Jap carbs

[Klaus Loske]

Hi,

 

I have heared that some people are now prefering japanese motorcycle carbs like Mikuni or Keihin FCR over Weber DCOE carbs.

They claim better performance and throttle response.

(e.g. www.prirace.com)

 

Has anybody tried the Keihin or Mikuni?

 

Ty

 

Klaus

[Peter Carmichael]

The Jap carbs from bikes are infinitely superior to the Webers which weren't even any good in their heyday.

 

On a different topic, why do throttle bodies cost so much when they are so much simpler than carbs? I know, I know. It is down to economies of scale. I still think that somebody is taking the pee.

[Klaus Loske]

Hi Peter,

 

do you know somebody who has played around with Keihins on a x-flow?

 

Rgds.

 

Klaus

[Morls]

I know someone who's looking for a set to try, (to replace the 40s on a twin cam with the extra complication of no seperate manifold), so would be interested if anyone's done this.

 

I think? that Dave Bogg at East Lutton near Malton in North Yorks has put this idea in Alisdair's head, so he may be the man to speak to.

 

 

 

Mark

[cdg]

For everyday use I would use a set of CV (constant depression) carbs from something like a GSXR1100. These are not so steeply downdraughted as things like Kawasaki ZX7R or Yamaha RI. However it is not a straightforward fitment as you need to alter the carb spacing to siut the X-Flow/Weber manifold, which involves extending the linkages,fuel Tpieces, and bracketry. These are 38mm carbs which is easily a big enough venturi for a X-Flow when wide open.

 

The other option is to go for a set of smooth-bore round or flat slides from Mikuni or Keihin (or Lectron). These bolt on using rubbers/flanges which can utilise the Weber manifold flanges, and are a very easy fitment. Benefits are instant throttle response, and top end power to match F.I throttle bodies, and would be the preferred fitment to a competition car. However they take some getting used to, and you cannot simply floor the accelerator pedal and expect anything to happen as the airflow stalls when suddenly faced with a huge gaping hole (Benoulli's Theorum). Gradual opening of throttle is what's required. Jets and needles are readily available which is good as you'll need to experiment a little. John Wilcox has experience with setting up both cars and bikes on the rolling road, so he could be the man for cars with bike carbs.

 

I have sets of 38mm CVs from both Yamaha and Kawasaki which you can try if you want. They've been sitting on my shelf for a few years, so a nominal sum would secure them if interested.

 

Chris.

 

[san]

Hi,

 

I have a set of Keihins off a CBR1000 FK.

 

Silly cheap to anyone wanting them.

 

Throttle bodies, well set of Busa bodies, 2002 model with 500 miles on them complete with regulator and loom £100+vat.

 

Simon

 

[san]

Oh and the other thing with the CBR1000 engines that the angle of installation is pretty gental, like almost none compared to the ZX9R or Busa, which means they'll be better suited to the xflow type install. Normally connect to head with rubbers.

 

Simon

[Klaus Loske]

Unfortunately, there is not much information provided on the Keihin website... there seems to be the Keihin FCR available in a pure side draught version.

 

I try to get in touch with one of the Spitfire guys to see how the setup works...

 

Rgds.

 

Klaus

[san]

Hi,

 

Look at the CV type carbs from them, fitted to CBR, FireBlades, ZX9Rs etc... cheaper than the flat-slides.

 

Or go for throttle bodies off a blade for £100 with say 100 mile on them?

 

Simon

[cdg]

Klaus,

 

Honda used CV bike style carbs on their Civic range before everything went to Fuel injection. In essence they work on the same principle as SU or Stromberg carbs, but are less bulky. Late eighties early nineties cars I think, and you would need two pairs.(They were used as twin carb installations).

 

Chris.