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Discussion Starter #1
Hey everyone, I'm new to this site. I just got a 400ex a little over a month ago. It's an 06, completely stock. It runs great but I've started to look into doing some basic mods. I'm looking to get more top end speed on it so I'm planning on changing the stock 39t rear sprocket to a 36. When I do that, I want to do some basic mods to recover some of that low end torque back after the sprocket change. I'm planning on doing a Lexx slip on exhaust and a uni air filter. I plan on keeping the lid on (for now) because I ride in a lot of dirt, dust, and whatever else.

My question is, how do I rejet the carb to accommodate these new mods? I'm totally new to this whole process, first time I've looked into aftermarket stuff on any machine I've had and really know nothing. I know that stock pilot is 38 and main is 148 I believe. However, those are just numbers to me and I dont really know what they mean.

I've seen dynojet kits for 50ish dollars that I wouldn't mind spending the money on because it comes with instructions and again, I have no idea what I'm getting myself into. I also heard that a lot of people switch to the 42mm pilot because apparently the difference in cold startup and idle is night and day but apparently the dynojet kit doesnt come with pilots? I'd like to go to a 42 but i cant find a dynojet 42 pilot and i heard somewhere that you arent supposed to mix brands? Not sure if this is true or not. Also if I could get any guesses on what size main I should start out with, thatd be awesome.

I guess my main (no pun intended) question is can I use a 42 pilot from whatever brand with a dynojet kit? Sorry for the long post but I'm trying to give everyone a background to my situation. Any help would be awesome. ??
Also if anyone has an estimate of price if I would just take it somewhere to get it jetted by someone who knows that they're doing, thatd be great too.
 

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Well idk anything about the sports but a little about carbs. But you have a QB11AB right?

You can buy larger jets; usually the local atv shop has a box of jets laying around you can pick through. find the part number for your current slow jet— 99103-420-0380? If you’re looking for a larger jet say a 42, then look for a part number last four is 0420. Same with main jet 99113-GHB-1480 look for a #150 (1500).

Or buy a jet kit—these are usually for tuning applications.

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149474
 

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Discussion Starter #4
Well idk anything about the sports but a little about carbs. But you have a QB11AB right?

You can buy larger jets; usually the local atv shop has a box of jets laying around you can pick through. find the part number for your current slow jet— 99103-420-0380? If you’re looking for a larger jet say a 42, then look for a part number last four is 0420. Same with main jet 99113-GHB-1480 look for a #150 (1500).

Or buy a jet kit—these are usually for tuning applications.

View attachment 149473 View attachment 149474
I appreciate the advice. I'm still pretty foggy on the subject tho. I've never dealt with carbs before and always turned away from ads for quads that say "just needs carb cleaned" if it's so easy, why not just do it yourself, right? Itll definitely be an adjustment for me. I'm always about doing stuff myself to save money especially if it turns out to be something pretty simple. I have yet to find a good, step video by step on how to do this. Thanks again for the reply!
 

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Well keep trying.
it would be best if one of our sport quad members would offer some guidance. Some members check in randomly and maybe didn’t see the post yet.
Ideally you’d get info on the whole package upgrade.
 

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Discussion Starter #6
Well keep trying.
it would be best if one of our sport quad members would offer some guidance. Some members check in randomly and maybe didn’t see the post yet.
Ideally you’d get info on the whole package upgrade.
I appreciate it. Guess I'll play the waiting game now (y)
 
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