Jetting a 400 with pro circuit t4??

[Dicestyle1912]

I have a stock 03 400ex with a SLip on pro circuit t 4 pipe. I was wondering if jetting would make it run even better? If so what jets should I go with?

[rob_990]

yea it will make it run alot better. has it ever been jetted before. if it hasnt i wouldnt even ride it. its probably running way to lean.

[Dicestyle1912]

It runs and sounds good. And it has stock jets

[BancheeFew]

I think it would run better but I have no idea which you should use.

[honda400ex2003]

REJET!! I believe when I only had my t-4 I used a 138 dj with needle on 3rd clip pos. and 2.5 or 3 turns out on the A/F screw. That and a k&n were all i had at the time with the box closed off. I am not absolutely positive on the fuel/air but it will get you really close. i am not at home now to look at my sheet. I am away at school. I am in WI and at about 1000 ft elevation. Good luck with everything I love the sound and power of mine. I wish it would have had some more low end torque from idle to about 1500 rpms but it still pulled hard thoughout the whole band. I would regularly beat my buddy on his stock 400 without a challenge. Steve

[Dicestyle1912]

Allright thanks,But when you say 3rd clip positive do you mean like 3rd clip from the bottom? or what?

[honda400ex2003]

I meant to say position from the top when the needle is facing down. It will be the seecond from the bottom with teh point of the needle down. I would start there and do a plug chop to check it. I left mine at that but you may be a tad different. Every motor is a little different with how they run depending on where they are and such. here is an article on plugs and plug chops.

plug reading article (http://www.atvriders.com/articles/sparkplug.html)

I was looking up a search on "Plug Chopping" And I think this will help you....


plug chopping
the plug chop is an essential step in setting up jetting. not only does it help you get good performance, but more importantly, it helps you make sure yr bike is not running so lean that it will blow up!

1. wind it out! . warm the bike up well (5-10 min) with a new or fairly clean plug, correctly gapped, then wind the bike out in a gear. generally, i like to do this in 3d, but it depends how fast yr bike goes in each gear and where y'r doing this test (trying to run a bike out in 4th is not advisable in, say, a school zone). at least get into 2d.

2. hold it there ... even though you will be nervous, hold it in gear at max rpm for a while... what you are trying to do here is simulate the hardest use the bike will ever conceivably see. if you jet for the most stressful conditions, then yr normal use will be well within safe margins. keep yr hand on the clutch, as you could (doubt it, though) seize if you are jetted too lean to begin with. as always, use yr own judgment!

3. kill it. simultaneously hit the kill switch and pull in the clutch. hitting the kill stops the plug sparking; pulling the clutch stops the clutch from turning the engine over (bringing in more unburnt fuel). thus, you get a perfect picture of what the sparkplug looks like at the moment you hit the kill switch.

4. pull over, pull the plug out you will want to have gloves or a set of pliers, cause the plug will be fking hot!!!

5. read the plug. if the plug is:

black and wet: yr jetting is too rich

chocolate brown: yr jetting is right on! you kick ***!

white and burnt smelling: yr jetting is too lean! upjet now . you might also notice a blistered insulator. this is real bad. you are lucky you haven't hurt yr bike worse!

6. important note: heat grade of the plug will also affect the color the plug reads... if you use a 'cold' plug like an ngk b9, you will be more likely to get a richer plug reading. however, in my experience, plug grade --as long as you are within the normal spread of plugs, f.x. malossi 210s take between b7es and b9es -- is not terribly important when doing initial jetting setup. for finer tuning, plug choice does make a difference, however.

i found this from http://www.exriders.com/vbb/showthread.php?s=&threadid=51968&highlight=sparkplug+chop

I did not thoroughly read this but I will get you really good info on how to read plugs. If you need extra help let me know. I will try my best. Good Luck Steve

[Dicestyle1912]

Thanks Man you explained it great. Ill try it

[honda400ex2003]

Did you get a chance to try it this weekend? I hope everything went good if you did. Steve

[Dicestyle1912]

I didn't get new Jets, But i did try choppin the plug. It worked great and My plug is burning nicely, So i suppose I am gonna leave my stock jets in?

[honda400ex2003]

Sounds great, good to hear everything worked out for you if you need anything else let me know, Steve