what valve clearance would you use?

what valve clearance would you use?
would you use a more closer gap or wider gap on either the inlet or the exhaust
bike: gpz810, std valves, std cam, rs34 mikuni's, k&n pods, vance and hines, street/track bike

inlet exhaust
close close
med med
wider wider
or a combination

were close is .08-.11
and med is .12-.15
and wider is .16-.18

How often do you want to check/adjust your valves?

Every 500 miles or less= run them close
Every 5000 miles= Run them on the large side.

Max power means minimum clearance, but you'll have to stay on top of them.

I would set them at .12 - .15. This would allow minor changes (plus or minus) without putting the clearance out of spec. That's where I set mine in 1977 on my KZ650C1 and they are still within spec (although very slightly wider) after 46,000 miles. Ed

steell wrote:

How often do you want to check/adjust your valves?

Every 500 miles or less= run them close
Every 5000 miles= Run them on the large side.

Max power means minimum clearance, but you'll have to stay on top of them.

I suppose i'm looking for max power, I just can't get around the theory of how each way works
if the clearance is large then would'nt that give higher compression and in turn mor power, and smaller gaps would allow more gas in, any comments?

Greater clearance equals less valve lift and less time for air to fill the cylinders. as an exaggerated example, if you have .050" clearance, and .750" lift at the cam lobe, the valve is only going to open .700".

As far as compression goes, it takes time for air to fill the cylinders, and the higher the rpm the less time is available for the air to flow into the cylinders. increasing the clearance reduces the time available, thus reducing the amount of air into the cylinders.
You "may" pick up a little low rpm torque, but it's going to decrease mid and high rpm power. Good for a tractor, not so good for a high rpm four cylinder motorcycle motor.

Here is an example from a Car Craft article:

Once the motor cooled down enough for safe disassembly (about five minutes), we pulled off the rocker covers and Brul relashed the valves to achieve 0.030 inch of clearance. A few pulls told us we&'d lost about 9 peak horsepower but gained a bit of low-end torque, exactly the result you'd expect if we'd installed a slightly smaller-duration and lower-lift camshaft.

Original lash was at .020"

www.carcraft.com/techarticles/valve_lash/index.html

650ed wrote:

I would set them at .12 - .15. This would allow minor changes (plus or minus) without putting the clearance out of spec. That's where I set mine in 1977 on my KZ650C1 and they are still within spec (although very slightly wider) after 46,000 miles. Ed

The factory spec on my 750 is 0.05 - 0.1 mm (.002 - .004" ). I try to keep them 0.075 - 0.1mm (.003 - .004" ), but would not care if one wandered up to .005".

650ed wrote:

That's where I set mine in 1977 on my KZ650C1 and they are still within spec (although very slightly wider) after 46,000 miles. Ed

The 810 engine that i have has not changed much in 25,000km as well, and have opend if anything
So if i was to set the clearances within the recomended range .08-.18 then if 1 valve is .14 then i'll drop that to .09 , within the range, and if 1 valve is .13 then I'll leave it and check them again in 2000km (in the endless search for more power)

Thanks Steell, that clears things up
I'v been doin the shims for over 30 years on 9's and 650's
and have mostly left them if they were anywhere in the range but now with more time on my hands I can experiment a little. cheers

650ed wrote:

I would set them at .12 - .15. This would allow minor changes (plus or minus) without putting the clearance out of spec. That's where I set mine in 1977 on my KZ650C1 and they are still within spec (although very slightly wider) after 46,000 miles. Ed

That's really unusual, normally the valve clearances on shim type valve trains close up over time, never seen the clearance increase.

Either the bucket or the cam is wearing, or you have deposits on the valve seat or face, that's the only reasons I can think of for the clearance to increase.

steell wrote:

650ed wrote:

I would set them at .12 - .15. This would allow minor changes (plus or minus) without putting the clearance out of spec. That's where I set mine in 1977 on my KZ650C1 and they are still within spec (although very slightly wider) after 46,000 miles. Ed

That's really unusual, normally the valve clearances on shim type valve trains close up over time, never seen the clearance increase.

Either the bucket or the cam is wearing, or you have deposits on the valve seat or face, that's the only reasons I can think of for the clearance to increase.

Yep, been there. Valve stem seal fails, oil runs down and bakes onto the valve seat. Over time, the gap does grow (and the compression drops because the buildup is not symmetric).