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folknride 12-11-2012 10:36 AM

Help - Valve specs and temperature
I'm doing a 30,000km valve check on my 2010 990 S here in my chilly garage in chilly Alberta. Specs are for 20C (room temp) and it's probably more like 5C in my garage. All valves are at the low end of spec except one exhaust that is about .03 mm tight. My question is does colder temps reduce or increase gap?
Should I change shims or leave it 'til next time?
Thanks for any advice from you good physics guys.

Black Hills 12-11-2012 10:44 AM

Clearance increases at colder temps (the metal contracts). But I have no idea how much.

dmn0507 12-11-2012 10:46 AM

I think the most affected part is the valve stem (since is pretty long)
With lower temps the gap should be increased, since the stem gets shorter, but i guess the difference it's not that big (let's wait for somebody who wants to do some math :D)

folknride 12-11-2012 10:54 AM

Thanks - kinda what I thought - but my brain sometimes "malfunctions". I'll pull the shims and shoot for the high end of spec.

markjenn 12-11-2012 10:55 AM

Hard to say. I think the big thing with setting a valve "cold" is for the engine not to be recently run - beyond this, the actual temp is probably not a big factor.

Whether you could let this valve ride is up to you. Nothing bad usually happens when you let one that is slightly out of spec go till the next adjustment. But I don't think you can assume it will be in spec if your garage was 15-deg warmer.

Personally, I wouldn't make extra work for yourself doing extra valves, shooting for the high end of spec. For one, the shims typically don't come in that fine an increment where you can nudge the clearance precisely to the top end of spec, and second, you may end up overshooting or causing some other issue. Further, valves don't necessarily tighten with wear as everyone thinks - sometimes they can go the other way so moving towards one extreme of spec may just be increasing the risk you're going to have to do it again the next adjustment. Not to mention the extra work and expense, especially if you end up messing around with a head you wouldn't have messed with otherwise. If you just have one valve out, I'd just shim that one.

- Mark

folknride 12-11-2012 11:26 AM

Thanks Mark - now I'm kind of torn. Harley shims come in .025 intervals and I could move close to looser end of spec on all valves. KTM - I could just do the one tight exhaust. Folks always say loose valves (within spec of course) are happy valves, and once i've pulled the cams .... Hmmmm?

Anyone else with advice?

gozirra 12-11-2012 11:30 AM

I know this may sound strange, but if you are elbow deep in the job and it is a huge issue, why not heat the garage (I know a waste and time and $$$) just to get the check done within spec.

Qwik 12-11-2012 11:32 AM

Well, You are already there.....

uraberg 12-11-2012 11:39 AM

I'm going to say that the temperature difference between room temp, and operating temp makes the 15 degrees difference in your garage insignificant.

gozirra 12-11-2012 11:47 AM

68 vs 41 degree fahrenheit, i think he listed celsius.

RadoR6 12-11-2012 12:05 PM

If you're not sure how about to put a heater into your garage:wink:?Wondering anyway how someone can do servicing in a cold garage with frozen fingers?

folknride 12-11-2012 12:06 PM

Thanks guys - I'm just going to do them all - now I'm in it - and the Harley dealer has lots of stock.
(except I can't get the freaking spark plug tube to move - swearing profusely as indicated)

folknride 12-11-2012 12:09 PM


Originally Posted by RadoR6 (Post 20226484)
If you're not sure how about to put a heater into your garage:wink:?Wondering anyway how someone can do servicing in a cold garage with frozen fingers?

Why am I doing this - because I'm a world class procrastinator and need to get ready to leave for sunny Kali!

Got my longies on and a space heater - and hey - I'm Canadian eh?


Sporting Wood 12-11-2012 12:14 PM

Boy, it looks like KTM is coming out with their new 1190 StarCruiser at just the right time. :norton

Hipster 12-11-2012 02:25 PM


I your local KTM or HD dealer doesn't have the shims you need on hand, shim kits can be had for about $65

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