what should i jet the main jet at? stock = 148
what should i jet the pilot to? stock = 38
should i move the needle up or down one? or just leave it?
im around 1000-2000 above sea level....also
im from michigan...
i need this info asap please.
thanks , Billi0

 

OK, first cardinal rule in jetting or any other type of adjustment: changeonly one thing at a time. Then test and change another if needed.I would start with two sizes fatter on the main..I'm not sure what the graduations are on Keihins, on Mikunis that would be a 152. Leave the jet needle in the 3rd position. Do a test ride at 3/4 to full throttle in any gear you choose for a mile, stop there & pull the plug & read it for lean or rich or correct mix.Dark or black electrode & insulator=rich. Gray or white=lean. Tan or brown=correct mix. Then you can try testing at other throttle openings to check pilot & needle jet. Normally they will be correct at nominal settings at your elev.

 

im looking for the exact jetting specs from someone that has jetted there 400ex already and it is running good...only thing that i need to know is if they are at the same height ahove sea level as i am, thanks anyways...

 

Lethal51
I have a complete Biggun on my 400ex. The jetting is going to depend on whether or not you are running the airbox lid or not. If you are you need to run a 152main. If not try running a 160main. I haven't adjusted my pilot jet or needle settings.

 

Lethal51, I also have the complete BG system on my 400. First time I jetted it was with a 158 main and a 40 pilot power was good but it lack acceleration and it was running really hot. So, I rejetted it with a 165 main and a 42 pilot. This made my bike feel so much better on top and in the midrange. I live basically at sea level but I feel like a 165 or 160 main and a 42 pilot would do fine for you. Also, my airbox lid is off with a Uni filter and make sure to seal the pipe and silencer junction up with high-temp sealant.

 

Hey he's right. Every 400 is diff. you just can't base it on someone elses settings. You've got to spend about 3 hours and do it right. Atv conection has a good story on proper jetting. Look into it. Also, a K&N jet kit would do ya right. For 45 bucks you'll get all the hardware and some decent instructions. If all else fails take it to a dealer. THey know what they're doing and it'll be money well spent.

 

i herd 152 main and 42 pilot and raise the needle 1 notch ... for a biggun with no airbox lid or snorkle...does that sound right..
i think a 160 is WAY to big

 

im gettin my exhaust tomarrow, woot! bt i still need jettin specs.

 

I'm running the exact setting callen74 described and they work great. I use these settings from sea-level to 3000 ft. When I ride at 5000-9000 ft
I run a 155 main, but I don't change the pilot and
needle, too much hassle and it works fine. I don't think there is a significant performance difference between the K&N and UNI. If you ride in dust, I'd stick with the UNI. For sand, use the K&N with outerwear.

 

Lethal51, I don't think a 160 or 165 would be too big. When I first jetted my quad I had a 158 main in it and when I jumped to a 160 and then a 165 (plus 42 pilot) it made a big difference. Also, I forget to mention that I did raise my needle one notch(drop clip to the next to last notch). My quad actually felt slower than stock with the 158, 40, and raised needle. But now like I said it is much better throughout the power range. Call Big Gun and talk to Paul he should be able help you out, too.