Topic: Is this CB550 bottom end bad?

[JBMorse]

Today I finished up the top end rebuild on my CB550 engine, and foolishly never gave a thought to the lower end! This is an engine I bought in unknown condition, and for some reason I believed the lower end to be in good shape.

Anyway here's the problem: it won't shift. Well, it shifts a little bit, but not nicely. I adjusted the clutch cable and clutch per the manual, and tried driving it out of the shop only to discover I couldn't get back into neutral. When I turn the engine off I can get it to shift a little better, but running it won't do much.

So I took the clutch cover off and everything in there looked okay, BUT the shaft that the clutch mounts on (Primary shaft?) is noisy. I hear knocking noises when I turn it by hand. That doesn't seem normal, you'd think it would be nearly silent? Tried to get a video, but I'm having technical difficulties in that department too.....

Before I commit my whole day tomorrow to tackling this, I thought I'd check in here and see if folks have other ideas.

[RAFster122s]

Can you post some photos of the bottom end condition...
Pull the oil pan, clean the filter screen and give a couple good pictures to see the underside of the gears and pump...
The pan might tell you if you have junk in the bottom end from a PO's deeds. The shift mechanism can be a problem if shifter forks are bent or worn badly and the shifter mechanism beneath the side cover can have issues from wear.
Forcing a bike into gear when it doesn't want to go in gear can cause some issues.


David

[BomberMann650]

yes it sbould be silent.

Was there any up/down/in/out play on the basket shaft?

[RAFster122s]

Bueller? Bueller?  Bueller?


Might have some damage in the gears or bad bearings on primary or secondary shafts of the transmission but if it feels rough in the primary shaft you could have cam chain or primary chain issues.  More likely cam chain issues unless all of the top end cam chain parts were replaced and then you might be looking at the primary chain problems.  Hard shifting is not good and it should be smooth but you should also have to rotate the rear wheel to advance it anything above 1st and maybe it would be possible to get it in second gear... but doubtful.

A video from your phone could be posted to flicker or some of the other video/photo web hosting sites.  That could help diagnose the shifting problems but pulling the left side cover is needed to see the shifting mechanism in action to help isolate issues in that department.  There are a couple points of play that can develop in the shifting mechanism that can contribute or cause shifting issues outside the cases/transmission.

[JBMorse]

Thanks for the help, guys. I did end up taking that engine out of the bike and swapping in a good bottom end.
I did have the oil pan off, and also took the clutch all apart to inspect it. Everything looked just fine. My hunch is there was something like bent shift forks or something wrong with that shaft. I believe all the gears worked, but shifting didn't.
I will try to post a little video of the noise I described later.
Thanks!

[RAFster122s]

Well, now you have it swapped out it would be good to start a thread and maybe title...Diagnose and Identify Bad components in a noisy shifting 550 bottom end/ transmission.  I think you might be able to get enough input to help id them if you don't know enough by yourself or what is in the Honda manuals.
Then you can scrap the bad parts and keep the good parts in a oil sprayed parts in heavy plastic to keep the dirt out, after cleaning of course. Marvel Mystery oil does a nice job of this and a cheap or recycled spray bottle does a nice job forspraying.  The little rechargeable spray bottles also are handy for this... Preval makes one and Northern Tools and Harbor freight used to carry them...not sure if they still do. The NT one being better quality.
The later two being knock offs of the Preval unit/design.
David