VM 28's

[Bison]

Folks,
Been reading about fitting Mikuni carbs to the 3 1/2. I'm confused as to which ones?, flat slide, round slide or a different CV type?. My sport is now 402cc, I wondered whether it might be worthwhile fitting 28's?. Where to start with jetting?, anyone done it?.
Thanks,
Alan.

[Steve Brown]

I fitted a pair of VM28 Mikunis to my 350 sport. The carbs are great but I'm not sure it's worth the effort and expense in the end. They are less tolerant of downdraught angle than the Dellortos and in my case it makes them a bit awkward to set up. I found an online Mikuni chart somewhere that specified a maximum downdraught of 17 degrees. The front cylinder seems to have a steeper angle than the rear, and I'm sure that's why my bike needs no choke on the front cylinder to start from cold. It raises the fuel level at the front of the float bowl too high. (ok I haven't yet tried adjusting that down to prove it!) I think it also affects the idle circuit. Idle jets are easily available but not many people keep the starter jets which I want to drop too. The idle is fine and pretty reliable but setting the idle air is a pain as the screws are on the opposite side to the throttle stop screws-i.e. on the inside!
I recently bought a pair of used Dellortos to put back on my bike! I'll probably use the Mikunis elsewhere...seemed like a good idea at the time!

[Bison]

Thanks for the reply, that's very interesting. I had a set of CV carbs from a 600 Divvy which were set up to work at 45 degrees, hhhmmm, I'm sure I still have one laying around, I'll have a look. As you say though, if it doesn't make a huge change then why bother.
Cheers,
Alan.