Quick Carb Jet Qeustion

enginemech · August 30th, 2010, 04:24 PM

I don't understand why on my 07 650 the book says to install (stock) main jet #138 on the front & #142 on the rear.
Why the difference? Seems like me they should be the same. Just wandering.

NMKAWIERIDER · August 30th, 2010, 10:29 PM

Quote:

Originally Posted by enginemech

I don't understand why on my 07 650 the book says to install (stock) main jet #138 on the front & #142 on the rear.
Why the difference? Seems like me they should be the same. Just wandering.

Its an effert to do two things. 1. The rear cylinder in any in-line V always runs hotter because of reduced airflow. By richening the mix, it does run cooler. and 2. the shorter exhaust pipe changes the back pressure and scvaging on the rear compaired to the front. It helps that too. Now if you were to but a Muzzy or Big Gun full system, their instructions for rejetting calls for them to be the same because they have made the rear pipe as long as the front. The heat-thing isn't an issue...or at least they don't worry about it. The 750s are the same way.