450r carb jetting question

[bodfper]

Hello I am finishing up a rebuild on my 400ex. Here is my list done to engine:

-P+P head with heavier springs and duncan race cam

-89mm big bore 12.5:1 wiseco piston

-DMC alien full exhaust

-k&n w/ prefilter w/ no lid

What I would like to know is where to start jetting with the 450r carb. I still have to set the carb up for installation just wondering what jets to buy and start with THANKS

[CJM]

52 pilot, start at 185 main and check the plug.

[Wheelie]

48 pilot and 185 main.

[CJM]

Wheelie, how are you getting it to run right with a 48 pilot. When I tried it I got nothing but horrible backfire on deceleration and it wouldnt kick over easily at all.

[Wheelie]

When I was still running gasoline or gasoline/race gas mix, the 48 was spot on. It worked great from sea level to 3000ft. If conditions were just right at the dunes it would pop on decel from time to time, so it was right on the edge. A 50 pilot would make throttle response suffer slightly at the dunes, badly anything over 1000ft.

At the time I was running a 48 pilot, I was alternating between a 195 and 200 main, depending on conditions.


I'm contemplating going with a 65 pilot and a 245 or 250 main jet so I can increase my Ethanol blend. I'm tired of mixing gasoline in with it during the summer months.

[CJM]

Interesting. I just couldnt get it to stop popping with the 48 in there and the 52 is slightly too rich so I went to a 50 but it pops again. I might try a 52 and screw in the f/a screw more.

[Wheelie]

I think the short rod stroker and cam profile might influence some of my tuning 'oddities'.

[CJM]

Originally posted by Wheelie
I think the short rod stroker and cam profile might influence some of my tuning 'oddities'.

I think I agree with you on that, totally not your typical machine at all.

[bodfper]

Thanks alot guys i appreciate all that you guys help with!