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Discussion Starter · #1 ·
when i get on my kawi hard, the motor backfires when letting off the gas.. it has never done this before.. i have a pc3 mapped with no baffle and no air box lid.. i live in south florida so the only gas down here has 10% ethanol.. im wondering if this may be the problem.. if so, are there any fuel additives that can be mixed in?
 

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Double check your throttle position sensor settings. Note that's going to affect your idle speed. So you a adjust the throttle position sensor first then adjust your idle speed second.

TPS should be .58 mV (stock)

1. remove engine mount
2. loosen torque bolt on TPS
3. using a digital ohms meter set on 2.5 DC tap into yellow w/white wire on ESC (left side/top)
4. warm up quad and set idle to factory
5. then attach the meter (may be easier with two people) adjust the voltage to specifications
6. tighten down the torque bolt and double check the voltage readings
7. doublecheck the idle speed
8. all done have a beer



One other thing that just came to mind make sure your header pipe is not cracked. This will deftly created backfiring and throw off all your settings.
 

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I think its the ethanol leaning your mixture out a bit. Call Dynojet (or the people that you bought the PCIII from), and see if they have a map for your mods under those conditions. That would be the safest and easiest thing to try first. Popping off throttle is usually a good indication of a lean situation.
 

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Discussion Starter · #9 ·
i called dynojet.. they said the deceleration pop and backfire is due to unburned fuel in the exhaust mixing with air rushing in. it can be caused by either an exhaust leak or if that wasnt te case, i was told to increase everything in the 0 column by 10-25, starting at 10, from the 2000rpm column-redline.. he said the backfiring ismt a big deal and doesnt affect performance or the motor.. i was told it has nothing to due with the motor..
 

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QUOTE (FiremanEMS06 @ Jun 4 2008, 09:19 PM) index.php?act=findpost&pid=9622
he said the backfiring ismt a big deal and doesnt affect performance or the motor..
Was this guy a sales guy????

I have Dynoed over 15 quads with 100's of runs and I strongly disagree with his statement. On a fuel injected quad backfiring should not accrue at all if everything is set properly. I have a lot of respect for some of the engineers over at Dynojet Research Inc., but there are a hand full of guys over there that repetitively give out very questionable advise/information.
 

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Discussion Starter · #11 ·
i talked to some guy from technical support.. it didnt sound right to me either.. and if it ws caused by too much unburned fuel, i would think it's running too rich.. i'll just get it dynoed
 

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And Then!!
 

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I think the dynojet guy might be right, if you read any sportbike forums, you will see this
comment alot, alot of bikes and quads in the US don't have O2 sensors in the exhaust
like all EU bikes do, so they rely on a cat in the exhaust to burn the extra fuel and
reduce backfiring, so whenever anyone changes there exhaust without adding a
FI controller always ends up with backfiring, maybe not the same on our quads but
it sure sounds like the same issue.
 

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i see that this is an old post from 08 but here you go all ive had my quad since 07 and have only changed the silencer. It has never backfired on me till this past summer when it got rolled down a hill that i was trying to climb. after that it has backfired like none other and i have always used 92-93 pump gas its had the recall tank put in so the fuel pump best not be out (as i doubt it coz it still runs) i would have to say its the TPS or some other sensor that has been tripped but any ways hope the problem has been fixed by now or you have another quad
 
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