help with shim size

[aSTerix]

My clearance is 0.22 mm (exhaust) which is at the exact lower end of the tolerance (0.220-0.280 mm)

My shim is

210 which is 2.100 mm

I now have a choice of

208 which is 2.075 mm = estimated final clearance of 0.245
205 which is 2.050 mm = estimated final clearance of 0.270

What would you recommend ?

Also, kindly check my maths and that I am going in the correct direction !!!!

 

[W0QNX]

No math needed atfer your first sentence.

"My clearance is 0.22 mm (exhaust) which is at the exact lower end of the tolerance (0.220-0.280 mm)"

it's not out of tolerance and will likely never be out of tolerance if left alone.

 

[Mellow]

+1 on what Raymond said... no reason to go to the hassle of changing it if it's not out of tolerance... I know many that will argue to change them so it's in the middle of the range but to me it's not worth the risk of doing that incorrectly and it's extra work that may never matter. If, during your next check it's outside the limit, THEN it makes sense to fix it but otherwise... pack it up and keep riding.

 

[aSTerix]

I double checked and it is actually closer to 0.21 say 0.215

 

[Mellow]

That's pretty close... I guess for peace of mind you could adjust them into the middle range. 208 size I suppose. But, no matter what.. ALWAYS check again once you do the adjustment and get it back together... I had to do the 1st one on my super tenere twice as I got my math reversed... glad I re-checked.

 

[W0QNX]

I double checked and it is actually closer to 0.21 say 0.215

How are you able to recheck the clearance? If you know the shim thickness found below the "bucket" then you must already have the cam out of the head. Did you put it back together and recheck it that fast??

 

[wjbertrand]

If it were me I'd put the thinner shim in and take the clearance to .270. The clearances will tend to decrease with wear so that would theoretically allow the most time before another adjustment (if any) is ever needed. The longevity of the exhaust valves depends on how long they rest on the seat to transfer heat to the cylinder head.

 

[ST1100Y]

What Mellow wrote, try to get within the best 50% between "tight" and "loose" of the tollerance (0.220-0.280mm on the exhaust side), if it doubts, stay on the "wide" side, this might cause ticking, which is maybe annoying, but better then too tight, which can/will lead to a burned walve + seat at some point...
And yes, swap the shims, adjust all as best as you find... then rotate the engine 2~3 times by hand and start over again...
Might take 2~3 runs though, but you ensure the best outcome...

Important: obey those torque settings given in the manual for all and everything...!
(a stripped thread in an engine head is a PITA to fix... TimeSert the only way to go, and their expensive...)

 

[John OoSTerhuis]

Go with the 208. Measure in thousandths of an inch (.001” = .0254mm) after it’s back together and you’ll be in the middle of the range. FWIW

John

 

[aSTerix]

How are you able to recheck the clearance? If you know the shim thickness found below the "bucket" then you must already have the cam out of the head. Did you put it back together and recheck it that fast??

I just removed the valve cover (which didn't have bolts installed) and inserted the feeler gauge, only took a few minutes. I wanted to do it again when the ambient temperature had dropped.

If what your asking is how I knew the shim size, its because this is an ex-police bike and the service centre keeps a record , this bike (I have two ex-police) has had 2 shim changes since new

 

[aSTerix]

Go with the 208. Measure in thousandths of an inch (.001” = .0254mm) after it’s back together and you’ll be in the middle of the range. FWIW

John

Thankyou for the guidance, I'll order a 208 (it is defintely a lot easier doing the math in inches rather than mm !)

Edit: and I now have a 2 week wait for them to arrive , so I am extremely grateful for the fact that the service centre had a record of existing shims installed, just hope it is correct ! on plus side they are only costing $2.1 each , it may take a long time for me to get my ST1100 parts in Dubai but they are very cheap

 

[aSTerix]

it came out nicely at 0.25 mm with the 208 shims

Edited to correct typo !

 

[W0QNX]

it came out nicely at 0.025 mm with the 208 shims

I hope you didn't type that right. In your first post you were looking for (0.220-0.280 mm). And you're now at .025?

 

[aSTerix]

I hope you didn't type that right. In your first post you were looking for (0.220-0.280 mm). And you're now at .025?

Good spot, I corrected to 0.250 so have plenty of clearance !!