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2013 fat bob 103. 30,000 kilometers on it. All stock except arlenness air cleaner and exhaust.
Compression test with acr valves unplugged and throttle wide open show 90psi rear 165 front.
k, not great.
So i borrowed a leak down tester and another compression tester (to double check it vs mine) from the shop i buy all my parts from.
same compression test results.
But leak down test on the rear was 10%
Which according to everything i can come accross 10% is not bad at all. Its getting on the tired side of good but its still fairly acceptable.
but why would my compression test be so shitty vs the leak down?
Initial reason for checking compression and what not was cause I was mad buddys 96ci all stock except exhaust and air cleaner pulls on me hard and my old ladies street bob with 103 and exhaust/cleaner has way more jam to.
Where do you here the air going using the leak down? That's your issue usually.
All I have ever used a leak down for is it a valve or a piston/ring issue. Hear air leaking into exhaust or intake or the crankcase. And hearing air into the crankcase of a Harley is tricky.
Now it could be a intake issue on that cylinder but running, you would think you would hear an issue from noise (bent pushrod or and adjustable one bad)
Then you could have low compression but no leakdown.
Last edited by Jackie Paper; Jun 15, 2025 at 06:59 AM.
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Compression and leak down wtf
