Jet Size?????

[kat400ex]

416 kit ,xr 400 cam ,WB "R" pipe , no air box lid....k&N ,JE 10-8-1 right now i have a 175 in there and its white......motor is not fully broke in yet i just dont want to do damage any suggestions on jet size would be helpful ......or should i just move needle/clip? thanks

Hey Kat,
Been meaning to holla at ya', I used to live in Gainesville and my folks still do. I've made thousands of trips to the beach, so I know where you're located.
Papaw has a 416 and don't know what he runs for jets but maybe he'll
see this and help you out. If your thinking your too lean, maybe raising the needle will help. 175 main sounds pretty fat, is that Dyno size or Keihin carb jet size?
John

[Leo]

your running a 175 mj, what about your needle and pilot jet?


Leo

[kat400ex]

175 main jet nothing has been touched in carb.....its just a stock jet no dyno...... i might get a 180 tomorrow and see what that does then i guess we'll try moving needle or clip what ever one you move cant think right now.....thanks........

[Leo]

With all your intake and exhaust mods you might want to consider trying a 40 or 42 pilot, and adjusting your needle postion...

I would think a 175 should be plenty at WOT...

Another important thing to conside is what brand of gasoline your running.. Some of the ones with lots of detergents, etc.. can make it tricky to get an accurate plug read.

Leo

Papaw and I were riding a couple weeks ago and he noticed it popping or backfiring when in the trails on the hills. He put a 48 pilot in to help, a little rich though. He has the 416 and said a 45 pilot would be about right.
John

As Leo said some types of fuel especially Race gas & "AV" gas burn real "clean" which will leave the plug looking white even when it isn't lean, another scenerio I've heard of is the motor is getting "extra" air from somewhere like a vent tube or improperly seated intake boot causing people to compensate with jetting and creating problems later. Someone had a "foolproof" way of checking if your jetted right, on here. I will look for it and post it here if I find it.

[kat400ex]

thanks guys.......going to marcums today try to let you know soon. i think were gonna try the pilot . later

[rhandw69]

PrETTY much i have the same problem. I installed the 416, and really never have goten it dialed in.
Weve raied, lowered, put 155 through 170 and it still runs like crap.
My mid to top is awesome. But after that the the motor prety much just shuts down. Wide open it pops and sputters and is way slower than stock exs and yes even scramblers.
So Im not sure where to go from here.
Yesterday i uped my main from a 165 to a 170 and at full throttle it pops, it sputters, and acts like it just wants to quit.
SO when you guys figure out the 416 jetting and why my motor is running slower, hopefully ill hear about it.
Im not sure if the 14 t sprocket has something to do with it or not, so im going to change that out. SOmeone told me that i just maybe hitting the rev limiter also. I have the WB rev kit on it.
My pilot is 42, my main is 170 and my needle notch is rite in the middle. I have a K&N with no air box lid. COuld that be the problem with it getting TO much air???
Help someone please help.
Rhan

[FlyinRed]

No such thing as too much air, you just have to get enough gas in with it.
I think you mean the low to mid is awsome.
I also think changing the sprocket will ease the pain of your problem, but I'm pretty sure your not hitting the rev limiter. One way to check, in neutral pin the throttle. It may rev all the way out and bounce of the rev. That should sound just like it did when stock. Mine hits the rev all the time, and it dont sound like that. Also my motor is wound out at a higher pitch than yours. Long story short, I don't thin its the box.