Just wodering if you pros can take the guess-work out of the re-jetting on my carb. The service manual says the main jets are # 138 for the front and # 142 for the rear. When I go to re-jet, do I keep the same difference? Hence, 142-138= 4. So if my front main is to be 142, would I have to get a 146 main for the rear? Or does it really matter. The book doesn't say whether or not it makes a difference. All help is appreciated

 

Yes, you should keep the same difference, since your motor is running cooler on the front cyl - meaning more densed air/fuel charge is entering into the front cyl. This is also true on many inline-4 cyl bikes - outer cyls having leaner main jets. That's why there are different main jet sizes for different cyls. However, the best bet is to read the plugs after some hard running (3/4 throttle for 5 minutes) to fine-tune the jet size.