OzVMX Forum

Clubroom => Tech Talk => Topic started by: oldyzman on October 17, 2009, 11:21:38 pm

Title: CR250 1976 convert to mikuni 38mm, Jetting?
Post by: oldyzman on October 17, 2009, 11:21:38 pm

Hello fellow VMXers,
I am considering pitting a 38mm mikuni on the red devil. The thing is, i really need an idea of what carby spec to start off with for dirt track by the way. I really do not have the experience to start from scratch. I cannot even seem to find the keihin standard specs.
My bike.
Standard up pipe through frame
will be running on lowlead 100 shell
still runs old points ign
What i needis the size of:
Main Jet
Needle
Needle Jet
Pilot jet
Air Jet
Cutaway i guess 2.5
Cheers and thanks for any help
Brett

Title: Re: CR250 1976 convert to mikuni 38mm, Jetting?
Post by: jimg1au on October 18, 2009, 12:11:34 am

I pulled a 38mm Mikuni off a well-sorted 74 recently and jotted down the jetting specs. Main 320; pilot 60; Slide 2.5; Jet needle 6DP7 middle groove.

The bike had a DG head, race pipe, and was ported and it ran really well.

And the bike is for for sale with a stock head and with a stock Keihin carb if anybody needs an Elsinore.

Here is what I use and I am in California. My 73 CR250 has a 38mm Mikuni Roundslide. 300 mj, 25p, q-6 nj, 6DH7 #3 N, 2.5 slide.

3rd over on the top end & a circle -F pipe at the time.
some set ups from the honda elsinore forum i asked this question and got these answers but its only a start you need to jet properly,i day at nepean practice would do it
i never rode my new motor much,think it has a 290main.my race bike runs on methanol so it s no help to you