compression test.
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Joined: Jun 2010
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From: Gillespie, IL
compression test.
was just wondering, we did a compression test when i first got my bike the first test we got around 200 psi on both cylinders second attempt around 145 +/- 5psi with the throttle closed(for both tests). what should i be able to learn from this? can you tell milage from compression test? I thought it was a stock 80 inch evo(on a 88 fxrs). only mod that i know of its different pipes & SE electronic module. any thoughts, knowledge would be helpful.
Road Warrior
Joined: Nov 2008
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From: Vancouver Island British Colombia Canada
Try again with the throttle wide open & the battery fully charged. A compression test will indicate the health of the engine but not the mileage. That is effected by oil change intervals, Riders abuse, climates like Arizona that can bake an engine etc.
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From: Gillespie, IL
Thanks.I'm assumming 145 is average shape motor? from other posts i've read about it 130-150 is a motor that is in decent shape right?*edit* is there a way to get approximate mileage? the speedo says 22k but its not the original speedo to the bike, or at least it doesnt look original.
Stellar HDF Member
Joined: May 2009
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From: Middle of Kansas
Not to many people will take the risk of putting the wrong mileage on a title, as the penaltys are pretty stiff in most states. If it said 22,000 on the title, I would say that is probably what it is. If it said mileage unknown, its anybodys guess.
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From: Gillespie, IL
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Road Master
Joined: Oct 2011
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From: Carlsbad Springs Ontario
A compression test is done with the throttle fully open / no choke , engine at op/temp.
All plugs removed , spark disabled , fully charged battery.
Use a comp. gauge that has a fitting/with oring seal that screws into the plug hole for best results. With listed above satisfied , crank engine until highest pres. is attained , write it down for both cylrs.
Try a few times on each cyl. and notice which cyl. comes to top pres. the fastest.
If you find a big difference in time to reach top pres. between both cylrs. you need engine work. If both cylrs. reach top pres. at approx. the same time and within limits ,OK!
All plugs removed , spark disabled , fully charged battery.
Use a comp. gauge that has a fitting/with oring seal that screws into the plug hole for best results. With listed above satisfied , crank engine until highest pres. is attained , write it down for both cylrs.
Try a few times on each cyl. and notice which cyl. comes to top pres. the fastest.
If you find a big difference in time to reach top pres. between both cylrs. you need engine work. If both cylrs. reach top pres. at approx. the same time and within limits ,OK!
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2009, 80, calculating, check, compression, engine, evo, harley, harleydavidson, inch, motor, psi, spec, stock, test
