Ok guys, this is what my raptor is doing. After 3 or 4 wide open throttle runs in 5th gear back to back (1/4 mile long) it starts to pop on decel and dies. It does not start to pop immediatley after I let off the throttle, it starts popping about 1/2 way down the rpm/speed range on decel. It seems that once the pipe is getting really hot after a couple of runs is when it starts acting up.

My modifications are a Sparks full exhaust, Prodesign filter kit, air box lid cut 4"x6" square. I am at sea-level running mikuni 160/165 mains, gytr needles 3rd clip from top, and currently running a 25 pilot with screws 2-1/2 & 3 turns out. I have always ran a 27.5 pilot 2-1/2 & 3 turns out. It acts up no matter which pilot I am running, the pilot jet and adjustment has had no effect on my problem. I went to the 25 pilot thinking I was sending to much unburnt fuel through the exhaust with the 27.5. I have an afterfire, not a backfire, and an afterfire through the exhaust can be caused from a rich condition. Other than the dying/popping on decel, it runs perfect. I can hold a steady speed in any gear without any coughs, pops, or burble's, and it pulls great through every gear. I do not have an exhaust leak, I changed the gaskets recently and had the dealer double check for any exhaust leak, and they adjust the valves. My floats are ok, I checked them using the clear tube method. one of them was a little higher than the bowl/carb mating surface, the other was perfect. I can ride wheelies and the floats do not give me any trouble. I have tried everything I know to try to resolve this annoying problem. I have run out of ideas. Anybody have a suggestion? Thanks.

 

mabey do a Right Carb 155 and Left Carb 150

 

Yup...and check your plug after a plug chop..that should tell you if your running to rich...

 

It does not die while I am running full throttle, my mains should not be too rich, I would be afraid to go any leaner. My mains are out of the fuel circuit when it starts to pop and die. I am thinking that maybe I am a tad to lean on the mains, and it is getting the pipe real hot, and that is why the fuel vapors are igniteing in the pipe.

 

I called Curtis Sparks and explained my problem to them. They told me to change my packing in the silencer. They said when the packing gets worn out it starts to act like a sponge and collects any vapors and unburned fuel, which causes it to ignite when it gets hot. They said they have seen them start to pop bad and die when the packing needs to be changed. I hope this fixes it. It is only 20 dollars, so it is worth a try.