Carb Jetting Gods Only!!! Please Help

[trx250rrider]

my quad will run good some days and then some days it won't. when riding, idle to half throttle will run fine, then when I get into half to full, it bogs down, spits and sputters, and blows billows of smoke out of the pipe. top speed will only reach around 50 mph or so when this happens. What is wrong. It know that the main jet controls half to full throttle. I have a 162 in it right now. Stock is i think a 152-155--- something like that for a stock 87' R. Right? Anyways, the only mods i really have on it is a full set of pipes, airbox lid off, k&n air filter, and a rad valve. If I take the main down to stock setting...... maybe a 155, will it solve the problem??? I just don't know why the problem happens intermittently. It will run fine all day and then at the end of the day, the problem will start. Have any of you guys had this problem before???? Other than that, the spark plug is still showing rich. At one time when I bought the quad, it was REALLY REALLY RICH. It had a 168 main in it and I bumped it down to a 162 and I bumped the pilot down too. The carb is clean as hell also, just letting you know. Should I go lower on the main??? Thanks guys for the replies, hope yall can help me out.

[lt250racer]

I do not concider my self a god, but I do believe that you symptoms are due to a rich running engine. I would go down two jets & see where you are, you may have to go lower. You may want to start witgh 1 jet lower, & continue going lower untill your running properly because of the colder weather.

[CR480R]

The reason your problem is intermittent is likely due to changes in the weather and engine temp.... I would get the needle position set before dropping main jets... If you dont you may still have the rich symtoms while being lean enough to cause a siezure....

maybe this will help:

http://www.duncanracing.com/techfaq/...-jetting.phtml

[fulltiltrider]

Originally Posted by CR480R

The reason your problem is intermittent is likely due to changes in the weather and engine temp.... I would get the needle position set before dropping main jets... If you dont you may still have the rich symtoms while being lean enough to cause a siezure....

maybe this will help:

http://www.duncanracing.com/techfaq/...-jetting.phtml

Yes, it is your needle not your main, well it can be your main also. Move the clip up one position and try that out. I would do a plug chop to check your main. Needle controls from 1/4 throttle to 3/4 throttle. main from 3/4 to wot.