Post by wayne on Feb 22, 2012 0:48:58 GMT -5
Anyone out there with a good understanding of rotary compression ?
I have a bike with compression readings of 116, 108 and 104 across the three lobes.
I can tell that it's a little down on power compared to the other bikes I ride and it vibrates a touch more than average possibly because of the uneven compressions (I'm not talking about the universal grinding vibration, it's comparatively smooth in that part of the rev range).
But it runs fine, starting easily, doesn't blow smoke and, surprisingly, will actually hit 100 mph indicated with probably another 5 mph left in it (yes, I know they are wildly optimistic).
When I first started it I did a compression test and noticed the uneven readings. I thought perhaps it would settle. After 150 miles, the overall compression rose 2 psi per lobe but remains almost identical in it's uneven spread.
Having only a cursory understanding of the way the rotors work and seal, I suspected that it might improve with time. However as for the unevenness, I thought that if that was going to improve, it would do so fairly quickly.
Is this likely to improve as the engine settles ? It probably hasn't been started in 20 to 30 years but is a very low mile bike which has been kept indoors all its life.
I have a bike with compression readings of 116, 108 and 104 across the three lobes.
I can tell that it's a little down on power compared to the other bikes I ride and it vibrates a touch more than average possibly because of the uneven compressions (I'm not talking about the universal grinding vibration, it's comparatively smooth in that part of the rev range).
But it runs fine, starting easily, doesn't blow smoke and, surprisingly, will actually hit 100 mph indicated with probably another 5 mph left in it (yes, I know they are wildly optimistic).
When I first started it I did a compression test and noticed the uneven readings. I thought perhaps it would settle. After 150 miles, the overall compression rose 2 psi per lobe but remains almost identical in it's uneven spread.
Having only a cursory understanding of the way the rotors work and seal, I suspected that it might improve with time. However as for the unevenness, I thought that if that was going to improve, it would do so fairly quickly.
Is this likely to improve as the engine settles ? It probably hasn't been started in 20 to 30 years but is a very low mile bike which has been kept indoors all its life.
