Gsxr750 carbs on b12

[wraith]

Do the gsxr750 flatslid carbs off a slabside work on a b12?

[Ben Slabby]

Yeah, got em on a B12 motor. Bored to 33mm they're OK but a bit breathless at the top end. 

[bluedog59]

Is that with a stock motor ?

[Ben Slabby]

Bog stock, just a 4-2-1 pipe. 

[bluedog59]

Strange, I would have thought you'd have got a good few BHP on the top with them, certainly better than stock or stock carbs with dual K+N's and the correct jetting.

[wraith]

Just asking as there was a cheep set on that site  but I think I will stick with the gsxr 38mm carbs.

Nice to know, thanks  

Edited October 27, 2018 by wraith
Add a bit

[Gixer1460]

10 hours ago, bluedog59 said:

Strange, I would have thought you'd have got a good few BHP on the top with them, certainly better than stock or stock carbs with dual K+N's and the correct jetting.

Why would smaller carbs (bored out to 33mm) be better than the std. 36mm bore carbs - the fella said they were breathless, guess why! Good for a 750 not an 1100/1200 with big lungs!

[nopokewithoutsmoke]

I thought that slide carbs generally flow more air than CV's of the same size. So a 33mm slide carb could flow as much air as a 36mm CV. Is that wrong?

[Gixer1460]

The modded 33mm slide carbs have nearly 20% less airflow area - the CV throttle butterfly doesn't get near that as an obstruction hence flow less even though unobstructed - now if it was a 36mm flat slide against the CV - no contest!

[bluedog59]

Interesting. It just shows how much CV and airbox design has come on. 

[nlovien]

i,ve aye presumed the reasoning behind a CV carb typically being +/- 3mm larger in throat to a direct lift is because the slide is fluttering - not being held open - it will initially lift to full open when you whack open the butterflies, then it finds a position relative to the engine draw - not necessarily full open even if the butterflies are

always wanted to see if there is a way to convert a CV to direct lift - to see if you can take away this characteristic and benefit from the bigger throat - probably remain in the bin box of like to do versus ever getting around to it

[Gixer1460]

Got to compare apples with apples! A 33mm anything is never going to match a 36mm anything for N/A airflow - simple physics!

Why would anyone bother converting a CV to direct lift when a) it doesn't have an accelerator pump circuit to stop it falling on its arse when the handle is yanked and b) a comparable direct lift carb is available in sizes 34mm - 55mm!

[bluedog59]

On 10/25/2018 at 10:02 PM, Ben Slabby said:

Yeah, got em on a B12 motor. Bored to 33mm they're OK but a bit breathless at the top end. 

Are they at least as good as stock up to the top end ? 

4/2/1 pipe , filters/airbox ? what were the setups please ? 

[Ben Slabby]

GSXR thou K-series stock titanium pipes, Danmoto can and linkpipe. Ramair dual foam filters with silicone pipe reducers to form an intake tract. 

Can't remember the jetting, from memory they're either 122.5 or 125 mains, I'll look when I take em off again. 

They're good,  nice and crisp most of the way up the rev range but struggle when you work them really hard. If that's a failing of the accelerator pumps or the jetting, I've not sussed out, but there's enough snap to spin the rear out of corners, so that'll do. 

If I get chance, I'll dyno it to satisfy your curiosity.