no power

[brb646]

my 09 yz250y lost power on the top end all of the sudden last weekend after five laps. Air filter is good, changed spark plug( the old one looked fine), checked the needle valve to make sure it wasnt flooding, checked the reed valves(looked good), cleaned the crap out of the power valve. I then checked the resistance on the tps according to the manual. The resistance was lower than the manual but it did increase with the throttle (from 0 to 2ohm). I then unplugged the thing and ran with it disconnected. Needless to say I have not fixed the problem with all my efforts :bang: . Is there something else I can do or try.

 

[sm7482]

blown head gasket? remove the head and look for a dark or burned markings all around the head gasket seat if the is one you have a blown head gasket or its not torqued down enough. check that is fine try torquing the headbolts back down they may have come loose

 

[brb646]

thanks, I will give that a go tomorrow

 

[RM85rider123]

how many hours do you have on the bike? Was this your first time riding it, due to it being an 09?

 

[whenfoxforks-ruled]

Loss of top end power, silencer packing, clutch going out, or reeds. After that, check the electrics, stator, pick up and dreaded cdi box. If the motor is overdue, it would lose power off bottom first. Or, simply your main needs to be adjusted.

 

[whenfoxforks-ruled]

Loss of top end power, silencer packing, clutch going out, exhaust valve, or reeds. After that, check the electrics, stator, pick up and dreaded cdi box. If the motor is overdue, it would lose power off bottom first. Or, simply your main needs to be adjusted, or the butt plug is still in it?

 

[RM85rider123]

Loss of top end power, silencer packing, clutch going out, or reeds. After that, check the electrics, stator, pick up and dreaded cdi box. If the motor is overdue, it would lose power off bottom first. Or, simply your main needs to be adjusted.

what I was thinking of was the top end going bad too, or if this was his first time riding it, he may not have broke it in right.

 

[whenfoxforks-ruled]

An 09, is a year old now, never seen an hour mark on the engine. When the rings wear out, the bottom end loses first. In advanced state of disrepair, of course it will effect the top end also.

 

[brb646]

The Bike is about 6 mo old. Its got my best guess is 50 to 60 hours. The clutch and reeds are good. It almost sounds like a rev limiter so I am inclined to think it may be the cdi box. It went bad all of the sudden. It wasn't gradual and there is alot of bottom end( about the same as new ) it just gets up to the power band and blah.

 

[IndyMX]

MY 2000 CR125 did that.. The main jet backed out and was laying in the bottom of the float bowl. Was running a tad rich on the main... ;)

 

[_JOE_]

Power valve stuck closed?

 

[whenfoxforks-ruled]

When was the last time you changed the spark plug and gapped it?