First 421 Cub build

[Ieat4strokes]

Just built a 421 cub for my friend, he ran across a great deal and got a complete top end crank head etc. Got it together tonight and fired it up 3rd kick, no leaks, nothing.......... now its a complete dog up top and seems to hit a wall around near the powerband. Now it was a trail bike and he has alot of extras.....its got 34 PJ's with 55 pilot and 160 mains at sea level so im thinking jetting should be close...... hes has T5's and im KNOW that the T5's are holding it back but should it be that much?

 

I have a fast 4mill drag ported with shearers and it will smoke it by 10 bikes or better by 5th gear, i had T5's when i first built mine but it still was faster than this...... should we try to swap pipes out and see if thats what it is?

[Ieat4strokes]

Bump

[beez33]

The t5's aren't holding it back that much. You got problems.

[252wheelieking]

I agree^^^....Jetting on the main should start around 165 IMO. check compession, fuel, timing & air fuel screws....just some things to look at off the top of my head.

[possum]

Just play with the mains. Go up and see what it does.

[EvilBanshee]

Give me your set up? What domes are you running? What fuel? Any porting done?

[vulvafan537240]

im in the middle of a similar build (421 cub, 35 pwk's, shearer inframes on pump gas) and the jetting advice i got was 55 pilot, cel needle middle clip, and 162 main. i have 165, 160 and 155 mains. i hope to fire mine up this weekend.

 

im about 300' asl.

 

maybe this will help you some.

[Nightmare]

i would check the main

[dave5.0]

Where's the timing? Did I miss that?