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Difference between revisions of "Bimota HB2"
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Take the lack of pillion seat as an example. It is not because of an over large petrol tank or a boy racer seat, it is because the perfect motorcycle can only be designed to carry one person and he is already seated as low as possible to keep the centre of gravity down. If bimota wanted a two seater they would have to redesign the whole chassis. The design concept is carried through into production without being modified or compromised by consideration of cost or simplicity. Just look at the naked bones of the two new bikes reveals the awesome truth. Unlike most bike frames which are simple cradles or spines, with bits tacked on to carry the extras, the bimota is a jigsaw puzzle of cross braces, using short tubes in a triangulated pattern with very little bending as such. It is a principle much used in aircraft construction because it avoids stress, which is inherent in long tube runs, which are bent, and then have to be gusseted at the joints for strength. There are hardly any gussets on a bimota frame. All the joints in the chrome moly steel tubes are made to take directional stress end to end along each tube, not only as joints themselves. The tubes may be compressed but they will not twist nor will they flex. The price of this rigid construction is complexity. The KB2 frame for the 550 Kawasaki, for example, has 44 individual tube members from the steering head to the swing arm pivot. This means pains taking welding on a precise jig - a very time consuming job for a craftsman only. Despite its web like appearance, the frame is in fact a cradle. It is just that it cradles the engine from side to side, not to bottom, keeping the height down whilst giving clearance underneath for the exhaust pipe. With the tank and seat removed, the rolling chassis is a virtually mobile workbench, allowing a top end overhaul with ease - something the Japanese tend to forget about. The only thing that is a bind to reach on the KB2 is the gearbox sprocket, which is behind the swing arm pivot. Outrigger forgings house the swing arm bearing directly in line with the countershaft sprocket to give perfect chain tension through swing arm movement. Bimota have done away with this on the HB2 frame for the bigger Honda engine, not so much for maintenance as to keep the overall width to acceptable levels. The Honda has a massive clutch housing on the right hand side of the crankcase, which would require too much hardware to clear. Instead they have gone for a neat alloy casting behind the engine which replaces frame tube members at the base of the cradle. The intricately connecting tubing of both frames forms a straight line between steering head and the swing arm axis, giving maximum rigidity between the two main load bearing pivots. The engine is just shoe horned into the cradle formed by the two spars of the backbone. When it is exposed, the Honda motor is revealed in all it's glory with it's cobby double cam boxes and the threatening open bell mouths of a bank of four 33mm Mikuni slide carburettors. Just stationary in the workshop it is a thing of real beauty, a solid structure of engineering finesse. | Take the lack of pillion seat as an example. It is not because of an over large petrol tank or a boy racer seat, it is because the perfect motorcycle can only be designed to carry one person and he is already seated as low as possible to keep the centre of gravity down. If bimota wanted a two seater they would have to redesign the whole chassis. The design concept is carried through into production without being modified or compromised by consideration of cost or simplicity. Just look at the naked bones of the two new bikes reveals the awesome truth. Unlike most bike frames which are simple cradles or spines, with bits tacked on to carry the extras, the bimota is a jigsaw puzzle of cross braces, using short tubes in a triangulated pattern with very little bending as such. It is a principle much used in aircraft construction because it avoids stress, which is inherent in long tube runs, which are bent, and then have to be gusseted at the joints for strength. There are hardly any gussets on a bimota frame. All the joints in the chrome moly steel tubes are made to take directional stress end to end along each tube, not only as joints themselves. The tubes may be compressed but they will not twist nor will they flex. The price of this rigid construction is complexity. The KB2 frame for the 550 Kawasaki, for example, has 44 individual tube members from the steering head to the swing arm pivot. This means pains taking welding on a precise jig - a very time consuming job for a craftsman only. Despite its web like appearance, the frame is in fact a cradle. It is just that it cradles the engine from side to side, not to bottom, keeping the height down whilst giving clearance underneath for the exhaust pipe. With the tank and seat removed, the rolling chassis is a virtually mobile workbench, allowing a top end overhaul with ease - something the Japanese tend to forget about. The only thing that is a bind to reach on the KB2 is the gearbox sprocket, which is behind the swing arm pivot. Outrigger forgings house the swing arm bearing directly in line with the countershaft sprocket to give perfect chain tension through swing arm movement. Bimota have done away with this on the HB2 frame for the bigger Honda engine, not so much for maintenance as to keep the overall width to acceptable levels. The Honda has a massive clutch housing on the right hand side of the crankcase, which would require too much hardware to clear. Instead they have gone for a neat alloy casting behind the engine which replaces frame tube members at the base of the cradle. The intricately connecting tubing of both frames forms a straight line between steering head and the swing arm axis, giving maximum rigidity between the two main load bearing pivots. The engine is just shoe horned into the cradle formed by the two spars of the backbone. When it is exposed, the Honda motor is revealed in all it's glory with it's cobby double cam boxes and the threatening open bell mouths of a bank of four 33mm Mikuni slide carburettors. Just stationary in the workshop it is a thing of real beauty, a solid structure of engineering finesse. | ||
