Sbn 38 carb,on a 420

B

Bobby l

Member
Hi . I want to run a bn 38 carb on a fully built 420 .308 cam 40mm intake valve .what would be a good jet size that would work with this carb .also does anyone have pictures,of there throttle set up on a go kart for this carb
 
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Thanks for the picture .looks like your not using the carb to pump fuel and useing external pump .? Do you need to run them this way ?
 
Bobby l said:
Thanks for the picture .looks like your not using the carb to pump fuel and useing external pump .? Do you need to run them this way ?
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I rather run it this way but you have to remeber when there on a ski there 2 of them and one is pumping for both of them. It may can work solo but rather it not run lean imo
 
Ok got to try kart out today runs pretty good with the sbn but cuts out at wide open adjusted high speed a little then it got worse acting to rich so screwed it in kart would take off again but then break down at like 5800 pulled plug and it looks lean acts like the the pump might not be able to keep up .should I run and external pump also? Or just bypass the internal one all together
 
Yes .didn't help so I believe it's starving for fuel at w/o throttle. So was wondering if the fuel on carb can lift and maintain fuel on it own .thats how it got to the fuel pump .
 
With how easy it is to add apump .I would addone in conjunction with the carb . it should meter the fuel from there .
Your running gasoline not methanol ?
 
Ted Hamilton said:
You can do a pumparound style with the secondary pump to ensure you're not overpressurizing the carby...
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Yes had someone tell me to just run a external pump and block off the one on the carb . But then some Say the one on the carb is more than capable of keeping up with fuel demand on the 420 .was hoping to here from some one that runs the sbn on a gx390 420 platform.
 
flattop1 said:
With how easy it is to add apump .I would addone in conjunction with the carb . it should meter the fuel from there .
Your running gasoline not methanol ?
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Yes.thats correct iam going put one on it this week and block off the one on the carb to see what it does .not sure how to add a pump in front off the one built in the carb without overwhelming the carb pressure
 
I think I would try it first.
The carb has a needle and seat setup too.
Only one way too find out .
The tilly has a internal pump too .
With auxlery pump .
 
The pump around would cure that as well .
The big fuel cap on a tilly is for fuel supply.
Maybe a large diameter fuel line would work or large capacity filter .
 
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