Patching a leaky base gasket?

[CatatonicBug]

I've been working on someone else's LH for the last few weeks, and finally got it "done" tonight. I gave it a bath and rode to the gas station to fill 'er up to prep her for delivery back to the owner in 2 days. When I got back home, I realized that there was a line of oil leaking from the front of the engine, just below the cam chain tensioner! The leak goes all the way across, and is definitely coming from the engine seam, and NOT the cam chain tensioner. Are we looking at a mandatory engine tear-down to stop this leak, or is there an easy fix? (like bubblegum smeared in the hole )

I feel really bad, because I was ready to give this guy back his bike, having done a TON of stuff to it, and costing him almost $350 in parts and my cheap labor, I expected to have it DONE! Now I have to tell him it's still leaking oil, and I don't feel comfortable taking HIS engine apart (never done that on anything but a lawnmower before).

[XJOK2PLAY]

CBug,
Far as I know, you can try to retorque the head... might score - might not.

That's unusual to leak there... I've had problems with base gasket leaks twice now on mine... but both times they've been in the rear center of the base gasket... the first time, we tore it down, replaced the gasket. Not long afterwards, it leaked again... same spot. Tried to retorque the headbolts... no luck. But this time, instead of a teardown, I cleaned the heck out of that area w/ brake cleaner... let it dry, wiped clean, and globbed high temp rtv all in that area...
I was told at the time it wouldn't work... but it has for over 10,000 miles now!
But, not sure if it will work along the front... in the back, you can't hardly see it, either. In the front, it would be REALLY obviously ugly...
Probably have to replace it... much as that sucks.

There may prove to be a major quality difference between the 'green' base gaskets that's coming in the gasket kits and the seperate Yamaha gaskets... not sure... just speculating... the one we replaced the first time on mine was from a kit. Cody told me he lost 3 or 4 green kit base gaskets the same way on Zilla before he bought a seperate one from Yamaha... which ended his leaks.

I only know for sure those darn Yamaha gaskets are high dollar! (Almost 50% of an entire gasket kit price!)

But, if it turns out to be true and the Yamaha's are the only one's that'll last... guess they're worth the $$.
Good luck, though... keep me posted with what you find works...
Bob

[petejw]

Ive had the same problems, with 2 engines,
once i had removed and replaced the head,
retorquing the head did nothing,
as xj stated i did the same thing, clean the area up
and apply rtv, its helped on mine. mine was also leaking
at the back.

[CatatonicBug]

If I was to retorque the head, would I just torque it down from where it is, or loosen all the bolts, and start the torque process from scratch? This is the one part of the bike I have absolutely no experience with, so I am just aboout clueless about this stuff. I've never even removed a valve cover...

Could I lift the head and jugs off the leaky surface as a unit (just 1/4" or so), add some RTV and set it back down, or is there something that links the units together, preventing this?

[petejw]

cb,
if your retorquing the head,
start from the middle bolts working out,
crack the nut to loosen then retorque, only
loosen the 1 nut at a time.
also after retorquing the head make sure u readjust
the cam chain.

also do the retorquing on a cold engine.

[TADracer]

If you had the whole thing apart it is wise to check the torque on everything after an hour or so of running time, especially the head. After that first startup everything is trying to settle into its most comfortable place. I never loosen anything up but re-set the torque from where they are right now using the correct tightening pattern.

If you loosen the nuts and bolts then re-torque you are releasing all the tension on the bolts and studs and starting from scratch. They may loosen again.

Do the head in the order of tightening in an X pattern from center out. Check the case bolts using the numbered pattern used to tighten the case halves together. Reset the cam chain.

Tightening is no cost and might fix your problem. If not, then at least you know you will need to go deeper.

[DGXSER]

I read what you stated, but if it were me, I'd pull the cam chain tensioner and replace the gasket there. It is very unusual to actually leak oil from the area your indicating where the jugs meet the crankcase. There is just no to very little oil pressure there to push it out.

[petejw]

you are only cracking one nut at a time,
not all of them,
i dont loosen the nut completely,
about an eight of a turn is enough.
if your retorquing after an hour or so it wont matter,
but if your retensioning after any length of time.
try either way and see what suits you best.

[randy]

This is the one part of the bike I have absolutely no experience with, so I am just aboout clueless about this stuff. I've never even removed a valve cover...

Hold it right there...over 3k posts and you've never removed a valve cover? Guru status revoked!

[psycoreefer]

Hold it right there...over 3k posts and you've never removed a valve cover? Guru status revoked!

yeah, all fluff or what?

[dbeardslee]

You said leaky base gasket, not leaky head gasket, right? I've got one that sometimes looked like it was leaking, but it wound up being that d#$% lower banjo fitting on the oil pipe. Just to varify you might try cleaning the oil off, and applying talcum powder liberally around the motor. Fire it up and watch it closely and the talcum will tell you where the oil is coming from. I think it's pretty rare for those base gaskets to leak.

[DGXSER]

Hold it right there...over 3k posts and you've never removed a valve cover? Guru status revoked!

You know Randy, I was wonderin what all he DID do if he has not checked and reshimmed the valves on any of these machines.

[CatatonicBug]

Hold it right there...over 3k posts and you've never removed a valve cover? Guru status revoked!

LOL! I actually thought about that last night... All my experience has just been elsewhere on the bike. I've been lucky so far, and not had to get into the engine itself.

You said leaky base gasket, not leaky head gasket, right? I've got one that sometimes looked like it was leaking, but it wound up being that d#$% lower banjo fitting on the oil pipe. Just to varify you might try cleaning the oil off, and applying talcum powder liberally around the motor. Fire it up and watch it closely and the talcum will tell you where the oil is coming from. I think it's pretty rare for those base gaskets to leak.

The leak is definitley the base gasket, not the head gasket, and I'm 95% sure it's not the cam chain tensioner. It's also only on the FRONT of the engine, so nowhere near the oil banjo fitting. I may try that talcum powder test though, just to be sure. Since the oil pressure at that joint is low, I think I may try using some RTV on the seam. It couldn't hurt!

[Ivan]

I swore that my cam chain tensioner wasn't leaking as well. Then I realized it was.

Just as a cheap test to keep you from tearing into an engine that may or may not need it, clean the area well with some brake cleaner, the low VOC stuff that won't strip the paint. Then dry it with compressed air. Next coat it liberally with foot powder. The same stuff used for athlete's foot. Spray can works the best since it will stick better. then run the engine and start scoping the area with a flash light. You'll soon find the exact place the engine is leaking.

If it is the base gasket, You'll probably have to disassemble it. However that cam chain tensioner has so many places for oil to seep out, I would want to make 150% certain that isn't it first.

[CatatonicBug]

I just did the powder test, and determined that the tensioner is NOT the issue, but the leak is much more localized than I thought. It IS coming from the base gasket seam, but only a tiny spot immediately below the tensioner housing. I'm going to wait for the engine to cool down a bit, then smear some RTV on that spot to see if that helps. I'll know tonight if that stops the leak.