Hey guys, currently have Kay's bike disassembled.  It would be real easy to pull the top cover right now and check the valves.  Are the readings drastically different between a hot and cold engine?

-Jessie

Suppposed to check em cold kiddo.
Hot ... well when fully hot they tend to increase a wee bit, but as we all know that aint no problem.
Check em cold, that's what the doctor and the buddha ordered.
Cool.
Buddha.

Thanks Buddha!

-Jessie

how about really cold, as in deep winter unheated garage and 0 farhenheit. Maybe a fraction of .001 difference? No worries? There is a reason I am asking.

Honda cold is below 35 Celsius / 95 Fahrenheit.
I don't know what Suzuki cold is though...

So 0 Fahrenheit... Can't you run the engine for couple minutes, and then check the clearances?
Or just measure if they are really off, then change a shim, if not leave them alone. (don't forget that shims come in 0.05mm / 0.002" increment)

Quote from: johnny ro on December 14, 2009, 07:08:35 PM
how about really cold, as in deep winter unheated garage and 0 farhenheit. Maybe a fraction of .001 difference? No worries? There is a reason I am asking.

No worries, it'll be fine. The difference between hot and cold is very, very small.

Well assuming steel, the change in length of a 2.5mm shim between -40 C and 40 C is about 2.6 micrometers.  The valve speck is 30 -80 micrometers, so I'd say you're probably ok checking it at any temperature you can physically check it.

If a shim gets up to 200 C (no idea if it does though), the difference could get up to 10 micrometer range.

Take away message is if a normal human being is capable of checking the valves, the temperature is probably ok.

Reference

p.s. Boosh those years in school are finally useful for something!
p.p.s.s. I should be in bed...

Quote from: PachmanP on December 14, 2009, 09:54:11 PM
Well assuming steel, the change in length of a 2.5mm shim between -40 C and 40 C is about 2.6 micrometers.  The valve speck is 30 -80 micrometers, so I'd say you're probably ok checking it at any temperature you can physically check it.

Should be calculating on the distance between the valve seat and the top of the shim.  Still, probably ok.

I should be in bed as well.

I will never understand why people worry so much about valve clearances. Suzuki quote a min and max figure and in Engineering terms its a barn door! Nothing will be gained or lost if its at the upper or lower end of the tolerance......... Hit it anywhere and you will be fine

The amount of thermal growth a valve sees is minimal but it is accounted for in the engines design, if a valves temperature exceeds its normal parameter it will likely start picking up and sieze in its guide way before the gap closes up.

Seat to cam in 1 heat path is aluminum - through the head. In the other path its steel - valve and bucket.
I dont think it can amount to anything significant.
Cool.
Buddha.

Quote from: Paulcet on December 14, 2009, 10:13:31 PM
Should be calculating on the distance between the valve seat and the top of the shim.  Still, probably ok.

I should be in bed as well.

I believe you are correct.  That said being in bed doesn't help, I realized I goofed lying in bed drifting off to dream of gs500s...

Check valves cold after bike sets overnight.  Doesn't really matter how cold it is, if you can stand it so can the bike.  The above discussion is based on steel only and doesn't take into consideration the different coefficients of thermal expansion of steel and aluminum.  Valve clearances increase considerably as the engine warms because the aluminum head grows faster than the steel valves and lifts the cam shafts away from the shims as it heats up.

Way back a couple decades ago I was wondering how much they changed as the engine warmed so I put on gloves and pulled the valve cover fast and checked some of my CB750 valves on a hot engine one day.  Valve gaps that were set to .002-.005" cold measured .015" or more on the hot engine.

If you can turn the buckets with your finger tip and the gaps are not much over .003" (.08mm) when checking cold the engine will run OK.  I personally have taken to setting my exhaust valves to .003-.005" and am getting much greater valve life that way with fewer if any shim changes.  If the exhaust valve gaps drop to .002" I re-shim them to .004-.005" now.  Your bike, your choice on that one.

My 97 GS had an exhaust valve down to a min 2.15 mm shim @ 80k miles but my current 02 GS with 77k miles on it still has all shims between 2.50-2.65 mm.  

http://img.photobucket.com/albums/v443/jcp8832/valveclearances.jpg

Quote from: gsJack on December 15, 2009, 10:21:22 PM
Check valves cold after bike sets overnight.  Doesn't really matter how cold it is, if you can stand it so can the bike.  The above discussion is based on steel only and doesn't take into consideration the different coefficients of thermal expansion of steel and aluminum.  Valve clearances increase considerably as the engine warms because the aluminum head grows faster than the steel valves and lifts the cam shafts away from the shims as it heats up.

Way back a couple decades ago I was wondering how much they changed as the engine warmed so I put on gloves and pulled the valve cover fast and checked some of my CB750 valves on a hot engine one day.  Valve gaps that were set to .002-.005" cold measured .015" or more on the hot engine.

If you can turn the buckets with your finger tip and the gaps are not much over .003" (.08mm) when checking cold the engine will run OK.  I personally have taken to setting my exhaust valves to .003-.005" and am getting much greater valve life that way with fewer if any shim changes.  If the exhaust valve gaps drop to .002" I re-shim them to .004-.005" now.  Your bike, your choice on that one.

My 97 GS had an exhaust valve down to a min 2.15 mm shim @ 80k miles but my current 02 GS with 77k miles on it still has all shims between 2.50-2.65 mm.  

http://img.photobucket.com/albums/v443/jcp8832/valveclearances.jpg

+1 for good info. the more distance on an object, the more overall change in thickness when heated. we shrink 3 foot shafts into holes that are .030" too tight with liquid nitrogen... and we're talking steel, not alu.

if i had a copy of my machinist handbook here at home, I'd tell you about how much steel / alu/ ti/ stuff shrinks with extreme temps... sorry

but since we're talking about the difference between cold meat and nice, wonderful bacon, i doubt we need numbers really

do it cold