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Thread: 40s problem

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    Bodger

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    40s problem

    Got a pinto with bvh, rl30 cam running 40s, problem is the carbs spit on part throttle and i'm getting hesitation at about 4grand. Ive got 36mm chokes, 145 mains and 190 air correctors using an f950 idle jet. Ive tried a few different jets but it still does the same thing, tried turning up the fuel pressure and it makes no difference either. they are balanced fine too....so....help...please....

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    Re: 40s problem

    36mm chokes are too big for 40's; are you sure they are 36mm and/or are you sure they are 40's?

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    Re: 40s problem

    Yeah the carbs are 40s, i know they are 36mm chokes because i made them! looks like i've fallen for the 'bigger is better' thing and maybe i need smaller chokes. Sorted the stutter at high rpm...the timing was a bit too advanced. The car goes like stink when flat out but on small throttle opening it spits and is generally unhappy. What choke would you reccommend, 34?

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    Re: 40s problem

    anything bigger than a 32/33 choke in a 40mm carb will just loose power without any top end gain

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    Re: 40s problem

    Thanks, ive just made up some 33mm chokes and gonna use 130mains and 180 correctors, will i need to change the idle jet size? its currently an f950

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    Re: 40s problem

    With 33mm chokes keep the jets as they were (145/190 50F9)

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    Re: 40s problem

    Ok thanks Graham and Minilite, let you know how i get on.

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    Re: 40s problem

    Well ive got it running with 33mm chokes, bottom end its much improved and it doesn't spit but its lost a chunk of top end, i think a trip to the rollers is in order. Minilite you sure 145 mains arent a bit to big? it doesn't seem to rev as well as it did...

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    Re: 40s problem

    what you really need are 45's!

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    Re: 40s problem

    I know I do! but as always its a money issue, still ive adjusted the timing and it goes pretty well, think i'll knock the cam timing back a bit to get more bottom end, feels like it comes on cam as a reach the rev limit at the moment. Still i'm doing well, ive never had it on the rollers and i'm a self taught tuner

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    Re: 40s problem

    Quote Originally Posted by K-J View Post
    Well ive got it running with 33mm chokes, bottom end its much improved and it doesn't spit but its lost a chunk of top end, i think a trip to the rollers is in order. Minilite you sure 145 mains arent a bit to big? it doesn't seem to rev as well as it did...
    145 mains aren't too big for a RL30 with 33mm chokes in my experience.
    Make sure the ignitiontiming is set at 4500-5000 rpm (advance full out) and check that the jets haven't been enlarged.

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    Re: 40s problem

    Ok thanks for your experience, it does run quite nice now i must admit, play with the cam timing and i think theres more in it

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    Re: 40s problem

    Advanced the cam timing and it got power all through the rev range now, nice torque to, much better than the 36mm chokes but not the outright power......45s next then...

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    Re: 40s problem

    Engine was bogging down big time at the top end so ive put 135s in the mains and it picks up properly now. Carbs still spit badly on light throttle, nothing i do will stop it though

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    Re: 40s problem

    That would normally suggest they're out of balance? Have you checked them with a flow meter?

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    Re: 40s problem

    Yeah ive got a carb balancing manometer, sure they are spot on but ill have another look later cheers

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    Re: 40s problem

    Quote Originally Posted by K-J View Post
    . Carbs still spit badly on light throttle, nothing i do will stop it though

    put some bigger idle jets in

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    Re: 40s problem

    The idle screws are turned out quite a lot which suggests needing bigger idles jets Graham, pretty obvious when i think about it! thanks people

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    Re: 40s problem

    After buying a bucket of jets and having idle probs on my tuned 2.0 pinto I ended up with 55 f2 idles. Worked an absolute treat!! Tried them all 45 50 55 f9 f8 f2
    Other innards include 34mm chokes, 135 mains, 175 airs, f16 em tubes. rev limit set at 5500 and pulled to that easily

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