421 cub jetting

[krauss4]

i just got a 421 cub and i call d and m who built the motor and they told me to start with a 178 main and a 55 piolet with dgh needle so that what i got and the plugs are wet so its obviously rich but it runs pretty good but it doesnt idle what changes should i make. i have 35 mm airstrikers with shears small bores and a clean up port job

[bennieben1]

my 421 has 35 mm keihins, no porting at all and i have 55 pilots and 162 mains. i dont know if this helps you. my bike runs perfect and the plugs are beautiful

[Bansh-eman]

What elevation and temps are you riding at? And hat carbs are you using?

[krauss4]

35mm air strykers pretty much sealevel in ohio will downsizing in main jet size have n e thing to do with idle

[Bansh-eman]

Most of the guys I rode with that had similar mods (including myself when I had similar mods) with 35 PWK's ran 155-158 mains, 50-55 Pilots, CEL Needle middle clip, 2.5 turns air screw. That was riding in SoCal temps from 80-110

[krauss4]

i have dgh needles will this change the way i need to jet

[J-Madd]

i have dgh needles will this change the way i need to jet

 

 

Most likely yes. Diameter, taper and length are all different with those.

[krauss4]

i had it out today and im pretty sure im rich all around bc i think its loading up at idle with a 55 pilot and im not sure but in 6th gear wot its either lean or way rich bc theres no power there with a 178 main and a dgh needle. i was wondering does the needle have n e thing to do with wot

[Bansh-eman]

Why are you trying to run that needle if the majority of others have had success with the jetting already posted?

[wesw]

your running a/s

 

they run different jetting compared to pwk

 

for some reason i think you will be in the 40s for a pilot mid clip or 2nd from top meaning lean clip and like a 145 main.

 

the guy throwing out info are running pwk and they are different than a/s you can do a search on 35 a/s and there was some posts back in the day offering pretty good results.