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yz_4_life

Brand New 06 YZ450F Backfiring

18 posts in this topic

I just got a new 06 450F. Just broke it in this weekend. Noticed it is backfiring alot when letting off the gas. Was getting very hot also (suspected too lean mixture) Messed with the air fuel screw, and adjusted the needle. Still backfiring but not running hot anymore. Has anybody else expirenced this? All suggestions and info will be appreciated. Also everything is still stock on the carb. Elevation from 0' to 200'.

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I have the same exact problem too. My 06' 450 backfires and occasionally hesitates on initial throttle input. Is there no way to fix this problem withough having to rejet to a 48 pilot and a 170 main?

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both of you guys with issues need to rejet your bike. try 48/170 and 2 turns on the fuel screw to start. it's not a big deal.

i think im just gonna stop replying to these threads - seems like there's one a day :thumbsup:

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Ya mines the same way, its backfireing when i let off and its only got like 30 mins on it... its colder here mid 40's low 50's so im sure its running lean, im not gonna run it hard and it will warm up here which will help so who knows.

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make sure you fuel screw is in there! i had after market zip-ty unit, and it was lose from day one, just had to keep an eye on it.

this weekend second lap in to the first moto my fuel screw, spring and o-ring fell out, bike was popping ever time i let off the gas, was think to myself damn we need to rejet this, and then luck would have it your running 5th on the last lap and the bike stalls from to much air and a lack of gas. restarts after the 3rd kick, and then stalls after the finish line.

good thing we still had the stock unit in the trailer!!!

just a lesson for you guys!!!!

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I tear about a 1 1/2 inch long piece of duct tape in half (thinner) and put it over the screw to keep in place. I don't like the "loose" feeling either (spring is in) and makes sure it stays where set. I do reset mine often, riding from the deseret one weekend (screw is usually 3 turns out) to 4,000 foot MX the next weekend (screw usually 1/2 to 3/4 out). It nice to have the quick adjustment capability; I had to go one richer on the pilot from new with a FMF slip-on.

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The backfiring isn't a "problem" with the bike. It's simply a symptom of improper jetting for the conditions. The factory can't jet the bike for every condition, so naturally some will need to be rejetted. Rejet for your conditions and your "problem" will go away. Jets are cheap and easy to swap.

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since we had the stock fuel screw with us, no spring or o-ring, all that we could do was get it in the hole and put some duct tape over it. we have a new screw coming free of charge, and the springs and o ring from the dealer. so far this is not the first bike we have had problems with aftermarket fuel screw, on my 03 250f and 04 450f, both were caught in time before they fell out!

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What is the stock pilot size on the 06 yz450f (50th anniv.)?

What is the easiest way to get to the pilot?

What jetting are you guys running at Glamis?

What is the easiest way to get to the needle? What is the stock needle position? Looks like I have to tear the whole bike down to get to it.

Sorry about the questions, but I'm working on a buddies Yammy, and I usually work on Hondas.

Thanks

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What is the stock pilot size on the 06 yz450f (50th anniv.)?

What is the easiest way to get to the pilot?

What jetting are you guys running at Glamis?

What is the easiest way to get to the needle? What is the stock needle position? Looks like I have to tear the whole bike down to get to it.

Sorry about the questions, but I'm working on a buddies Yammy, and I usually work on Hondas.

Thanks

45 stock, getting to pilot see below link

http://www.thumpertalk.com/forum/showthread.php?t=335759

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I thought stock was 42-165, maybe you have different in USA?

No you are right it is a 42, my mistake.

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Do yourself the favour and raise the needle to 5th clip when you are there. You can get the carb cover removed from top (after removing seat and tank), remove the needle screw (don't drop the spring and washer), then keep the throttle twisted and remove the needle with thin pliers, and finally put the clip one notch down to the 5th. Runs better without surging than only with 48-170 jet change. Stay in balance with your jetting. :thumbsup:

Tips: use a magnet pen to remove the carb cover screws and the needle screw, you don't want to drop them. And remove the clip from needle by laying the needle down on a hard flat surface and press the needle so that the clip pops out. Reinstall the clip the same way.

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