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Earlystocks 748 carb choice


R1guy

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Going to be running 748oil boiler in my Katana.

Earlystocks rules state I can either use up to 29mm flat slides or up to 36mm cv carbs with this engine/chassis combo.

Obviously 36mm cv carbs are just under 25% larger so what will give more top end power?- for a bike that will be ridden WOT for a large amount of its life, would I be better using vm29ss or a Mikuni 36cv?

Engine is a standard 748 oil boiler and I’ve got a choice of Micron or Yoshi exhaust system .

 

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That could also be true, it's one of those things where what may appear obvious may not actually be correct. Your point about the less "punchy" response of CV's is also important, when you start to make big bhp/ltr an engine will generally become more "peaky" and you may gain a little more bhp with slides but CV's make it more rideable.  Which leads to my question of having both types and swapping according to weather/circuit, you can bet the rule makers have done their sums and concluded there is little or no clear advantage over the season as the pendulum swings between advantage and disadvantage................................ unless you play smart and track that pendulum.

Rule 1 of building a race bike. Read what the rule book says.

Rule 2 of building a race bike. Read what the rule book doesn't say.  

Perhaps, if R1guy is willing, we could rustle up a set of each so he can dyno and track test both options 

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21 hours ago, Gixer1460 said:

Maybe, but if that shaft costs 10% of the area, you are still up 15% BUT airspeed will be lower so giving a less 'punchy' response which is probably why racers like slide carbs? But Suzuki didn't fit 38mm CV's to the Race 750RR's for no reason - just sayin'!

GSXR 750 RR (RK) - CV 40mm.

 

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I assume you're saying that his 29's are bored out to 33 which would hand a "top end" advantage to the 36's however, I think the 29's (unbored) would still retain a lot of their advantage out of slow corners. Swings and roundabouts, just like I said earlier. The only way to sort it is dyno and track test both.

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2 hours ago, Rene EFE said:

@Leblowskiand myself do trackdays together, both with pretty much stock 749's. His is on 29 (33) Flatslides, myself on 36CV's. 

Power on the dyno is roughly the same but coming out of a slower corner, I'm fucking nowhere...

I don’t see my flatslides as a plus i cant just wank the throttle i have to rolllll the throttle on high revs and the bike is unforgiving when in wrong gear 

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2 hours ago, bluedog59 said:

I assume you're saying that his 29's are bored out to 33 which would hand a "top end" advantage to the 36's however, I think the 29's (unbored) would still retain a lot of their advantage out of slow corners. Swings and roundabouts, just like I said earlier. The only way to sort it is dyno and track test both.

My bike has been on the dyno we did 28 runs to get the bike as i wanted.

And yes my 29’s are bored to 33

Powerdelivery probably  makes a big difference compaired to rene’s bike also

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