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jetting on my cub


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my oppinion at your altitude i'd start with 55 pilots and 158 mains with clip on needle in middle position airscrew 1 1/2 turns out.just be sure to do a plug check before you ride it much.we're at 3000 ft and i think this should put you close.as you go up in altitude you normally need to go down a bit on your jetting.

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Shouldnt be 78 pilots ! :confused: Give me a call and i will get you fixed up. :cheers:

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Well I guess it is back to the drawing board for me, but can someone explain something to me? When the motor (er, ah engine) is openened up with say a 4 mil cub and v-force reeds, 35 carbs, and pods, why does the jetting go down? Unless I got that backwards but the lower numbers mean smaller jets right? If so, you are pushin' more air through the motor then don't you have to run more fuel through as well. I mean I hear people runnin' 320 and 340 mains on a ported motor with pipes and all the goodies...........

 

I may be way off base here, but can someone clear this up for me. Thanks for the info...... :cheers:

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Well I guess it is back to the drawing board for me, but can someone explain something to me?  When the motor (er, ah engine) is openened up with say a 4 mil cub and v-force reeds, 35 carbs, and pods, why does the jetting go down?  Unless I got that backwards but the lower numbers mean smaller jets right?  If so, you are pushin' more air through the motor then don't you have to run more fuel through as well.  I mean I hear people runnin' 320 and 340 mains on a ported motor with pipes and all the goodies...........

 

I may be way off base here, but can someone clear this up for me.  Thanks for the info...... :cheers:

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for what ever reason cubs dont like fuel down low and in the mid as much compared to stock jugs. dont know if its the extra transfer ports or what. was told the cubs could be more efficient. they do like bigger mains.

 

thats not saying throw a big main and its going to run.

 

 

340/320 are mukuni carbs,

 

140-155 are keikins(spelling)

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I put a 152 main and a 48 pilot to start and it ran a lot botter all the way through and by the way I am sorry for saying it was a 78 pilot it was a 58. Whats the best way to check if I am to rich on the main. Do i run it wide open then shut it down real fast and check the plugs or what?

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hmm

 

its called a plug chop

 

put it in 5th gear hold it wot, then pull the clutch adn kill it, try to stop as quick as possible, if you dont have a pancake bearing it could weld your rod and ball.

 

let it cool for a bit. remove a plug and look it over.

 

white = lean

black = rich

tan/brownish close.

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