Hi I'm new to this site and kinda working on engines in general. I just bought a 2001 raptor 660 an its backfires a lot when going through the gears or slowing down. So I checked out the air filter and it was clogged with sand so I took it off to clean it and noticed there was sand going up through the air hoses into the carburetor. I'm wondering if cleaning the carb will do the trick or what else I should do or inspect?
WAYNE - you are confusing two different things - each carb has a PILOT JET and a PILOT SCREW (sometimes called 'fuel screw'). The pilot jet controls how much fuel gets to the engine during idle and up to about 1/4 throttle. The pilot jet will have a number (probably 22.5 or close to it) on it. The pilot screw acts like a valve to adjust this fuel from the pilot jet - the jet controls the max flow, the screw just can turn flow down.
The carb also has NEEDLE jets and MAIN jets - the needle jets control fuel flow from about 1/4 to about 3/4 throttle and get moved up and down in their bore (adjusting fuel flow dynamically) by vacuum from in front of the butterfly. Main jets control flow from about 3/4 to full throttle - mains will have numbers somewhere between 140 and 170, if they are typical Mikuni brand.
So with this info in hand, what is your question now, Wayne?
Travis - this is your 3rd post on the same issue - the moderator is gonna get mad at you! :wink
hey so i have a 01 yamaha raptor 660r with a slip on HMF exhaust & i have the jet kit for it i just want to know what jet to use in the carbs and what is the adjustment i need to do so it can run good and everything else is all stock