The Kawasaki Rule, Circa 1972

If it can go faster than anything on the road, it is a Kawasaki.

If it is a Kawasaki, it will go fast for about 8,000 miles, and then it will die.

If it is a Kawasaki, you can only go straight, when you come to a turn you must slow down or die.

Who made up these rules? They did…Kawasaki.

In 1969 Kawasaki released the Mach III. It was a 500cc, three cylinders, two-stroke motorcycle that had to be updated with a heavier frame after its debut because the original design was prone to wheelies. Officially, the bike was called the H1. The Mach III was only a prelude to the Mach IV, a 750cc version of the same bike that was known as one of the first superbikes of the ‘70s.

The Mach IV, or H2, had its own flaws over and above that of the Mach III. First off was its steering wobble at high speeds. In 1973 they added two steering dampeners, one hydraulic and one pure friction. I had a ’72 and all the mounting holes were cast into the steering head for the equipment and after I had my first experience at 120 miles per hour of losing complete control I ran out and bought the equipment that was included in the later versions.

Part and parcel to the bike’s inability to maintain control of its steering was its lack of stability when leaning into a turn. Today, motorcycle design teams know all the geometry factors and crank out a significantly predictable product, but back in the early ‘70s, it was all something new to the Japanese. If you go back to the chapter titled “Bullshit,” it was there that I mentioned our discussions that included motorcycle issues of this nature (in other terms of course). It was there that I became informed of the design flaws Kawasaki was burdened with and possible solutions.

So when I was faced with the complete rebuild of my dead Kawasaki, and believe me I had no other thoughts than to rebuild that blown engine based on my roots of resurrecting that Honda twin in Germany, I decided to go all out and make the bike exactly what I wanted. So it is here that I will try to list all the items I had issues with at that time.

The engine

Hindsight is 20:20, right. If I knew then what I know now I would have…

…Put premix oil in my gasoline.

I averaged 8,000 miles on each engine rebuild. Fortunately, it was easy enough to replace a piston and rings. Pop the tank off and pull the heads starting with the outside working towards the middle. This time though I needed to replace the crankshaft, weld up the holes in the case, and rebuild the engine.

I spoke with the local Kawasaki mechanic at the Honda, Yamaha, Kawasaki dealer and Chevron gas station there in Mountain Home at great length about the repairs I needed to do to get my bike back up and running. He recommended a welder who would do the needed repairs to the crankcase so I pulled it all apart and brought to the welding shop and one week later they had my case repaired.

Ordinarily I would have refrained from such a repair to something so critical but in this case I believe the repairs they did with the TIG welder and a slab of copper to back up the repair proved to withstand the test of time. As the welder’s wife explained it to me when I dropped the aluminum case off at their shop, they clamped a thick slab of copper to the backside of the hole in the case as a backup to the repairs to be made. Copper because they could weld right up to it and it would not fuse together. Then they assembled the two halves and torqued the cases together so when they weld they would not warp.

Ah success, they did an excellent job and the rest of the repairs to the engine were expensive as far as parts go but simple as far as labor goes. I spent over $200 for a new crankshaft, because the broken connecting rod was part of the pressed together assembly and rod replacement was not feasible in Idaho. I put a new set of jugs (cylinders), pistons, rings, and a gasket and seal kit to finish the engine’s overhaul.

Since I was going to all the trouble of rebuilding the motor, why not get a set of expansion chambers? This was Jim Stobo’s Idea but I liked it. I chose the black pipes with glass pack silencers and a power range of 6000 RPM and up. Two-stroke engines do not have a camshaft, valves, or lifters. You can’t just replace the cam and get better performance. Instead, two-stroke engines benefit the most from porting the jugs and from the exhaust system. Expansion chambers are the way to do it with the least amount of modifications. Based on the idea that backpressure is timed for the exhaust port in its design of length v diameter of the pipe. When the previous pulse of the exhaust reaches the narrow end of the pipe, it is time for the piston to clear the exhaust port and viola, instant power. For free!

