Contents:

Specifications

Why a 2-stroke from the 70's?

When I bought the H1

First run

To do

Improvements

Tuning

Resources


Crank

Kawasaki H1 500

This page tells the story of my motorcycle, a Kawasaki H1b 500 1972, also called a "Triple". The Triples really were the monsters at the drag strip back in the seventies.




Kawasaki Triple

This is how an original H1B looks like, although the color should be more against orange than red.



Specifications:

Engine

  • Engine type: 2-stroke, three cylinder, radial
  • Displacement: 498 cm^3
  • Power: 44 kW (60 hp) / 7500 rpm
  • Torque: 57.4 Nm (5.85 kgm, 42.3 lbf.ft) / 7000 rpm
  • Carburetion: 3 Mikuni VM 28 mm
  • Oil system: Separate oil injection
  • Clutch: Wet
  • Ignition: Contact breaker with separate coils
Engine

Performance

  • Top speed: 196 km/h (122 mph)
  • Standing 1/4 mile: 13.16 s / 156.57 km/h (97.29 mph)

The Kawasaki H1 MACH III 500 was produced from 1969 to 1976. The 1976 model was called KH500. There were a whole line of Kawasaki Triple bikes. The S1 250, S2 350, S3 400, H1 500 and H2 750. The S models were later replaced by KH models, but there was no KH model of the H2.


Why a 2-stroke from the 70's?

I have always been interested in engine construction. Especially the two-stroke engine has fascinated me, because of it's simplicity and power. A two-stroke produces in theory the double amount of power compared to a similar displacement four-stroke engine. Because of modern emission regulations, two-strokes are becoming rare nowadays. Manufacturers have not spent enough money to develope pollution-free injection systems for the two-stroke engine, except for a few that have shown that it is possible.

In the beginning of the 70's the two-strokes ruled on the road. The Kawasaki H1 Mach III 500 was called the first real superbike when it was released in 1969. This bike is still competitive with modern four-stroke bikes, but some modernisations have to be done to make it so. Better suspension and steering, a little better flowing engine, mainly accomplished by fitting modern computer calculated exhaust chambers.

The Triples are still being run in drag racing. The H1 500's bigger variant, the mighty H2 750 2-stroke Triple, has proven to be the quickest two-stroke bike ever built. The fastest H2 has run the 1/4 mile in 7.77 seconds, which makes it outrun over double displacement four-strokes.


When I bought the H1

Kawasaki Triple

The bike when I bought it 1999

This bike was in quite bad condition when I bought it in the summer 1999. For instance, the kick starter was not working and it was welded(!) to the shaft. A lot of original parts were missing. The seat for instance is from the -71 model. The handlebar was cut off and reshaped, welded. The brake master cylinder was leaking. The second gear didn't work! Some parts were broken in the transmission. The chain guard was gone. The rear grab bar was missing and instead replaced with some unkown part. One engine mount in the frame was cracked. The clutch cover has been repaired, there is a little crack in it that is visible. One clutch spring screw mount was broken. The right hand exhaust pipe have seen better days, and the silencers were missing. The engine seems to be restored after some serious breakdown, because the crankcase walls look like someone has thrown in gravel while the engine was running. The center cylinder was replaced with an earlier model that has a bridged intake port. The cylinder heads looked like they had been shot with a shotgun inside. This is a sign of detonation.


First run

After a few years of collecting and also making new parts the bike began to be rideable. The first thing I did was to completely disassemble the engine. The 1st and 2nd gears were quite worn up so they were replaced with a set from a spare engine that I had bought later. The carbs were cleaned up. Every possible seal in the engine was changed. At last, after many visits to the Kawasaki Triples Worldwide Messageboard the bike was examined and registered in 2002.

Kawasaki Triple

The bike in running condition 2003

When I got the bike runnning, I feared nothing and was driving almost 1000 km the first two months. The bike failed only once when a capacitor in the ignition burned. This gave indications that the stock braker ignition, which unfortunately only exists on the 1972 model (1969-71 and 73-76 had CDI ignition), should be replaced by a more modern version. A lot of other things were not good, though. It was obvious that the suspension had to be done something to. The engine did not perform either as expected, quite far from the stock 60 hp. No mean wheelies like all horror stories tell about these bikes. I suspected the crank seals. The crank has to be gone through the incoming winter. The stock exhaust pipes that were missing the mufflers, didn't make the thing any better. I had made some silencers and fitted them, which made the bike a little more quiet.


To do

This is my plan: Fit some bigger carbs, tuned expansion chambers, rebuilt crank and tuned cylinders with reed valves. First target is about 75 hp. Also new shocks have to be fitted, and the front end has to be rebuilt in some way.


Improvements

I have gradually upgraded the bike with new parts. Some of these parts are not mounted yet.

shocks

New 3 cm longer shocks lift the rear and improve steering geometry.

TMX35

New Mikuni TMX35 carburetors:

TMX35

Modified H2 gas wire to fit the TMX carburetors.

Crank

Crank fitted with new main bearings...

Crank

... and new labyrinth seals.

Swingarm

Aluminium swingarm from a Yamaha FZR 400. Weighs only 3.8 kg.

  • Digital Ignition

In the summer 2003 one capacitor gave up and when the bike now and then also fouled a spark plug I decided to upgrade the ignition. I bought a Kawasaki S2 350 stator, rotor and rectifier. I also bought a Boyer Bransden electronic ignition from Hahne-Power. This ignition was a major upgrade to the old points system and has not yet fouled any plug.



Tuning

Under construction...



Resources

Kawasaki Triples Worldwide Resources - everything about Kawasaki Triples