Best way to test 0 clearance valves?

myself i like to use .006" clearance on the exhaust valves and .004" clearance for the intakes so if this was me doing it i'd go at least 3 sizes smaller for the exhaust and 2 for the intake thats if you can spin the bucket if you can't then i'd want to go even more to make sure i got clearance why did you get this guy to lap the valves in the first place and not get a real valve job done instead.any decent mech would have done a proper bench shimming before you ever got the head back.

.006" is .15mm and .007" is .178mm. You like to roll near the end of the limits? I've also heard that the gap tends to shrink after the motor runs for a while. Is that true? So if I go with a general clearance range around .16mm, it should snug up to maybe .13mm after a while?

If that's true, my plan is to go to
(valve. new shim, new clearance)
1. 250, .163
2. 250, .178
3. 240, .176
4. 245, .150?
5. 230, .150?
6. 240, .176
7. 235, .152
8. 235, .150?

Bonus question, how do you get specificity like .15mm in the back and .178 in the front if shims only come in increments of .05mm?

Time for a post in the shim trading thread!

(As for the mechanic, they knew I was on a serious budget, as I brought the head and cylinders in separated from my bike.)

Much KZ750 info and FSM is downloadable from:

kz.mbsween.com/

Good Fortune!

I just downloaded that yesterday! If I ever meet mbsween, I'm bringing beer.

i always try to stay to the loose side of clearances i don't like having burnt valves and that what can happen if you run them to tight also the major cam companies call for that type of clearances so i figure smarter men than devlop these cams so they must know what they are doing

You're totally right. I was thinking about this backwards. Starting with larger clearances, especially after a lapping, is clearly the better choice. I'm aiming for .15-.18 now.

If you lap or recut the valve seats, the valves are likely to bed in over the first 50 miles - roughly 1-2 thou (0.001"-0.002") or 0.025mm-0.050mm.

I tend to set my own valves a shade wide after the valves are lapped in. So when my target clearance is 4 thou (0.1mm) - I set the valves roughly 5-6 thou (0.125mm-0.15mm) to give room.

Generally the clearances on these bikes will always shrink with wear - so setting clearances at the wide end of the range is not a bad thing.

One more thing to think about....
Stock pistons, cams and head work?

As I have learned in my build, due to higher compression pistons, performance cam and P&P head with +1 up valves, she'll run a little hotter then a stocker...

With this in mind, for my build, exhaust runs a tad hotter then normal so instead of spec .05mm - .10mm...

I set my clearance as follows:
.08 to .10mm for the Intake +/-.01mm
.09mm to .13mm for the exhaust +/-.01mm...

As mentioned, after the first 500 miles, found the exhaust side clearances decreased by one shim size....

OMR

Old Man Rock wrote:

One more thing to think about....
Stock pistons, cams and head work?

As I have learned in my build, due to higher compression pistons, performance cam and P&P head with +1 up valves, she'll run a little hotter then a stocker...

With this in mind, for my build, exhaust runs a tad hotter then normal so instead of spec .05mm - .10mm...

I set my clearance as follows:
.08 to .10mm for the Intake +/-.01mm
.09mm to .13mm for the exhaust +/-.01mm...

As mentioned, after the first 500 miles, found the exhaust side clearances decreased by one shim size....

OMR

:woohoo:

1) You guys are the best.

2) Is there some trick I don't know about to get tolerances to within .03mm? I mean, shims only come in .05, so how can you specify a range of .09-.13? I mean, in general, the best you can hope for is that all your cams are within .02 or .03 of your ideal, so what does it mean to make the exhaust .02 looser than the intake? The only goal I can really set is between .14mm and .18mm for exhaust and between .12mm and .16m for intake, but I'm still quite likely to have some intakes at .16mm and exhausts at .14mm, right? Am I making any sense?

3) I will certainly be aiming for the high end on all of these. My new clearances should be 0.15mm - 0.17mm (spec on my bike is .08-.18mm) on the ones I can know, and at least 0.13mm for the ones that are at 0 clearance now. I'm expecting to get a couple extra shims just in case. I'll have to install the cams one extra time, but bolting them down three times isn't too bad for one top-end job, right?

staniel wrote:

1) You guys are the best.

2) Is there some trick I don't know about to get tolerances to within .03mm? I mean, shims only come in .05, so how can you specify a range of .09-.13? I mean, in general, the best you can hope for is that all your cams are within .02 or .03 of your ideal, so what does it mean to make the exhaust .02 looser than the intake?

3) I will certainly be aiming for the high end on all of these. My new clearances should be 0.15mm - 0.17mm (spec on my bike is .08-.18mm) on the ones I can know, and at least 0.13mm for the ones that are at 0 clearance now. I'm expecting to get a couple extra shims just in case. I'll have to install the cams one extra time, but bolting them down three times isn't too bad for one top-end job, right?

the exhuast runs hotter than intake valve on any motor,thats the reason for more clearance.
as valve heats up it expands eating up the extra clearance.

Yeah, I gotcha, and that makes sense. But let's take a weird scenario.. I have a one cylinder bike. My ideal going in is .17mm for the exhaust and .15mm for the intake.

I could wind up with my intake valve being at .17mm and all my exhaust being at .14mm, because shimming up or down in either direction would take me out of range.

I realize it's tricky. Given the ranges you guys all specify, it'd sure be nice if shims were in .02mm increments.