421 cub jetting (pilot)

[Oregon dunner]

Hi guys.

I am wondering on pilot size with porting. Is it common to go up in pilot size when you get a aggressive dune/drag port on a cub cylinder. Whats the best way to determine the pilot jet? how may turns is to much or not enough? My current setup is a 4mill 421, 35pwk, 52 pilot, 155 main and I think the needle is 3 clip and I am running + 4 timing I am at sea level on the Oregon coast running HJR porting

[252wheelieking]

Hi guys.

I am wondering on pilot size with porting. Is it common to go up in pilot size when you get a aggressive dune/drag port on a cub cylinder. Whats the best way to determine the pilot jet? how may turns is to much or not enough? My current setup is a 4mill 421, 35pwk, 52 pilot, 155 main and I think the needle is 3 clip and I am running + 4 timing I am at sea level on the Oregon coast running HJR porting

 

Come on guys help him out here....I'm interested in the answers to this.....

[Hilarious]

Hi guys.

I am wondering on pilot size with porting. Is it common to go up in pilot size when you get a aggressive dune/drag port on a cub cylinder. Whats the best way to determine the pilot jet? how may turns is to much or not enough? My current setup is a 4mill 421, 35pwk, 52 pilot, 155 main and I think the needle is 3 clip and I am running + 4 timing I am at sea level on the Oregon coast running HJR porting

 

Your main sounds small. Might want to up it if you are running long distances or in real deep sand.

I have the same pilot as you, i think 1.5 turns out on the air screws. Mine is a little rich though.

Sync your carbs and set your idle and you can fine tune your airscrews from there.

I would say you get to 3/4 ~ 1/2 turn out, go to the next size up.

Past 2.5 turns out, go the next size down.

[Hilarious]

You should notice an increase or decrease in rpm at idle while adjusting your airscrews.

If not, you may have trash in your pilot jet or the wrong size. Good luck....

[locogato11283]

I'd say your main is too small and your pilot is too big. I'd try a 50 pilot and 162 main.

[Oregon dunner]

Thanks guys. I dropped my pilots back down to 50 and I went up to a 160 main and 1.5 turns out. I will see what happens when I head back out to the dunes.

[vulvafan537240]

Your main sounds small. Might want to up it if you are running long distances or in real deep sand.

I have the same pilot as you, i think 1.5 turns out on the air screws. Mine is a little rich though.

Sync your carbs and set your idle and you can fine tune your airscrews from there.

I would say you get to 3/4 ~ 1/2 turn out, go to the next size up.

Past 2.5 turns out, go the next size down.

 

what size mains do you run?

[Hilarious]

what size mains do you run?

 

I used a 175 in my drag bike when it was on gas.

Im also using a 175 in this new motor I just built and it seems to like it as well.

[Sweet1]

Im at a 50 pilot, 160 main, non ported 421 cub. it may be tad rich, on the oregon coast. ever come to coosbay? pics of your bike so i know when i see it?

[Oregon dunner]

Im at a 50 pilot, 160 main, non ported 421 cub. it may be tad rich, on the oregon coast. ever come to coosbay? pics of your bike so i know when i see it?

I come to the coast all the time. I usually ride my CRF 450. When I get tired of the that I head to the steep tree shots or Idiot holes right next to the water. This is what my banshee currently looks like. Soon to have white plastic with some paint.

[Sweet1]

thats funny, mines all blue plastic, candy blue frame...... i like blue have you run it with the 155 main? just curious.

[Oregon dunner]

thats funny, mines all blue plastic, candy blue frame...... i like blue have you run it with the 155 main? just curious.

 

I have ran it at the drags with a 155 main. Seems to run fine.