4mm Cub jetting

[Long Rod Todd]

I just finished up assembly of my new cub motor I need a starting place for jetting, mains,pilots and needles. I also need to know what heat range of plugs to run, and what would be a recommended front sprocket with the stock rear and 22'' tires. This is what I got.

 

4mm crank,68mm cub cylinders unported, coolhead 21cc domes, Boss racing intake 35mm pwk carbs,VF3 reeds, Shearer Inframes, timing kit, and lightened flywheel. I'm at sea level. I already have CEL needles and 55-50 pilots on order.

 

Thanks in advance

[locogato11283]

id start with 162 mains, and 48 pilots and work from there. its really common jetting in 33, 35 and 39 mm pwk carbs to run 42 to 48 pilot and 158 to 162 main jets. and yes, use the cel needle..

[theshee]

Your setup is very close to mine. I am running 165 mains at 5280 ft. I may be a little rich. On the gearing I am running a 15t on the front.

[dajogejr]

I just finished up assembly of my new cub motor I need a starting place for jetting, mains,pilots and needles. I also need to know what heat range of plugs to run, and what would be a recommended front sprocket with the stock rear and 22'' tires. This is what I got.

 

4mm crank,68mm cub cylinders unported, coolhead 21cc domes, Boss racing intake 35mm pwk carbs,VF3 reeds, Shearer Inframes, timing kit, and lightened flywheel. I'm at sea level. I already have CEL needles and 55-50 pilots on order.

 

Thanks in advance

 

You have the same setup I did in my cub. I used CELs, mid clip. 48 pilots (still a hair rich) and 150 or 152 mains.

 

And I had a lot more timing than you're running, too!! Run good old BR8ES, gapped .028.

I ran stock gearing on a 21" paddle, 72" rollout, and launched in second.

 

Not to be a smart ass, Todd...but, did you complete the cub package?

Longer swinger, better clutch or lockup, override tranny?

[Long Rod Todd]

Thanks for the input guys. I did the longer swingarm and clutch also a TZ bearing on the PTO side of the crank and had the crank trued and re-welded (FAST Racing). I'll have to do the override tranny this winter.