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I have a 92 yz250 problems. Please help.?

This is a discussion on I have a 92 yz250 problems. Please help.? within the YZ forums, part of the Yamaha category; This bike starts first kick without choke. It idles fine but, in first gear she appears completely fine, but in ...


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Old 12-27-2008   #1
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Default I have a 92 yz250 problems. Please help.?

This bike starts first kick without choke. It idles fine but, in first gear she appears completely fine, but in second it hits the power band and a surge of power follows but for a very short time, it is then quite flat and when the rpms increase just sounds like its bogging down. A friend of mine suggested probably using a hot plug but when I checked it is a cold plug. I am going to try a new plug but does anyone have any other ideas as to what could be the cause. Thank you
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Old 01-19-2009   #2
pmk
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sounds like it could be a couple of things but I suspect it's getting time to put a top end (piston, ring, etc.) in her. this is a common occurance and you really start noticing it more and more in the higher gears as it is working the engine harder the more gear ratio pressure is applied.first thing is run a compression check and see if you are within tolerance (not sure on a'92 YZ250, but guessing in the 125-175 psi range) ... check in a shop manual to get specific pressure your bike should be.second thing it could be a plugged (or partially plugged) pipe/muffler. when was the last time your repacked your muffler (or spark arrestor)??? once the packing gets somewhat saturated with the unburned oil, the air doesn't flow out well, causing additional back pressure, causing loss of power.several other things but those two are more than likely your problem.
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Old 02-27-2009   #3
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I agree with pmk about needing a top end.If you don't have a compression tester -Remove the exhaust pipe and look in the exhaust port with a flashlight and mirror.An scoring of the piston and cylinder wall, or discoloration below the rings, the top end will need to be rebuilt. ------
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