Dear fellow ATV dudes:

I have a challenge for all techno wizards in ATV Land. Thus far, I am completely stumped and in between a rock and a hard spot. Here is the scenario:

1999 Yamaha Warrior 350, purchased used in 2005. From the day I brought it home, it runs "like" it is mixing rich beyond 3/4 throttle (more accurately, at a specific RPM). I had the cylinder bored with new piston, the carb has been overhauled and rejetted more times than the sun has set. Airbox has been modified; pickup coil, pulse coil, and magneto have been replaced. The White Brothers exhaust baffles have been subtracted and added. When I removed all the baffles, it ran lean AND "rich" at the same time (if that makes ANY sense at all). Every single thing I have done to fix this problem has had ZERO effect.

I recently was in a helo accident overseas and had to return to the States for recovery. I state this only because I am a private military contractor hence I am unpaid while mending (not working). I NEED to sell this quad ASAP (Christmas and all), but will not sell it until I fix this problem. I paid a "specialty" shop to fix the problem while I was gone, but the knuckleheads obviously did not ride it after adjusting the valves (they said that was the problem). I am wondering if it is the CDI box.

Can anyone offer suggestions? I need to fix and sell this quad as soon as possible.

Thank you for reading this post.

R. G.

 

it is possible to run RICH and LEAN...

you could be to small in the pilot jet, needle, main, a/f screw... but it is possible... and if u just had the valves adjusted.. then i'd suggest maybe doing a plugchop yourself...

idle-1/8(pilot) 1/8-1/2(needle) 1/2-WOT(main)
and 2 extra incase u foul em

 

Thanks for the reply, Mate. All combinations of jets have been tried. I have done numerous plug reads (is that what you mean by plug chop?). At the base of the ceramic, the ring is black, but not sooty. Every single, dog-gone time, regardless of adjustments I get the same plug read. Please clarify what you mean by "plug chop". Thank you.

What I meant by "too lean and too rich at the same time", was that I created a too lean condition by removing all the baffles (did the same thing by removing the airbox as well), but at the same RPM point, it begins sputtering. That is why I am wondering if it is an electronic problem. In your pro riding pursuits, have you encountered a similar problem?

Thanks again for the quick reply!

Cheers!

 

what are the factory jets in a warrior and what do you have in there? including needle clip positions...

 

I believe that factory is 138 and currently I have a 145 installed. I have tried all sizes from 132 to 165, all without result (obviously the larger main jets worsened symptoms, but even the smaller main jets did not lessen the symptoms). The needle is on the 3rd clip; once again, I have tried all clip settings without improvement.

Thanks for the help.

RG

 

hmmm....not sure.

 

do warriors have a damn sensor by the clutch lever???? i know the blasters do, or at least did....and they failed a lot from what i saw.


what rpm does it sputter at? i think you are rich somewhere. maybe the stator is going. possibly the spark plug or plug boot?

 

also, what are all of your mods? slip on silencer and what else? is the air box stock now or is it modded still? if so what is modded?

 

stock jets are 42.5 pilot 145main

 

It may seem that its rich and lean at the same rpm, but its only throttle position which determines what carb circuit is working. Not rpm. If the thumb is off the throttle, even at redline, its only on the pilot circuit. If you go wot and its at 2000 rpm, its on the main. RPM is meaningless.
Heres a good how to article on jetting.click here
Id start by checking for vacumn leaks, especially the intake tube, between the carb and head. If its cracked, or not snug, the vibration will let air pass at certain rpm(engines resonate diferent at different rpm). Check it over good.
Then id check the spark plug coil and wire. It can be ohmed out , you dont need to replace it unless its alot out of spec.
I wouldnt suspect a bad cdi unless i had no spark. They either work or they dont. The only way to test one, is to exchange with a known good one, and see if theres a difference. But i dont think a cdi will help this issue.