Way back when in about 1983 I started riding the Yamaha RD series of motorcycles. I was bitten instantly by the performance of these great little bikes and I spent many hours learning how they worked and how to make them even better. By the early 90s I was so serious about this that I decided to go racing with my 350. I had a lot of fun, learned that being a fast guy on the street is not necessarily being a fast guy on the track, and met a guy who would turn into a great friend and racing partner named Pete Furkey.
With Pete riding my bike a season later we had won a USCRA class championship and many races bumped up into the bigger machines classes too. By then people were asking me to help them, so I started to build motors and port cylinders for other racers and street riders. Chris Stein won the class the year we retired , using an engine I built for him. Here I'll go a little further into the details of what I like to do to turn these modest yet fun street bikes from the '70's into real fast race bikes in the '90's.
But first a disclaimer, if you will.... There are many ways and philosophies in regards to tuning any two stroke engine for higher power output. The methods I use work for me, but they are not the only way to get results. I learned what I know from many years of hands-on experience, and reading over and over again anything I could get my hands on about the subject until I felt comfortable with it, and from talking to people whom I think know more about the subject than I do (or did at the time!).
I need to mention Gary Shumake, Kevin Cameron, Dale Alexander through direct discussion and Gordon Jennings and Gordon Blair through their published works as people who have enlightened me when I had reached a supposed dead-end in my thought process. Along with these guys, the pro tuners are people who's efforts I followed just as closely as I did the top level riders of the day.
Guys like Kel Carruthers, Erv Kanemoto, John Lassak, Steve Johnson, Mike Sinclair..the list goes on. I knew that these people, often seen in photos but rarely mentioned, where part of the secret behind the best riders in the world. On the rare occasion when they were interviewed I read every word hoping to glean some small bit of technical revelation from them. These were the guys I wanted to be like. As I said earlier, I tried roadracing myself, but at 6'6" and not especially gifted with a feel for a race bike at the limits I knew I could never be really good at it.
Tuning was something I could do, so I attacked it with that same determination.
In the " old " days, it was take a guess, educated or not, and make a modification and see what happened. Now it's computer and calculator and notebook time before I even touch the porting tool or lathe. I like predictable results. I keep notes on what I did to every cylinder I port, and the feedback I get from the people who ride the bikes. It has paid off. As I mentioned earlier, my stuff has won a lot of races. I must say I've been lucky to work with some really skilled riders, so I cannot take all the credit. But I do get a good feeling when one of my engines comes on the straightaway and just gobbles up the bikes in it's path. That's a bit of good exit speed (the rider!) and a lot of Horsepower at work.
So enough already, here's the stuff, NB. each page can be downloaded in PDF format for your note book.
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 © Geo of K.G.B. of T
& T. 
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