KDXRIDER.NET

Alright so I have been holding onto this KDX80 engine for the last 10 years I cut it out of a bike to use in an unknown future project, well that project came along and it is a rare 1971 mini Sear riding mower (front engine mounted scaled down)




Now parts are very hard to find, I plan on drag racing this engine and I need to build it up the best I can. Is this the correct factory carb on this engine? MIC?



I would like to put a KX80 carb on it, or possibly a KX100 carb? Would a KX carb have any benefits in performance or just parts availability and reliability? Any mods anyone can think of? I think I will run a an aftermarket coil for a stronger spark, and put a kill switch on the shift linkage so I can shift without throttling back or using the clutch I may even be able to skip 2nd or 3rd gear this way as long as I do not do harm slamming gears (no spark = no load on gear case)

Any flatslide carb is better than those old round slide carbs. Youll see a definite improvement in response.

Thank you, I will have to check the mouth sizes of a KX80 & KX100 carb

As far as parts availability, that Mikuni VM is probably the most common 2-stroke motorcycle carb in history and is still in production and equipped on new bikes leaving the factory, so you're not gonna do better in that regard.

Common does not always mean good though, this day in age it means cheap and universal. I did not realize they were still being made, I looked into KX carbs and from what I can tell the KX80/85/100/125 all used the same carb.

There must be some differences in the carbs, I read a few threads on people using KX carbs on their larger KDX bikes and getting better response.

yup, Cheap, universal, reliable.

Newer-styled carbs are generally more tuneable in the partial throttle ranges. Not sure if that is an issue for drag racing.

I'd think you'd probably want to port the bike for over-rev, and then maybe size the carb accordingly.

food for thought...
the smaller displacement 200 KDX has a larger carburetor than the larger displacement 220 KDX
why?

intended use and desired powerband

so like sarrant said, consider your intended use an desired powerband and carb it accordingly