400ex still to lean

[mopar2dvs4u]

hey guy's just wanted to say i really think this is a grate site glad that i found it . but here's my problem i put a pro circuit slip on and a k&n fliter and open air box ,42 pilot 170 main third groove and its still lean and stumbles on top end used dyno jets the only thing that i can think of the barrel where jet go's game looose when removing jets to put on adpator run's good down low and starts right up thanks for the help :cuss:

[GPracer2500]

I'm guessing you're rich not lean. A 170DJ is huge.

[mopar2dvs4u]

no put new plug in came out white but thats what i thought to fuel screw is out 3.5 i went with what dyno jets instrutions said also went throught all the jets in kit just to solve problem but thanks for reply

[mopar2dvs4u]

sorry about that left this out but still have problem

[Wheelie]

You're way too rich.

When my quad was stock internally w/ a slip-on, no filter lid, K&N and no choke I ran a 40 pilot and a 155k main jet. A 170DJ is too rich.

Since your plug isn't giving you accurate feedback, tune by throttle response/power/ and how the engine runs.

[GPracer2500]

What wheelie said about not using the plug.


Plugs reading is tricky business. You need to "color" the plug a certain way and then read the plug by looking way down on the insulator at its very base. This can require actually cutting the threads off the plug to see the place you need to see. As you've discovered, you can be pig rich and a new plug's insulator tip can still come out bone white. This seems to tell you lean when the issue is not leaness but how you're reading the plug.

Also, DJ's jetting recommendations tend to error on the way to rich end of the spectrum.

[REPOMAN]

good way to check richness or lean is the end of your exhaust pipe. noone can actualy tell you over the internet if it is rich or lean at best they can guess right. call dynojet in the morning and tell them what is going on. i run a 170 and its perfect. i have a few more mods though

[07trx400ex]

Like Repoman said....

Exhaust gases are an indicator of the richness of the A/F mixture.

Take a white rag and wipe the inside of the end cap off. Take it for a test run and wipe it off again.

The color needs to be a light gray.

This is not exact by any means but can tell you if you are too rich (thick black color).

You can see my mods and I also started out with a 170DJ because it was recommended by K&N/DJ, but eventually settled on a 160 keihin, which could still be leaned out more for more hp.

[REPOMAN]

i honestly think i am way rich at the 170. but it runs good and i am tired of jetting lately.

[Wheelie]

When I got my Yoshi exhaust last year, the instruction called for a 175k jet on an otherwise stock engine. I was running a 178K with a built 440 stroker w/the stock carb.

Exhaust manufacturers err way on the rich side, that way, under no circumstances could they be blamed for a engine failure due to lean running conditions.

Mopar: IMO--Install a 40 pilot and a 158k main jet and see how it runs.

[mopar2dvs4u]

when i was on my way home stopped at shop and got some answers the tube the jets screw into is called emulsion tube well i screwed my back until it bottomed out .runs ok but now it has a stumble off idle now gonna ride tomorrow and see if it still lean or rich. but thanks for reply
:huh