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compression question

   
Old Jul 9, 2009 | 10:08 AM
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while breaking in a fresh engin at around 75 miles i lost a cylinder due to ignition failure resulting in overheating new engine,my stupidity. I later ran a compression test,135 lbs front 125 lbs rear.this is on an 88 ci buell std heads red shift 585 cams 263 duration 580 lift j&e pistons at around 10 to 1 static compression. what do you think ? is this normal with this set up or do i need to tear it down and re-ring. thanks al
 
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Old Jul 9, 2009 | 10:13 AM
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If you only have 100 miles on the engine I think those numbers look pretty good. I'd keep going and keep the throttle open but not wide open for another couple hundred miles and check comp again.
 
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Old Jul 9, 2009 | 12:25 PM
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When you did the test did you have the throttle wide open?
 
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Old Jul 10, 2009 | 12:53 AM
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cylinder presure should be in the 175 to 180 range.

my bike is just over 10.2, and its 195
 
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Old Jul 10, 2009 | 05:39 AM
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throttle wide open yes i just hate to put this back in with the cranking pressure that low
 
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Old Jul 10, 2009 | 10:22 AM
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Originally Posted by sliderg47
while breaking in a fresh engin at around 75 miles i lost a cylinder due to ignition failure resulting in overheating new engine,my stupidity. I later ran a compression test,135 lbs front 125 lbs rear.this is on an 88 ci buell std heads red shift 585 cams 263 duration 580 lift j&e pistons at around 10 to 1 static compression. what do you think ? is this normal with this set up or do i need to tear it down and re-ring. thanks al
I would fire it up, see if it rattles at all, warm it up a little, shut it off and do a leak down test, and take it from there. Warm, around 5-7% would probably be about right. If more, and air is hissing out of cases or oil bag, rings are needed.
 
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Old Jul 10, 2009 | 10:49 AM
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I was 190/190 stock and 180/180 after cams "37's".
 
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Old Jul 10, 2009 | 12:18 PM
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can't fire it up motor is on the bench , what abought a cold leak down test any figures in mind ? thanks al
 
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Old Jul 10, 2009 | 01:36 PM
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Cold, say 10-12% max assuming rings are not fully seated yet. Listen for where the air is escapping, that will tell the story.
 
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Old Jul 10, 2009 | 04:22 PM
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appreciate the input ,it will be a day or so before i can get back on it , i will throw up some numbers as soon as i can , thanks again . al
 
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