Kawasaki KX125 by Bernie Summers

( How to win an Australian championship in only 26 years !!!!! )

In 1976 ex “Continental Circus” rider & Wollongong Yamaha dealer Kevin Cass built a KX125 based Kawasaki road racer for the late Dave Burgess to ride in that year’s Australian Road Race Championship. Dave finished the year 2nd in the Championship to fellow Wollongong rider Geoff Simm (Yamaha TA125). Coincidently Dave & Geoff also recorded the only motorcycle dead heat at Bathurst that same year!

The KX was chosen as a race contender to the recently released TA125, Yamaha production racer. Due to its more controllable intake port rotary disk valve 2 stroke motor, Kevin figured more horsepower and consequently a better race package could be achieved from the Kawasaki. Methanol was chosen as the fuel of choice for the KX as for most 2 strokes in those days (banned in 1978). Methanol allowed the 2 strokes to run cooler than petrol fuelled motors thus extending their durability considerably.

Kevin’s KX changed hands after the ’76 season, initially to Fraser Stronach, the following year to Trevor Liversidge, then to myself in 1980.

At that stage I was working as National Ad Manager for REVS Motorcycle News, debatably, Australia’s leading fortnightly motorcycle sporting magazine. My road racing interests were enhanced by the relationship with the magazine & sponsorship by its parent publishing company, enabling me to have one of the better “privateer” sponsorship packages for a Yamaha TZ250 Australian Road Race Championship contender. My best showing was a 3rd in the Australian 250 Road Race Championships in ’83. That same year I was 5th (3rd in class) on a VF750 Honda in the Castrol 6 Hour Race at Amaroo Park, primarily due to the

efforts of Rob Scolyer, a late conscripted co-rider after intended team rider Kevin Magee fractured a leg in a fall from his TZ350.

Despite the tuning efforts of renown 2 stroke tuner Garry Treadwell & Trevor Liversidge (now in his 2 stroke exhaust system manufacturing business), having to run on petrol put an end to the competiveness of the air cooled bike. A few rides on the Kawasaki during this time showed its lingering potential but not quite any longer at a Championship level. I moved to Queensland in 1986 to the Company’s new Qld office but this move ended the REVS’s sponsorship.

I ran the KX a couple of times after the move to Queensland. Garry Treadwell had by this time had it running 2 carburetors; the rotary disk controlled one & a reed valve carb on the rear of the cylinder. It had heaps of grunt around Amaroo Park but I found it a bit of a bitch to tune the 2 odd sized carbs on the longer & faster Lakeside circuit. I was about to try 2 same size carbies but gave up after I seized it at Lakeside in 1987. Shortly after that I retired from road racing activities and the KX lay dormant for nearly 20 years.

In 2005 I was lending a hand to Bernie Hatton’s Top Rider training school at Darlington Park. “Hatto” had leant me a VFR400 for the school activities & suggested I should ride it in his Superbike Lite race series at Darlington Park, later at Carnell Park (Stanthorpe) & Morgan Park (Warwick). I had a ball & the racing bug had bitten again. The SuperBike Lite rules changed the following year to allow further modification to the 400s. I couldn’t see the point of spending money on Bernie Hatton’s bike & decided I would restore the KX & have a go at historic racing.

Initially with the help of Rob White, a motorcycle nut & machinist friend, we got the bike log booked. Trevor Liversidge had by then also moved to Brisbane & leant a hand in the restoration. Another mate Rex Dell (RD250 & 350 racer) & I headed off to the 2006 Historic Champs in Mt Gambier. A clutch problem was resolved in practice & the racing resulted in a 2nd place in the Australian Period 5, “Forgotten Era” 125 Championship. I was beaten by a much faster water-cooled Honda RS125 production racer ridden by Trevor Lusby from Sydney & 3rd place went to Les Rowe on a water-cooled TZ125. Les should have beaten me it was only that I was fitter & had more stamina that I managed to hold him off; his bike was also faster than mine. Racing over the next year further illustrated that we were never going to beat a good rider on good water-cooled bikes on our air cooled bike at least not without the use of the prohibited methanol.

There was an attempt primarily by the Period 5 sidecar contingent to get the historic rules changed to allow methanol – it was defeated. Trevor Liversidge & I decided we would have to water-cool the Kawasaki. Kevin Cass had tried it in 1977, when he made a brief come back at Bathurst, by grafting on a cylinder & barrel from the 4 cylinder Suzuki RG500 (Barry Sheene style) race bike. Kevin’s bike showed a lot of potential too but was never developed any further.

