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+--- Thread: Valve Shimming - which side of spec? (/showthread.php?tid=4648)
Valve Shimming - which side of spec? - bflint - 01-30-2021
Getting ready to re-shim my valves after 52K miles. Recommended shim sizes (per calc) either put new clearance on low side or high side of spec (IN 0.006, EX 0.011). I noticed, via calcs, that I could deviate from the recommended shim size to push new clearance from low side to high side or vice versa, while still staying within spec range of +/- 0.001. WHY? Because I noticed that the measured clearances historically show the EXHAUST getting tighter (or staying the same) and the INTAKE getting looser.
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The recommended shim size for EXHAUST is fine, but I have two choices for INTAKE. For INTAKE I have choice of 0.065 (recommended) or 0.051 new clearance. I was thinking I should pick 0.051 with the assumption that they will loosen over time.
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General mech theory states that looser is safer. Am i crazy to go to the tight side? Thoughts?
RE: Valve Shimming - which side of spec? - the Ferret - 01-30-2021
I really wish I was smarter about his stuff, but isn't it go-no go, and as long as it's in spec, it's in spec?
RE: Valve Shimming - which side of spec? - Tev62 - 01-30-2021
(01-30-2021, 05:18 AM)bflint_imp Wrote: Getting ready to re-shim my valves after 52K miles. Recommended shim sizes (per calc) either put new clearance on low side or high side of spec (IN 0.006, EX 0.011). I noticed, via calcs, that I could deviate from the recommended shim size to push new clearance from low side to high side or vice versa, while still staying within spec range of +/- 0.001. WHY? Because I noticed that the measured clearances historically show the EXHAUST getting tighter (or staying the same) and the INTAKE getting looser.
*
The recommended shim size for EXHAUST is fine, but I have two choices for INTAKE. For INTAKE I have choice of 0.065 (recommended) or 0.051 new clearance. I was thinking I should pick 0.051 with the assumption that they will loosen over time.
*
General mech theory states that looser is safer. Am i crazy to go to the tight side? Thoughts?
If I was committed to a shim change because I was out of range and I had a choice of the looser end rather than tighter I think I would go the looser. The theory that the clearance always closes up doesn't ring true for many either.
RE: Valve Shimming - which side of spec? - Houtman_imp - 01-30-2021
Just toss a shim to see which way you should go !
RE: Valve Shimming - which side of spec? - bflint - 01-30-2021
(01-30-2021, 06:37 AM)Houtman_imp Wrote: Just toss a shim to see which way you should go !Can always count on you Mr Houtman! Maybe a fortune cookie from the Chinese Buffet?
RE: Valve Shimming - which side of spec? - peterbaron - 01-30-2021
(01-30-2021, 06:37 AM)Houtman_imp Wrote: Just toss a shim to see which way you should go !
![[Image: 6e12c13723775e353738fee441dfd4a3.gif]](https://cb1100forum.net/forum/uploads/imp/202101/6e12c13723775e353738fee441dfd4a3.gif)
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RE: Valve Shimming - which side of spec? - GoldOxide_imp - 01-30-2021
(01-30-2021, 07:26 AM)bflint_imp Wrote:(01-30-2021, 06:37 AM)Houtman_imp Wrote: Just toss a shim to see which way you should go !Can always count on you Mr Houtman! Maybe a fortune cookie from the Chinese Buffet?
RE: Valve Shimming - which side of spec? - bflint - 01-30-2021
(01-30-2021, 05:20 AM)The ferret_imp Wrote: I really wish I was smarter about his stuff, but isn't it go-no go, and as long as it's in spec, it's in spec?Hey Mr Ferret, I can see you don't worry enough ... stress and concern and etc are part of my DNA ... that's why I ride ... My CB1100 saved my life
RE: Valve Shimming - which side of spec? - the Ferret - 01-30-2021
Where's Max when you need him?
Valve Shimming - which side of spec? - Cormanus - 01-30-2021
Riding in New Zealand!