Topic: Is there a miracle goop for leaky valve seals?

[DammitDan]

So here's my situation...  My bike smokes a bit after it warms up (I can't tell which cylinder cause I run a 4-1), and it gets worse especially at stoplights after it's been idling for 15-20 seconds or more.  This leads me to thinking it's leaky seals, since I stole the head from a parts bike and stupidly forgot to put in new seals when I lapped and reinstalled the valves.

I'm pretty sure it's not worn rings, cause when I rev the engine up the smoke puffs a bit more, but then the smoke pretty much goes away.  And when I'm riding or pushing the throttle up the smoke is (to me) non-existant.

So, is there any kind of miracle stuff for leaky valve seals?  Or am I going to have to do ANOTHER head job?

[kghost]

No miracle cure that I know of.

Little more information would be useful......

Why did you replace the head?

When you removed and replaced the head what did the cylinder walls look like?

Was there a taper or a lip at the top of the cylinder bores? Was there any scoring of the cylinder walls?

[DammitDan]

I replaced the head because I had badly crossthreaded a sparkplug hole on the original.  The cylinder walls looked fine, although I admit I didn't check them that closely.  I was spending more time carefully carving the old gasket off the bottom of the block.  Of course, I did remove the block and reinstall it, so perhaps the rings could have been damaged when I did this (although I doubt it... I've done it before no problem and I consider myself experienced at taking apart and reassembling this particular motor)

I should have just spent the $200 and gotten new OS rings and honed the bore, but the bike had never smoked before this rebuild and I didn't think to do it (and I didn't have an extra $200 at the time).  The head I put on there was in pretty bad shape before I cleaned her up...  I'm almost 100% positive that the seals on one of the cylinders must have been bad.  Stupid of me not to replace all the seals, since I even had a set of new ones that came with the top end kit.

So, no oil additives I can put in to make a "stop leak" mixture?  *sigh*

[kghost]

Boy that sucks brother.

If the head was open and stting a long time before you got it. You can bet they shrank, hardened, or split. Maybe all three

If you have a 750.......hope your friends stay your freinds lugging it in and out twice.

[DammitDan]

Nah fortunately it's an '82 CB650...  Engine-in job 

I'm just not looking forward to it.  This will be the 6th time I've torn down and rebuilt the top end on this motorcycle.  And something always seems to go wrong when I get into it, too.

I just hope all the headbolts hold again...  I was lucky none of them stripped last time (and yes, I use a torque wrench on EVERY engine bolt!)