My 03 Raptor has a full FMF system, k&N filter, hotcam, and dynojet kit...I just bought it, and it stumbles under acceleration when the choke is off..is this because of all the mods? is this what i should expect? Will it hurt the engine to run it with the choke at half? Where are the mixture screws, and is there just one or two? I would love any advise!! Also..it really cracks when you let off on the gas....

 

any time it runs better with choke on your too lean and need to rejet.

 

cant i just adjust the mixture ??

 

mine likes the choke too, it starts twice as easy with it.....it sometimes stalls i dunno why but whenever the choke is on it never does

 

"Raptor loves to be choked!!"

I have a chicken like that. (Sorry, couldn't resist)
[img]i/expressions/face-icon-small-happy.gif[/img]

 

Do a search under "raptor jetting" and you'll have enough reading to last you til' morning.[img]i/expressions/face-icon-small-wink.gif[/img]

 

The mixture screw will only effect the idle mixture to about 1/8 throttle. Yes try going richer, that will improve the crackling also.
Modern 4 strokes dont have chokes any more, but the lever is still called a choke. It actually lifts a plunger, which exposes a starter jet, and this will richen all the circuits. Actually it doesnt hurt to have it on..unless you start fouling plugs. But you should rejet, richer.
Heres a good site with info on jetting.
jetting

 

I had the same issue, went to 25 pilots and 160/165 jetting from 150/155 probelm solved.

 

Definately too lean. If it's that bad, then the mixture screws probably won't help unless they are screwed completely in. Try to find out if a jet kit was installed and what size jets they used. Also, let us know your elevation and if you have holes in the airbox and if the lid is on. We can give a starting point on where it should be or a max. that it could be. Don't run it very much like this, it will be an expensive fix if it cooks the cylinder and piston.

 

thank you for replying..It does have a dynojet stage 2 jet kit, the airbox is stoke except for the front flaps that were taken out..(saw it in the install directions)..Im in Minnesota , about 2700 ft. above sea level i believe. I changed the spark plug, and the whole lower threaded part of the plug was scorched black..This didnt help..The previous owner said it was always coldblooded, but this is ridiculous...Another quick question...regular unleaded, plus with ethanol, premium, or premium non-oxygenated fuel..?