Leaky Valves?

[Anonymous]

Hello,
I have a 79 gs 550L and the exhaust valve is leaking on the first cylender, so i am loosing compression. Does anyone know a cheap and easy way to fix this with out buying new valves and having a machine shop re-cut the angles on the head? I have the head off and it all looks pretty carbon'd up. Other than that the valves dont look too bad. Thanks for your thoughts

[DMPLATT]

You should be able to just get new seals, clean up the valves and lap them back in. Just make sure to get ALL the lapping compound out when done.

Any auto parts store has the Valve lapping compound. They also have a tool, actually it's a wooden dowel with a rubber thingy on the end that makes Valve lapping much easier.

It's really not a hard job at all. Since you already have the Head out, you won't have any trouble.

Now, an Auto mechanic friend of mine tought me a little trick. Haven't tried it on a Bike head. Anyway, after you are done, lay the head down so that you can fill the area around the valves with Water. Then let it sit for a while. Come back and check. If any of the Valves aren't seated right, the water will drain out.

Good Luck.

[jimcor]

Dave2, This is explained in your shop manual...you do have a manual right?

And as far as cheap and easy goes...ain't no such thing!

[robinjo]

You should be able to just get new seals, clean up the valves and lap them back in. Just make sure to get ALL the lapping compound out when done.

Any auto parts store has the Valve lapping compound. They also have a tool, actually it's a wooden dowel with a rubber thingy on the end that makes Valve lapping much easier.

It's really not a hard job at all. Since you already have the Head out, you won't have any trouble.

Now, an Auto mechanic friend of mine tought me a little trick. Haven't tried it on a Bike head. Anyway, after you are done, lay the head down so that you can fill the area around the valves with Water. Then let it sit for a while. Come back and check. If any of the Valves aren't seated right, the water will drain out.

Good Luck.

Totally agree, but I would use petrol to check for leaks.

[DMPLATT]

You should be able to just get new seals, clean up the valves and lap them back in. Just make sure to get ALL the lapping compound out when done.

Any auto parts store has the Valve lapping compound. They also have a tool, actually it's a wooden dowel with a rubber thingy on the end that makes Valve lapping much easier.

It's really not a hard job at all. Since you already have the Head out, you won't have any trouble.

Now, an Auto mechanic friend of mine tought me a little trick. Haven't tried it on a Bike head. Anyway, after you are done, lay the head down so that you can fill the area around the valves with Water. Then let it sit for a while. Come back and check. If any of the Valves aren't seated right, the water will drain out.

Good Luck.

Totally agree, but I would use petrol to check for leaks.

Petrol, as in Gasoline?

[robinjo]

Yes gasoline, it is thinner as water so the leaks will show better/faster. This was told me by my mechanic.

[SqDancerLynn1]

Use gas, solvent. water will make things rust

[Anonymous]

Ditto on the gas. Were the cams still in when you decided that the valve was leaking? Is it possible therefore that you have a tight tappet setting on that cylinder regardless of whether the head is off or on?

[Anonymous]

Hey first i want to thank you all for the answers. I originally checked the heads with gas. It leaked as explained. The cams were out so no chance there. Does lapping compound work well? I have heard about it, just never knew anyone that did it. Thank you all again!!!!

[DMPLATT]

Hey first i want to thank you all for the answers. I originally checked the heads with gas. It leaked as explained. The cams were out so no chance there. Does lapping compound work well? I have heard about it, just never knew anyone that did it. Thank you all again!!!!

That's what is used. Any mechanic or factory that does valves has to lap them in.

It's really pretty easy. WHen you do it, you can actually pretty much see it when you get it lapped in. It'll be a nice even line all around the valve and seat. Not hard at all.

As stated, just make sure to get it all out and nice and clean when done.

[Anonymous]

O.K. just one more thing and then I'll shut up. Is there any junk, carbon or such preventing the valve from shutting? From experience, i always check the small things first. You could however rebuild the entire head never knowing that there was nothing wrong in the first place and be quite happy with the outcome.

[Anonymous]

First - make sure all parts are clean. Clean the carbon off the valves and seat areas of the head. Careful not to nick the sealing surfaces or the stem.

Clearance on the valve stems - how is it? Check.

Pitting on the valve faces - how is it? Check. Any pits go across the face of the seat = a leak....

Lapping - requires technique. Know how to do it? You need to randomly rotate the valve if using a dowel - suction cup type or use a tool that incrementally rotates the valve around in a circle while moving it back and forth about 20-30 degrees for the lapping action.

Lastly - I didn't see mentioned face hardness. Aren't valves and seats face hardened? How much lapping can be done? I think the seat can be ground, but the valve needs replacement.

And - use rubbing alcohol-91% as a solvent - or laquer thinner - or acetone - all are very "thin" and non-corrosive. Good luck - Dieter

[DMPLATT]

First - make sure all parts are clean. Clean the carbon off the valves and seat areas of the head. Careful not to nick the sealing surfaces or the stem.

Clearance on the valve stems - how is it? Check.

Pitting on the valve faces - how is it? Check. Any pits go across the face of the seat = a leak....

Lapping - requires technique. Know how to do it? You need to randomly rotate the valve if using a dowel - suction cup type or use a tool that incrementally rotates the valve around in a circle while moving it back and forth about 20-30 degrees for the lapping action.

Lastly - I didn't see mentioned face hardness. Aren't valves and seats face hardened? How much lapping can be done? I think the seat can be ground, but the valve needs replacement.

And - use rubbing alcohol-91% as a solvent - or laquer thinner - or acetone - all are very "thin" and non-corrosive. Good luck - Dieter

Hmm. I've only ever just spun the valves with the Dowel tool and suction cup. Spinning with a low RPM drill and lapping compound always lapped both vavle and seat together. Lapping compound will lap hardened steel. I've never heard of moving it 20-30 degrees before? I don't see how that could work with a manual operation like this. I always that that the poing in lapping was to make sure the valve and seat mesh, so not sure what the moving 20-30 degrees would accomplish. But, I'm not a pro either.

[duaneage]

GS valves should not be lapped. They are hardened on the face and lapping is not recommended by Suzuki. Do so at your own peril.