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TheUSMC1775

2009 yz450f

15 posts in this topic

Hey everybody so I own a 09 yz450f and valves just bin done cam chain just replace, now I'm lost for words on tuning I noticed when in first gear cruising down the street and slowly accelerating it's a mixture of hesitating and chocking but when I shift to second and crack the throttle it's fine not perfect but rideable and are these bikes soppose to get like hot where you can feel it when just riding around ? Not agressive just up and down the street? Thanks

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Sounds like a clogged pilot jet.  Get a new stock sized pilot jet or one step bigger.  Start there and report back.  Make sure no air leaks on the boots.  

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Start by trimming out the idle mixture first.  You may find that the adjustment process points you toward a clogged pilot jet, or one that's too small.  If the idle mix adjusts out OK, try unplugging the TPS and run it. 

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unplugging the tps fixed my 07 from stumbling at slow constant throttle

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I vote for TPS Sensor unplug. Worked on mine. Much smoother

What is this TPS sensor you speak of?  I haven't heard of this one :smashpc:

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Throttle Positioning Sensor - there are a couple of threads about it. Disconnecting basically makes the Cdi box think the throttle is wide open. Does not affect anything, gets rid of the choppy throttle. I disconnected mine. It removed the chop and no issue with power/idle/etc..

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I had to go up 3 or 4 pilot jet sizes with my 2006 yz450. Ran perfectly afterwards. I would need to play with the air/fuel mixture screw to compensate for air temp. Cools down the operating temps considerablly.

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