The HB2 chassis is obviously higher and wider to cope with the larger powerhouse beneath and inside it, but other than that there are a similar number of components. The rear suspension system is a particular bimota innovation. The Japanese first introduced rising rate systems on production Motor cross bikes two years ago. Bimota introduced one that works in 1975. It has been moved around in the chassis quite a bit because of the variety of frames, but the essential single De Carbon unit arrangement is retained. It is compressed at both ends, being mounted nearly upright, with an aluminium rocker arm levered by pushrods mounted on rose joints above it. The set-up gives an exceptionally high leverage ratio of 8:1 (rear wheel movement to damper rod action) which gives precise control; but makes it particularly difficult to set the shock correctly for rider weight and riding style. A small adjustment of the shock translates into a much bigger alteration in wheel travel. A continuous thread sets preload, and a click stop knob gives both ten compression and rebound damping settings. Such great leverage imposes much higher stress on the frame than conventional twin shocks. Therefore it is doubly important that the chassis is integrated with the system instead of just having it bolted on the back for reasons of fashion. The essential difference between Bimota's system and that used on some large Japanese sportsters is that Bimota's woks better the j=harder it is pushed. That is the way Bimota's are designed and that is the way they work. The majority of modern super bikes have a high centre of gravity, long travel suspension and an excess of power. The combination, while technically impressive, is potentially highly unstable in inexperienced hands and often barely manageable even in experienced ones. The sobering thing about riding a bimota is that it has achieved such a perfect balance of those forces. You have to learn to ride all over again - or more to the point, un learn a lot of the instinctive reactions bred by relatively poor handling machines. There are other, lighter machines with less horses that can approach a similar standard, but bimota have harnessed the giant Japanese power houses and made them work in a motorcycle. It is a development that has historical validity with a sounder basis than the sketchy memories of those who just seem to remember that bikes did handle better in the good old days. They did, but not through any particular ancient wisdom - the simple fact was that they generally less power and weight to cope with compared to nowadays. | The HB2 chassis is obviously higher and wider to cope with the larger powerhouse beneath and inside it, but other than that there are a similar number of components. The rear suspension system is a particular bimota innovation. The Japanese first introduced rising rate systems on production Motor cross bikes two years ago. Bimota introduced one that works in 1975. It has been moved around in the chassis quite a bit because of the variety of frames, but the essential single De Carbon unit arrangement is retained. It is compressed at both ends, being mounted nearly upright, with an aluminium [[rocker arm]] levered by pushrods mounted on rose joints above it. The set-up gives an exceptionally high leverage ratio of 8:1 (rear wheel movement to damper rod action) which gives precise control; but makes it particularly difficult to set the shock correctly for rider weight and riding style. A small adjustment of the shock translates into a much bigger alteration in wheel travel. A continuous thread sets preload, and a click stop knob gives both ten compression and rebound damping settings. Such great leverage imposes much higher stress on the frame than conventional twin shocks. Therefore it is doubly important that the chassis is integrated with the system instead of just having it bolted on the back for reasons of fashion. The essential difference between Bimota's system and that used on some large Japanese sportsters is that Bimota's woks better the j=harder it is pushed. That is the way Bimota's are designed and that is the way they work. The majority of modern super bikes have a high centre of gravity, long travel suspension and an excess of power. The combination, while technically impressive, is potentially highly unstable in inexperienced hands and often barely manageable even in experienced ones. The sobering thing about riding a bimota is that it has achieved such a perfect balance of those forces. You have to learn to ride all over again - or more to the point, un learn a lot of the instinctive reactions bred by relatively poor handling machines. There are other, lighter machines with less horses that can approach a similar standard, but bimota have harnessed the giant Japanese power houses and made them work in a motorcycle. It is a development that has historical validity with a sounder basis than the sketchy memories of those who just seem to remember that bikes did handle better in the good old days. They did, but not through any particular ancient wisdom - the simple fact was that they generally less power and weight to cope with compared to nowadays. | ||
