Heres another "What Size Jet" question

[JP400ex]

I've got a 2002 416ex that is ported, has a aftermarket cam in it (I think its a web cam) and I has a high compression piston (maybe 10:1). I have an FMF pipe and silencer on it and wan't to put the stock one back on because of my neighbors! I would also not mind being able to run it with the airbox cover on.

Anyways. I know stock jet is 148 but being ported and with the other mods to the engine what size jet should i start off trying. Obviously i want to be a little rich more than lean. Oh, also, the temp is running on the average mid 20's here right now and my elevation is like 650ft.

Any recommendations???

[LazeR]

Originally posted by JP400ex
I've got a 2002 416ex that is ported, has a aftermarket cam in it (I think its a web cam) and I has a high compression piston (maybe 10:1). I have an FMF pipe and silencer on it and wan't to put the stock one back on because of my neighbors! I would also not mind being able to run it with the airbox cover on.

Anyways. I know stock jet is 148 but being ported and with the other mods to the engine what size jet should i start off trying. Obviously i want to be a little rich more than lean. Oh, also, the temp is running on the average mid 20's here right now and my elevation is like 650ft.

Any recommendations???

So i'm guessing were talking kehien jets which im not familiar with.. but if i had a guess i would say put a 152 or so on it....and try that.......when you decelerate if you notice any popping (backfiring) then your most likely running lean.......... and thats when you let off the throttle from having it WFO! If it doesn't pop but seems sluggish in the higher rpms then your to rich, again i'm not sure but that would be my guess for a jet

[zephead400ex]

How does it run with the 148 main? With your mods, imo you should try a 155 main with at least a 42 pilot. Dropping the needle down a clip would also be a good place to start.

But with your mods, putting the stock exhaust back on will definately hinder your mods. Do you have to put the stocker back on? Running with the lid off will make it run a little more lean, might go up on the main when you do this too!

good luck

[JP400ex]

It won't make it run any worse than stock right? Im not too concerned with the mods, a stock 400ex has enough power for me. THis stuff was just on the bike when i got it.

[cals400ex]

if you rather run rich than lean i would put in a 160 to 165. that should be a tad rich.

[JP400ex]

I pulled the main jet out last night and it was a 200 Kehin. With the fmf pipe on it i dropped it down to a 190 and it runs alot better with alot less pops. It mostly would pop when i would stab the throttle and let off which most people have told me that means your running lean. But i don't see how i could be running lean with a 200 main jet and now it runs better with the 190. I bought a 185 and a 175. I may try them today although it is very cold here and maybe the 190 would be a good jet to run in this kind of cold and switch to the 175 in the summer

[cals400ex]

Originally posted by JP400ex
I pulled the main jet out last night and it was a 200 Kehin. With the fmf pipe on it i dropped it down to a 190 and it runs alot better with alot less pops. It mostly would pop when i would stab the throttle and let off which most people have told me that means your running lean. But i don't see how i could be running lean with a 200 main jet and now it runs better with the 190. I bought a 185 and a 175. I may try them today although it is very cold here and maybe the 190 would be a good jet to run in this kind of cold and switch to the 175 in the summer

my motor is very similar to yours and i am running a 158 main in 30 degree weather with my airbox lid on. i would put the 175 in. it will run the best out of any jets you have. however, you could still be running lean but just not with the mainjet circuit. you could still be lean on the pilot jet/ fuel skrew or on the needle. put the 175 in and tell us how it goes. by the way, it is really easy to change the main. turn the fuel off and unskrew the 17mm bowl bolt on the botton of the carb. the main is in right there. i believe you use a 6mm socket to get the main out. good luck