Super Jet how much does a bigger bore change your tune?

[rossthaboss11]

blew my motor and the sleeves have some damage. a .5 or 1mm bore should get it all cleaned up. will it require new jetting with that small of an overbore or would screw adjustment be enough? screws were 7/8 and 1.5 turns out and the ski was probably on the richer side. also how important is it to get the pistons before boring to have them matched?

 

[ryan]

it wont have an effect. its not that much bigger. i have 2 boats that are running the same setup other then the bore's one is a 701 and the other is a 771. same carb jetting. (blackjack 44's)

 

[rossthaboss11]

damm really? never would have guessed that with a 70cc difference.

 

[SUPERTUNE]

If your running high compression on the limit, a 1mm overbore is a big difference in compression ratio. A little richer setting will be needed.
Keep in mind, aftermarket big carbs handle this situation way better than stock LEAN burn oem carbs!

 

[superjetkev]

and you definatly gotta get your pistons before you bore it....otherwise you wont have anything to measure when you bore.

 

[rossthaboss11]

ok thanks for the advice. it had 170-175 psi compression so nothing crazy. i know the compression will go up with a bigger bore. The carbs are dual taper bored sbn 44's.

 

[SUPERJET-113]

IMO, bore that baby to 83mm. Thats when a 701 really starts to wake up!

 

[Freakrider]

IMO, bore that baby to 83mm. Thats when a 701 really starts to wake up!

Amen ! I got one...735cc