Kawasaki KR500 – Classic Motobikes – Bike Reviews | Motorcycles catalog with specifications, pictures, ratings, reviews and discusssions

Kawasaki KR500 – Classic Motobikes – Bike Reviews

19 Mar 2015 | Author: | Comments Off on Kawasaki KR500 – Classic Motobikes – Bike Reviews
Kawasaki Square Four 2 Stroke Prototype

Kawasaki KR500

Kawasaki has had a fleeting romance with premier class of GP racing over the last thirty odd years or so, first of all during the early seventies with Dave Simmons and Ginger Malloy on the air-cooled, roadster based triples and then with a full on radical design for a short period during the turn of the eighties before returning in more recent times with a four stroke Moto GP machine. Only the roadster-based racer to date has been ultimately successful with the Malloy chasing Agostini and the MV home for second overall in the 1970 championship and the late Dave Simmond’s winning the 1971 Spanish GP, so far the best result in a 500/Moto GP race by latter day Kawasaki is third place.

That first triples along with the modern day Kawasaki racers were and are quite conventional when compared to the rest of the opposition while the bike in the middle stood no such comparison against any machinery of the day or indeed since. The KR500 featured a monocoque aluminium chassis and a completely new design of engine based upon the same thinking behind the all-conquering square four disc valve RG500 Suzuki.

We say all conquering of course but this isn’t strictly true, as “King” Kenny Roberts on the ancient Yamaha inline four had quite convincingly won the 500cc class for the three previous seasons. Although the Yam wasn’t such an advanced design it would appear that the nut holding the handlebars was sufficient to take the title for the tuning fork brand. A very similar thought could be aimed at the KR500 because on paper at least the square four machine is so very nearly there performance wise and the imaginings could well be if only they had sat a top jockey upon it, it may just have won something.

The trouble with those thoughts is it did have several “top jocks” sat firmly upon the lengthy lime green machine including four times 250 and 350 world champion Kork Ballington, antipodean superstar Greg Hansford and future multiple world champ Eddie Lawson, all had a punt around on it and still never got to the very top step of a GP podium. Ballington did make it into the first three at GP level on several occasions, also nabbing the UK domestic 1982 Shell 500 trophy as well as finishing second in the open class against stiff opposition from the Haslam’s and the like of this world.

What’s it like?

Sat in the pit lane warming this twenty three year old machine up before the off amongst a whole host of open megaphone and rasping race bikes, the KR felt very crisp and responsive to throttle inputs. From the moment we took to the track the Kawasaki was “rev happy” and willing to hoist its skirt up and get on with it.

Braking into Redgate for the first time felt absolutely spot on and as the session went on this sensation got better and better and is perhaps one of the finest machines ever in this area. The chassis stays flat and stable, never trying to stand on its nose like so many other race bikes of the period, this is directly attributable to the mechanical anti dive that uses the caliper action upon the disc to lock up the front end and prevent it from diving into oblivion. This pays dividends a few yards later on when the gas is applied as the chassis is not out of shape and struggling to rebound, it just sits square as the brakes are let off and the rear refuses to squat into the all too common potential high side.

The result is a confident application of power all the way to max revs quite quickly. Acceleration is brisk and business like with the engine pulling very strongly above the 7 k mark and maintains a good hefty pull to 11 and above. If anything the engine is as good if not slightly better than the opposition certainly once a bit of momentum is gained within the workings although low down it does lack grunt compared to the benchmark RG500 of the time.

Several laps into the test and things were starting to get more race like in pace and the KR still behaved impeccably although Coppice corner began to be one long, but predictable, tail slide as the lengthy chassis struggled to keep up with the speed of cornering.

Technically speaking

Chassis wise the 1980/81 spec Kwak, being a true monocoque, construction that sees the tank formed as part of the aluminium chassis, is like few others from the period or since. The thinking behind this is to keep the weight down for a low centre of gravity and the frontal area small for high-speed aerodynamic effectiveness. The bike is so slim and aerodynamically effective that the front mudguard has to be formed into a duct at the rear to force air into the huge radiator.

