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wr250f backfiring under load

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Hi can some one guide me in the right direction..I have an '07 wr250 aussie model,JD needle,170mj ,Fuel screw,zy pipe.

Bike starts first touch,idles, no flat spot BUT from 1/2 on to WFO it's Bang! Bang! Bang!

I'm assuming if i had an air leak i'd have erattic /high idle?

Is it electrical or lean fuel?

The bike did sit around for a while,I drained the tank,new plug,taped up the plug/coil,blocked up the air decel diaphram.The only think i havent done is strip down the carby.I think maybe thats the next step.:thumbsup:

Any idea's

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Misfire under load is too rich or a bad coil or CDI.

Disabling the decel valve only makes it want to back fire on decel.

I thought back firing under load was a lean running condition and backfiring on decell was rich ie blocking the air supply on the decel valve?(this is not a poping/decel noise)

Anyway this feels like you crossed cyls 2 and 3 on a 4 cyl car and have that backfiring,ignition timing wrong sound.

I have a snap-on spark tester,i will have to connect it between the coil and the plug and see if the spark dies off.

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I'm confused...does the bike ride OK, but it bangs at WOT on the stand? Is it hitting the limiter? Why do you want to punish your bike?

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On the stand isn't exactly under load... Any why would you want to go WOT on a stand anyway? It's much more fun off the stand!:thumbsup:

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When my primary fuel runs out before I switch it to reserve I get the BANG BANG.. then i hold my clutch in and the bike dies from loss of fuel.. turn on reserve and all is good :thumbsup:

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When you have the carb apart, check the float level and make sure it's not too low and the bike is starving for fuel. May not be the problem but definately something to look into

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Yeah,thats what its like-That 'just running out of fuel' banging-

It does it riding or on the stand,I would'nt normaly hold it WFO on the stand,its just for testing and it wont rev to the moon or limiter when breaking down anyway.

The float level is a good idea too :thumbsup:

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