42 pilot jet

[oldschoolsdime9]

I've seen a lot of talk about a #42 pilot jet solving the cold start issue, along with running cooler. My bike is bone stock, just as it came in 99. Would I benifit from this 42 pilot ??

[Crosshairs]

Yes, my 2000 400EX was also stock when I changed the pilot to a 42..its helps tremendously.

I don't even need to use the choke anymore

[oldschoolsdime9]

Do I need to change anything else other than the jet?

[Crosshairs]

When my bike was stock, I ran just the 42 pilot with the stock 148 main.. and it ran good..Ive since added a pipe and and airbox so I also changed the main jet....

you should be fine with just changing the pilot, unless you want to experiment and see if a larger main would benefit you also.

From what I understand, the bikes come pretty lean from the factory so a small bump in the main jet may not be a bad idea
The main is easy to change, you don't even need to remove the carb, so its pretty easy to play around and find the one that works best

[honda400ex2003]

for 99% of cases the 148 main is a good size. if you are right at sea level or something a 150 could be used or if you ride where it is really hot alot of times.

otherwise 42 is all you need. 150 is optional if you want to run it.

steve

[Zakradu398]

42 pilot is great for me warm or cold out. No use for a choke anymore either

[oldschoolsdime9]

What's the best place to.purchase said jet?

[Stickman400]

JetsRUs.com Unless you have a local shop around you, they probably have a 42 pilot for a 400 in stock, just make sure it's a genuine kehin jet. It'll have a weird lookin K on it.

[Drfat400ex]

Myn really helped for the cold. Always starts great and warms up good too!

[CJM]

Well worth it for stock, I have a 42 and it starts up great when its like 80F outside, but when its colder it needs some choke. Granted mine is far from stock and I know the pilots slightly too small b/c I get a slight backfire on decel and have since I redid everything.

[oldschoolsdime9]

42 jet ordered! thanks guys! will i have to adjust my mixture screw at all?

[Stickman400]

Everyone on here (including me) runs it at 2.5 turns out from fully seated (fully turned in). Or you could start at 2 turns out, then slowly back it out from there until it idles to your pleasure.

[Drfat400ex]

Don't go out more than 2.75 turns though or it could fall out.

[oldschoolsdime9]

42 jet installed, and set 2.5 turns out.Runs a million times smoother. Bike idles great, has great throttle response. Starts easy. I can't believe they didn't come stock like that.