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Discussion Starter · #1 ·
Hi guy's I was curious to know why would the bike backfire when changing gears at wide open throttle.I took a lot of time getting this thing dialed in (p.i.t.a.) plug burn runs.I finally had it burning a pale brown and it would still backfire.I'm almost fed up with this crap.The bike runs like a bat outta hell but it still backfires.I had the feeling that I need to do a little more tinkering with this bike but it seems that what ever you do it runs good for awhile then it's back to dealing with something again.I just want to know if my bike is the only one that does this because the dealer doesn't have a clue as to what to do.The jetting seems perfect so the only other thing is that I need to get another cdi but i'm leary of spending that kind of money with no garantee of any improvement.So guy's what should I do.
 

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hard to say what your exact problem is, but if you are wide open when shifting, there is a good chance that you are actually hitting the rev limiter which basically shuts off the ignition and sends unburned gas into the nice hot exhuast and gives the posibility of a backfire type explosion in the header area. i'm not an engineer or anything so i'm open to critisism here, but this seems to make sense to me. if this is what is happening, the cdi will raise the rev limiter and stop or at least reduce your problem - james
 

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Jeepman is TOTALLY right on this one.Mine does the same thing.I would almost guarentee you this is your problem......Your rrvvin out thats all it is....Time for a CDI.I know Im ready.......TINA
 

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Discussion Starter · #4 ·
So basically there's nothing to worry about.I've been thinking about getting that cdi box from Rath Racing but right now I can't afford to spend the cash (Schools only a few day's off),but that was my first conclusion that it was reved out and hitting the limiter but it does it all the way through the gear range 1-5th so I was a little concerned about doing damage to the engine,but other than that It runs fine.The only bike that's beaten me around here are highly modified banshee's.The bike really preforms well and other than the backfiring everything's great.I just put in some engine ice and I'm going to order some scoopes here pretty soon.So thanks Jeepman and Tina for your advice.
 

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Hey, no problem. I isnt good to constantly REV out on your quad, its hard to not want to rev it ,but I guess until you can get the RPM;s up.. just try not to rev it out too much cause Its not good on your motor in the long run. Also, do you notice this more or less when hitting whoops,does it sputter at all? reason I ask is alot gets overlooked with the float. This made a HUGE difference with cutting out and sputtering.TINA
 

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Being used to riding two stroke's
It took me awhile to get the idea of not shifting at the peak of the rpm's
Having ridden the bike long enough I have learned to shift up quickly and not get to the rev limiter. This was infasized (sp?) to me last weekend when I let a buddy run my bike up Old's hill ( Glamis), Pretty funny really after I had beaten everyone that cared to race with no popping what so ever, he took it up the hill and it popped and backfired like crazy.

Just a thought
 

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Discussion Starter · #8 ·
Thanks guy's preciate the advise
 

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Well if u dont run premium or high octain fuel with how much compression the pred has it will back fire try that or check the timming
 

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Ok my cents, try puting the stock can back on. And see if it still doe's it. You can buy a tac for it also. Or modquad has a shift light for sell that might help you out.(Thats if your pushing the cdi) or your carb is still not right.
You never said how many disc or your carb set-up. Maybe more of us can help.


later
 

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Try running with 110 octane fuel...that should help, it will also get rid of the stock dead spot if you still have it!!!!
 

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Discussion Starter · #12 ·
Well guy's My set-up is the #2 main jet with the needle in the stock position.It took me awhile to figure out that the needle was not in the stock position from the factory and therefore my bike ran rich I started with the #3 main jet.It popped really bad up top and would not get to the limiter in 4th or 5th gear.I Switched to the #2 jet and finally got it to stop popping but it backfires.The plug looks great and after countless hours of F-ing with the jetting I thought that it was right but the backfireing concerned me so I wanted to see if this was a common thing with our bikes.I met a friend of a friend that has a predator with a big-gun full system and his bike does the exact same thing.I burn 92 or 93 octane and I only buy chevron gas w/tecron.I been riding 2 wheel bikes for a long time and this is my first 4 wheeler so I was just curious,I like to ride hard and I ride my bike hard but I don't abuse it so that's why this toppic was Started.I run my pipe with the spark arrester/7discs/end cap in that order.
 

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HHmm what is your float set at. Also how many turns do you run the air screw at.
Also have you called Gary(?) and ask him. Seems to me gary should be able to help you better on this set-up. Since you got the kit from him. I do'nt know what sebatian, florida is for elevation but I run #1 jet and I live at 5000' I would think num #2 would be to lean. I do'nt think your carb is set right.



later
 

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Also on the poping,NEVER,NEVER,NEVER,has my mach pop on the top end, low end whatever. I run it like it's a 2-stroke. Gas and shift the hell out of it. Full thottle WFO. Yea I ride the hell into it, not out. If I can'nt push this mach to my limits. I'll buy something else.


later
 

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Jeepman is right, mine does the same thing at high RPM's it's not a backfire but the Rev limiter doing it's job. I use the best gas you can get at the pump and it pop's at certain times at high RPMs.
 

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Discussion Starter · #16 ·
Gary did the carb for me when I bought the kit .He also has helped me to get a handle on the jetting because when he set it up it was a lot cooler there and here so the temp change effected the jetting.I'm really not too concerned about the jetting b'cause I've Checked the plug and it's good a nice light tan color and 110 av fuel did do the trick but I don't want to run that stuff all the time.Like I said earlier another predator that I saw a few days ago did the exact same thing so I'm almost sure that its the limiter.Thanks guy's
 

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most of the time back fire is caused by to much gas try moving down a jet size. its just like a old carborated car if you pump the gas to much before starting it will flood, but if it kicks over it always backfires.
 

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Not to drag this out! But why are you running 110 av fuel? Is the motor re-done. Are you running a 13/1 or 14/1 just wondering. Did you change your timing. Ported ect. I'm getting lost.

But maybe it's just the CDI HHMM

later
 

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I'm running 110 octane on a stock engine, it burns slower and cooler than 91 or 92 octane....my buddies has a pred too with k&n ....and rejetted, and all I'm running right now is 10 octane and he has a hard time keeping up on the flat track
 

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Discussion Starter · #20 ·
I tried it b'cause someone suggested it in a reply to this topic.I can say this for sure it stopped the backfireing,but I don't want to burn av fuel all the time and no nothing was done to the motor.Hey guy's I was just trying to figure out if there was a problem that's all.My bike runs hard and I've taken down everything except highly modded banshee's,but if there was a problem then this is the best place to find out about it(right).
 
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