Yamaha SR400 Modifications

Some time back I mentioned modifying the SR400. After thinking about the possible mods I decided to lose a few pounds instead of making direct changes to the bike. Personal weight loss gave me a lighter bike/rider combination, improved acceleration, improved braking, improved handling, and maybe even top speed. 

Of course I don't ride it hard enough to notice any difference at all. Still, I wondered what gains could be made by modding the bike. Thinking the exhaust could be opened up a bit and the air intake could be opened up a bit to get some performance gains. 

These two mods likely would make the engine run leaner so a fuel mapping modification would also be needed. I don't rev my engines high trying to get the last bit of horsepower from them. Mostly I like the feel of low and mid-range punch. The plan was to use a Power Commander to get control of the mixture first then change the exhaust, then open the air intake.

 I spoke with the good folks at Power Commander and let them know what I planned to do. I learned I could expect a 10 to 15 percent increase in low and midrange punch with the mods I am going to make. Now, know that the SR400 puts about 25 horsepower to the rear wheel and it has a max torque of approximately 20 pound feet. (Depending on where you get your specs) The full 15 percent increase would up the numbers to nearly 29 horsepower and 23 pound feet of torque. 

 The salesman at Power Commander told me Yamaha has the fuel mixture near perfect on the stock bike and there would be very little gain with the PC only, but it would be wise to be able to control mixture as the other mods are made. 

 Those are nice increases and may be worth the several hundred dollars needed to complete them. Not yet sure if I will make the changes but likely I will. Also not sure when I will get around to starting the mods, but do expect to get started in 2026.