Valve Machining vs Valve Lapping vs New Valves

To lap or not to lap, that is the question. I pulled all the valves in preparation for a valve lapping job, only to find some of the angles in a slight concave state. The attached drawing may be over exaggerated, since most of the valves barely show light through the gap where the straight edge is held.



The issue is that the valves are near their minimum shims on a couple. The local shop owner stated that there are two sets of shim sizes for different models, and that I was about to be in between them due to valves wearing. Valve stem installed height max of 37.54mm was close, with the one I measured coming in at 1mm under max.

Q1 - A local machining shop can hand grind the seats using a stone that they re-square using a diamond tool. The other process uses a machine that re-surfaced them. Which is a better process, the hand grinding or the machining?

Q2 - should I just buy new stainless steel valves and have the valve seats matched to them? Where do you order quality stainless valves from?







Q3 - What is Valve Stem Runout 0.05mm

Thanks in advance!

if the valve faces are concave they need either re-ground or replaced.
an experienced operator can get just as good of a result using stones as can be achieved with a seat and guide machine.
the best place imho to buy valve train parts is www.kpmivalvetrain.com/ .

leon

531blackbanshee wrote: the best place imho to buy valve train parts is www.kpmivalvetrain.com/ .

Damn, $40 for each valve in blank form that needs to be ground would be $320 just for the blanks. I may have to get some local quotes for grinding the existing valves.

Were the seats looking good with enough room for a grind?

what bike are we working on ? i have a set of 4 ne S.S. exhaust valves for 750 turbo if its the bike in signature that I am sure are the same that i will sell for $60.00 + shipping I also have viton valve seals available. email me direct at b.flood@myactv.net

DFIGPZ wrote: what bike are we working on ? i have a set of 4 ne S.S. exhaust valves for 750 turbo if its the bike in signature that I am sure are the same that i will sell for $60.00 + shipping I also have viton valve seals available. email me direct at b.flood@myactv.net

Bike is the one in the signature. I would like the viton seals. Someone stated the valve seals that come in the gasket sets are rather poor in quality, and I should get OEM seals. Do you know what material the seals are that ship with the complete Vesrah set?

I would like the valves. Let me check the budget and see what the local shops say about grinding the existing set.

Your valves look to have enough meat on the face to be reground. The stem height is adjusted by "tipping" the stem to the correct assembled length. Standard good old fashioned valve really. If done with the good cutters and lapped to fit when done it should go another 30 years or so. In fact a well done regrind can be much better than the factory valve job because the machinist can take time and make sure everything is just right, they didn't have that luxury at the factory.

Overall length can be set using a gauge like APE sells.



I like the "armored" valve seals with a full steel cup. Z1 Enterprizes sells then for the 7mm valve stems. They say Suzuki, but they fit the KZ's too. Much better than the ones that come in gasket kits, and probably better than the factory ones too.

www.z1enterprises.com/ItemDetails.aspx?i...uki&item=KL14-6386-1

FaultedGeologist wrote:

DFIGPZ wrote: what bike are we working on ? i have a set of 4 ne S.S. exhaust valves for 750 turbo if its the bike in signature that I am sure are the same that i will sell for $60.00 + shipping I also have viton valve seals available. email me direct at b.flood@myactv.net

Bike is the one in the signature. I would like the viton seals. Someone stated the valve seals that come in the gasket sets are rather poor in quality, and I should get OEM seals. Do you know what material the seals are that ship with the complete Vesrah set?

I would like the valves. Let me check the budget and see what the local shops say about grinding the existing set.

Just shoot me an email when you figure out what you need to do keep in mind having a machine shop that knows motorcycle engines with shim adjust valves I have seen many ruined by cutting the seats to deep and then trying to tip the valve to compensate resulting in the cam bucket pushing on valve retainer vs pushing on the valve tip viton seals are what you want to use if you plan on keeping this bike they stand up much better under heat than the standard seals do a worthwhile upgrade IMO.

Id have the seats ground the minimal amount to clean them up with a machine or hand held cutter,do the same with your stock valves if theyre salvageable.
Imo lapping valves is just used to fine tune them after grinding them for a valve job.
As far as the valves being out of spec for shimming,you should be able to have them tipped after the valves and seats are ground.
Generally I consider stainless steel valves to be overkill in most situations,but if the price is right what the hell! :laugh:

FaultedGeologist wrote:

531blackbanshee wrote: the best place imho to buy valve train parts is www.kpmivalvetrain.com/ .

Damn, $40 for each valve in blank form that needs to be ground would be $320 just for the blanks. I may have to get some local quotes for grinding the existing valves.

Were the seats looking good with enough room for a grind?

Photo says it's a 750 head. Here's my advice to you..

Completely decarbon the combustion chambers and inspect the valve seats closely for chipping. 750s sometimes chip badly and carbon fills in the chipping. Sometimes they are fixable. Sometimes they need seats.

You could reface the two valves shown and the rest if they're all like that. But the wise move is to call Z1E for some OEM replacement valves. I just got some for a 650 and they were very reasonably priced.

The seats definitely need cutting. If you reface those valves, the amount of work on the valve job will increase considerably.

Trust me.... just buy new valves and be done with it.

Agreed, new valves should give back adjusting room too. I'd put the new valves in with some lapping compound and see if the surface is even all around. If not it's time for new guides and a seat grind.
Steve

New valves aren't cheap. Before spending the money I'd find a machine shop with a centerless grinder and see how much material needs to be removed to clean up your existing valves. As long as the margin remains in spec after grinding I think you are good to go. After cleaning the face have the end of the stem touched up as well. This will shorten the valve a little and move you up the range in shim thickness.