View Full Version : mikuni vm30 help

07-15-2017, 7:53 PM
pretty sure im close on jetting but it seems like a fuel starvation problem. kz400 twin running both carbs through a 1/4 inch fuel line. tank is set up with a 1/4 inch outlet at the rear on each side. is the single line enough or should i use a petcock and fuel filter set up foe each carb?

07-15-2017, 8:01 PM
A single line should work just fine......... Unless it's a drag bike..... And even then it might be just fine...... That's not that big of a motor.....

07-17-2017, 10:07 AM
I've done single VM carbs on the KZ400/440 bikes, but never a dual carb setup. My baseline for the VM30 is: 140 main, 25 pilot, 159 O-4 needle jet, 2.0 air jet, 6F4 needle, and 2.0 TV...same as the one DCC sells "pre-jetted" for the KZ400. Couple things I learned:

1. Use only genuine Mikuni parts. Generic parts had me chasing my tail and normally aren't sized the same.
2. Free flowing intake needs to have the exhaust opened up a little too. I had one that gave symptoms of running lean, but you could smell unburned fuel. Threw on a set of pipes that had been gutted some and I was able to get it tuned and running great.
3. Sintered metal "small engine" type fuel filters can cause fuel starvation issues due to air bubbles. I ended up using the metal screen type used on gravity fed lawn mowers. I've never had a problem with the sintered ones before, but after that instance I just stay away from them.