421cc cub Jetting

[WIKDSVT]

I've done a lot of research and pease tell me if I am close.

 

It's a 421 cub, no additional porting, CPI in frames, 15/44 gearing with 19" tire.

Lockout clutch

 

CEL Needle, middle clip

air screw 2.5 turns out

Pilot - 50-55

Main 155-158

 

I'm in Michigan and ride primary at silve lake dunes - on the coast of lake michigan.

 

am i close with jetting?

[RadarRacing]

Yep I've had near the same setup a couple times. I know you aren't gonna have a 19" dune tire but other than that jetting should be right about right. I ran a 48 pilot and my 421 jetted perfectly on the dyno ended up with a 148 mainjet. I ran around for a long time with a 155 main but picked up 11 hp goin down 3 jet sizes.

[WIKDSVT]

dune tire is a 12 paddle extreme, I think its 22" tall.

 

 

gearing is currently high. I think i'll drop it down to 14/44 gearing for the sand.

 

I rode last night and I thought I was in the top of 6th gear, but was actually top of 5th. (running a 22" tall tire). Just to see where the gearing should be. I had to be going 90mph+ in 5th gear. At least that is what it felt like.

[RadarRacing]

i'm assuming you are running a +10 or 12" swingarm. Thats a bit too high for gearing probably on a gas motor by a bit. Thats fine gearing for an alky motor launching in 2nd gear with 12 extremes. I think 14/43 or 14/44 will get you rolling good out of the hole but you might have to use 1st gear. I have a 421 Cub too with a 10 over and 12 extremes. Vid from 2 weeks ago.

[WIKDSVT]

i'm assuming you are running a +10 or 12" swingarm. Thats a bit too high for gearing probably on a gas motor by a bit. Thats fine gearing for an alky motor launching in 2nd gear with 12 extremes. I think 14/43 or 14/44 will get you rolling good out of the hole but you might have to use 1st gear. I have a 421 Cub too with a 10 over and 12 extremes. Vid from 2 weeks ago.

 

 

Thank you.

 

work has been hectic, I'll be changing the jetting tonight for weekend riding.