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Hi, I am new to the forums and I recently bought an 05 Raptor 350RT. When I bought the atv the guy had just put a new White Brothers MX4 exhaust on it. He also told me that he re-jetted the carb when he put the new exhaust on, otherwise the atv is stock. When I start it up cold, the carburator backfires and the atv stalls. This is only on the first couple of tries, once its warm it wont stall but sometimes i hear the carb backfire when I let off the throttle. I have searched and I found that I am probably running to lean? I just wanted to check with you guys before I mess with anything to see if you guys have ne other ideas? Thanks a lot in advance!
 

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Yes backfiring means running lean in most cases. If your on the throttle and let off then it backfires then thats lean for sure.
Bad part is you dont know what the guy did to the carb. Maybe he didnt do anything, And thats a very good possiblity. If thats the case you need to re-jett to fit your mods. Also Im hoping you got an intake on there too? If not i would recommend doing that then re jetting. You dont want to have to re jett again after you put intake and intake is very good place to start with perfomance.
 

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integlikewhoa said:
Yes backfiring means running lean in most cases. If your on the throttle and let off then it backfires then thats lean for sure.
Bad part is you dont know what the guy did to the carb. Maybe he didnt do anything, And thats a very good possiblity. If thats the case you need to re-jett to fit your mods. Also Im hoping you got an intake on there too? If not i would recommend doing that then re jetting. You dont want to have to re jett again after you put intake and intake is very good place to start with perfomance.
Thanks a lot for clearing that up for me. I dont have the intake yet, just the exhaust. I have a White Brothers MX4 exhaust and I am planning on getting a K&N filter. When I buy the intake is there a certain jet size or kit you would recomend? Will I need to replace the pilot jets also? Thanks again
 

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05Raptr said:
integlikewhoa said:
Yes backfiring means running lean in most cases. If your on the throttle and let off then it backfires then thats lean for sure.
Bad part is you dont know what the guy did to the carb. Maybe he didnt do anything, And thats a very good possiblity. If thats the case you need to re-jett to fit your mods. Also Im hoping you got an intake on there too? If not i would recommend doing that then re jetting. You dont want to have to re jett again after you put intake and intake is very good place to start with perfomance.
Thanks a lot for clearing that up for me. I dont have the intake yet, just the exhaust. I have a White Brothers MX4 exhaust and I am planning on getting a K&N filter. When I buy the intake is there a certain jet size or kit you would recomend? Will I need to replace the pilot jets also? Thanks again
To be honest I suck at carbs. Im too young and like computers to much to play with jets insted of power commanders. I swaped out the stock carb on the 350 for an edlebrock carb that has no jets to change out. So I couldnt help you much on which size jetting and such. Im pretty sure you can find some jetting help on the exhausts instuctions, which if you dont have you can probley download from their website. I would think usally there is a certin jet kit to use with a certin intake and exhaust, but i could be wrong. Also you would still have to fine tune it due to different gas and altitudes and such, so every bike will be a little different. Hope this helps a bit.

Also if you dont have intake, make sure you get one before the jet to save from jetting again after you install the intake. I have the prodesign with k&n and love it. They cost around 100 bucks give or take 10.00 depending on the deal you find or dont find.
 

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Looky looky what i found in 30sec's. If you go to www.whitebrothers.com under products and atv's then pick which exhaust you have, they have a drop down menu to select YAMAHA then it opens a PDF manual about which size jet for which model yamaha and weather or not you have a factory intake with the box lid removed or if you have an aftermarket intake.
You didnt say which white bros exhaust you have, but heres a link to the E2.

http://www.whitebrothers.com/2007/JettingSpec/E2/Yamaha_E2.pdf

Looks like you would probley only have to change the main jet. If you lid was removed. Im sure these are just recommened sizes every bike and place varies a bit. But this should get you started.
 

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i just got an rejet kit from dynojet and it has very detailed instructions that come with it to help pick the right jet size according to the altitude and mods.....the kits are very inexpensive......mine was $46.00.......try that out..you can also go to there website they post the instruction on there.......and as far as the intake its a must have.....rejeting is not really that hard just time consuming and you dont want to have to do it multiple times...... :thumbsup:
 

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slozuki said:
i just got an rejet kit from dynojet and it has very detailed instructions that come with it to help pick the right jet size according to the altitude and mods.....the kits are very inexpensive......mine was $46.00.......try that out..you can also go to there website they post the instruction on there.......and as far as the intake its a must have.....rejeting is not really that hard just time consuming and you dont want to have to do it multiple times...... :thumbsup:
Good info. And agreed with the intake.
 
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