As of late, the Vgas Carburetion system has been the topic of conversation in various chat rooms, message boards, etc. Although a lot of what is said about Vgas system is factual, there are a lot of myths about the system as compared to the stock system. Therefore, we are writing this article to clear some of the common misconceptions about our system.

First off, a 35 mm CV stock carburetor cannot physically flow more than a 39mm flatslide carburetor. That is the whole design concept of the flatslide carburetor. Any time a CV carburetor is under throttle you have a slide AND a butterfly valve (slide is vacuum controlled),(butterfly is attached to your throttle cable via a throttle shaft) that is also in the venturi or air stream of the carburetor. The flat slide only has a slide in the air stream.

Less turbulence, cleaner air we call it. It will atomize the fuel with the air better. Any fuel that is not mixed with air has no energy and is wasted. The higher the particle volume, the bigger the bang you will get. Once you are at full throttle the only thing left in the air stream is the needle, which is introducing the fuel to the air.

The CV on the other hand still has a throttle plate hanging in the airflow area. As a matter of this fact, this is why the engineers at Yamaha created the V-boost system.

When the bike was created in 1985, Yamaha had designed a beautiful four valve cylinder head. With the cross-sectional areas available by the introduction of two 30.5 mm intake valves they had found that just past the 6000 rpm range the intake system and 35 mm carburetors limited the flow of the cylinder head.

We have compared dyno runs of the Max with the V-boost opening normally at 6K and keeping the V-boost closed. The horsepower and torque will fall off to the tune of 9-10 with the boost closed.

The 35mm Mikuni was the largest available for their application at the time so they found an alternative. By sharing the intake to the cylinders front to rear, and now two 35mm carbs introducing air to the intake, the horsepower would continue to climb to the tune of an average of 110 rwhp.

Conversely, the 39mm flatslides will independently allow a clean volume of air to even more so enhance the flow of the head. If you look at the dyno charts CLOSELY, you will see that the flatslides really shine in the midrange, even more so than the peaks. For all practical purposes, we spend very little time at shift point. Most of our riding is done in the midranges.

The flatslide on my bike makes 125 hp @ 7K, the CV only makes 115 hp. Not to mention, having peak torque of 92 is a beautiful thing to have as well. Any roadracing bikes today which are not fuel injected are flatslide bikes........why ?........they mix fuel and air better than a CV.

Thanks for taking the time to read this article. Hopefully, you found value in our findings. Jon Cornell