Its all in the wrist. A quick & cheap improvement for the race Ninja
After having a great time with my FZ1 on the big track during my California Superbike School experience, I more than ever wanted to fix an issue with the Ninja on the track. The FZ has a quick turn throttle. From closed to full open throttle is about a 90° twist of the wrist. The Ninja's throttle has a much greater degree of twist needed to get to full throttle. The faster you get to full throttle, the faster your lap times are going to be. I was perusing the Ninjette forum in search of a solution and this is what I found.
There are many popular brands of sport bikes that have custom go fast parts available on the aftermarket. One of those parts is a quick turn throttle. The throttles have different cam profiles where the throttle cables attach that can change the amount of motion required to get to full throttle. Some even have interchangeable cams so that you can change your setting based on track conditions. The pre-gen Ninja 250's do not get that luxury so it is up to intrepid owners to come up with their own solution. On the Ninjette forum, one method is to use a zip tie glued to the throttle tube to act as a bigger cam. Another way is to swap out the throttle tube for one from a model with a bigger cam. I chose the latter method. I picked up a Motion Pro Yamaha R6 throttle tube, part number TR-061094, from Parts Giant on eBay. It was only $11.94 and no shipping charges. For that price it was worth a try.
Here you see the stock Ninja throttle tube on the left and the new Yamaha R6 throttle tube on the right. You can clearly see the extra plastic on the left hole in this pic. This is what gives the throttle the quicker action. I set about installing the new part eager to see what the differences felt like.
Here I am in the initial disassembly phase. The blue tape is from when I marked full open with the old throttle tube so that I could check to see the amount of reduction in twist needed with the new part. At first I thought I had really found something great. That was until I couldn't get the bike started. More on that later. The reassembly process was easy. The hardest part was getting the grip off the old tube. They are new grips installed when my friend first installed on the bike before I bought it off of him so I didn't want to ruin them.
Here is the finished assembly. Nothing special about this picture other than my cool Woodcraft brake lever guard. After all was said and done I did end up removing the return throttle cable. It was binding and really just isn't needed. I know the theory is that if the pull throttle cable brakes, having the return cable allows you to push shut the throttle. Two problems: 1) there is a great big return spring on the carbs. If the pull throttle cable breaks, this spring will snap the throttle closed immediately. 2) When has a properly maintained throttle cable ever broken? The throttle snaps back which is a requirement for most race organization tech rules. I lubed the pull cable before the final assembly of the whole set up.
I was initially blown away by how much the twisting action was reduced then I tried to start the bike. It wouldn't go. I let it be until the next day, Thanksgiving day. In between kitchen work, I got out to the shop to troubleshoot the problem. I finally realized that, as it was, the throttle was almost halfway open. I hadn't adjusted the cable length the day before after installation. There was no way the bike would start with that much throttle. I adjusted the cable and found that the new tube only reduced the twist by a few degrees or so. It did make it so I could go to full throttle without adjusting my hand position on the grip however and that was what I really wanted all along.
What better way to test out my new quick-ish turn throttle than to avoid Black Friday and go to the kart track? It was a beautiful day for the track and I was eager to take my newly installed parts and run them through their paces. I was also eager to take what I learned at California Superbike School and see if I could improve my lap times around the tight turns of the kart circuit. This trip also gave me a chance to use the new race trailer and test it out as well. The trailer handled flawlessly. It tracked perfectly behind my Honda Pilot. The Pilot didn't even feel the weight of the trailer as I wound my way through the Valley towards Riverside from the Ventura Coast. Loading and unloading went just as I had practiced at home in the driveway. I set up my pits and got to work.
The track was busy. There were two sets of go karts and the arrive-and-race karts in between my bike sessions. I only managed four sessions for the day. Sessions one and two were marred by power loss problems that I diagnosed and fixed. The coil wires to the left coil had become partially disconnected. On the second session, despite my power problems, I did touch a knee down. Boosted my my new found confidence that I was working my body position better and having fixed my power issues, I hit it hard and heavy my last two sessions. I was rewarded by being able to get low and off the side of the bike, touch my knees down and rail through the corners. I was still a bit inconsistent which is my new biggest thing to fix, but man was it awesome to hear the sound of plastic melting away as I Rossi'd my way around the track.
Even though I had to wait an hour between sessions, had power loss issues that really frustrated my second session and my GPS lap timer app crapping out leaving me with almost no lap data, I had a great time and learned a lot. I have to travel for work for two weeks in December which means I will miss out on all of the December big track track days. I will use my time off around Christmas to get back to the kart track and punish my knee pucks some more.
See you on the next lap!
Blue
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