Easy Peazy Valve Shim Calculator

[yamagrl]

...while adjusting Big Red's valves today I made discovery. Probly nuthin' major but it hit me like a "Profound Revelation"!

 

...if you "Think Metric" it's simple math. No need for an Excel spreadsheet or shim table. After a few times it just comes to ya.

 

...of course it works the same for the intake and exhaust valves and whether the valve is too tight or too loose.

 

First Gen Specs

Intake .11-.15 mm (.004-.006 in) ideal/average .13 mm (.005 in)

Exhaust .16-.20 mm (.006-.008 in) ideal/average .18 mm (.007 in)

 

THINK METRIC

Measured Clearance

+ Existing Shim

= Existing Total

- Ideal/Average clearance

= Ideal new shim size.

 

 

Example:

exhaust valve measuring .13 mm clearance (a bit tight) with an existing installed shim 2.80 mm

 

Measured Clearance .13 mm

+ Existing Shim 2.80 mm

= Existing Total 2.93 mm

- Ideal/Avg Clearance .18 mm

= Ideal new shim size 2.75 mm

 

We all know that numbers rarely work out perfectly like the above example. And we do not always have the exact shim we might need. So I'll work out another example:

 

Exhaust valve measuring .13 mm clearance (a bit tight) with an existing installed shim 2.68 mm

Measured Clearance .13 mm

+ Existing Shim 2.68 mm

= Existing Total 2.81 mm

- Ideal/Avg Clearance .18 mm

= Ideal new shim size 2.63 mm Your choice may be 2.60 rendering .21 mm (slightly over the loose end of specs)

2.65 rendering ..16 mm (limit on the tight end of specs)

I think slightly loose might be better. It will wear into the specs, whereas max tight will soon wear out of the specs.

 

And ya probly wanna verify things with a micrometer.

 

 

"Close enough for government work"

Measured with a micrometer...Marked with a grease pencil... and cut with a chain saw!

 

Attached is a PDF Worksheet. Print it out.

 

Heather

 

Easy Peazy Valve Calculation Sheet.pdf

 

 

Edited April 25, 2016 by yamagrl

[MiCarl]

Excellent description Yamagrl!

[yamagrl]

Profound Revelation!

[Squidley]

Good thinking Heather, or "Profound Revelation"

[Flyinfool]

After reading your explanation, I realized that that is what I did when I did mine this spring. The only difference is that I still had to also do the mental math to convert to SAE because I have SAE feelers and my surface grinder (to get in between sizes) is also SAE. I was able to get all of mine exactly on the high limit.

[yamagrl]

I added a printable work sheet to the original posting (above). This has also been added to the 1st Gen Tech Library so it can be easily located.

 

Click the PDF link above and print it out.

[madaboutbikes]

thanks for this post , gonna check my valve clearances this weekend . Engine must me at TDC on compression stroke right ? or lobe portion of cams pointing horizontally away from each other ? i have a Yamaha FZR750

[Bob K.]

thanks for this post , gonna check my valve clearances this weekend . Engine must me at TDC on compression stroke right ? or lobe portion of cams pointing horizontally away from each other ? i have a Yamaha FZR750

Your service manual will have the specifics for your particular model.

 

For the Venture, I'm satisfied with ensuring the cam is anywhere on the base radius of the lobe: https://www.venturerider.org/forum/showthread.php?33290-Proper-way-to-measure-valve-clearances&p=1046013#post1046013

[Bob K.]

...while adjusting Big Red's valves today I made discovery. Probly nuthin' major but it hit me like a "Profound Revelation"!

 

Another thing that really helped me was making little chits to represent my existing shims (little square pieces of paper with the shim number on it). Then I could easily move them around on the piece of paper in order to see where else I could utilize them. That also helped me ensure that I only bought new ones to cover what I didn't already have.

 

Oh, and I wrote down and stored the shim numbers in every position. Because I didn't have this data to start with from the PO, I had to go through and pull every shim out one by one to see what size it was before I could then make calculations and buy necessary new ones.

Edited March 15, 2020 by Bob K.