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Old 12-24-2007, 05:46 PM   #1
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Default Motor compression by hand???

Hey guys.

I bought a O.S RG .21 from a guy that said it had new bearings and was pinched.

With the flywheel on how hard should it be to turn the motor over?
I can turn it over almost with ease. There is a bit of resistance at TDC.
Not alot? The motor has not been ran since the pinch. Should it inprove?

What about a higher end motor like a RB. Should it be able to tunred over by hand?


Thank you for all your help.
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Old 12-24-2007, 05:53 PM   #2
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If it was pinched, it should have resistance when close to TDC. If it was a light pinch, with no metal scratchiness at TDC, then it should have a lot of compression, and should push back when spun past TDC. Turn & hold the crank at the compression point and place the engine body at a 3 o'clock position. If it has good compression it should hold the engine case at the 3 o'clock. If the compression is low, then the engine will continue to turn and end up at TDC.
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Old 12-24-2007, 06:36 PM   #3
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Originally Posted by ezveedub View Post
If it was pinched, it should have resistance when close to TDC. If it was a light pinch, with no metal scratchiness at TDC, then it should have a lot of compression, and should push back when spun past TDC. Turn & hold the crank at the compression point and place the engine body at a 3 o'clock position. If it has good compression it should hold the engine case at the 3 o'clock. If the compression is low, then the engine will continue to turn and end up at TDC.
Great tip... The motor makes it way down from the 3 o'clock postion. Does that mean the pinch is no good?
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Old 12-24-2007, 07:32 PM   #4
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Great tip... The motor makes it way down from the 3 o'clock postion. Does that mean the pinch is no good?
Yes, the pinch is no good. After a pinch or on a good motor, the engine should hold the 3 o'clock position by either compression hold or by piston to sleeve pinch tightness (new engine or fresh pinch).
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Old 01-05-2008, 09:16 PM   #5
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want to unload the engine? i am in need of some parts
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