Valves shims

Jon56

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Good day
New here and working on getting a 80 750k running properly. Low compression on 3 of 4 and what got me to this point is that cyl. 2 was cold at first.
Valve cover is off at this point and about to check clearance.
Looking for advice and or someone in the cedar rapids IA area with great knowledge of the cb750.
Thanks
Jon56
 

dirtdigger

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Do some searching on this sight. Valve clearance checking and adjusting on the dohc motor has been beat to death. Make it .005" and carry on and hope it didnt burn the valves.
 

Jon56

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number 2 stayed cold at startup until high rpm but my readings are intake 5 and 4 exhaust 5 and 3, does that make sense?
 

Jon56

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Hope you can read that this is what I came up with
 

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Jon56

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Am I correct in thinking if I have a clearance of 2 and it's a shim of 308 and I go to a shim of 3 it would be enough
 

dirtdigger

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not really following what your numbers actually are??? not sure if its inches metric etc. The shim size is directly related to clearance, if you need .002" more clearance then get a .002 thinner shim.
 

Jon56

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Ok sorry for the odd numbers, if I have a clearance of. 002 and the existing shim is 308 and it looks like shims now only come in. 005 increment ,, 300,305,310 then the 305 would be the correct choice, am I correct?
 

Rampton

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Yes you are correct 305 would make your gap 0.005" . Does any one know what to do if you can not get 0.005 because the shims only go up in increments of five? As Jon says, therefore it makes it impossible to reach the 0.005". If you get a gap of say 0.003" is it good practice to increase the gap by 0.005" and settle with a larger gap than recommended by so many on the site, clarification would be appreciated. Stay safe and good luck jon
 

dirtdigger

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your shim thicknesses are in mm not inches. such as 305 is 3.05mm and 310 is 3.10mm....this makes a difference of .05mm or about .002" not .005" either convert you clearances to mm or the shim thickness to mm so it is less confusing.
 

Rampton

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Wow it's just sunk in so best is to measure all in mm shim thickness and gap. Will have to convert my gap sizes to mm or start again and re-check valve gaps. Thanks ☺️
 

Jon56

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not really following what your numbers actually are??? not sure if its inches metric etc. The shim size is directly related to clearance, if you need .002" more clearance then get a .002 thinner shim.
Thanks very much for your advice, got her running very good.
 
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