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Valve lapping yes or no?

  • Thread starter Thread starter robinjo
  • Start date Start date
Same here. However, my engine builder is lapping mine and says you have to when replacing the valves as we are. The seats were professionally cut but he says to still lap them. He has been doing this for 30 years successfully so I am hoping he knows what he is talking about.
 
Hoomgar said:
Same here. However, my engine builder is lapping mine and says you have to when replacing the valves as we are. The seats were professionally cut but he says to still lap them. He has been doing this for 30 years successfully so I am hoping he knows what he is talking about.
Click to expand...

IIRC you are using new stainless steel valves on your project bike right?
I man the stock Suzuki ones, seems those are hardened on the surface only and when you lap them you uncover the soft bits (no pun intended :wink: ) and they wear fast.
 
robinjo said:
Hoomgar said:
Same here. However, my engine builder is lapping mine and says you have to when replacing the valves as we are. The seats were professionally cut but he says to still lap them. He has been doing this for 30 years successfully so I am hoping he knows what he is talking about.
Click to expand...

IIRC you are using new stainless steel valves on your project bike right?
I man the stock Suzuki ones, seems those are hardened on the surface only and when you lap them you uncover the soft bits (no pun intended :wink: ) and they wear fast.
Click to expand...

I heard the same thing Robin. Yet, I am still told to lap them. I would think there is merit to the removing of the hardening being an issue though? But yes I am doing the one peice stainless valves on mine.
 
Doesn't matter how well valves are ground on a machine, they will not seat perfectly until they're lapped. A normal lapping isn't going to leave a groove in the face of a valve or in the seat, but simply forces them to mate at an almost microscopic level. It's the final honing step of a proper valve job. What are assumed to be perfectly ground valves and seats will many times leak gasoline if poured into the combustion chamber. They simply don't fit that well yet. lapping is that final step. A valve face/seat that leaks even a tiny amount is a valve face/seat that leaks hot gas under pressure, allowing the seal to erode away more quickly. The higher the performance expected of the engine, the better that seal is desired.
 
Not that it is the final authority but the Clymers manual specifically states not to lap the valves, that they will seat after 600 miles. I suspect that is why the valves should be readjusted after 600 miles. Other sites I have found where GS motors are being built state not to lap the OEM valves because of a surface treatment they received.

I am sure this has been of little help.
 
Yea well the Haynes Manual says you can grind and lap both the seats and valves, so the arguement goes on, but if you have a bad fit you wont have a valve that transfers the heat well, be short lived, blue dye and lap them babys in, I have never had a problem doing it but I dont get carried away either, and I only reuse a valve if its a garbage engine to start with, in other words I'm fixing to sell or the customer has zero bucks but needs to ride
 
Only valves I know of that you specifically cannot grind are sodium filled valves used in some early unleaded bikes.

stainless valves do get lapped in, at least on an automotive head, for certain. they will not "seat themselves" although I could believe it from the stock ones. on a new valve job with new valves and good guides, lapping should be minimal. as soon as you see a proper seal you are done.

depending on the application as to how much contact area you should have, a street vehicle should have a pretty good contact area closed so the valve can cool a little while seated. a drag racer wants a narrow seal, so the valve is flowing more, faster, as the valve opens.

hand radiusing the seats is a good trick to get a head to flow more, but requires a steady hand. same deal, remove restrictions so the valve flows more air as the valve begines to open.
 
Lapping rules, I was taught to lap until you can fill the intake port with solvent and not have any fluid leak out , that is with valves and springs in place , just make sure you clean all that lapping compond out

jay
 
valves

valves

built my 1170 motor in 1995, lapped the valves in propperly. thrashed it mercilessly ever since, even taking the engine out and putting it into my second katana. big carbs came, loud pipe too. open carbs with no filters, 1/8th mile sprints every year since 1998, 1/4 miles since 2003, just done the uk katana club end to end run( from one end of the uk to the other, 870 ish miles, all at sustained high speed.) and have only had to adjust the tappets three times in all this time. never had a problem with the valves in 10 years, so i say, lap them in. if you are worried about going through the surface hardening on a valve, then either you are lapping them too hard, ( do it by hand, none of this drill lapping mullarkey!) or you are thinking about it too much. these big gs and gsx motors have hugely over engineered components, thats why we all enjoy making them go faster. all i can say about not lapping them in is its a good way to risk burning a valve or seat.
 
So it looks like votes are favoring lapping. That's what the experienced guys I know are telling me too. I guess not every thing you read is 100% true, even if it makes sense.
 
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.
 
Quoted from Suzuki Manual:

"DO NOT use lapping compound after final cut is made. The finished valve seat should have a 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".

IMHO, I think Suzuki knows what they are saying.
 
I think we need a forum survey on this one. Include high octane gas and whether to use synthetic motor oil or not.

Winner gets a new Busa
 
valves

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
 
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. :oops:
 
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 :)
 
Re: valves

Re: valves

Buffalo Breath said:
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
Click to expand...


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

Hoomgar said:
I guess not every thing you read is 100% true, even if it makes sense.
Click to expand...
 
Billy Ricks said:
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.
Click to expand...

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...
 
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