10 replies to this topic

[Verbaliser]

Has anyone got any experience of using a single bike carb with a supercharger? Vmax do a twin 38 mikuni kit but it's expensive. Why not just use a single carb? I have been looking at a Mikuni HS40 or HSR42 which are popular upgrades on a Harley davidson. I know nothing about bike carbs- what size i would need, and how easy they are to fit & tune? I have worked out that my setup flows 160cfm at 6,000rpm. Surely even 400cc bikes are flowing this much even more given the high rpm and similar hp. Would I manage with a smaller bike carb?

Not too much info on the web about this.

The hope is- the smaller the carb, the closer it can be mounted to the charger which makes for a shorter intake pipe. I also like the idea of "pumper" bike carbs that mechanically squirt petrol into the throat at low revs to improve pick up - like injection without the faff.

[Wil_h]

160cfm is around 100bhp, so choose a carb off a bike with a similar output., at least that's what i'd do.

[Chris_R]

Most modern, or relatively modern bikes use a carb per cylinder though - I can't think of any single carb'd bikes that get anywhere near 100bhp

[Verbaliser]

I agree, there's the Harley though which is why I looked at the larger mikunis. I can't find anywhere on the web that gives flow rates of bike carbs. I am guessing really- but due to high flow design of modern bike carbs I'm pretty sure one slightly smaller than my hif44 would flow just as much. The mikuni HSR42 flows 213cfm which is ample. On that basis the 40 must be ok.

There is a guy on YouTube with charged 998cc with a single bike carb but can't see which one. So it is possible.

[Verbaliser]

Seldom come up on eBay though and pretty dear to buy new

Edited by Verbaliser, 20 December 2010 - 01:25 PM.

[Verbaliser]

Ok, due to budgetary restraints and the fact got the vizard book for Xmas, I have decided to stick with my HIF44.

Next question, on my 998 charged mini, is there any point improving the flow of my SU by modifying the butterfly, throttle spindle, removing protruding screws - vizard style? You can improve the flow by 30% apparently...Getting close to the flow rate on one of the barrels of a weber 45. Can there be too much flow?

I don't want to waste my time but if there is a noticeable improvement in throttle response then i think it's worth it.

Advice welcomed.

[mini_mad69]

Ok, due to budgetary restraints and the fact got the vizard book for Xmas, I have decided to stick with my HIF44.

Next question, on my 998 charged mini, is there any point improving the flow of my SU by modifying the butterfly, throttle spindle, removing protruding screws - vizard style? You can improve the flow by 30% apparently...Getting close to the flow rate on one of the barrels of a weber 45. Can there be too much flow?

I don't want to waste my time but if there is a noticeable improvement in throttle response then i think it's worth it.

Advice welcomed.

I did those mods on my N/A 1380 and noticed a definate improvment in bottem end power. Made a big difference.

[Gr4h4m]

I run a single 38mm bike carb on my SC setup on my 998. no loss of power over the HIF44 and no more dash pot oil, choke seals or bi-metallic strip. you find most of the jap stuff has modd'd throttle spindle as standard and come with tuned ram pipes. My fuelling has been more stable since I converted so I like it.

[Verbaliser]

Sounds good. What make of carb have u got and which bike is it off? I expect you had to make your own intake manifold to join to S/C. Do u have any pics?

[Gr4h4m]

A bit late, I had a small stub manifold made that had the su 4 bolt pattern and then used some fuel tank hose to connect the carto the car. A filter sock over the standard ram pipe

http://s132.photobuc...;mediafilter=no flash

[Verbaliser]

Cheers Gr4h4m - your carb seems to be quite neat. It would work well with an Eaton set up because of the reduced height.

I'm gonna stick with the HIF44 just because I'm determined to get it working! If I had my time again, I'd use a bike carb. Next mini project maybe.