Valve lapping yes or no?

[mixongw]

I had to laugh at myself on this topic! I thought you guys were talking about valve timing overlap like on my Diesel. I'm calibrated now.

[DaveDanger]

A properly performed hand lapping job, will be minimal, and will provide a velvet finish. The only time I've ever seen a shiny polished finish is after a short run on a fresh valve job. I've also lapped countless sodium filled exhaust valves, admittedly they were mostly from 540 Cubic inch aircraft engines with valve faces the size of a moonpie, and stems like utility poles

[Hoomgar]

Re: valves

Suzuki may know what there talking about but the person that transcibed the manual may not, kind of like the factory DR manual that shows and tells you how you put the thrust assm. together, wrong witch will total your trans out in a short amount of time 8O 8O 8O also keep in mind that some parts of manuals were procedures are mentioned are quit often taken from other manuals, also that the manual you get is not a true factory manual unless its written in Japanese

Thanks BB, that's all I was trying to say as well:

I guess not every thing you read is 100% true, even if it makes sense.

[tkent02]

they were mostly from 540 Cubic inch aircraft engines with valve faces the size of a moonpie, and stems like utility poles

Odd that the only I have ever had break were on airplanes.
What's up with that?

[Road_Clam]

Well, my Suzuki manual says to cut the seat face to velvet smooth finish and final seating will take place in the first few seconds after an engine is fired. When my head was done no lapping was done.

Yea, here is the valve face tech description take directly out of my factory Suzuki manual:

"After the desired seat position and width is achieved, (with the factory 15, and 45 degree cutters) use the 45 degree cutter very lightly to clean up any burs caused by the previous cutting operations. DO NOT use lapping compound after the final cut is made. The finished valve seat should have velvety smooth finish and not a highly polished or shiny finish. This will provide a soft surface for the final seating of the valve which will occur during the first few seconds of engine operation".

So they must want a roughed valve seat surface, then the valve face pounding action when the engine is running must complete the seal process. I agree with that...

[Nessism]

I agree also, no lapping...other than very lightly to check the sealing pattern. The worse thing is to lap the valves agressively to try to remove imperfections in the valves/seats.

[49er]

After visual inspection, checking specs and de-coking, I lightly lapped the valves on my 850. You get good feelback as to the quality of the seating areas this way.
After 77k kms, I would have expected the seat areas to be over width but they weren't!! I can only assume that the valves and seats were machined at some time (no evidence of this on inspection), or that they are indeed well hardened from the factory. With a finishing paste, they did take a while to hand grind to the desired seal.
As for drill grinding/lapping, don't even go there. I have hand finished lap jobs on all my race and road engines with good results.
Good things take time!!!!

[fcchavez]

You also have to take into consideration where the motorcycle is actually sold. If is over seas the jungle juice they run is extremely more potent then the stuff in the states. different seat material and hardening abilities. You always want to use seat cutters with the different angles to get the seat/ sealing ability that you want. And after 500 miles or so the valves will seat themselves. Lapping is just a way to mask a problem i think

[terbang]

I have lapped 16 valve heads for years, with good success.

[TheCafeKid]

But is NOT lapping them destructive to them or the motor in any way?

[49er]

But is NOT lapping them destructive to them or the motor in any way?

I doubt that there are any major concerns with imperfect sealing at the valve seats. Any carbon build up proir to normal sealing would be burnt off during the combustion process. This is assuming that the seats and valve are soft enough to eventually seal as Suzuki suggests.
I believe that they are right. If not, why would it be necessary to re-shim our 2 valve engines every 5-10k kms. The seats and valves both get hammered and wear.
Many new GS owners report poor running engines, only to find that the PO hasn't checked the valve clearance for eons. After re-shimming these engines often perform as normal.

[chuckycheese]

Lapping?

I must admit, I have absolutely no idea what valve lapping means. For the benefit of us folks with less knowledge, could someone please briefly explain what it means and how it affects the engine? Thanks!:-D

[rphillips]

Put lapping compound on valve seat & valve, put valve in head. With very little pressure on the valve, spin it against the seat. This action supposedly just makes the valve & seat fit perfectly together.

[rapidray]

I absulutely REFUSE to put any of mine or my customer's engines together without lapping the valves! I have NEVER had an issue with STOCK or aftermarket valves in doing this. I have also ground the faces of cupped STOCK Suzuki valves & re-used them WITHOUT issue! I think the manuals are CRAP on the no lapping advice. I have built more than 200 Suzuki engines lapping valves on EVERY one & NEVER had an issue. And they LIVE! The choice is each person's to make but as for me & my shop, we lap! Ray.

[Suzuki_Don]

I absulutely REFUSE to put any of mine or my customer's engines together without lapping the valves! I have NEVER had an issue with STOCK or aftermarket valves in doing this. I have also ground the faces of cupped STOCK Suzuki valves & re-used them WITHOUT issue! I think the manuals are CRAP on the no lapping advice. I have built more than 200 Suzuki engines lapping valves on EVERY one & NEVER had an issue. And they LIVE! The choice is each person's to make but as for me & my shop, we lap! Ray.

I was always taught that not lapping valves was the lazy mans way of putting a head back together. People in establishments I worked in were shown the door if they dared put a motor back together without lapping the valves.

Don