Fredette porting with RBD carb?

[KarlP]

A buddy of mine started on a hybrid a while ago. It is a 2002 KX125 frame with 220 KDX motor. He got bogged down with other things, I kept asking how it was going, I finally suggested he bring it over and I'll finish it. He did great work so far and it is coming together nicely.

I have a Ron Black carb and a standard carb. My buddy sent the cylinder and head to Fredette for porting work. It seems to me I recall the RBD carb and Fredette porting not getting along too well together. I did several searches but I'm not finding what I think I remember. Does anyone else have any input?

[scheckaet]

wasn't it the head and porting cylinder that didn't work well together?

[KarlP]

Nothing I have found so far says the RBD carb won't work with Fredette porting.
On the other hand I'm sure Fredette had the standard carb in mind when he developed his porting, and Ron had the OEM porting in mind when he developed his carb.

I'll start with the standard carb and go from there.

[adam728]

There shouldn't be any black magic voodoo in either that won't allow one to play nice with the other.

When I had Fredette port my 220 and cut the head he also bored out the carb to about 35.5 mm. Worked great, so great, that even 6 years after selling it I was offering to buy it back.


Really though, the RB carb changes (aside from bore and divider) really focus on cleaning up the idle circuit. You'd have to go fairly buck-wild with porting to throw that change out the window. Run a different jet size? Maybe. Make enough airflow/pulse tuning changes that carb passage machining needs to be modified? Not likely.

[Julien D]

Yeah I think the RB modded carb will be in improvement in any case.

[Slick_Nick]

I have a ported 220 and RB carb and head. So mint.

[KarlP]

Sounds good, Thanks.