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Discussion Starter · #1 ·
hello,

I have a Honda CRF450R 2003 that we are currently trying to repair. Looking for some guidance.

Per the Honda Manuel our valves were out of spec on the larger end. We re shimmed the valves to get them back within spec. This morning we performed a compression test and received 30 PSI compression (we got 30 PSI compression before the valve adjustment also) This afternoon I did a leak down test on the bike. Placed the engine at TDC and placed it in first gear to help from having the engine roll over. On our leak down tester gauge at 100 PSI it is saying that we have 80% leakage. I tried listening to see if I could hear it leaking from the intake or the exhaust side but I did not notice anything. I could hear the oil in the bottom of the engine gurgling. Could it be the cylinder rings are bad? please help with what the next step is. Thank you
 

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Nice job doing the leak down test - most folks don't make it to that step.

Yes, it sounds like something really bad is going on with the piston or rings. Could be wiped out rings or cylinder wall, or a holed piston. Do you have access to a borescope? That's what I would do next, even if you have to borrow one, or buy a cheap one.
 

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Hmmm...how's the head gasket? If your leak down test is sending air into the oil sump, I'd think it's getting into the oil passages, like through a gap in the gasket. Your bike may have external oil lines for all I know, but just a thought...
 

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Discussion Starter · #4 ·
Thank you for you response.I would think that if there is 30 psi compression than there cant be a hole since it is at least building some compression right? I have not taken the head of cylinder off yet but by just looking at the outside of the gaskets i cant see anything leaking without pulling it. I am in the process of locating a scope to look at the piston. We have been out of town so i will be working on it Thursday.
 
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