Compression on 750 - what is normal?

Joined
Oct 16, 2006
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32
What is normal compression on a 750?

I took a reading after a good long ride, both spark plugs out, throttle wide open, it came out at 190 pounds psi...which seemed a little high to me, I thought the valve clearances might need adjusting but they are spot on.

Is there any other adjustment which might change the compression reading?

It is possible that the head has been skimmed a little too much I suppose, but I'm not sure how I could check this. If this is the case I know I could fit a spacer under the barrel, but I don't really want to tear things down if I don't have to.

I'd welcome your comments. Thanks, Alex
 
Joined
Jan 10, 2005
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Alex, if you have that good a reading on both and have no pinking or pre-ignition I would be happy. Mine is about 180/185 with std cam and 9.3:1. This is with a Combat head and 030" base spacer and no base gaskets just thin bead of silicone. You can see if the head has been skimmed much by checking the gap between top barrel and lowest head fins. Combats or anything with the same 040" skimmed off will look like half the gap of the rest, roughly speaking. That assumes a std head gasket at around 030".
High performance cams can lower the reading. Sounds like you have healthy top end compression wise!
 
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