We now know that a low centre of gravity is not necessarily a good thing for high speed as a bike has to lean further for any given corner speed although the advanced streamlining is a very good idea. Originally the one piece ally frame was attached to the front of the engine via down tubes running from the headstock but early tests proved these to be the cause of a severe vibration so bad that the clip-on’s had to be rubber mounted which in turn gave a squidgey feel to the steering.

Kork’s brother Dozy was also the chief mechanic on the project and he elected to run the first bikes with these down tubes loosely attached instead of firmly bolted and that all but cured the vibes. As can be seen here the later variants did away with the tubes altogether.

The suspension is pretty radical too with the mechanical anti dive operating via the brake calipers torque reaction to the discs and the rear “rocker arm” suspensions soft, compliant approach to damping. Almost all of the rear suspension travel can be used up just sitting on the bike but in use this absorbs all of the track bumps and hollows effectively giving a sure footed ride particularly around the recently resurfaced Donington circuit.

Kork’s take on it

We took the opportunity to ask Kork about his experiences with the KR500, catching up with him at his home in Brisbane where he now runs a successful fasteners business.

The bore and stroke was about the only similarity between the KR500 and KR250. I think the emphasis of the factory was stability and strength, we could have hung a V8 in that Chassis! The KR500 was at least 100mm longer than the Yamahas and Suzuki’s of the day so it did feel incredibly stable but was more suited to touring rather than racing.

The 3 cylinder Hondas that appeared around ’82 were possibly a bit shorter still than the Yams and Suzys. Their years of experience in GP resulted in wheelbases that were more appropriate for racing. Kawasaki’s inexperience in 500 racing led them to develop a bike around the requirements of their test riders who were doing the bulk of their riding on the bumpy 5.5 km banked oval test track near the town of Yatabe called J.A.R.I. (Japanese Automobile Research Institute).

This is why the KR500 is exactly as you describe it. It was very stable on very fast corners and very difficult to change direction on, the approach to Maclean’s a good example.

It was terrible in chicanes and no settings would get it through them effectively. The only solution would have been to shorten and lighten it, which the factory steadfastly refused to do. Unfortunately in GP’s chicanes were becoming prolific and fast corners were disappearing.

I had no problems in that dept. Gregg never complained, however he never did too much racing on it due to injury. Eddie Lawson raced one in the states without success. I would love to get his view. I know they stopped racing the ’82 model because, as written by USA Journalist Dean Adams: “Kawasaki packed up and pulled the KR500 out of the class halfway through the season after Eddie Lawson hurt himself trying to keep up” (with Mamola and Roberts.)

It was awesome on brakes and was the only real area where I was at an advantage against the others.

I think they did develop the bodywork in a tunnel so it was probably as efficient as you could get a 500cc machine.

The ’81 KR500 was never as fast as the Yam or Suzy, particularly accelerating from slower corners, so it was difficult to beat them to the corners in the first place! No traction at the rear once the tyre was hot made it extremely difficult to keep up let alone stay ahead.

If a long wheelbase such as the KR500′s created faster cornering speed then all factories would have made their bikes as long. Shorter, well-balanced GP 500s have just as high a cornering speed. Short wheelbase bikes are less harsh on the rear tyre, grip like crazy and tend to have a more violent breakaway whereas long bikes get to a limit and drift lazily (causing unwanted extra heat in the rear tyre) limiting what you can do but do not have a higher cornering speed than the short bikes.

Long bikes might be a bit easier to ride in fast corners but not faster under GP racing conditions. Short bikes achieve the same corner speed with slightly less lean than longer bikes. Hardly a problem when touring but it makes a difference at the limit particularly with rear tyre profiles designed around the short bikes.

I learnt to ride around the bikes faults where possible but the biggest problem we had was one nobody could do anything about and was by far the most frustrating and debilitating thing imaginable. When ridden hard heavy bikes heat up the rear tyre more than light bikes and long bikes heat up the rear tyre more than short bikes. A heavy long bike heats the rear tyre up quickly and effectively to the point where it has no useful grip to be able to race competitively.

