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My brother has a 2001 F4i with less than 10k miles on it and it's in pristine condition. For some reason though, when he is rolling off of the throttle, during de-acceleration the bike will backfire between the 5000-7000RPM range and shoot a kick *** flame out of the exhaust. It happens randomly, but starting to be more frequent. He also says that the throttle is inconsistent, he cannot seem to keep a solid RPM/MPH while riding and it seems the bike just sort of accelerates and de-accelerates all on its own.

As of right now, these are the aftermarket parts and tune up parts:
K&N Air Filter
M4 Shorty Exhaust
Fresh spark plugs
Fresh Oil
Newer/Operational ECU
91 Octane gas

*****THIS IS NOT A STUNT BIKE****** It's just a leisure bike and has never been wrecked, 12'd, NOTHING.

I can only think of a couple things, most likely a module or sensor of some sort, can anyone help???

Thanks in advance!!!

CRA$H AZ

i thought it was normal for fuel injected bikes to shoot flames in the high rpm range

seen it alot on high rpm downshifts/upshifts

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5000-7000RPM isn't high RPM range. You're thinking 12k and above.

John LegionST

make sure all the vacuum lines on the bottom of the airbox, on the MAP sensor and on the throttle bodies are hooked up... one of those lines off could cause that...

CRA$H AZ

very true.....sometimes i read and don't fully comprehend what i'm reading and just start talking :YEAH

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Wouldn't that throw a code?

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Can anyone think of something else it might be?

havok

it shouldnt.....when i got my bike back from the stealer ship they had all the vac lines crossed...and the bike did bog like **** and the rpm were deff not consistent ...soo i put them where they were supposed to be and the bike ran ten times better...


oh yea plus if the stock idle was messed with (the prob i had) and the fast idle wax unit went bad the bike will run like crap....

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The bike does have a problem with the stock idle cable, it is seized and won't spin anymore plus when you start the bike it won't go into high idle at all. Guess I'll start there.

havok

then thats deff the prob...does the bike at all sound like a quad sometimes...

the fast idle wax unit controls the fuel to air mix,and throws off the throttle bodies so sometimes when you install a new one you have to adjust the valves...my bike had the same prob....my bike would jump all over the place....and when you first start it ,it would just sit a 1 1.5 and took for ever to warm up....the bog would stop after 6-7 rpm

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Can't say that it has ever sounded like a quad. It does ride crisp after 7k RPM but anything before that and it just feels sloppy.

Thanks for the info.

NAARDEN INC

sync your throttle bodies

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This wax unit for the idle... where and how do I replace it? Pictures would really be helpful. Also, I was reading all over the internet that after replacing the wax unit I need to resync the throttle bodies, (which I plan to do anyways) is this true?

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Also, where can I buy a throttle body sync setup?

havok

its under the throttle bodies...so you have to take of tank air box throttle bodies, and its on the left side you cant miss it ,,its like $16-20 for the fast idle wax unit if i remember correctly ...and when i said adjust the valves i meant (resync the throttle bodies...)aka valves..

and for the resyncing part i have no clue.....

havok

oh ok so yours isnt to bad then...cause if it was its flooding ,and fouling plugs...

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Nevermind... I ordered one through TuckerRocky so now I can sync all of my bikes on my own.

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I've read they can be cleaned by boiling them... true/false?