No compression after gasket replacement.

jimid

jimid

Active Member
had a running cb 550. Was leaking oil out of head gasket. Took top end off, replaced gasket, re assembled using honda manual. Now very low compression. I'm getting about 30psi in each cylinder.

Need some guidance as what to do next... Thanks.
 
Jimi D said:
had a running cb 550. Was leaking oil out of head gasket. Took top end off, replaced gasket, re assembled using honda manual. Now very low compression. I'm getting about 30psi in each cylinder.

Need some guidance as what to do next... Thanks.
Click to expand...

Did you replace the piston rings?

Walk through how you're testing compression, if you would.
 
Hmmm. Did you mess with the rings at all?

edit: too late. Btw, are you getting low compression or no compression at all?
 
I didn't touch the pistons at all. Only the head came off.

Testing procedure:
All plugs out.
Screw in tester.
kick engine over a few times with an open throttle and choke off (with both kickstart and electric)
Read meter.

getting very low readings. Wont blow finger off if i leave it over the plug hole.
 
No compression after gasket replacement.

Readjust your valves and check your cam timing
 
The base gasket could have been disturbed but that shouldn't effect compression that much. Either your piston rings got totally stuck and f-ed up (unlikely) or maybe your cam timing is so far off that they're both open at the same time...

Btw I would be VERY careful with turning the engine over right now. If the cam timing is off you can very easily bend all kinds of stuff. Did you hear any clunking sounds when kicking it over?
 
Jimi D said:
had a running cb 550. Was leaking oil out of head gasket. Took top end off, replaced gasket, re assembled using honda manual. Now very low compression. I'm getting about 30psi in each cylinder.

Need some guidance as what to do next... Thanks.
Click to expand...

You either have the cam out of time, and that could have caused catastrophic valve damage, or you have the valves maladjusted. (A word sometimes used to describe me on this forum.) <G>
 
Everyone, thanks for the replies.

Cam was off time. Not even remotely close, Or 180 off.

Guess this is what happens when its 4am and your still putting things back together. tdc must have moved or something when lining things up. Quite confident i checked. but no disagreeing with it being off. No way it could have moved once that chain is on right?

anyway. compression now. getting about 130psi off the kick start on each cylinder. still have to fine tune the valves

But thanks, back on track again.
 
Lucky. That mistake can bend valves. Congratulations on getting past a major fuck-up unscathed. :D
 
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