valve lapping process

[alke46]

Does anybody have any helpful advice on getting the suction cup to stay on the valve when lapping? This one that I am using is fighting me every step of the way.
Especially the exhaust valve with their smaller size. I'm even considering a drop of glue on the cup but then it will just take some heat to make it release when I finish each valve.

I am currently on my 3rd and final pass on each valve as I started with the compound straight out of the tube then adding a couple of drops of water for the 2nd pass and now that I am on the final pass with even a finer grit the darn cup just does not want to cooperate.

Any suggestions?

Thanks

[Nessism]

Sounds like you should just stop. Lapping is just to clean the debris/burrs off the seat, not to renew the seats. People that hammer away at the valves risk creating grooves in the valves and wearing down the seat.

[alke46]

you're probably right. Also sounds like a good idea to me to stop.

[sharpy]

get some fuel hose and run it over the valve stem and pull down from underneath, presuming you have the head on V-blocks or a friend holding onto it as half the head hanging over the bench if ure game. simple

[Tom R]

Agreed, do it from the stem side. Those cups are worthless. I’ve used a tap holder lightly clamped on the valve stem.

[Steve]

I use a short piece of hose (breather hose works well) pressed over a bolt head that is chucked into my cordless drill. No suction involved, just friction. However, since you need to apply a bit of pressure to take advantage of that friction, it also applies that pressure to the valve face, making it VERY hard to turn. I just press on the valve stem with my finger, then turn the drill on and spin the valve. Light pressure is accomplished by allowing the valve to seat lightly while spinning.

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[alke46]

Thanks for all the good suggestions. I never thought about doing it from the opposite side.

Anyway, after stepping away from it for 4 hours, when I went back to it, I was able to get the job done.

[cowboyup3371]

I use a short piece of hose (breather hose works well) pressed over a bolt head that is chucked into my cordless drill. No suction involved, just friction. However, since you need to apply a bit of pressure to take advantage of that friction, it also applies that pressure to the valve face, making it VERY hard to turn. I just press on the valve stem with my finger, then turn the drill on and spin the valve. Light pressure is accomplished by allowing the valve to seat lightly while spinning.

.

There is a video of this on Basscliff's site

[Eli69]

I held a ball point pen against the center of the valve while spinning it with a piece of hose and a cordless drill.

[TxGSrider]

The last few valve jobs I had done didn't cost very much and didn't need to be lapped. Ive had a couple machine shops tell me that with any type of decent valve job equipment that they seat immediately. So why do want to lap them?

[Nessism]

The last few valve jobs I had done didn't cost very much and didn't need to be lapped. Ive had a couple machine shops tell me that with any type of decent valve job equipment that they seat immediately. So why do want to lap them?

Probably because he didn't have a valve job performed.

[TxGSrider]

Probably because he didn't have a valve job performed.

If im going to go through the work pull the head off and remove the valves, its getting a valve job and new seals at the least. But I understand.

[alke46]

Valve job was not necessary. Just needed to be lapped. And yes, new seals installed. Cylinders honed and new rings -- trying to reduce the oil consumption.

[jdion81]

I think it kind of depends on what resources are available in your area. I lapped the valves on mine instead of sending it to the machine shop to do after they charged me $68 to drill out an exhaust stud and put in a heli-coil.

[sharpy]

thing is never take a bike head to a car place. well infact any plce unless you know they do great work. Most car places just "attack" a head and leave it with deep valve seats. true there are some good places but just be carefull where you take your pride and joy. We always lapped the valves in even when the head was done on a serdi.