Flat slide carbs anyone?
 

Does anyone have any info on using flat slide carbs.... I think Mikuni was the brand of choice..... I also heard that these, though may not necessarily give you more power, however the response is way better....

Yes, response is better, but only if you have a very smooth throttle hand. If you whack it open it'll bog hard because the fuel won't catch up with the airflow for several seconds. Great for a race bike and a seasoned racer. Bad for a streetbike. Want more power? Get high comp pistons. It'll be more forgiving on the street.

Keihin actually does the hot setup. Had them on the Ducati, have one on the Duke. Razor sharp throttle response. Lots of backfiring. Rotten gas mileage. I don't believe they're made as big as the stock carbs on the Hawk.

Maybe I'm just cofused, but the honda specs already list flat slide carbs as used on the superhawk.

Kendrick

They are not flat slide.. But not a full round CV design either. Kind of an in-between.. CV deal. FCR's are a great carb, and very much could be used in this app If one wanted to do the custom work of mating a set, working out the linkages issues, fuel issues. I very much doubt it is worth it as far as performance. Throttle response with an FCR is instant, with no lag at all. I've used them on several bikes, including a GSXR and my current toy a DRZ450

The VTR's carbs are indeed flat-slides but of the CV (constant velocity) variety. In essence they have flat slides but have a secondary slide that helps to control airflow (reacts to intake vacuum) so as to overcome the stumbling problems typically encountered in carbureted fours-strokes (when you crack opne the throttle, vacuum drops and so does the aux slide, tehrery keeping intake velocity decently high, once the engine vacuum builds up again, teh slide open allowing the engien to ingest more air).

Also, the unusually large diameter of the carb venturi on the VTR's carbs results in relatively low velocity airflow which makes the carb/engine combo all the more sensitive to hesitation and bogging. (note: non-CV flatslides work very well on two-strokes however). I don't think that replacing the VTR's carbs with non-CV units would be desirable unless you want to deal with all of the bogging issues (you would need a very smooth throttle hand to say the least). Accelerator pumps do help to overcome this bogging to some extent, however (squirt raw fuel into air stream to compensate for loss of vacuum and hence decrease in fuel draw from jets) .

Not sure if this is possible but I know that in some instances (snowmobile carbs) people do machine the venturis to increase the diameter and generate more airflow (perhaps an oval or offset bore would work best as it wouldn't alter the low-end too much but still generate more airflow on top-end)

cheers
Mikstr

Fair enough, Thanks for the clarification.

Hi guys, I don't get on here much any more as I just don't have time nowadays.

The Keihin FCR carbs that are commonly used for the VTR are 41mm, no doubt due to some of the reason listed by you guys. Pretty common mod in Japan. Have a look on Japanese ebay.

Personally I think the throttle rsponse would be too savage.

Keep your eyes on "ozfirestorm.com.au", we have a member who is doing this mod at the moment, and no doubt there will be astory on there when he is done with it.