I have a 1995 Scrambler 400 4x4 with mudlites, this year it has been in the shop for a carb. cleaning, and the jets were cleaned, and a oil pump spring and its oil pump has been adjusted. Ok my problem is i'll be riding on the trail and it will all the sudden change noise and quite , it will crank right back up and it may do the same thing in a minute or so or it may not till 30 minutes. the noise that i'm talking about is like it will be doing great, the normal 2 stroke noise "pop pop pop pop pop pop pop pop" but right be for it getting ready to stop the noise goes to brrrrrrrrrrrrrrrrrrrrrrrrrrrrr. it starts to sound like a 4 stroke.i don't know whats going on but i need to find out so i can spend some money of my quad

 

This sounds similar to the problem that I had when my gas vent line got kinked. Try loosening you gas cap and see if it does it then. If it doesn't then trace down you gas tank vent line and see where it is kinked. Hope this helps you!

 

Sounds like you are running out of fuel to me. Take your carb apart and check your float height. Sounds dumb, but I had my Wolverine carb rebuilt and began having problems. Turns out that the float height got moved during the rebuild and was never checked during reassembly. Instead of having an almost full bowl of fuel, it basically had nothing.

 

Thanks Guys i will see about the follow , next time i'm free,i'm always busy, and trying to get back into the great sport of quads

 

ANY OTHER IDEA'S?

 

Yep, check the choke cable adjustment and the oil pump adjustment. Most times when you hear the 4 stroke sound, you are running too rich.

 

I second Cowboy35, my 250 did the same thing when the vent line kinked. I waited til it started to die and then opened the gas cap and sure enough it kept right on runnin'.