Why is it hard to tune a Mikuni carburetor?

Why is it hard to tune a Mikuni carburetor?

The point of all this, is to show that many “non-carb” related items can make it much harder to tune your carb perfectly. A 125 that is fitted with a new large inlet manifold and a 36mm carb will be very hard to jet properly because the inlet signal from the crankcase has been so badly weakened by the added volume.

What should venturi size be on Mikuni bike?

If you put on too big or too small a carb, your bike is going to run like kaka – if at all. Let’s say your bike is basically stock. You pull off the old carb and determine that the venturi size is 28mm on that carburetor (this can be done by measuring with a caliper).

When did the Mikuni round slide carburetor come out?

Mikuni was founded in Japan in the early 1920s. During the 1930’s they were reproducing carburetors under license by Amal. The new Mikuni round-slide carburetor started hitting US and European shores in the mid 1960’s mounted on two-stroke, Japanese motorcycles.

Are there any Mikuni carbs on a snowmobile?

The very popular, round slide, VM aftermarket series carbs can be found on vintage street bikes, racing motorcycles, snowmobiles as well as experimental aircraft and farm equipment. I mentioned a third group of Mikuni carbs – but they’re not really Mikuni at all. They are cheap, imitation, Mikuni knockoffs.

When to use Mikuni round slide VM carbs?

Often there is no published starting point for tuning as when Mikuni round-slide VM carbs are applied to engines that predate them. Because it’s stupid to re-invent the wheel, you’ll ask someone with a similar conversion for a beginning jetting combination, but the final tuning will be your own responsibility.

The point of all this, is to show that many “non-carb” related items can make it much harder to tune your carb perfectly. A 125 that is fitted with a new large inlet manifold and a 36mm carb will be very hard to jet properly because the inlet signal from the crankcase has been so badly weakened by the added volume.

If you put on too big or too small a carb, your bike is going to run like kaka – if at all. Let’s say your bike is basically stock. You pull off the old carb and determine that the venturi size is 28mm on that carburetor (this can be done by measuring with a caliper).

What should float arms be on Mikuni carburetor?

On most Mikuni stuff, setting the float arms to be parallel to the bowl gasket surface when the carb is inverted is a good starting point. If the level is too high, a tilted-towards-the-engine carb position, plus vibration, will make fuel dribble from the idle holes at the lower, engine-side edge of the slide, making the mixture rich and irregular.

Posted In Q&A