i understand that zxr400 has 34mm carbs and my rvf400 has 30mm, instead of installing the nc30 carbs (common mod with 32mm carbs) has anyone tried to install vfr750 (34mm keihin) carbs onto their nc30/nc35?

if so was it sucessful or what was the outcome?

thanks for any input,
Slowsport.

The ZXR400 has 32mm carbs if you have a UK model, some of the JDM L models have 30mm carbs.

The NC24 / NC30 has 32mm carbs.

Think the NC21 might have 30mm's too, not checked.

The 34mm carbs would require bigger inlet rubbers.. I think the inlet port isn't big enough.. can get very good results with standard carbs so I don't think there is a need to install anything bigger than 32mm carbs onto engine.

Even thoug the RVF has 30mm carbs.. they are supposed to flow better with imprvoed velocity stacks.. along with having the T shaped slider which improves throttle response.

What is it your trying to do exactly.. would help with suggestions

Stick with the 35 carbs unless you plan going for big power, in that case its 30 carbs you want. as neo says fitting RC30 carbs will be hassle for little gain if any.

   

Neosophist wrote:What is it your trying to do exactly.. would help with suggestions

I wasn't trying to do anything specific, it was more of a curiosity question of 'level the playing field' as such.

I was more interested in the thought that Honda reduced the carb size to abide to their unofficial restrictions of Japan, and i was thinking what the bike would ride like if they thought f*ck it let's go all out.

Interesting idea, but carb size doesn't maketh the bike. The inlet diameter probably limits any gains from a larger diameter carb. I think the pain in setting it up (making them fit, linkages plus fueling) would probably do your head in. I'd love to see it done though

Ok well you have to bear in mind all of these bikes were originall designed to produce 60hp, albeit the RVF which makes 53 - 55 ish.

'All out' you'd want to look at things like the TT-F3 / HRC version of the 400's that raced in the 400 class. Theres a sticky thread in the general section.

These bikes produced circa 75+ bhp.

There are part manuals etc available.. the HRC parts include things like cams, pistons, ecu, exhaust systems and bigger carb jets / needles.

None of the HRC 400 bikes (to my knowledge) used anything other than standard carbs with bigger jets and needles, which says to me Honda deemed it uncessary.

So I think you'd have to do a lot of work before the size of the carb body would be your limiting factor (if it ever would with this engine)

Even the ZXR SP's / F3 models that use the CR flatslides have same body diameter

thank you for that clarification! that was a very in depth answer and i see i was wrong in thinking the zxr400 was 34mm. i think i may of gotten info mixed from the 250cc carbs

Thanks for all the help,

Neosophist wrote: So I think you'd have to do a lot of work before the size of the carb body would be your limiting factor

I think that sums it up pretty well.

I reckon the nc30's carbs are very big for it's capacity (over-carbed?), partly explains why they don't fuel too well in the lower/midrange (not enough velocity through the large carb).

Makes sense cammo :-)

I think most of the 250's had 28 / 30mm carbs, that i know of.

34's would be massive on a 400!