Pete Ingley (Dunlop’s chief technician) and I proved that the rear tyre was getting way hotter than was considered acceptable by taking the tyre temperatures out on the circuit after laps and comparing them with a shorter bike. Front: reasonable. Rear: too effing hot!

Dunlop had developed their slicks over many years around feedback mainly from the lighter shorter Suzuki. They were not prepared to go to the expense of building a stronger construction slick and experiment with compounds for one very heavy bike so we were stuck with a tyre clearly not suitable.

The rear tyre used to cook within laps and for the rest of the race I would be nursing it home. On a few occasions I finished within metres of podium positions but was unable to challenge because the bike was already sideways everywhere.

If my memory is to be trusted the bike weighed in at around 40lbs more than a works Suzy, Yam or Honda. Although of ally, the monocoque weighed a lot more than a good steel tube or twin spar ally frame. It and a lot of the chassis parts were too robust and It all added up. The mechanical anti-dive was probably a couple of kg more than a hydraulic setup. Original mag cases were substituted for ally ones which weighed more.

The ’82 bike came out even heavier!!

Kawasaki Square Four 2 Stroke Prototype

One thing I must say is that the motor was always in the ballpark. In 1981 a little short of grunt but by late 1982 with a major ignition upgrade, possibly the most powerful 500 on the circuit. Had Kawasaki gone for a conventional chassis with appropriate weight and geometry it would have done itself proud.

It is really not easy to explain or convince people of the strange, often counter productive way in which they approached the “development” of a GP bike. We often took one small, meaningful step forward in our quest to get the thing competitive only to get shunted 2 huge steps back by some strange decision from far away!

Basically the engineers did not share our opinions therefore did not see things such as the long wheelbase or weight as a big a problem as we did. They had little or no understanding of what was needed to get through chicanes possibly because of lack of experience and meaningful feedback from the test riders. They had no experience of the tyres getting cooked testing in Japan.

I am not even sure if it was ever raced there.

Once they had decided to use monocoque construction it was against their policy and character to deviate. That was no real problem because I think it had huge potential. The chassis would have succeeded beyond their wildest dreams if they had made it small and light.

In my opinion the chassis designer, Cowboy Hiramatsu, simply would not take heed of what we (Dozy, Stuart Shenton and myself) needed to improve performance.

Case in point: At the end of 1981 Cowboy told me his design for 1982 would only fit a 16 inch front tyre because he wanted the smallest possible frontal area. I was horrified and got him and the Chief tech for Dunlop together to stress that they were not going to develop the 16 inch any further and that 17 inch was the way to go. Amongst a long list of requirements was the fact that the 1982 bike must be able to use 17 and 18 inch front wheels.


Was it such a good idea to gain .1 sec on the straight because of a few sq. mm less frontal area then lose .1 sec on every corner on a dodgy front tyre!!

I can only assume that Cowboy’s design was too far-gone to change and have ready in time for the first GP of ’82. There is a good chance that he might not have changed it even if he had the desire and manpower because he had decided that the bike should have the smallest possible frontal area for aerodynamic purposes.

There was no problem with the 1981 spec monocoque except weight and dimensions. My recommendation to them was to shrink the chassis to as near the weight and dimensions of the Suzuki as they could get it. We had it handling very well as you have experienced but to stop cooking the rear tyre and do better lap times consistently it was going to need to be lighter and shorter.

The major design change for ’82 came about because the engineers believed the ’81 chassis was too rigid, an opinion I did not share. They redesigned the ’82 chassis to allow some flex. This deviation from monocoque to an aluminium “spine” style meant the chassis could no longer hold enough fuel so a large heavy tank was added!

1981 Kawasaki KR500 Specification

Engine . water cooled four cylinder two stroke disc valve induction

Bore Stroke . 54mm x 54mm

Carburetion . 4 x 34mm Mikuni round slide

Transmission . six speed, dry clutch

Chassis . aluminium monocoque

Wheels . front 300 x 16” Dymag (18” used sometimes). rear 400 x 18” Dymag

Kawasaki Square Four 2 Stroke Prototype

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