JR50 Performance Tune

The JR50 has a washer with a small diameter hole in the middle that goes between the exhaust pipe and exhaust port of the cylinder to reduce flow and slow down the bike.

It looks like this.

You can see the new/altered one I have next to the stock one still in the pipe. It connects here to the cylinder.

As you can see without the washer the port is about 7/8″. With the washer and the stock hole it’s reduced to 15/64″. Without getting too crazy I decided a 1/32″ increase was probably a good place to start.

I ordered a couple of new washers for some variability. On the left is the stock washer at 15/64″. On the right is the one I made at 17/64″. Maybe it doesn’t make a difference? Maybe it does? Either way i hope I cleaned it up enough to not suck in a tiny flake of metal and lock up the piston.

I got it back together and started it. Seemed fine. No idea if it’s better until the girls get on it and give me their “seat-of-the-pants” expert opinion.

Though it was decided today, that there would be no more performance improvements on either bike until they started using the brakes. At least on the Honda they can reach the hand brake (but they don’t). On the Suzuki they’re only real option is the rear (foot pedal) brake (the hand brake is too far from the bar and I can’t adjust it). Their complaint is that they can’t feel the pedal with the boots. My response is get used to it. The boots are made that way for a reason, and you will get used to it. So far both of them mostly rely on letting off the gas to slow down or stop, but that doesn’t really work when you’re going down hill. And though they try to use their feet on the ground to stop (flintstone style), it’s not very effective for an 80 lb bike with a 40 lb kid on it.

As a side note. Working on these little things is a bit of a pain. Ideally you need a table. I had the JR50 propped up nicely until I knocked it over. It left a little dent in the 100, before it hit the throttle squarely on the concrete floor and broke it. Though as I look at this picture, I think a lot of my problem is my garage. It obviously needs some cleaning/organizing.

Regardless, ordered a new throttle ($7 + $6 shipping). It should be here by the weekend, and the rippers will be on their way if they’re not skiing instead.

– b