Jetting Advice needed : Mikuni VM18ss on a DT50.

[karl1275]

Hi all,

Without wanting to get bogged down in the argument of tuning a 50cc I'm after two nuggets of information, (1)a guesstimate of the main jet /needle + jet to actually make my bike run at over 1/4- 1/3 throttle and (2)a UK supplier who would have the parts...

Basically: DT50M 1980

I have a Mikuni carb supposedly off a DT80, I think it's a Vm18ss -a very rough measurement of the bore suggests it's 18-20mm this is fitted with a yambits big bore kit giving 59-60cc, hytech racing reed, a cone air filter and the restriction to size has been removed from the expansion box to take it to the same diameter as the rear silencer, there was also a crimp put in the rear silencer pipe that effectively halved the diamter of the pipe, this has also been removed.

Starts fine from hot/cold, idles fine, pulls fine from low throttle openings but past about a 1/3 the engine cuts out totally (with an occasional misfire if I coast and hold wide open throttle). I assume it's going super rich, I also assume since it idles and pulls okay from low throttle openings that it's not over carbed.

Any help would be greatly appreciated.

Cheers

Karl.