda dealer which made me give it back and use a 3.5mm rubber rope cut at the required length instead.

my gasket is leaking so it is replace or try some gasket maker with it or just gasket maker never thought about the rubber rope not sure where to buy.

[Volker_P]

I think you still can buy the head cover gasket rubber rope at Honda.
But have a look at the quality of the surface then.
But this rubber only requires replacement when it its hard.
Typically the key is cleaning the surfaces carefully. I use additional sealant, but probably this is not really necessary.
Moreover more torque won't help! My head cover is tight with 10Nm or even a bit less (and no helicoils).

[davesee]

i am at the exact same stage of my rebuild (replacing the valve head). i would have suggested running a tap through all the threads and a die over all the bolts, but it looks like you have everything under control.

nice job!

[Totaled108]

Got the old girl up and went for a test ride! Loving it! Just needs some carb adjusting because of slightly hanging revs when throttle is closed.

Lots of power!