Building a new RWYB 4 cycle need help with some info

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Shampy9

New member
So we have a 3 inch tilly block and a EC carb Evo1 head that’s been ported and all that with a welded intake tube. The guy sent us a Mikuni SuperBN carb for it and it’s apparently a 34.

My question is because I have no clue about this carb.

I’ve read online it’s a jet ski carb and I’m worried that my dad who builds our motors got basically jipped on this carb for this head. Can anyone give any opinion or anything on this because I’m clueless.


And he ordered this stuff from Paul’s karts which I’ve told him multiple times not too but he’s paying for it. I’ve got photos and all that also if anyone needs them to see
 
Not sure who He is but it sounds like there are a lot of hands in the pudding. If youre running RWYB Im thinking that just bolting parts on an engine its going to be a struggle. Somebody with a dyno and tuning abilities will be the only person who can tell you if its what you need.
 
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Shampy9 said:
So we have a 3 inch tilly block and a EC carb Evo1 head that’s been ported and all that with a welded intake tube. The guy sent us a Mikuni SuperBN carb for it and it’s apparently a 34.

My question is because I have no clue about this carb.

I’ve read online it’s a jet ski carb and I’m worried that my dad who builds our motors got basically jipped on this carb for this head. Can anyone give any opinion or anything on this because I’m clueless.


And he ordered this stuff from Paul’s karts which I’ve told him multiple times not too but he’s paying for it. I’ve got photos and all that also if anyone needs them to see
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I have seen some videos of motors Pauls Karts has built and they are violent. But it is gonna cost a fortune buying from him. He makes good stuff is what I hear but just know you will have a bunch of money in this motor.
 
The super BN is a wicked carb. If you’re not comfortable tuning it may not be your cup of tea. It has a high, low speed adjuster and uses pop off pressure like a tilly, a low speed and high speed jet like a slide carb, has a built in fuel pump and was never intended to be used on industrial 4 cycles but guys are making them work well on the insane billet builds like what’s ran at Big O. learn the operation of the carb, where to start when things aren’t right. A lot of good info on the jet ski forums but take it with a grain of salt being that those carbs are made specifically for those engines.
 
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As TwoStroke said, it's not a bad carb. Again, it is a Ski carb that is capable of supplying fuel for an engine in the 300-600cc range. There are quite a few different Super BN's. If they're tuned for the application it doesn't matter what it originally came on. As long as it can supply enough fuel (Which it definitely can.) and it's tuned correctly once assembled it should perform adequately. Assuming it's also going to be used on Methanol, which is another reason guys use these carbs as they're able to supply enough methanol because it's larger original purpose. So I'm sure the guy has got it at a decent starting place, but there are no guarantees in life.
 
Unfortunately, it's in pieces and IDK if I'll ever get it back together since we keep raising the cc limits it kind of puts the 200cc's out to lunch competition wise. If we get a good indoor track I might get it back together.
 
Maximum flow may not be the only factor to consider but If you compare a 38mm SBN carb and a 38mm flat slide Mikuni the flat slide will out flow the SBN because it's secondary venturi is quite a flow restriction.
 
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