SoCal Jet Boats
Tech Talk => Engine Mechanical / Electrical => Topic started by: challenger76 on May 14, 2014, 06:58:09 PM
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What's up guys I just did a leak down on my bbf lowest was 6psi and the highest was 11psi also the motor was cold not warmed up at all...I was told if I start loosing more the 15 psi I should start considering a rebuild... what do you guys think?
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Curious what you're using for your leak down? Most of the testers I'm familiar with show percentages. Still doesn't seem bad though.
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Curious what you're using for your leak down? Most of the testers I'm familiar with show percentages. Still doesn't seem bad though.
not sure of the tester its my buddy that did it for me and it was pecentages 6% was the lowest 11% was the highest that I lost
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so what happened that caused you to start doing leakdown tests, etc? what are the actual numbers for each cyl?
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so what happened that caused you to start doing leakdown tests, etc? what are the actual numbers for each cyl?
well I was at my friends house he was doing his motor so I figured lets do mine for the hell of it no reasson just see I gues... well # 1-8% 2-10% 3-11% 4-7% 8-11% 7-10% 6-11% 5-11% I guess 7% was my lowest
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I've seen late model engines with higher numbers than that. That's actually pretty tight, I'd say you're good to go.
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The higher the number- the more air is escaping. The lower the number the better.
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The higher the number- the more air is escaping. The lower the number the better.
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So when should I be thinking about doing a rebuild
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So when should I be thinking about doing a rebuild
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before it gets this bad
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fuk.boats.com%2Fboat-content%2Ffiles%2FBlack-smoke-_MG_9854-copy.jpg&hash=4d396c5275cc48409dd1413fff98cb32e7b9b328)
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before it gets this bad
(https://www.socaljetboats.com/proxy.php?request=http%3A%2F%2Fuk.boats.com%2Fboat-content%2Ffiles%2FBlack-smoke-_MG_9854-copy.jpg&hash=4d396c5275cc48409dd1413fff98cb32e7b9b328)
lol well I would hope so....
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Under 20% is considered acceptable. Frankly, I use this more to diagnose a problem, finding out why a motor isn't running right. Racers like to do these looking for any little edge they can find. If your motor isn't an all out max effort race motor, and you're just monitoring wear, this kind of searching for trouble can drive you crazy. :screwy:
If you rock the crank back and forth a couple degrees while doing a leak down you can change the readings quite a bit. What I mean is, at TDC you may have 20% + leakage, but you can rock the crank a couple degrees one way or the other and all of a sudden your leakage drops to 6%. So is the cylinder bad? Do you maybe have a valve that's worn a little and not sealing quite as well as it used to? Maybe a little carbon build up. Is there a scratch in the cylinder? See, this can make you go crazy.
Monitoring how the motor starts, idles, accelerates will tell you a bunch about your motor condition. Watching your spark plugs for things like oil consumption or excessive unburned fuel will tell you you're getting close to maintenance time. hope this helps.
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I might be wrong but isn't leakdown used for mostly two strokes to check leaks? Like seal failure and such. I think compression test is my #1 for rebuild time "gauge" and leakdown for fine tuning. vacuum and stuff.
Yeaaaah buddy
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