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help please with jetting a 421


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hey guys i recently got a cub cyl and im gonna run it with 34mm pj i was wondering what the jetting would be like? my elevation is sea level and temp ranges from 73-89F.I will be running my pro circuits(only for a short time until i can get enough cash for inframes) +4timming,boyesen pro reeds,21cc pump gas redline domes and stock airbox with K&N with lid off and upp intake.

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Honestly that's an oddball setup for a 421 cub no one has that set up high rpm cyl, low rpm pipes and carbs that arnt big enouph and you better check your comp numbers a few I have ran with 21cc domes were still in race gas trim . If it were me I'd start 55 pilot 180 main and work from there

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Carl is close. I'll bet with the PC's it'll wind up with about 52-55 pilot and main will probably dial in around 168ish. Set the idle with the choke knob. Run it all the way in (clock wise) and back it out 7-7 1/2 turns. Use paint pen to keep track. What needles do you have, CGL or CEL?

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Carl is close. I'll bet with the PC's it'll wind up with about 52-55 pilot and main will probably dial in around 168ish. Set the idle with the choke knob. Run it all the way in (clock wise) and back it out 7-7 1/2 turns. Use paint pen to keep track. What needles do you have, CGL or CEL?

i still havent bought the carbs im buying them soon,was wondering would the tm36 be good enough since i. cant get pwk35 they are out of my price range.i heard that with the tm u have to change some stuff in the carb to make it work with a banshee is that true?

 

 

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Honestly that's an oddball setup for a 421 cub no one has that set up high rpm cyl, low rpm pipes and carbs that arnt big enouph and you better check your comp numbers a few I have ran with 21cc domes were still in race gas trim . If it were me I'd start 55 pilot 180 main and work from there

im only running these pipes for couple of months b4 changin to inframes

 

 

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I can't imagin 34 pjs being much diffrent then a pwk , I would run stock carbs over pjs till u get the money . 35s would be the smallest i would buy for that motor 39s are optimal. IMO save up do it once do it rite . 35 pwks used are like 250 if u get the rite deal

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Make sure u check your compression before running pump fuel through that motor

i still havent bought domes but redline says 21cc would be fine at sea level my pump fuel is 95oct. What do u think of the tm36?

 

 

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Lol, if you go with. Tm carbs your pretty much on your own for set up advise. Not very many run them. And as far as what I think , it's a few posts up

ya i kinda figured that out since there r no post .If i buy the carbs from a sponsor wouldnt he send them prejetted?

 

 

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