While the engine was being repaired I had to get and perform the modifications I wanted to bring the bike up to my standards.

Suspension

Trick shocks and forks were not available back then. There were no books about suspension tuning of your sport bike. Shocks were made for cars and adapted to motorcycles. Geometry was a high school subject, not a part of motorcycle design. However, I had made it a point to collect magazine articles on everything I owned or rode and the consensus of the “experts who wrote those magazine articles was that the factory swing arm bushings were inferior, also the swing arm was too short for the bike to handle well in turns, and the bike lacked in steering dampers.

All of these design deficits were the reason the bike was only good for going straight, stop light to stop light was the term used back then, and the reason for the tendency for it to wobble at high speeds. Once I was traveling about 120 MPH on one of the isolated roads in southern Idaho when the handlebars became more like a propeller on an airplane. My hands were just a blur as the front tire wobbled back and forth uncontrollably. As I slowed it got worse. Then my training kicked in, I guess I was a little slow on the uptake.

“When you encounter a high-speed wobble, don’t try to control it, your efforts will only make it worse. Instead push on the handlebars, and it will come out of the wobble.”

They told me that if I try to adjust my speed, the wobble would worsen. And it did.

So…

…I opened my hands and pushed on the handlebars.

And…

…The wobble stopped.

I slowed down and pulled over for a cigarette. While I was calming down on the side of the road I realized that I had to do something about that. I ordered the parts from Kawasaki as soon as I got back. 10 days later I had my steering dampers but until then I tried to keep the bike under 120.

Back in Germany, when Calvin sent his Honda CR250M to himself, he had cut the frame with a tubing cutter and when it arrived he machined some pins that would fit inside the tubes he cut, then he welded the pins and frame to reassemble his bike.

Putting it together for myself, I mail-ordered a swing arm bushing kit from a magazine ad that assured the reader that this would replace the factory bushings and eliminate the tendency for the swing arm to become unstable while in turns. I removed the swing arm and had the tubes cut with a large tubing cutter and I hauled all the parts down to a local machine shop to have pins made.

Convincing the machinist was the most difficult part. He was the first of many individuals I needed to convince as I modified my motorcycle, one part at a time. We agreed that the pins he was to make were to add 2 ½” to the length of the swing arm. A local welder made the final installation after the pins were ready.

This also meant I needed to add 5” to the chain, but that was handled after I got the bike back together later.

Stopping Power

In 1974 the idea of disk brakes with holes in the rotors was novel and questionable. The magazine articles stated increased stopping performance, so I wanted it. While the bike was down, I took the rotor to the local machine shop, where I had the pins made and he referred me to a shop in Boise for several reasons.

In Boise, I had a long conversation with the machinist. He was more than reluctant to drill my brake rotor; he really didn’t want the liability of my killing myself. I showed him photographs and magazine articles that stated the enhanced braking merely from drilling the rotors. I had to draw the design on a blueprint, only in white. So I returned with the blueprint and all the specifications I had wanted. I thank my high school drafting teacher for my ability to make that drawing.

One week later I handed over the $20 bill and the machinist explained that he should have charged me $50 because not only was it difficult laying out the design, the rotor was extra hard material and he had to use special drill bits. Whatever, I had my brake rotor and I was elated.

Final Assembly

It took forever to get everything together, pay all the bills, and put everything in its place but when I kicked that bike over with all the stuff I had done I was in heaven.

There is nothing like the sound of a two-stroke motorcycle engine, and Kawasaki had it in threes.

The expansion chambers were the biggest change I made. I could rely on having power under my throttle almost in any gear before. Now I had a different monster between my legs. Now I had nothing below 6,000 RPM. I would have to crank and wait for the speed to bring the revs up to the power band. But when it did, it did!

I had me a wheelie monster now. I had to be careful with the throttle over that 6,000 minimum.

Next, I needed a better seat, a new paint job, clip-on handlebars, rear sets, and if I could find one a fairing.
All of that is to come…