Help please with calculations

[93trident]

Hi all i am hoping one of you will take pity on a thick c##t and explain the sum/calculation for my new valve shims. Watched and read so much i am getting confused over mm and inch. I would like to work in mm as thats what i measured in. I have the clearance numbers and my micrometer measurements from the old shim but havent a clue how to use them.Yes i have manuals etc but i have suffered a few brain injuries and somethings no longer stick. So if i have measured at the correct point with feeler gauges on number 1 exhaust number one shim i have a reading of 0.05mm gap and a measurement of 2.81mm on the micrometer for old shim what do i have to do?add subtract clearance very confused. Any help would be greatly appreciated

 

[Nunya Bidnes]

I found that markings on the shim mean little. I did the math and found the results are dubious. In short, I use dead reckoning. I keep the shims that I have measured marked , I measure clearance, in inches, goal being .005 inches. then pull the original shim, measure it in MM, then replace it with a thicker MM shim,-if the gap was More than .005 inches. If the gap was less than .005 inches then replace it with a thinner MM shim. Once I have replaced a shim, I spin the crank a few spins, then remeasure the GAP. Again, and again.

 

[93trident]

Using the posted chart these are my numbers i calculated. The red numbers are my micrometer readings. The measurements below the red numbers are my feeler guage readings at points stated in manual. The new shims according to the chart are in the new shim portion of the chart. Are these correct? Thanks

 

[Bo82CB]

If i am reading your chart right, you set your gap at 0.05-0.08mm. Is this a typo?
.005 inch = 0.127mm!?

 

[93trident]

If i am reading your chart right, you set your gap at 0.05-0.08mm. Is this a typo?
.005 inch = 0.127mm!?

I think I am getting more confused here. Here's what I have done so far. I used the feeler guage to measure lobe gaps at A B C and D like the Clymer says. They are the black readings. 0.05mm etc. Then I removed one shim at a time and recorded those measurements in red. Then I followed the manuals flow chart which I posted on here so you can see what I am using to get my new shim number. So if No1 exhaust cylinder shim No1 measured 2.81mm and I measured an actual gap of 0.05mm with feeler guage I went along the top of the chart for present shim size then down to left side of chart saw 0.01-0.05mm and followed chart giving me 2.75mm new shim size. Am I doing it wrong? Thanks

If i am reading your chart right, you set your gap at 0.05-0.08mm. Is this a typo?
.005 inch = 0.127mm!?

 

[Bo82CB]

That stuff is too complicated!
Here is how I do it:
Adjusting intake valve gap, turn your cam until one of the lobes point towards AIRBOX and LEVELED with the head. At that lobe your valves are going to be at full closed position, now CHECK valve gap. If gap is .005 INCH you are good if not adjust, continue on...
Adjusting exhaust valve gap, turn cam until one of the lobes point towards EXHAUST HEADERS and LEVELED with the head. At this point your valves are going to be at full closed position, now CHECK valve gap. If gap is .005 INCH you are good if not adjust, continue on...
After you adjusted ALL your valves, rotate engine couple FULL revolutions and recheck your valve gap following procedure for CAM placement from above. If satisfied with valve gap results after rotating the motor, wrap it up and go ride that thing.
I hope this helps, this is how I adjust my valves and has been doing it like this for years. My bikes run like charm.

 

[93trident]

That stuff is too complicated!
Here is how I do it:
Adjusting intake valve gap, turn your cam until one of the lobes point towards AIRBOX and LEVELED with the head. At that lobe your valves are going to be at full closed position, now CHECK valve gap. If gap is .005 INCH you are good if not adjust, continue on...
Adjusting exhaust valve gap, turn cam until one of the lobes point towards EXHAUST HEADERS and LEVELED with the head. At this point your valves are going to be at full closed position, now CHECK valve gap. If gap is .005 INCH you are good if not adjust, continue on...
After you adjusted ALL your valves, rotate engine couple FULL revolutions and recheck your valve gap following procedure for CAM placement from above. If satisfied with valve gap results after rotating the motor, wrap it up and go ride that thing.
I hope this helps, this is how I adjust my valves and has been doing it like this for years. My bikes run like charm.

My engine is a 1981 cb750f dohc are you talking about sohc motor on here. I am getting very confused with measure .005 inch and adjust.

 

[Bo82CB]

I am talking about DOHC engine, we are in DOHC section of CB750 forum aren't we!?

 

[Bo82CB]

I'm not sure which part are you confused about... when your valve is at full closed, you stick your filler gauge between shim and cam. If .005 inch filler gauge can go in between with a little drag you are good to go. Check next valve.

 

[dirtdigger]

Your original post stated .05mm which is close to factory spec but is too tight in reality. set gaps to .127mm. So your gaps are tight which means you need a thinner shim. desired gap is .127 minus your actual gap is .05 so the difference is .077mm You need a shim about .077mm thinner than the one that was in there. A little more clearance wont hurt but too tight will cause issues.

 

[93trident]

It's the part you put on here "CHECK valve gap. If gap is .005 INCH you are good if not adjust, continue on... so I check a gap with .005 Inch/0.127mm and can't fit it in. The gap is too tight. My gap reads .002/ 0.05mm. What is the adjustment? So if it's too thick I go a size down or too thin I just go up a shim size. So 295 would be 290 or 300. This is where I am getting confused.

 

[Bo82CB]

If your .127mm feeler gauge CAN'T fit that means your gap is too tight and you need to insert THINNER shim to achieve MORE gap. How much exactly is matter of available shims you have and install / measure procedure. If you shim is let's say 300, put in 295 and measure, if gap is better but not .127mm, than take out 295 and put in 290...until you get satisfactory value.

 

[93trident]

If your .127mm feeler gauge CAN'T fit that means your gap is too tight and you need to insert THINNER shim to achieve MORE gap. How much exactly is matter of available shims you have and install / measure procedure. If you shim is let's say 300, put in 295 and measure, if gap is better but not .127mm, than take out 295 and put in 290...until you get satisfactory value.

Thanks Bo82CB that bit sank in, sorry it can take a while .

 

[93trident]

Your original post stated .05mm which is close to factory spec but is too tight in reality. set gaps to .127mm. So your gaps are tight which means you need a thinner shim. desired gap is .127 minus your actual gap is .05 so the difference is .077mm You need a shim about .077mm thinner than the one that was in there. A little more clearance wont hurt but too tight will cause issues.

Thanks