valves lapping

hi!
i have kz 1000 1978 and it needs lap valves.i'm just wonder what kind of a grinding compound are you using?
i got one in a tube and it is a bit coarse.dont want mess up seats.
any recommendation?
thank you D.

Ive always used the coarser grit and it works great. Anything too fine will take too long to get a seal. I always test the seal with water and comp. air and every valve passes the test. As soon as i noticed the compound id been using was coarse, i recalled how id never had a problem with valves and had run several heads for several seasons and hey, i beat the heck out of the 900s with heavy springs i havnt bent a valve but once on a sec. gear pop out at 140000 or more. So yup the coarse grade is perfect. After u spin a valve backnforth, clean the seatnvalve wth a rag, put the vlv in,push down and twist half a turn then let go. Fill the chamber w water, hold the valvedown with your thumb and shoot about 90lbs of air in the port. If u have tiny bubbles, lap some more, and sometimes it takes a while, but not to worry as long as there is no reciever groove starting to show on the valve face. If u see a groove its time to cut the seat. If a bent valve is suspect change to another and use it if it laps in. Its easy to see that the valve face is ok and still has its orinal angle. If the seats dont have crisp angles on the seats and they look mushy, i have them cut, then lapping is a snap and so is picking out a bent valve. The compound will cut a nice grey margin into the valve face. u can see it developing right away. Sometimes it will start to come in all crappy looking and stay there for awhile, then next time u lok its forming out great, so be patient and keep watching for groove in the valve. Some valves will lap in fast. U may see a margin that concentric but the valve still lets tiny bubbles out. Ill tell ya, from my experience, engines run excellent when all the valves are sealed tight. I would spray out the guides and lube the valve before lapping. Ive ruined guides from using compound to hone them (it works super) and not cleaning the guide properly. Valves that have a hardened face will sow no grind marking from the compound the first time you spin em, see if they seal then if they dont spin em some more. Sometimes they will show a part margin forming and will pass the pressure test. Other times hey seal at the time the margin comes in full. So dont be nervous working with those (nitrided valves. when switching heads or holes, they need to be lapped and will lap into any seat that has retained its angle.

Post edited by: nads.com, at: 2005/12/27 03:04

Nads I love you man, I really dig your "its not rocket science" attitude. I can usually figure out what you're talking about but I want to ask a couple clarifications this time:

nads.com wrote:

After u spin a valve backnforth, clean the seatnvalve wth a rag, put the vlv in,push down and twist half a turn then let go.

That's interesting, why?

Fill the chamber w water, hold the valvedown with your thumb and shoot about 90lbs of air in the port. If u have tiny bubbles, lap some more,

I really, really like this tip. I've tried lapping, with some good results, but I was only going by the look, and the blueing. This really gives some positive feeback to what you're doing. It took me a little bit to picture this in my head but I guess you hold a blow nozzle in intake or exhaust port, and use your hand to seal the rest of the opening? or does it work if you just blow up its skirt?

But as far as coarse vs. fine, wouldn't it really be just like any other finishing process, e.g. paint sanding -- start coarse, work down to fine?


thanks,
Ricky

the reason for blowing the air around the valve is to make sure its seating,but ive allways done it the other way around i fill the port and hold the vave down and blow the air around the valve/seat if i see bubbles in the ports i know there not sealing i suppose it works the same way though!ive used this to check spare heads many times.a far as valve lapping goes ive allways been a little sceptacle i never thought the amount of material removed really made a differance in performance once the engine was warmed up and things started expanding,unless you have a real good set of valves and seats that you just had ground and just need to fine tune them a little but thats just my experiance.ive got some valve lapping compound around here somewhere,i think its called "CLOVER LEAF"

Post edited by: wireman, at: 2005/12/27 21:33

Or you can put the valve in, hook the vacuum tester to the port and see if it will pull vacuum and hold it

As for lapping, we never use course. Then again, we never lap a valve and seat that hasn't been ground and machined. We buy the lapping compound and it comes with two tins in the package. Course and fine. We open the pack, throw the course away and use the fine ( after doung a valve job.)

I guess if you are trying to lap worn seats and valves to get some seal back, then it wouldn't hurt to use the course, but that stuff will grind a groove in the valve face.



Jay

Post edited by: APE Jay, at: 2005/12/27 19:49

Post edited by: APE Jay, at: 2005/12/27 19:51

The simple and easy way I found to check the valve seal after lapping is to spray brake cleaner into the port and see if it leaks out.

thank you guys!
for all your tips and tricks.
i remember someone told me to check the valve job with gasoline poured in chamber on cylinder hed and wait if it will go thru, if yes lap more.
ok i will do it.i like the test eith air and water.
thankx again Draho