stutter stutter stutter

[sickassjay]

im not that great with carb related problems so I need your guys help. Its a 416 11:1 piston and everything else is stock except aluminum airbox with no lid. From ¼ to ¾ the thing stutters like no tomorrow but runs fine wide open. Pulled the plug and its blacker then asphault. Ok so its running rich, so i pulled the air filter and seat off and rode it down the street standing for maximum air and it ran perfect, but i dont wanna ride in the woods with no filter and seat. So my question is how do i tune it? the jets in it are 38 and 146. Thanks.

[CJM]

Jay, I live literally 20 mins from you in freehold and can tell you without doubt the jets you should be running are a 40-42 pilot and 168-172 main. I ran a 42 pilot and 170 main with my 416 and worked excellent.

it shouldnt be running rich with the jets you have-if anything its lean. Doesnt explain the black plug however. You did change your plug when you began right?

I can recommend an excellent mechanic if you need, hes quite cheap but I cant say if he might be backed up at the moment (hes quite busy).

[sickassjay]

Yes it was a new plug and thats why im so confused. As for mechanics i know a few but cant afford to pay them.

[CJM]

Sorry you cant afford someone, fwiw this guys very cheap.

Id try putting the jets I spoke of in and see what happens.

did you try running no airbox lid? The bike shouldnt even run without a filter-least mine wont.

Something isnt right....odd

[Drfat400ex]

Are you 100% sure you're using genuine keihen jets? Because that would explain a lot.

[sickassjay]

Ive tried running a 42 and 158 (all i have right now) and it floods it out, spark plug is real wet. The 38 and 146 are what came in the bike when i got it and it ran fine then except it was smoking so i did the rebuild and seen the piston and cylinder was scored. The way the bike is sitting right now is exactly how it was before the rebuild except the new piston and rings

[HondaRacing83]

Originally posted by Drfat400ex
Are you 100% sure you're using genuine keihen jets? Because that would explain a lot. I run PRO X Keihin jets they work great to btw. A 38 Pilot and 148 Main is what comes stock in 400exs so as to why the previous owner went down to a 146 is beyond me.

[JOHNDOE83]

Minkuni, keihin, pro x and Dyno jet all do the same thing.

Although I do reccomend and prefer using genuine kehin or oem equivalent.

You can even use minkuni jets in keihin carbs, they have different scales for their sizes and thats the only real difference.

I would suggest trying what CJM suggested, You might be Bogging not flooding out, bogging is from being to lean and the jetting CJM suggested is generally what people use with your type of motor.

I would check your needle setting, the problem your describing of bogging or flooding at 1/4-3/4 throttle generally comes from the needle.

A wet plug in a fourstroke isnt normal, maybe there is a install issue with the new motor?

[Drfat400ex]

Originally posted by HondaRacing83
I run PRO X Keihin jets they work great to btw. A 38 Pilot and 148 Main is what comes stock in 400exs so as to why the previous owner went down to a 146 is beyond me. Exactly what I'm saying, if it's a different kind of jet the scale might be different and their 146 is really a 220 in genuine or something.