wont run 5th gear out

[Blkmaroman]

I just got a 99 400ex, and he told me its got an 03' engine on it as well as a high rpm cdi box, cam, yoshi exhaust, k&N, bigger jets in the carb and a smaller rear sprocket. My question is when im in 5th gear it sounds like im just giving it 1/4 throttle when ive got it pinned all the way, when i got the bike a had to put a new plug in because the old one was fouled and black from running too rich a assume, could the rich condition be causing it to not run up in the rpm like its supposed to. Even in 3rd or 4th gear i cant get it to hit the rev limiter.

[88blaster]

yeah, if the new plug is black also than put a smaller main jet in it and see if that helps:cool:

[400eXr1d3rZ]

Take the airbox lid off see if it runs better.

[Blkmaroman]

ill see about testing everything out, my buddy has and 01 and he only has a filter, pipe and jet kit and his will scream in 5th gear with a 15 front sprocket, mine is more like a sunday cruise and my fenders are shaved also his are not.

[400eXr1d3rZ]

Well, did you take the lid off?

[Blkmaroman]

No not yet my quad is at my moms house right now but tomorow i should be able to test it out.

[Unverfehrt400ex]

Correct me if im wrong but he said it has a smaller rear sprocket. Wouldnt that make it harder to pull 5th gear and seem like it has less power?

[tim colston]

If you have 22" tires that may be the problem. I had purchased a set of 22" mud machines for winter riding and my 400 would not rev 5th gear out.

[slodsm]

With the smaller rear sprocket, you just have the breath knocked out of it. It's effectively geared higher so it just doesn't have the power to turn the tires that high in 5th. Put a stocker back on there and give it a shot.

[Blkmaroman]

I took the carb apart today and the main jet in it was a 155K, the pilot was a 38K and the needle was on the 3rd groove from the top. I took my plug back out to look at it and everything above the threads was black and charcoalish except for the electrode and the metal tab that bends above it and they were white. So i dont know if its lean because the electrode was white or if its rich because everything else is black and charcoalish. I also noticed my fuel screw was only like 1/4 turn out, almost all the way in. Im getting a 42 pilot jet to help out the cold starting blues, any idea of a main jet size for a 400 ex with a pipe, cam, rev box, K&N filter and altitude of about 350 ft i know every bike is different but just something to get me close as i dont really want to go out and buy a jet kit if i can get away with it. I also went out and counted the sprockets and i got 15 on the front and 38 in the rear, these sound like stock teeth to me but i dont know, but these shouldnt be causing my to only putt putt in 5th gear. And i never had a chance to test out the no lid because by the time i remembered i already had the bike apart.

[Blkmaroman]

Ive also got 22' razrs in the front and 20' razrs in the rear.

[Unverfehrt400ex]

Yeh if its 15-38 thats stock so thats not causing it. the 22 in tires definetely arnt helpin but thats most likely not the main problem

[Blkmaroman]

does a 155k main jet seem about right for my mods?

[clubert]

With all that, i really doubt that a 155k is too rich. I just have a slip-on pipe, air filter, and holes in my airbox, and i run a 155k, and when it gets real cold out, i think i'm just a wee bit lean, if anything. i'm at about 700ft elevation. I'd think you would be lean if anything, instead of rich, with a 155k.

[tim colston]

Originally posted by Unverfehrt400ex
Yeh if its 15-38 thats stock so thats not causing it. the 22 in tires definetely arnt helpin but thats most likely not the main problem

Please explain how it couldn;t be the main problem. Not being a dick or anything i am just interested to know. I switched back to 20" and it reved out fine.

[Chin_Chilla]

Originally posted by Unverfehrt400ex
the 22 in tires definetely arnt helpin but thats most likely not the main problem It doesn't matter if the fronts are 22in. It matters about the rear, which are indeed 20in. So that shouldn't be the problem...

[rneal]

Check your compression with a tester.... It sounds like low compression, or maybe the timing is off......

What kind of cam is it?

The 155k should be just about right. The clip position sounds good, and the pilot is stock.

You are running stock gearing and the stock tire size.

I run a 160k main with a slip on, 11:1 piston, and stock cam. I am a tad rich at WOT.

[Blkmaroman]

Could it be the fact that the fuel screw was turned all the way in, I havent ran it yet with the screw turned out some as i am waiting to put the pilot jet in just curious if that could do it. And i dont know about the cam he just said its got a bigger cam in it and i can see where they had the top of the head off before because of gunk around the edge, but a few other people have told me its got a cam also but i dont really know for sure and i dont guess there really is a way to tell other than what pulling the thing out and measuring. The guy that owned it before the the guy i got it from had it raced for a living and he is now going pro he can have the whole thing tore down and put back together in a few hours, he also said there was a bigger cam in it and he was the owner a few years ago. They never say stage one or stage two they just say bigger?

[Blkmaroman]

They had an 11to1 piston in it a few months ago but he took it out because he said it spark knocked with pump gas, so the topend on it is pretty fresh and it dosent smoke or nothing either.