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Leakdown Test vs. Compression Test
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Leakdown Test vs. Compression Test - August 21, 2013, 03:55 PM

I'm into work on my bikes, and I may buy a leakdown tester, probably the harbor freight unit. My question is this. Will doing a compression test on a cylinder provide any additional, necessary information after already doing a leakdown test?

It seems to me that a leakdown test will reveal any valve or ring problems and that a compression test will be redundant. On the other hand, a compression test seems to be less informative. Is there a good enough reason to do both? Do I need to buy/borrow both?

I don't really suspect there are any cylinder problems, but while things are apart I want to verify this. The intake valves have noticeable carbon and oil on their stem sides.


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August 21, 2013, 04:49 PM

Both test are important when diagnosing engine issues but only if you know what to look for. In your situation I would just have a leakdown tester.

Last edited by REDLEVEL; August 21, 2013 at 04:57 PM..
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August 21, 2013, 06:02 PM

Thanks Chris. Yeah I want to catch any "big" problems before I button everything back up. I hate the idea of a valve job, but I hate the idea of a bad seat even more, especially after full reassembly.


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August 21, 2013, 06:24 PM

Quote:
Originally Posted by OrangeShirtDude View Post
Thanks Chris. Yeah I want to catch any "big" problems before I button everything back up. I hate the idea of a valve job, but I hate the idea of a bad seat even more, especially after full reassembly.
A leakdown test will tell you everything you need to know. Most modern 4strokes use an auto decompression system that'll cause a low compression reading unless disabled. What bike are you working on?
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August 21, 2013, 06:29 PM

2004 ZX-10R. I'm finishing a valve adjustment that has been pending forever lol. It is a giant PITA so I want to catch any and all issues that might be lurking.

The bike was running well but overdue for valve clearance check/adjustment. I was out one day and noticed that once it hit about 8K rpm, the engine sputtered and lost power. I garaged it right away, thinking it was valves. We'll find out--50K original miles on the clock.


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August 21, 2013, 06:42 PM

Hope it fixes your problem but usually valve sealing issues cause problems during startup and low rpms.
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August 21, 2013, 07:42 PM

John, I recently just did a head gasket and a valve job on my R6 and it wasn't fun at all. Let me know if you need a hand with your ZX-10. Since your only minutes away now, I'd be glad to come over and help you with your bike.

-Brian
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August 21, 2013, 07:55 PM

Thanks Brian. I have the valve cover off now and am going to get some gap measurements tonight. Do you happen to have a leakdown tester?


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August 21, 2013, 09:42 PM

Sorry I don't, but a compression tester I do have if you need that.

-Brian

Quote:
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Thanks Brian. I have the valve cover off now and am going to get some gap measurements tonight. Do you happen to have a leakdown tester?
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