I have a 2001 Yamaha Raptor, I have modified it with a Big Gun Race Header and Exhaust, I have removed the Air box and I am running 2 K&N Airfilters off the carbs. I have jetted the carbs according to what Big Gun recommends for this type of setup. Its been awhile, but I believe I am running a 170 and a 175 main jet, I cant seem to recall off hand the pilot jet size.

My bike seems to backfire right as I shutdown the motor. I adjusted my valves and it still would backfire. Could this problem be an indication of something other than the valves being too tight?

Another problem I experience is occasionally during abrupt stops or hard landings my bike stalls. I asked my Yamaha dealer about this and they say that they have never heard of this type of problem with any Raptors.

In the past I have had my carbs blow off the intakes, what setups would anyone recommend to secure the carbs so that you dont have to worry about this happening again.

 

First off, your pilot screws need to be turned out about 1/8 turn each. That will usually stop the backfire issue. Make sure that your headpipes are not leaking as this could also cause a backfire issue.

On the stalling during a jump landing, you can thank the CV carbs for that issue. The slides drop and cause a fuel/air condition problem. Fix it by spending $750 on a pair of FCR carbs (Sparks seems to have a good deal on them if they are actually in stock).

 

What size K&Ns do you have? I ordered some that don't fit just right.
720 is right about the screws. Mine was doing the same thing and after a little adjustment it stopped.

 

Although I don't recommend it for most people, I run two 3x8" K&N filters without an airbox.

 

I solved my carbs blowing off by 1. Turning the idle screws out 3 turns from the seat. 2. Replacing the clamps with the narrow style radiator clamps used on import cars. 3. As a back up, I used a long nylon tie strap around the center of the carbs and to the head.

 

I will take a picture of my air filter intake setup for my Raptor when I get home and then put a link to it.

Running a "no airbox" setup on the Raptor is difficult because unlike the Banshee,the carbs are very close in proximity to each other. This means, that the body of the filter would have to be the same size of the opening of the filter. To get around this I used the velocity tubes that already run from the intake to the air box and then mounted K&N Air Filters onto them.

Like I said I will add a link tomorrow of this setup for others to view.

 

This is the same setup I used. I tried to get them on the carbs with angled necks but it didn't work for me. I ran out of time, as I have a ride trip planned this weekend at LA Dunes. I just stuck the old Pro Design back in there.

720 are yours right on the carbs, if so are the necks angled and are they tappered or round filters? I know thats a bunch of questions but I haven't found much help on this and I believe this would be the best setup for me. Also will my stock raptor engine flow that much air?

 

Pictures of my Raptors air filter set up w/ out AIRBOX