Low compression
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Joined: Jul 2012
Posts: 66
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From: new england
Low compression
I just did a compression test on my bike and found that the front cylinder has only 15 psi ! But the back one has 90 psi, what could be the problem? Could it be worn rings? And if so will changing just the rings fix the problem? Could it be a sticky pushrod not opening the valve? And if the timing was off would that give a low compression reading too? Any suggestions of where to start would be great!
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Joined: Jun 2012
Posts: 89
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From: Kansas City
worn rings/cylinder wall, valve sticking open, burnt valve seat, cam timing off. do a leak down toest to see where the problem lies. you can take an old spark plug, knock out the ceramic piece, weld on a male air tool connector and plug into an air compressor. air coming out exhaust or intake indicate valve problem, through crankcase indicate rings/cylinder wall.
Cruiser
Joined: Sep 2007
Posts: 171
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From: Clayton, NC
Sounds like a rebuild is in your future. You can get lots of help on the Ironhead forum. https://www.hdforums.com/forum/ironhead-66
Good luck!
Good luck!
Cruiser
Joined: Jan 2012
Posts: 222
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From: Kansas
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Joined: Jul 2012
Posts: 66
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From: new england
ok that's great that we narrowed it down to the rings I thought that's what it was,,now my next questions. 1.) If I change just the rings, will this help fix the low compression? 2.) Do I need to change the pistons too? Or can I get by just changing the rings if the pistons look good? Thanks! Im getting there!
I already have the tank, exhaust and carb off.
I already have the tank, exhaust and carb off.
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Seasoned HDF Member
Joined: Feb 2007
Posts: 5,067
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From: Edmonton Alberta Canada
If the pistons check out good you can re-hone the cylinders and install oversize rings.
Have the pistons checked by someone who knows what they are doing, it's not just a visual check and after all the work it would be a drag if you had to tear it all apart again.
You should talk to Dan at NRHS, he can advise on this best and hook you up with good quality parts.
Have the pistons checked by someone who knows what they are doing, it's not just a visual check and after all the work it would be a drag if you had to tear it all apart again.
You should talk to Dan at NRHS, he can advise on this best and hook you up with good quality parts.