With my last paycheck, I ordered a few more items from ebay. The brake panel (with decent pad material), the Nighthawk axle which also came with the swing arm parts for securing the axle, chain adjuster and a nighthawk chain guard. I also ordered the drive mechanism along with the cush drive parts.
I'm trying to be careful to order the parts that come with more bits because if I'm missing something and need to order another part, it's another shipping charge. I'm quickly discovering that though these parts don't cost a lot of money, the shipping charges can be easily 2-5x the cost of the part. Free shipping is your friend if they don't pad the cost of the shipping into the part (surprise, they do).
One of the first options I have to consider is swapping the wheel without swapping the swing arm. Since the Nighthawk (NH) wheel has a 17mm axle and the CB750c (CB) has a 20mm axle I would need to look into widening the NH wheel to accept the larger 20mm axle. I suspect that I could just find a 20mm sleeve to slip onto the 17mm axle where it attaches to the swing arm, but it seems like other people on the web have drilled everything out to 20mm. The brake panel has enough meat to drill out that first hole to 20mm. I'm expecting to need to decrease the CB spacers to accommodate the wider NH wheel (measurement TBD NH vs CB spacers). The NH wheel bearings could be replaced and the spacer between these bearings would need to be replaced.
The potential trouble spot is in the drive assembly (I like to call it the cush drive). There is a coupling which doubles as a spacer. It ensures that when the axle bolt is tightened down, there is no excess pressure applied to any of the bearings because the spacer takes the tightening pressure. I could not find a suitable size of bearing as part of the swap. I'm listing in #3 below the closest wheel bearing that I could find. I think a washer of suitable diameter could make up for the lost height of the bearing. The drive bearing is actually 20mm ID and you could just slide the CB axle in there without changing it but without a spacer, the outer bearing will get damaged when the axle nut is torqued down and there's no easy way to just throw a couple of washers in the drive assembly because you would not be able to put the axle through it and keep the washer in place. I think keeping it simple would work better especially for whoever owns and maintains this bike after me. In 10 years I may no longer remember what I changed on this bike over the years. Hopefully, this blog will still exist so I can remember all the parts that come from other bikes.
parts needed for retaining the 20mm axle (guesstimate, I have not performed a test fit with these parts):
After I washed the new NH wheel with some wheel spray cleaner and hosed everything off, I got some discoloration since the wheels are likely bare aluminum. I was planning on painting them black so I cleaned and lightly sanded off whatever junk was left and then painted them with Rustoleum Automotive etching primer, Automotive gloss black and Automotive Clear gloss. I really wanted matte black, but decided to keep all the paint in the same family for compatibility and hopefully durability.
I'm not building a show bike. I'm happy looking at it from about 5 feet and not with a magnifying glass so the finish just needs to be durable and fairly even. Now it even matches the black brake panel that I got from ebay.
The cb750 swingarm weighs approximately 13lbs compared to the Nighthawk swingarm's 10.4lbs
By swapping over to the Nighthawk wheel and swingarm I would save approximately 5-6 lbs of unsprung weight (just for the wheel and tire)!!! This is a pretty good weight savings and should translate to an improvement in ride quality and (maybe) acceleration over the stock parts. After adding the weight of the axel, brake panel and cush drives into the comparison, I save an additional 2.5 lbs since the nighthawk parts are smaller and lighter compared to the cb750. Figure a 9-10 lb savings overall.
nighthawk parts diagram
=======
I'm trying to be careful to order the parts that come with more bits because if I'm missing something and need to order another part, it's another shipping charge. I'm quickly discovering that though these parts don't cost a lot of money, the shipping charges can be easily 2-5x the cost of the part. Free shipping is your friend if they don't pad the cost of the shipping into the part (surprise, they do).
One of the first options I have to consider is swapping the wheel without swapping the swing arm. Since the Nighthawk (NH) wheel has a 17mm axle and the CB750c (CB) has a 20mm axle I would need to look into widening the NH wheel to accept the larger 20mm axle. I suspect that I could just find a 20mm sleeve to slip onto the 17mm axle where it attaches to the swing arm, but it seems like other people on the web have drilled everything out to 20mm. The brake panel has enough meat to drill out that first hole to 20mm. I'm expecting to need to decrease the CB spacers to accommodate the wider NH wheel (measurement TBD NH vs CB spacers). The NH wheel bearings could be replaced and the spacer between these bearings would need to be replaced.
The potential trouble spot is in the drive assembly (I like to call it the cush drive). There is a coupling which doubles as a spacer. It ensures that when the axle bolt is tightened down, there is no excess pressure applied to any of the bearings because the spacer takes the tightening pressure. I could not find a suitable size of bearing as part of the swap. I'm listing in #3 below the closest wheel bearing that I could find. I think a washer of suitable diameter could make up for the lost height of the bearing. The drive bearing is actually 20mm ID and you could just slide the CB axle in there without changing it but without a spacer, the outer bearing will get damaged when the axle nut is torqued down and there's no easy way to just throw a couple of washers in the drive assembly because you would not be able to put the axle through it and keep the washer in place. I think keeping it simple would work better especially for whoever owns and maintains this bike after me. In 10 years I may no longer remember what I changed on this bike over the years. Hopefully, this blog will still exist so I can remember all the parts that come from other bikes.
parts needed for retaining the 20mm axle (guesstimate, I have not performed a test fit with these parts):
- 2 wheel bearings: 6204-rd 20mm ID, 47mm OD, 14mm width
- spacer tube (see #5 "axle distance collar" from the parts diagram - measurement TBD)
- 6005-2RS 25mm ID, 47mm OD, 12mm width
- shouldered coupling (see #6 "axle distance collar" from the parts diagram - measurement TBD )
- resized wheel spacers
After I washed the new NH wheel with some wheel spray cleaner and hosed everything off, I got some discoloration since the wheels are likely bare aluminum. I was planning on painting them black so I cleaned and lightly sanded off whatever junk was left and then painted them with Rustoleum Automotive etching primer, Automotive gloss black and Automotive Clear gloss. I really wanted matte black, but decided to keep all the paint in the same family for compatibility and hopefully durability.
I'm not building a show bike. I'm happy looking at it from about 5 feet and not with a magnifying glass so the finish just needs to be durable and fairly even. Now it even matches the black brake panel that I got from ebay.
The cb750 swingarm weighs approximately 13lbs compared to the Nighthawk swingarm's 10.4lbs
By swapping over to the Nighthawk wheel and swingarm I would save approximately 5-6 lbs of unsprung weight (just for the wheel and tire)!!! This is a pretty good weight savings and should translate to an improvement in ride quality and (maybe) acceleration over the stock parts. After adding the weight of the axel, brake panel and cush drives into the comparison, I save an additional 2.5 lbs since the nighthawk parts are smaller and lighter compared to the cb750. Figure a 9-10 lb savings overall.
nighthawk parts diagram
 |
| Brake panel already painted black by previous owner |
 |
| Brake panel |
 |
| Cush drive - sprocket side |
 |
| cush drive - damper side |
 |
| shouldered coupling |
Comments
Post a Comment