I got the gyt-r jet kit, my bike ran very well on its recommendations. I couldnt be happier.

 

i just got a cobra 4-stroke on my 400ex like 100 miles & 5 hours ago on my quad & it is running fine (no jets needed, just slipped it on)....Will problems maybe arise? how soon & what will it be like?

 

how are your plugs looking. with just a slip-on and stock box you might be ok.

 

im not modifying anything...stock filter, stock box, stock head pipes. The only thing i am changing over stock is the slip on yoshi. Should i just go up one size from what stock is? If i can almost leave it without jetting, then one size up should be more than enough no? thanks

 

dude....try it leaving the way it is......if theres any problems than jet it, u may not even have to jet..i didnt have to....

 

If you are just installing a slip on you will be fine with the stock jets. When you get an after market filter with the pipe combo it will be a good idea to rejet.
It's a pain in the booty to change jets on a raptor. If and when you get an after market filter I would suggest getting a jet kit. It will simplify your dial in and make troubleshooting a lot easier.

 

My bad Warrior86, I thought you were changing out everything. You shouldn't have to do anything with just a slip-on. It wouldn't hurt to check you plugs though.

 

warrior86, I installed a Sparks slipon on my Raptor when I first got it and the stock jetting did not work with it so I put the dynojet jet kit in and this cured everything and the bike performed very well for a slipon. I'm not telling you to buy the kit but this was my experience with a slipon and the kit is what fixed mine. You will be real lucky if the stock jetting works because the slipon will flow more air and the bike will need more fuel. You can get the mikuni jets individually and rejet it also but I did like the better throttle responce from the dynojet kit. Good luck, SLIM

 

Jetting Instructions

Good Luck if you choose to do it yourself. It can be a pain, but it's nice to be able to do it yourself.

That's what pushed me into doing my own work.............one to many screwins' [img]i/expressions/face-icon-small-shocked.gif[/img]

 

Rejet it yourself; its pretty simple. It will take a little time but you can do it. Hope things go well. SLIM