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freddy420

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Jul 22, 2025
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Oxford, Me
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Bike was running great . No issues . Next day I go and start it and it was like it lost half of its power. Sounds different. Sounds more like a 400 now . Acceleration is shit. Idles and starts fine. No code. Changed the fuel. Spark plugs. Tps wasn't that. Anyone have any idea ? It's a 2009 fz1 obviously. 34k miles. Just did oil change 1000 miles ago. Last year did 30k miles maintenance. The shop i brought it to gave it back twice saying it's fine and they can't figure out what's wrong with it . Doesn't seem to be misfiring. It's not throwing any codes. It definitely seemed to eat a ton of fuel on the way home. And didn't really get hot .
 
freddy420 said:
Bike was running great . No issues . Next day I go and start it and it was like it lost half of its power. Sounds different. Sounds more like a 400 now . Acceleration is shit. Idles and starts fine. No code. Changed the fuel. Spark plugs. Tps wasn't that. Anyone have any idea ? It's a 2009 fz1 obviously. 34k miles. Just did oil change 1000 miles ago. Last year did 30k miles maintenance. The shop i brought it to gave it back twice saying it's fine and they can't figure out what's wrong with it . Doesn't seem to be misfiring. It's not throwing any codes. It definitely seemed to eat a ton of fuel on the way home. And didn't really get hot .
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Try shooting each header for temp while running. If you don’t have a heat gun then spray it with water while someone is giving it a little throttle. That will tell you if which cylinder isn’t firing. Than we can go from there.

Also, sounds like it could be an air leak on the intake. Especially given the sound change and fuel consumption. If you have an intake leak the engine will compensate with more fuel.

You say it sounds like a 400 and lost half its power, a misfire sounds accurate as well. I have had misfires over the yrs and lost power and it never showed a code.

Do some looking around for dislodged or broken rubber stuff.

Just a few things to check first.,
 
freddy420 said:
How much of a difference in temp would there be? And if they are all testing the same than no misfire ?
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There should be a big difference in temp between the pipes that are working and the ones that aren't. Basically, the cylinders that are misfiring will be about room temperature if the cylinder is not firing at all. The ones that are firing will be hot. Water won't evaporate quickly from the misfiring cylinders. If they are all hot then no misfire.
 
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