I have a 01 raptor 660 w/ full exaust, k&n filter and box w/ no lid, high compression piston. I have been attempting get the main jets right. At 3/4 throttle it sounds like it chokes out and dies. I am at 170 on the lean carb and 175 on the rich carb. The plug is still reading lean. Does my jetting seem too high already, or should I continue to go bigger.... maybe other probs besides jetting????

 

if you ride it around at 1/2 throttle or less, then do a plug check, what does it tell you then? the choking out does sound like it is running out of fuel. i would think if it was too much, the plug would show that under low throttle riding.

 

The plug check was done after low rpms. I did order 180 and 185 main jets. I was just wondering if I was chasing something that wasn't the prob. How much is definitly too much 190----200???

 

this is how you check your plug:

Use a fresh plug and clean air filter. This works best in top gear or an upper gear on a slight uphill area. After running the engine at full throttle do the following at the same time: pull in the clutch and stop the engine. DO NOT let the engine idle and DO NOT let the clutch out until the vehicle has come to a stop. Remove the spark plug and examine the color. White is lean and black is rich.

 

also how many turns out are u on the fuel screws? and what position is the clip on the needles?

 

this may also help you:

Pilot Screw - Idle
Pilot Jet - Idle to 1/4 throttle
Needle Jet and Jet needle - 1/4 to 3/4 throttle
Main Jet - 3/4 to full throttle

1) Idle Screw
Allow the engine to reach operating temperature. turn to smooth idle. If unable to obtain smooth idle, go to Step 2, Pilot Screw

2) Pilot Screw
If unable to obtain smooth idle: turn the pilot screw in all the way GENTLY until it bottoms, then turn the pilot screw 1/4 turn at a time until achieving a smooth idle. The pilot screw should be correct between 1- 2.5 turns. If idle is between 1-2.5 turns, the jump to step 4, Main Jet. If idle is NOT smooth between 1-2.5 turns, then jump to step 3, Pilot/ Slow jet.

3) Pilot/Slow Jet
If idle is not smooth with pilot screw between 1-2.5 turns, then the pilot/slow jet needs to be changed. There are 2 choices. either A or B
A - If the pilot screw has been turned more then 2.5 turns to smooth the idle, then install a bigger Pilot.
B - If the pilot screw has been turned less the 1 turn to reach smooth idle, then install a smaller Pilot.

Note! A larger pilot jet will eliminate the popping sound that may occur when letting off the throttle.
A larger will improve cold-weather starts.

4) Main Jet
Start with the richest (largest numbered) main jet and test at full throttle. the engine should "stumble" at wide open throttle (If engine does not stumble, then the engine is not rich enough and a larger main jet should be installed). Once you have a rich "stumble", install the next smaller jet one size at a time until full throttle results in normal operation. Once main jet step is complete, go back to step 2, Pilot Screw, and perform pilot screw adjustments one last time.

Note! If quad runs faster at 3/4 throttle then at Full throttle, then the jets are lean and a larger jet must be installed.

Needle
If carburetor has an adjustable needle, this step CAN be performed. If you have a slight hesitation but NOT a hard stumble between 1/4 -3/4 throttle, then the needle is probably lean. Raise the needle by lowering the clip.

Reading Spark Plugs
Once the main jet is set correctly by dropping a main jet size after the "stumble", confirm the jetting of the engine by reading the spark plug. This works best in top gear in a slight uphill area. After running at full throttle, do the following at the same time: pull in the clutch and stop the engine, DO NOT LET THE ENGINE IDLE! Remove the spark plug amd examine the color. It should be a Light Tan. If it is white, then the engine is running lean and a bigger Main Jet must be installed. If the color is Black, then the engine is running rich and a smaller Main Jet must be installed.