It is almost indecent to comment on what it is like riding a bimota, revealing secrets shared by so few. It is harder still to put the experience into adequate words, so often misused by the bland description of other mere motorcycles. How do you compare them? By how much do they steer better? handle better? brake better? There is no suitable graph on which to plot the relative performance; other than to say that all comparisons are irrelevant. On a scale from 1 to 10 the Bimota's come in at around 15. The only reasonable contrast is between the tow models. I rode the Kawasaki first, some time back, and it felt big and strange. You just cannot sit on a bimota and cruise around on it. You are forced to conform to it, squeezing your legs onto the footrests, backside into the seat and dislocating your shoulder blades to reach the handlebars. This is called assuming the riding position. Once there, very little else you do seems to make a lot of difference to the bike. It knows it has got you where it wants. Now it is in control. You think you have a hold of the throttle, you think you are using the brakes properly, but the bikes just sat there chuckling away underneath you because it knows it is not even trying. Like the GPz550 engine, which is its heart, it thrives on revs. The KB2's motor has a 600 conversion, although it is not noticeably more powerful, probably because of the slightly higher overall gearing to make use of the bikes aerodynamics, in fact if anything it is underpowered, due to the excess of handling performance. Once you are into the feel of the thing, you find you can use all of its rpm because the chassis can cope. In comparison, the Honda feels like a monster. Once your limbs and tendons have been stretched and contorted by the KB2, they are ready to be further extended by the additional bulk of the HB2. It feels big; it is big, the weight being evident in slow speed manoeuvring. After the KB2, it takes a bit of getting used to. Actually on the road, and at speed, those extra pounds are a help in some circumstances as they press the bike more firmly on the tarmac. The KB2 may start to skip on some bumps under acceleration - the HB2 just thunders over them. Its additional power, of course, is equally dramatic. Although the conversion will accept standard carbs and airbox, our test bike had Mikuni racing units and open bell mouths, creating a gorgeous burbling beneath the tank. They do not like having the throttles yanked open, so swapping from the fast revving Kawasaki model needs little bit more finesse, but once under load it surges like a stream train. It is outrageously fast in a straight line, but the thing that takes longer to appreciate is that it is extremely rapid through turns. All turns not just long sweeping ones, you can apply the power smoothly, though tight fiddlely turns where a smaller bike may have an edge. What bimota have done is made a 900 handle like a 500. | It is almost indecent to comment on what it is like riding a bimota, revealing secrets shared by so few. It is harder still to put the experience into adequate words, so often misused by the bland description of other mere motorcycles. How do you compare them? By how much do they steer better? handle better? brake better? There is no suitable graph on which to plot the relative performance; other than to say that all comparisons are irrelevant. On a scale from 1 to 10 the Bimota's come in at around 15. The only reasonable contrast is between the tow models. I rode the Kawasaki first, some time back, and it felt big and strange. You just cannot sit on a bimota and cruise around on it. You are forced to conform to it, squeezing your legs onto the footrests, backside into the seat and dislocating your shoulder blades to reach the handlebars. This is called assuming the riding position. Once there, very little else you do seems to make a lot of difference to the bike. It knows it has got you where it wants. Now it is in control. You think you have a hold of the throttle, you think you are using the brakes properly, but the bikes just sat there chuckling away underneath you because it knows it is not even trying. Like the GPz550 engine, which is its heart, it thrives on revs. The KB2's motor has a 600 conversion, although it is not noticeably more powerful, probably because of the slightly higher overall gearing to make use of the bikes aerodynamics, in fact if anything it is underpowered, due to the excess of handling performance. Once you are into the feel of the thing, you find you can use all of its rpm because the chassis can cope. In comparison, the Honda feels like a monster. Once your limbs and tendons have been stretched and contorted by the KB2, they are ready to be further extended by the additional bulk of the HB2. It feels big; it is big, the weight being evident in slow speed manoeuvring. After the KB2, it takes a bit of getting used to. Actually on the road, and at speed, those extra pounds are a help in some circumstances as they press the bike more firmly on the tarmac. The KB2 may start to skip on some bumps under acceleration - the HB2 just thunders over them. Its additional power, of course, is equally dramatic. Although the conversion will accept standard carbs and airbox, our test bike had Mikuni racing units and open bell mouths, creating a gorgeous burbling beneath the tank. They do not like having the throttles yanked open, so swapping from the fast revving Kawasaki model needs little bit more finesse, but once under load it surges like a stream train. It is outrageously fast in a straight line, but the thing that takes longer to appreciate is that it is extremely rapid through turns. All turns not just long sweeping ones, you can apply the power smoothly, though tight fiddlely turns where a smaller bike may have an edge. What bimota have done is made a 900 handle like a 500. | ||