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dwlarsenFri Nov-21-08 10:36 AM
Member since Mar 18th 2009
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"Compression Check on a 1975 850"


  

          

What is the expected compression reading on a 75 Norton 850 with stock everything? The motor has 12,000 easy miles on it and has never been apart. I read somewhere that 145 psi is typical. I read elsewhere that 100 psi is OK. Who knows for sure?

  

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dynodaveSun Nov-23-08 06:23 PM
Member since Mar 18th 2009
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#1. "RE: Compression Check on a 1975 850"
In response to Reply # 0


  

          

135-145 is what I have gotten on the stock 850's Ive been involved with.
If you are not skilled on kicking over a big twin then you will see it register artificially low. I have seen this several times. Big guys used to electric start bikes that could not kick them over fast enough to get a sufficient spin and were able to register only 70-80 lbs. Then when I kicked I got the required 140psi.

Oh well.....

  

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