Opinions or experience with flatslides in 750 enginesn cc

[Leblowski]

Been building FI bikes for 8 years now and have no experience what so ever with NA engines so i am a bit in the dark.

Here's the case: 

I am building a yoshi rep for racing using a dothead 750 engine and a mix up from a vampire downpipes with open yoshi can and planning to use pipercross filters

The engine stays completely stock 

I really want to use the stock slabby flatslides wich are in good nick

I am worried that using the rather small slabby flatties wil choke the engine and bring down the horsies.

Can anyone tell me if this wil be the case and i need to buy bigger carbs ? Or can i get away with this set up using the slabby flatslides

It would be much appreciated if you can share your thoughts or experiences with me

Thanks in advance

[markfoggy]

You might see more horses on a dyno with bigger carbs, but what I'm often seeing is that a lap-time is delivered by the way that the mid-range works. 

Not such an issue with FI as you can usually get it set right, and cover all the bases for a particular circuit with a bit of work on the lap-top.

It's gonna depend on the circuit, the smaller carb will be easier in a tight track and give you more, if you go somewhere with big open spaces and long straights, you might want something bigger.  IOM, NW200, Paul Ricard, Doha, Indy, you'll see why they sell the bigger bodies for the bike.  This sells carbs as they're the ones reported as used in these places, bigger is always better right.

[Leblowski]

Great info thanks

well not such of a racer yet and hopefullymostly racing in the Netherlands on probably Assen Zolder in Belgium and Offcourse Spa it seems like i can get away with the slabby carbs

 

[Gixer1460]

The std 750 flatslides may be a bit restrictive although plenty of people have bored them out to 33mm to release a bit more airflow but compared to the 38mm CV's fitted to the DOT head models, i'd say they'd come up short. I'd imagine 36mm Flatties would be the best compromise between mid to WOT power on a 750?

[Captain Chaos]

DOT headed Slingy has 36mm carbs, not 38mm.

And I think those 36mm CV's are good on a 750, or 34mm flatslides, not bigger.

[Leblowski]

Found a chap that can bore my slabby flatslides to 33 mm i think this wil do on the standard engine i will use according to the previous given advice.

Plans for the future is to go 884 then i wil probably need bigger carbs.

 

[Ben Slabby]

Got a set of VM's bored to 33mm on a B12 motor. Good bottom end, run out of puff a bit flat out, mind.  Otherwise a very good cheap alternative to pukka 36/38 mikki flatslides. 

[kokolis]

You can easy use the vm,s bored out to 33 them are very good.

People forget that cv,s although stated as lets say 36mm have the butterfly in the way witch actually makes them 2mm smaller

[tabby59]

Larger CVs should be more forgiving anyways. They aren't a bigger carb until the vacuum slide is pulled completely out of the way.

[HDTboy]

My VM29s are bored out to 33 on a mild slabby engine, and it goes well. Need to mess about with jetting for a while, but it's all doable. I'm also from an EFI background. Setting up the carbs will do wonders for your understanding of how fuel mapping works