Post by timpa136 on Feb 10, 2013 14:34:48 GMT -5
THE LOW-DOWN ON A ROTARY - BY DANA VAN POOL
After many thousands of miles, and twenty years of service, Marie Bellinger's 1976 RE-5 was beginning to show that wear and tear. Its suspension was showing signs of instability, and handling performance was suffering. Having many spare GS1000 parts, and a fair amount of mechanical foresight, I proposed a total update of the aging RE with GS1000 suspension, front and rear. This, along with a sixteen inch rear wheel, is intended to sharpen up the handling, smooth out the ride, and lower the seat height.
The mechanical goals were:
1. Adapt a GS1000 rear swingarm.
2. Fix GS1000 front forks, triple clamps and steering bearings.
3. Make it a totally bolt-on modification so that it can easily be returned to its original condition.
I have another long-term rotary project going on, so I had a rotary in partial disassembly. That made it easier to take measurements and do some mock-ups to check out the possibilities. I began with the rear end. The GS1000 swingarm is the same width at the pivot as the RE5. The only difference here is in the inner and outer diameters. Both are larger. The GS1000 uses a 14 mm diameter pivot bolt, and the RE5 uses a 12 mm pivot bolt. The larger outside diameter is due to the difference in bearings. The GS1000 uses needle bearings and the RE5 uses nylon bushings which, as we know from the GT750, are not very durable. The other main differences also made for improved ride and handling. The first is that the GS1000 swingarm is longer, increasing the wheelbase, and improving stability. The second is the location of the shock mounts. They are about 10 cm farther back, allowing an increased shock angle, greater leverage on the spring, and a lower seat height. It will also accept a wider tire as found in most 16 inch tires.
To accommodate the difference in pivot bolt diameter, I made a sleeve 14 mm in O.D. and 12 mm in I.D. for each side. To keep the center spacer indexed, I made the sleeves 10 mm longer than the inner bearing race, welded it to the race, and re-heatreated the races. When the races were reinserted, the added length of the sleeve fit into the center spacer and held it in place. The next task was to adapt the GS1000's rear disc brake. I had to mount a hydraulic master cylinder to the frame and attach it to the rear brake pedal. This was accomplished by using two metal compression clamps, mounted to the rear frame spar, and a small custom bracket, and rotating the Rotary's brake rod attaching arm clockwise to reach the actuator rod of the master cylinder. By using a master cylinder with a remote reservoir, I was able to mount the reservoir under the seat next to the oil tank. I simply replaced the 4 inch stock hose with 18 inches of transmission cooler hose. When bolting up the shocks, it was necessary to add additional spaces to the top shock mounts, moving them out to the end of the shoulder of the mount bolt, as the GS1000 swingarm is wider at the shock mount. With the added length of the GS1000 swingarm, a 100 link chain is needed in place of the RE5 96 link chain. Then the rear wheel, with a brake disc from either an GS850, or a GS1000 and GS1000 spacers, and disc caliper mount, completes the rear end conversion. The RE5 chain guard can easily be adapted or a GS1000 chain guard can be used. The same can be said for the shocks. I kept the RE5 shocks to keep the set-up as low to the ground as possible. GS1000 shocks would provide a better ride. (Tim's note: We later put on Gs1000 shocks and custom springs.)
Now on to the front suspension... In order to mount GS1000 forks to the RE5 steering head, I chose to use the triple clamps from a GS850, as they have more offset than GS1000 units. I was unable to find tapered roller bearings to fit both the triple clamps pivot shaft diameter, and the inside diameter of the RE5's steering head. I bought bearings that were very close and had both outer races ground down and the lower inner race ground to fit as well. I had to cut off the steering lock and stop notches from the lower clamp. The crash bar around the radiator became the new stops. Not ideal, but safe, as it turned out to be very close to stock in turning radius, and just as solid in normal use. (Tims' note: We had previously mounted a custom fatter radiator guard.) The RE5 headlight nacell and mounts will fit up to the GS1000 forks with some enlargement of the locating rings. That being so, I removed the RE5 fork tubes from their triple clamps, before removing the triple clamps from the steering head. This left the wiring intact. Then, by installing the GS1000 parts in reverse order, after changing out the bearing races, I saved time and further disassembly. The instrument cluster requires longer bolts and spacers to raise it up to fit into the upper triple clamp. I slid the forks into the triple clamps so that the air caps faced forward and just cleared the handlebars. This lowered the front end to match the changes in the rear. The front brake calipers have to be swapped over to GS1000 units, but the RE5 rotors can be used.
Tims note: DVP meant to say the calipers are stock RE5 and the rotors match the front wheel. I had asked DVP to recap the procedure long after he did the conversion.
Again, the GS1000 axle and spacers are needed, but the RE5 speedo drive can be kept. The RE5 front fender can be used with 3/8" spacers between the fender and the forks. A GS1000 front fender can be used, but radiator clearance is a problem. The fender must be lowered by drilling new mounting holes in it. They should be 3/4" above the original holes, center to center. If using GS1000 shocks and a 17 inch rear wheel, the forks should be set at standard height, and the fender modification should not be necessary. Bolt it all together with proper fork alignment procedures and there you have it ! An RE5 that rides and handles more like a 1978 GS1000. Stability and comfort were significantly improved. With all the changes, the result was about a 3 inch reduction in seat height. Overall, a very satisfactory conversion. All of the weaknesses were improved, the worn parts replaced, and the ride height lowered with a dramatic improvement in handling and comfort. I realize from a purists standpoint, a project like this is somewhat sacrilegious. But, as I mentioned at the beginning, it can be returned to its original condition, as no permanent modifications were made to the RE5 itself. I like to think of it as an RE5E, as Suzuki might have made it.
