Engine problems

[TheGrandEnigma]

Hey folks,

I'm finally trying to get my '78 going. (Posted about it a couple years ago.) Compression was low (about 95psi) except cylinder 3 compression is 0. Took the head off and there's no damage I can see to piston, cylinder wall, nor valves. Would stuck rings cause that? Probably more likely a stuck valve? The bore is really shiney, would it be worth it to take the pots off and hone them? I'm told that can cause compression loss.

My goal is to get the bike running on a shoestring budget before the end of the month. I'm no mechanic either, so I'm pretty sure I dug myself a hole.

Trying to figure out what makes sense to do while the motor is apart. That's the main issue right now. I'll deal with dirty carbs, missing lights, and bad wiring later, I just want it out ONCE this year before the snow flies!

I appreciate you all, thanks in advance!


Matt

[DiverRay]

Check the valve clearance on ALL the valves while the head is off!
These bikes have the valves go from 0.012 to 0.000 as they "wear", so the valves can't close.
put about 3 oz. of ATF into each bore with the pistons in place. this will take care of most sticking ring problems. ATF is Automatic Transmission Fluid, just use the cheapest.
Turn the crank over by hand after the ATF has been in for overnight. You should be able to turn it without feeling any real difference in effort for a full revolution.
Line up timing marks and re-assemble the head/engine.

[TheGrandEnigma]

Awesome, thanks Ray!

Where does a guy get replacement shims for valve adjustment? My local dealer?

Once I get some cash and can breath a little easier, I'll maybe properly rebuild the whole bike, but I want back on 2 wheels first!

Too bad I won't be able to make it to the vintage Yamaha rally.

[DiverRay]

Post a list of the shim size you need. I do a "swap", as I've collected a few in my years of owning these bikes. As I remember, Kawasaki and Suzuki both used shims of the same diameter on some of the models they produced, so that may also help. Without looking at anything, I think they are 22mm, but PLEASE double check first.
Whatever you do, do NOT BUY "aftermarket" or Chinese shims! I tried once, and had them break under normal use!!!

[Radioguylogs]

I believe the shims are 29mm diameter.

[bikerphil]

And the Suzuki uses 29.5MM

Ours are 29MM

[DEEBS11]

I have used Japanese K&L on 3 of my old bikes (Yamaha & Kawasaki) with success. Lots of Chinese crap out there to avoid.

[DEEBS11]

You can't pull apart engine components without new gaskets. Do NOT use RTV to reseal an old gasket. That will officially make you a Hackmaster. Gaskets go on dry with a clean mating surface. Vesrah is good quality. Athena gaskets are total crap as well as any "unbranded" & Chinese gaskets. Dealer prices on bike parts will make you faint and will have a very long shipping wait.

[Radioguylogs]

I agree with Deebs about Athena gaskets - many of the gaskets in their kits are made of a thin green material than doesn't have much squish-iness to fill the unevenness between the mating surfaces.

[DEEBS11]

and they crack after time because they are so thin. Complete garbage.