75 GPX Jetting

[techman]

I am converting my GPX 433 from the stock Keihin butterflies to 36mm Mikuni slides.
I am not sure where to start re the main jet size.
Any ideas?

 

[YAMMIEGOD3:16]

i would start with a 340 main for 36 MM 3:16 (yammie tony)

 

[techman]

Thanks for the information.

 

[yammy]

I am converting my GPX 433 from the stock Keihin butterflies to 36mm Mikuni slides.
I am not sure where to start re the main jet size.
Any ideas?

I have those carbs with the jetting we used to run ....let me go look for em and ill get back with ya.

 

[yammy]

well the main jets I found that we ran were 410's, I also have a set of 310's that I found along with them so ..not really sure, but they might have been for the old 340 trail twister!

 

[Yamaha Nutz]

for 36 mm set up start out with std thunder jet jetting as 36mm carbs came stock on them
2.5c/a
30 pilot air screw 1 turn
6dh3 needle in 3 clip position
q-8 tube
and main jet well 260 was stock for the thunder jet but I would bet 310 mains is what you will need depending on Relative Air Density

I have not run my gpx drag sled in the winter yet since I switched from 38 mm to 36mm carbs but my 433 oval sled with 36mm carbs runs between 290 and 340 mains with filters ......

 

[techman]

Thanks for the replies.