Mikuni Round Slide Jetting?

[ccambern]

Anyone have a good starting point for VM30 jetting on a 250? I'm OK dialing it in, but I'd like to come up with something to work from. I've been able to find some decent info on Brit bikes and old Hondas, but haven't come across anything for Ducs.

[DewCatTea-Bob]

" I've been able to find some decent info on Brit bikes and old Hondas, "

____ What-ever spec-figures are given for the 250-BSA or 250-Triumph, ought to be close enough,, however if that size motor is not given by your source, then try the 500-twins or 750-triples which were also made by either of those two Brit-brands.
I'd suggest using the specs given for the later-model 650-BSA twins, cuz I've mounted stock Amal carbs from that model to 250 & 350 DUKEs, with good results (without messing with the jetting).
__ If your source for recommended jetting also gives the jetting-specs required for the early-'70s Honda XL-250,
then they ought to be pretty-much spot-on for a 250 DUKE (if using the same muffler) !
If you indeed find specs intended for those XL250s, then I'd recommend choosing jetting with spec-figures which are close to right-in-between them and those which are given for the BSA-650.
____ As for jet dialing-in of any carb, it's been my experience that unless ya make quite large jumps in jetting-sizes, it's next to impossible (without a dynamometer) to notice any good or bad change ya make (from a near correct starting-point). _ Thus it's all a big waste of time (if you're just guessing at it) !
So the 'dialing-in' work really has no pay-off (unless you're really lucky and also plan to go competition-racing).

____ So how about telling us how you intend to mount your Jap-carb to your DUKE cyl.head?


Ducaddy-Dukes,
-Bob

[ccambern]

Shouldn't be too tough. I plan to weld up a short manifold and then use a piece of coolant hose to mate to the carb.