jet size???? 416 kit

[kat400ex]

Got motor back today .....didnt get any help on jet size we bought a 175 i know lots of yall have 416 what are you running ??any help would be appreciated thanks!!!

[86atc250r]

I'm at 1000' - I currently run a 170, but that's in an FCR which will take about 1 or 2 sizes fatter main than a stock carb.

A big portion of the jetting will depend on what you've done to the intake side - if it's very free flowing, I'd recommend starting with around a 168 based on your location, cam, compression ratio, and pipe.

If your airbox/intake is still stock, it will likely take a substantially smaller main.

Where were you jetted at before? The jetting for a 416/XR cam is not much different than that of a stock bore and stock cam. This is because the higher compression and slightly wilder cam balance each other's effect on jetting.

[kat400ex]

no air box lid, k&n filter,xr 400 cam.......JE 10-8 to 1 white brothers "r" series which is straight thur......had 165 in it but motor has all this new stuff now figured i might need to go up....we bought a 175 .......and a new plug......should know more tomorrow once we put motor back on.....thanks and let me know what you think

[86atc250r]

The engine should be pretty happy with a 168 if the 165 was dead on...

Before I did my engine, it was a tad fat with a 165 (darker plug than I would have liked, otherwise ran fine) - when I went to the 416/XR, the 165 was dead on.

That was with the stock carb.

[kat400ex]

well i appreciate it i got a new plug so we'll find out tomorrow and i can always swap that jet for a smaller one......during the winter is was lean a few times....that was with the 165. whats some signs to look for in the way it feels if the jet is way too big.....besides what it does to the plug? i have not run the 416 yet this is all new the 165 jet was with everything stock motor wise....now motor work has been done i have always run with airbox lid off. thanks again

[86atc250r]

The most common occurance with a 400EX jetted too rich is a bog in the lower mid. If bad enough it will "skip" until you back out of the throttle.

If really rich it will happen in other areas of the powerband when you roll on the throttle, as well.

where is the best place to get a JE 87mm piston (11-1 compression) oh and how much?

[kat400ex]

GET with terry the sponsor of the website i know him personally and he has the best prices .....i took my motor to him wed i picked it up sat......MARCUMS ATV.....EMAIL him he will answer you back....good luck.....i am extremely happy with my motor its nice and i went with 10 -8 to 1 because i didnt want to have to run race gas ......i dont know which ones you do but i think thats as high as i could go....tell him a girl told you he will know who i am .