DVP - March 1996
After many thousands of miles, and twenty years of service, Marie Bellinger's 1976 RE-5 was beginning to show that wear and tear. Its suspension was showing signs of instability, and handling performance was suffering. Having many spare GS1000 parts, and a fair amount of mechanical foresight, I proposed a total update of the aging RE with GS1000 suspension, front and rear. This, along with a sixteen inch rear wheel, is intended to sharpen up the handling, smooth out the ride, and lower the seat height.
The mechanical goals were:
1. Adapt a GS1000 rear swingarm.
2. Fix GS1000 front forks, triple clamps and steering bearings.
3. Make it a totally bolt-on modification so that it can easily be returned to its original condition.
I have another long-term rotary project going on, so I had a rotary in partial disassembly. That made it easier to take measurements and do some mock-ups to check out the possibilities. I began with the rear end. The GS1000 swingarm is the same width at the pivot as the RE5. The only difference here is in the inner and outer diameters. Both are larger. The GS1000 uses a 14 mm diameter pivot bolt, and the RE5 uses a 12 mm pivot bolt. The larger outside diameter is due to the difference in bearings. The GS1000 uses needle bearings and the RE5 uses nylon bushings which, as we know from the GT750, are not very durable. The other main differences also made for improved ride and handling. The first is that the GS1000 swingarm is longer, increasing the wheelbase, and improving stability. The second is the location of the shock mounts. They are about 10 cm farther back, allowing an increased shock angle, greater leverage on the spring, and a lower seat height. It will also accept a wider tire as found in most 16 inch tires.
To accommodate the difference in pivot bolt diameter, I made a sleeve 14 mm in O.D. and 12 mm in I.D. for each side. To keep the center spacer indexed, I made the sleeves 10 mm longer than the inner bearing race, welded it to the race, and re-heatreated the races. When the races were reinserted, the added length of the sleeve fit into the center spacer and held it in place. The next task was to adapt the GS1000's rear disc brake. I had to mount a hydraulic master cylinder to the frame and attach it to the rear brake pedal. This was accomplished by using two metal compression clamps, mounted to the rear frame spar, and a small custom bracket, and rotating the Rotary's brake rod attaching arm clockwise to reach the actuator rod of the master cylinder. By using a master cylinder with a remote reservoir, I was able to mount the reservoir under the seat next to the oil tank. I simply replaced the 4 inch stock hose with 18 inches of transmission cooler hose. When bolting up the shocks, it was necessary to add additional spaces to the top shock mounts, moving them out to the end of the shoulder of the mount bolt, as the GS1000 swingarm is wider at the shock mount. With the added length of the GS1000 swingarm, a 100 link chain is needed in place of the RE5 96 link chain. Then the rear wheel, with a brake disc from either an GS850, or a GS1000 and GS1000 spacers, and disc caliper mount, completes the rear end conversion. The RE5 chain guard can easily be adapted or a GS1000 chain guard can be used. The same can be said for the shocks. I kept the RE5 shocks to keep the set-up as low to the ground as possible. GS1000 shocks would provide a better ride. (Tim's note: We later put on Gs1000 shocks and custom springs.)
Now on to the front suspension... In order to mount GS1000 forks to the RE5 steering head, I chose to use the triple clamps from a GS850, as they have more offset than GS1000 units. I was unable to find tapered roller bearings to fit both the triple clamps pivot shaft diameter, and the inside diameter of the RE5's steering head. I bought bearings that were very close and had both outer races ground down and the lower inner race ground to fit as well. I had to cut off the steering lock and stop notches from the lower clamp. The crash bar around the radiator became the new stops. Not ideal, but safe, as it turned out to be very close to stock in turning radius, and just as solid in normal use. (Tims' note: We had previously mounted a custom fatter radiator guard.) The RE5 headlight nacell and mounts will fit up to the GS1000 forks with some enlargement of the locating rings. That being so, I removed the RE5 fork tubes from their triple clamps, before removing the triple clamps from the steering head. This left the wiring intact. Then, by installing the GS1000 parts in reverse order, after changing out the bearing races, I saved time and further disassembly. The instrument cluster requires longer bolts and spacers to raise it up to fit into the upper triple clamp. I slid the forks into the triple clamps so that the air caps faced forward and just cleared the handlebars. This lowered the front end to match the changes in the rear. The front brake calipers have to be swapped over to GS1000 units, but the RE5 rotors can be used.
Tims note: DVP meant to say the calipers are stock RE5 and the rotors match the front wheel. I had asked DVP to recap the procedure long after he did the conversion.
Again, the GS1000 axle and spacers are needed, but the RE5 speedo drive can be kept. The RE5 front fender can be used with 3/8" spacers between the fender and the forks. A GS1000 front fender can be used, but radiator clearance is a problem. The fender must be lowered by drilling new mounting holes in it. They should be 3/4" above the original holes, center to center. If using GS1000 shocks and a 17 inch rear wheel, the forks should be set at standard height, and the fender modification should not be necessary. Bolt it all together with proper fork alignment procedures and there you have it ! An RE5 that rides and handles more like a 1978 GS1000. Stability and comfort were significantly improved. With all the changes, the result was about a 3 inch reduction in seat height. Overall, a very satisfactory conversion. All of the weaknesses were improved, the worn parts replaced, and the ride height lowered with a dramatic improvement in handling and comfort. I realize from a purists standpoint, a project like this is somewhat sacrilegious. But, as I mentioned at the beginning, it can be returned to its original condition, as no permanent modifications were made to the RE5 itself. I like to think of it as an RE5E, as Suzuki might have made it.
DVP - March 1996
