Walk me through "Lapping Valves"

[McD]

Would someone be so kind as to help me understand exactly how valve lapping works?
Is it an only intake valve thing?
Where exactly to I get the 'kit' from?
I skipped it last time, and now I'm thinking its coming back to bite me in the booty.

[The Buddha]

If the head is out, which it has to be for you to lap it, you might as well do a 3 angle job, way better than lapping it in.
Cool.
Buddha.

[Trwhouse]

Hi McD,
Are we to believe that you replaced valves previously without lapping the new ones in and now you are planning on doing it correctly?
If so, I do have a few suggestions.
My worry, though, is that you describe that you replaced valves without knowing you have to lap them in the first place.
That tells me a couple things -- that you maybe did this work without knowing exactly what you had to do.
Do you have a shop manual for the bike?
Lapping valves isn't something you can do with a "kit."
Yes, lapping is done on all valves in a cylinder head, not just intakes.
Lapping is the process of using a thick, gritty cream on the face of the valve and then carefully spinning the valve a small amount with a special suction cup tool or a piece of fuel line on the valve stem to help the face of the valve and the valve seat better fit each other. That way there can be no leakage of intake and exhaust gases past the valves during combustion and exhaust cycles.
Nowadays, three-angle valve jobs are a more accurate way of getting the valves to perfectly match the valve seats, without hand-lapping.
Honestly, these kinds of engine building steps require you to do some research ahead of time to make them successful.
I can't say enough that a good manual is something you should get.
But even a shop manual won't give the kind of detail you need to do a valve job like this. That kind of info comes from other sources.
Good luck.   

So what happened with your cylinder head?
Yours,
Trwhouse

[McD]

After pulling my head to replace a VERY stuck bucket (on my left cylinder), i did pull out a valve or two, to inspect.

I just reinstalled the old valves, figuring the bucket was the problem.
I did not lap the valves.

My RIGHT cylinder is now sputtering heavily, and i cannot for the LIFE of my remember if i pulled that intake valve or not, as this has been a few week process. This, before my stuck bucket, was my 'good' cylinder.

I have to replace the head gasket anyway (ordered wrong one last time, thought i'd chance it, wrong) because of a heavy leak.
I've got compression - finger to hole test
And I'm pretty sure I've got the timing correct (otherwise it wouldn't run at all)
When running on only the LEFT cylinder, she revs decent (as decent as a one cylinder gs can), but when the second plug is connected, Sputter sputter, as if the little explosions are making it difficult.

So I'd like to lap the intake valve on my right cylinder (or both, whatever is reccommended) to make sure its getting a good 'seal' which I'm assuming might make it sputter/choke like its doing now, AND i'll have the head off anyways, so might as well.

[Trwhouse]

Hi McD,
Thanks for the extra info.
Since you reused your valves, that is a bit different.
I believe that lapping valves is only necessary for NEW valves, though it probably can't hurt to relap your old valves if you remove them.
What you CAN do is check for leakage, and whether lapping is needed, by installing the valves, springs and retainers in the head, turning the head upside down and pouring a thin liquid, such as some kerosene, into the chamber dome. Let it sit there for a minute and see if any of the liquid comes dribbling out of the intake or exhaust ports. If it does, then it is leaking and should be relapped.

There is valve lapping info all over the Net.

http://www.burnyourbonus.info/rec.autos.tech/thread581.html

http://www.v6z24.com/howto/valvelapping

These are generic car sites, but the idea is the same.

You don't turn the valve very much to lap it in. You can use water-based valve lapping compound. You MUST get it all off of the valve faces and seats because it is VERY abrasive and will prematurely cause wear on all surfaces.

A trick is to use a piece of fuel line on the valve stem to turn it in the head after you put the lapping compound on the valve face.

This is NOT a job for the faint of heart.
There's a lot to go wrong and you need to have skills to do this well.
Best of luck,
Trwhouse

[the mole]

McD, did you absolutely, positively put the valves back where they came from (ie. left valve to left cylinder etc).
If not, that could be your problem. Sounds like you have a leaky/sticky valve.

[McD]

I am positive that the valves did not switch cylinders
I am NOT positive that my valve is even the problem, I just wanted to 'lap the valves' cause i thought it was necessary.

It seems I may make that a last resort/ leave to a professional and try a different route first.

Thanks for all the help gentlemen.

[The Buddha]

Carbs ... muhahaha hahaha hahahaha ...
Valves bend and die and kill off a whole cyl.
Carbs, fuel with crap in in etc etc sputter. Air filter too. Electrics too.
Cool.
Buddha.

[qwertydude]

How much of a difference in power could you possibly gain with a 3 angle valve job on the GS?