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Crf250r lost compression

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My 06 250 gave out the other day i think it is the valves but im not that sure because you can kick it with your hand and it will pop start but not idle or run right any ideas i have a jday in 4 days and im stumped

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Hows the compression?is it really easy to turn over by hand? And long has it been that easy to turn over?

Edited by minimadness047

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it did all of a sudden kinda but I don't think its the piston the engine was rebuilt 56 hours ago I took the readings and the exaust was way off on bolth sides is that the problem you think

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No clearance on the exhaust valves? Make sure you checked the clearance when the engine is coldThat will give you a compression lost

Ya im having a buddy who knows alot about bikes help me take the cam off i dont want to mess up the timing

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Check the valve clearance first. the cam doesnt have to come out for this, just have to pop off the valve cover. Then get back to us. If any valves are at zero clearance, the valve will never close properly and you WILL lose compression.

Edited by nzgsr

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The intake was fine but the exhaust was of by .025 mm on bolth sides this is the problem right i have a race on sunday and all my buddies left me hangin so im doing it from the power of the internet

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Incorrect clearances will cause poor running, but you will only lose compression through the valve if its at zero clearance, or if the valve/seat has been damaged. At 56hrs the piston is getting up there, esp if its running in the original worn out 06 cylinder.

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Incorrect clearances will cause poor running, but you will only lose compression through the valve if its at zero clearance, or if the valve/seat has been damaged. At 56hrs the piston is getting up there, esp if its running in the original worn out 06 cylinder.

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So they are off by .178mm if im doing it right they are .004 from being closed will i get better compression with better shims?

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Don't write it off just yet, find out if you are losing compression, get some compressed air hooked up spark plug hole and with all the valves closed, piston held at TDC, listen where or if your losing compression. You may just have a plugged low speed jet in the carb.

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I did run lolder gas in it but i usaly run 93 with a octane boost and i have the shims off the exaust

Valves off along with the cam

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-improper valve clearance 

-worn valve and/or valve seat

-cam timing wrong 

-blown head gasket

 

 

Edited by mlatour

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