Technical Information

First, a little bit of science. The question is often asked, "What are the advantages of a single carburetor conversion"? The first, and most obvious answer is being able to access your carburetor for tuning or repair. Every adjustment of the TM40 is accessible without removing. Change main jets, move the needle clip, adjust the pilot mix, all with the carburetor in place. And if it does need to be removed, it takes about five minutes instead of twenty five. The second, and less obvious answer, has to do with the physics of having an intake vs none. Runners and plenum create a resonant volume that affects the amount of air going into the engine via something called intake charging. A vibrating wave in the intake has highs and lows, and if the valve opens during a high, you get a little bit of extra air into the engine. The frequency is related to the RPM, and there will be a primary resonant frequency and several harmonics. A carburetor bolted straight to the head has a very small resonant volume, and can only produce intake charging at high frequencies/rpms. It is well-known in automotive engineering that a larger plenum and longer runners produces more low-end torque. Dyno tests show that single carbureted Viragos produce more torque at lower rpm. This means better throttle response, snappy acceleration, and roll-on power in any gear.

Installation notes:

I recommend removing the AIS or MCV and eliminating all vacuum lines except one to either the petcock or boost sensor, depending on your bike. The intakes come with o-rings now, so installation is very easy. Avoid over-tightening the bolts, but be aware they can handle 65 inch-lbs without issue. The aluminum intakes are flexible, you can safely tighten them until the flanges touch without fear of cracking or failure. If you are getting a complete kit, the vacuum port on the TM40 is on the right, toward the back, with a black cap on it. The three hoses are vents, tie them down out of the way. The white knob is idle, adjust that before messing with any other adjustments. Please read through the Mikuni manual for more information on tuning the carburetor. 

Additional Mikuni notes: The XV1000-1100 requires a 2.0 needle and seat unless the fuel pump has been deleted. This needle and seat is metal to metal contact, and the slightest bit of dirt will cause the float needle to leak and the carburetor to overflow. A clean tank and fresh filter are essential. Also, please remember that all motorcycles prior to 1986 have single cables, and you need dual cables to safely operate a TM40.

Note: Installation of these kits requires some mechanical ability. Some tuning is required. If you do not feel comfortable working on the bike yourself, please consider enlisting the help of a qualified mechanic. I make every attempt to support my customers, but please make an effort to understand what you're doing. I have a lot of work to keep up with and my time is valuable. Thank you.