To jet or not to jet

[darrell43031]

my 350x after 22 years has stated smoking. so now that the top end is apart it has to be bored! so my question is if i go just .20 over am i going to have to re-jet my carb? i'm not doing anything more to it just the next size bore.

[400exrider707]

Perhaps. Its hard to say, every motor is different. Installing a fresh piston and rings will probably send a stronger vacuum pulse to the carb and essentially suck in more fuel in the same amount of time. I would rebuild it, run it as it is, and then go from there.

[darrell43031]

thanks man i appreciate it. and that does make sence.

[bwamos]

I'm assuming you meant 0.020" over, not 0.200"

IMHO just to be safe I'd go up 1 size on the main jet.

It's better to be a tad rich on a fresh rebuild than lean.

[400exrider707]

Originally posted by bwamos
I'm assuming you meant 0.020" over, not 0.200"

IMHO just to be safe I'd go up 1 size on the main jet.

It's better to be a tad rich on a fresh rebuild than lean.

However in theory, there should be a much better "seal" now between the rings and the cylinder wall, thus creating more of a vacuum pulse on the carb, which would already make it more rich than it was before. Like I said, run it and see.