lost of compression
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1st Gear
Joined: Aug 2012
Posts: 5
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From: trion ga
lost of compression
i have a 1982 sportster coming home yesterday i hear a taping noise so i shut my bike down and had it hual home. when i got home i had no compressionon my front cylinder.i check for leak around cylinder heads and found nothing.when i started to take cylinder off to check rings and rocker arms i found when i taking off push rod i found the top o ring had a chunk missing will this cause the compression lose and cause the noise i was hearing
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Joined: Sep 2011
Posts: 89
Likes: 1
From: A bit west of Dodge,MA
Probably not, but I would look at a few things.
First, before pulling everything apart, pull the spark plug, and look in the plug hole and crank the engine, see if the piston is moving. If it doesn't move, you have a bad piston or connecting rod.
Then drain the oil, check to see if it smells like gasoline, if so, you have a bad set of rings.
Then pull the head, check the valves, make sure they aren't bent and seat fully. A bent valve or non seating valve can loose compression fast.
Check the push rods for length and straightness. A bent rod or too long a rod will cause problems with the valves opening and closing.
Last thing is check the cams and the timing, a miss timed cam can keep a valve open too long and cause you to loose compression, along with valve damage.
Good luck.
First, before pulling everything apart, pull the spark plug, and look in the plug hole and crank the engine, see if the piston is moving. If it doesn't move, you have a bad piston or connecting rod.
Then drain the oil, check to see if it smells like gasoline, if so, you have a bad set of rings.
Then pull the head, check the valves, make sure they aren't bent and seat fully. A bent valve or non seating valve can loose compression fast.
Check the push rods for length and straightness. A bent rod or too long a rod will cause problems with the valves opening and closing.
Last thing is check the cams and the timing, a miss timed cam can keep a valve open too long and cause you to loose compression, along with valve damage.
Good luck.
Advanced
Joined: Sep 2011
Posts: 89
Likes: 1
From: A bit west of Dodge,MA
Unless the o ring affects how the push rod moves or works, probably not. A broken o ring will cause oil leak problems or loss of oil flow and oil pressure to some parts depending on location though.
Road Master
Joined: Jul 2010
Posts: 1,045
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From: Waukesha, WI
Exhaust valve guide pulled out of the head on my front cylinder once, going up a hill no less. Turns out the poor maintenance and sitting from the previous owner had caused a fair amount of corrosion and pitting on the valve stem. Eventually when things got warm and parts expanded, the guide began to get pulled out, until it eventually jammed the valve open. Prior to this I had a cold knock on that cylinder, and I had no idea what it was. Had the heads gone through and ended up replacing two valves as a result, the pitting was pretty unbelievable.
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