The competition said that we didn't even have a dyno, so I bought one from Michael's Reno Yamaha and parked it in my driveway. There! I now had a dyno.

But all of our early jet kits were actually designed by "feel" on the streets of San Anselmo, CA and the roads on the hillsides of Marin and Sonoma counties. It took a couple years to set the dyno up after we moved.

The Hartzell recirculated fluid with a hydraulic pump and to create load, restricted the flow with an adj needle valve and measured how much pressure the bike needed to hold it at a steady rpm. If you take the flow and pressure, you can calculate the horsepower. The limit for the pump was around 90ish true rear wheel hp.

The Hartzell had a digital readout that used analog circuitry to create and display a hp number. As delivered, they read the actual hp delivered to the surface of the drive roller - rather depressing to see "70" and thought you had 100hp! Other dyno companies addressed that issue by bumping up their number.

I semi-crosschecked the hp numbers with our later dynos (which I know read the actual true hp) and guesstimated that the Hartzell hp numbers were pretty close to true hp.

We wore our hydraulic pump out and replaced it with a higher volume pump and then we were able to "just barely" hold a 1986 gsxr1100.  I think we got a pump built for us from a company named Component Technologies.

We eventually stopped using regular hydraulic fluid and changed to a light multigrade synthetic as the hydraulic fluid would oxidize and scored the pump internals.

In one of our rather spectacular dyno failures, the backup pressure gauge broke off at the threaded mount and blisteringly hot hydraulic fluid shot out of a 1/8th" hole at near 3000 psi - oxidizing and instantly filling the dyno room with dense, opaque smoke!

I do remember retapping the load control rod threads to 10x1mm for quicker manual load control.

If I was staying with that concept, I would have added a open / closed "shunt" fluid path to bypass the load valve.

All in all, it was a good, simple, easy to maintain piece of machinery from the good folks in Minnesota.

Then we made our own low inertia eddy current dynos.