After a hunt around on eBay & through various historic racing contacts, I was eventually pointed in the direction of Ray Berry, Sydney based owner of the, now Malcolm Campbell ridden, RG500. Ray had some spare barrels he sold to me in Sept 2008. We first ran the bike at the AMCN Phillip Island Classic in Jan 2009. It went quite fast but vibration of the motor resulted in many component failures at Phillip Island, later at the Easter Barry Sheene Memorial meeting at Eastern Creek & then at September 08’s Aust. Historic Championships

at Oran Park. Trevor had been working hard on solving the vibration problems by changing the crankshaft balance factor. We tried the generally recommended 60% then later as low as 49% & other set ups in between – it still broke things. Finally we decided to isolate the vibes. Trevor made up some engine mounts using initially polyurethane then later rubber bushes. That fixed it! We now had a bike that would run in consecutive races without falling apart.

Trevor had also been developing the RG cylindered engine. Initially he made up removable head inserts so we could make relatively easy changes to compression ratio & squish clearances/combustion chamber shapes. He constructed & we tried several different chamber designs to suit the various head designs. Sealing of the water cooled barrel & heads had also initially been a problem. We were running longer “Hot Rods” than standard KX set up with a spacer under the barrels to get the port timing without major timing changes to the standard RG porting. This had meant shaving the top of the barrels & consequent elimination the RG’s sealing o-rings. Initially we were trying to seal the the parts with Loctite 518 but this made life difficult for the frequent engine rebuilds. Eventually I tracked down a friend who had access to a CNC mill at work – he organized new o-ring grooves. We have rarely had a sealing problem since.

Period 5 rules allow any modifications that are “externally visually indistinguishable” from bikes of the era. This allows any internal modifications of engine & suspension components & for programmable ignitions to be used. At the Barry Sheene Festival at Eastern Creek in 2009 Garry Treadwell turned up in the pits. I hadn’t seen him for about 10 years or more. He offered to “have a look at” the cylinder porting. I sent him a barrel a couple of weeks later. Garry did his tricks to the cylinder & recommended I send the barrel to England for a ceramic composite coating of the bore rather than the usual local “Nikasil” treatment. I was reluctant at first to send my cylinder to England but eventually gave in to Garry’s logic, after all he had devoted his time & efforts to the cylinder work and had offered to lend me an “old model” Vortex programmable ignition the least I could do was to follow through with his recommend ations. The cylinder treatment cost about $500 by the time it got to England & back but has proven so far to be worth every cent. The barrel has done the 2009 Australian Championship meeting & practice sessions at the 2010 Phillip Island Classic. I won the Australian Championship & had a gearbox put me out of action at Phillip Island but on dismantling the motor after Phillip Island the cylinder looks almost as good as it did when it went together. There is very little wear & the hone marks are still “sharp”.

The 2009 Championship meeting at Morgan Park was won (almost) relatively easily. The bike performed initially very well. I’d got down to a 1m16.6sec on the Thursday’s ride day but then found the (Kart style air/fuel ratio) Oxygen sensor had broken out of the header pipe of the exhaust. Trevor patched it up that night. I qualified well – 3rd at 1m19.69 – I was happy a front row grid and only 0.5 sec behind the pole sitter Stephen Kairl & 0.35 sec behind 2nd placed Lindsay Mackay. And I knew I was capable of a 1m16sec.

My best lap times were 1m18.034 in Race 1 & 1m17.038 in Race 2.
The 2nd race was won by Lindsay McKay when he pulled a couple of 1m16s from up his sleeve & passed me on the 2nd last lap. I wasn’t too concerned as I knew I’d won the championship as long as I finished 2nd.

The 2010 Australian Historic Championships at Phillip Island will be a different story.

To see all Bernies pics from project start to finish click here.

Many thanks to Rob White & Trevor Liversidge for their endless hours of work. Garry Treadwell for his Vortex ignition & tuning abilities. Serco for Wiseco & Hot Rods, Al’s Bikes N’ Bits, Ron Angel Wholesale for Rock Oil, Ficeda Accessories, John Titman Racing, Cutgrafix & Wiring Looms Australia.