Evo Leakdown Test Results

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Dec 19, 2008 | 02:13 PM

#21

miacycles

Elite HDF Member

Joined: Sep 2007

Posts: 4,468

Likes: 12

From: Bluffton, South Carolina

Quote:

Originally Posted by jpooch00

OK, I'll ask a question that shows my ignorance! Is a leakdown test the same as a differential pressure test that's done on airplane piston engines where you feed a specified amount of pressure into the cylinder and note the pressure difference on either side of a calibrated orifice? I did this type of test on my '94 FXDL and got 78/80 on the front and 79/80 on the rear. On an airplane engine that's considered excellent. I did a regular compression test too and got 125 PSI on both. My engine is bone-stock. Any advice/info much appreciated!

Yes except thye guage is a little different. You set it to the set point (zero) on the guage. Then you open the valve and the needle will move up the guage indicating what percentage of leakage you have. On an everyday V-8 engine 20% is ok. However a V-Twin having only two cylinders 10% and more can affect performance and mileage. That being said always treat the patient not the gauges. If you are happy with the way the bike runs, then by all means ride it. Hope this helps.

Dec 20, 2008 | 09:34 PM

#22

blackjack66

2nd Gear

Joined: Dec 2008

Posts: 6

Likes: 0

+1 by all means ride it, just be aware that there is a problem, and you will be going in soon to rebuild, assuming you have a true and correct 305 leakage. I would unadjust the pushrods and reset the piston just below TDC compression and check again. 30 is alot! Your compression is OK for a stone stock bike, but with some headwork, I look for higher, like 180 or so, my bikes have 10.5-1, and with edelbrock .600" cams they show like 200 psi. they make 85 - 90 HP from 80 in., though