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Night_Train01
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Posted: Wed Aug 27th, 2008 12:20 pm | 1st Post |
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| I continue to work on my 83 Interstate, I swapped motor due to a damaged piston. With the new motor in place I decided to check the compression. I got a reading of 110 PSI on all four cylinders. I am not sure what "normal" should be.......I did not have the thread in style tester, I used the rubber cone method so it may not be as accurate as I would like.
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Addicted to motorcycles
1978 Kawasaki Z1R
1981 KZ1000 J
1987 VTwin Custom
1983 GL 1100
1984 V65 Magna
1984 Interstate
1980 RD 400 Daytona Special
1981 KZ1300
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WingerDave
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Posted: Wed Aug 27th, 2008 12:39 pm | 2nd Post |
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Normal compression is 171 psi, below 140 psi things could be getting quite worn, but..........
In your case all cylinders give the same reading (good), just to low (not good), although I doubt if the readings are professional enough.
Try and get them done with the screw-in type tester, I'm sure you'll find the compression turns out to be quite acceptable.
Dave.
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If it ain't broke, don't fix it !!!.
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RB
Senior Member
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Posted: Wed Aug 27th, 2008 12:40 pm | 3rd Post |
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170 is perfect..in the 160's is good, 150's not bad, 140's getting close to needing some attention..below one 140 rings or valves need work..of some kind..110 is not good..but if the engine has been sitting a while the rings may loosen up after a few miles and improve things..if you put some oil in the cylinders and test it again and the pressure comes up it's rings if not valves. But get a screw tester..
and download the manual in the reference section or buy one.
____________________
1981 GL1100I Daily rider
1979 GL1000 parting out..PM if you're looking for something
1975 sold
1978 sold
1981 sold
1982 sold
FAIR WINDS,
RB
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Night_Train01
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Posted: Wed Aug 27th, 2008 12:44 pm | 4th Post |
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| I have a screw type tester but not with the proper thread size. I will machine an adapter today and then test again.
____________________
Addicted to motorcycles
1978 Kawasaki Z1R
1981 KZ1000 J
1987 VTwin Custom
1983 GL 1100
1984 V65 Magna
1984 Interstate
1980 RD 400 Daytona Special
1981 KZ1300
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Whiskerfish
Senior Guru
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Posted: Wed Aug 27th, 2008 02:04 pm | 5th Post |
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| Make sure you are holding the throttle wide open and all 4 plugs are out and the choke is off for the test or it will be inaccurate. The throttle can make a 30 psi difference.
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Whiskerfish
1978/9 Nekid Streetfighter 50k miles
1978 Dressed Daily Rider w/150k plus miles
1976 Windjammer dressed SOLD
1975 Nekid Recently Acquired (next street bike project)
1975 Nekid 22k miles running, Currently use as engine test stand
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RB
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Posted: Wed Aug 27th, 2008 02:37 pm | 6th Post |
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Take an old spark plug that fits..knock out the insulator and tap it for an adaptor you have..now you have a threaded adaptor that will fit in the GL plug hole
____________________
1981 GL1100I Daily rider
1979 GL1000 parting out..PM if you're looking for something
1975 sold
1978 sold
1981 sold
1982 sold
FAIR WINDS,
RB
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Night_Train01
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Posted: Wed Aug 27th, 2008 05:38 pm | 7th Post |
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| Thanks RB....thats a good idea.
____________________
Addicted to motorcycles
1978 Kawasaki Z1R
1981 KZ1000 J
1987 VTwin Custom
1983 GL 1100
1984 V65 Magna
1984 Interstate
1980 RD 400 Daytona Special
1981 KZ1300
|
newbiker
Very Active Member
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Posted: Thu Aug 28th, 2008 03:18 am | 8th Post |
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I don't worry too much about compression. I had a good running car with 0 compression and Wing too.
Good engine can have low compression: dry rings, seized rings(they will get out), bad battery, bad starter.
Spray oil or ATF in cylinders
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84 Aspencade.
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hatchetman
Senior Member
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Posted: Thu Aug 28th, 2008 05:15 am | 9th Post |
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| get that thing up & running for a bit. let the engine oil re seal those rings & try again. At least she sounds equal across the board!!!
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If your not lead dog in a sled dog team, The scenery never changes!
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redwing52
Very Active Member
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Posted: Thu Aug 28th, 2008 01:15 pm | 10th Post |
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| The test does not mean much if the engine has not been run. Warm it up and try again. It will be much higher.
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Whiskerfish
Senior Guru
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Posted: Thu Aug 28th, 2008 01:19 pm | 11th Post |
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| Sorry but I gotta disagree with that. I have tried these early engines hot and cold and there is virtually no difference. Besides the book spec of 171 is a cold spec.
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Whiskerfish
1978/9 Nekid Streetfighter 50k miles
1978 Dressed Daily Rider w/150k plus miles
1976 Windjammer dressed SOLD
1975 Nekid Recently Acquired (next street bike project)
1975 Nekid 22k miles running, Currently use as engine test stand
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redwing52
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Posted: Thu Aug 28th, 2008 02:01 pm | 12th Post |
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Whisker,
I am thinking that the motor has been sitting for a while. Dry as a cobb. Don't you agree that getting it running and let everything get run in a bit might help compression?
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Whiskerfish
Senior Guru
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Posted: Thu Aug 28th, 2008 02:09 pm | 13th Post |
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| Yes agreed if the engine has sat for a while. I thought you were referring to the Hot verses Cold test.
____________________
Whiskerfish
1978/9 Nekid Streetfighter 50k miles
1978 Dressed Daily Rider w/150k plus miles
1976 Windjammer dressed SOLD
1975 Nekid Recently Acquired (next street bike project)
1975 Nekid 22k miles running, Currently use as engine test stand
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