Topic: rosewood's cb550F restomod - swing arm dilemma, frame damage & custom bushes

[HondaMan]

Rats...something's happened to our picture viewer? I can't see pix.

[MauiK3]

For some reason I'm not able to make the jpg's come through.
Nice project

[rosewood]

Rats...something's happened to our picture viewer? I can't see pix.

Any idea what's up with the picture viewer? Is this just a temporary thing or will it get sorted? I know I've added alot, maybe too many?

I've added the last picture again to see if it works....have plenty more to share with this project but would be a shame if I cant post any images..

[denward17]

picture issues:

http://forums.sohc4.net/index.php/topic,206017.0.html

[HondaMan]

Pix are back!
3 cheers for the webmasters here!

[rosewood]

Pix are back!
3 cheers for the webmasters here!

Not so sure Mark....I'll go through and reload my images on this thread when I get a chance...

Just checking some notes and wanted to correct a couple of things I've mentioned. I used phosphor bronze (PB1) for the swing arm bushes not LG2 bronze. I think i may have purchased a new swingarm bolt with the grease holes already drilled and not drill these myself...

[rosewood]

With the frame temporarily repaired for now I started working on other areas of the bike...Not wanting to rebuild my wheels completely and respoke I decided to mask the rims and  bead blast the inner hubs to clean them up, the spokes also had surface rust so these got a clean up in the process. I removed the tyres to find the rims rusted inside, this was cleaned up with wire brush on a drill. I had the wheels trued by an old local that did this as a side business...painted the inner surface with a rust converter to help protect, replaced the bearings and had them wrapped in new Avon's. Another job off the list.

Attention then went back to the frame, with the damage around the swingarm I wanted to check frame frame geometry a bit closer, I built a jig to sit the frame on, I figured this may also come in useful during the assembly. With the engine back in the spine looked good but a closer look at the swingarm showed something was off...The sprockets weren't aligned and after some head scratching I concluded that my swingarm must have been bent. I sourced a replacement on ebay and once that arrived and assembled sure enough the sprockets aligned perfectly. I could then look at the front a bit closer, using stringlines the best I could I found the front wheel was not aligned to the back, I turned up some cone fittings to check the steering head/stem and sure enough this showed it was bent/twisted. The bikes original front guard had seen some damage as well as the headers consistent with a crash/hit from the front....Great!!

[HondaMan]

That's a sad bunch of damage, but I might mention this: in 1972 (when my 750K2 was but 9 months in my hands) I was hit from behind on the right-side exhaust pipes by a Suzuki GT750 waterbike rider going nearly 50 MPH: I had just [been] stopped to avoid hitting the train (which he did). This pushed the right side of the frame forward about 1/4" (also bending the engine mount bolts and aiming the 2 right mufflers at the sky to do it), which became a little over 3/8" when I pulled the engine later. This made the swingarm pivot to the right about 1/2" from the bike's centerline.

With the engine out and the front of the frame lashed to the floor-mounted tire-mounting machine in the shop, and 3 guys (all 3 bigger than me) with thick water pipes (I think 2") we were able to get the misalignment a little bit over-corrected by pulling the right side of the frame back via the passenger footpeg mount (which also hangs the mufflers, hence the bend). When all was put back together, I have to run the left-side chain adjuster about 1/10 turn (distance) more than the right to make the wheels parallel (they are offset about 1/8", rear to the left).

That was over 150k miles ago. Although I see a small difference in the rear-wheel's wear pattern on the left side of the rear tire, this hasn't otherwise made the bike cantankerous to ride since then - although it has made the bike like certain tire tread patterns more than others: it REQUIRES a central groove (at least as much as the ones found in the Avon Roadriders) for good high-speed stability. It carries a Vetter fairing all the time, too. The bike handles well all over the Rockies, although I haven't raced it [as much] since the accident.

[rosewood]

That's a sad bunch of damage, but I might mention this: in 1972 (when my 750K2 was but 9 months in my hands) I was hit from behind on the right-side exhaust pipes by a Suzuki GT750 waterbike rider going nearly 50 MPH: I had just [been] stopped to avoid hitting the train (which he did). This pushed the right side of the frame forward about 1/4" (also bending the engine mount bolts and aiming the 2 right mufflers at the sky to do it), which became a little over 3/8" when I pulled the engine later. This made the swingarm pivot to the right about 1/2" from the bike's centerline.

With the engine out and the front of the frame lashed to the floor-mounted tire-mounting machine in the shop, and 3 guys (all 3 bigger than me) with thick water pipes (I think 2") we were able to get the misalignment a little bit over-corrected by pulling the right side of the frame back via the passenger footpeg mount (which also hangs the mufflers, hence the bend). When all was put back together, I have to run the left-side chain adjuster about 1/10 turn (distance) more than the right to make the wheels parallel (they are offset about 1/8", rear to the left).

That was over 150k miles ago. Although I see a small difference in the rear-wheel's wear pattern on the left side of the rear tire, this hasn't otherwise made the bike cantankerous to ride since then - although it has made the bike like certain tire tread patterns more than others: it REQUIRES a central groove (at least as much as the ones found in the Avon Roadriders) for good high-speed stability. It carries a Vetter fairing all the time, too. The bike handles well all over the Rockies, although I haven't raced it [as much] since the accident.

How did you deal with sprocket misalignment or is 1/8th inch acceptable tolerance?

I debated making some custom spacers to correct my sprocket alignment but decided to source a new swingarm as the safer option..

[HondaMan]

That's a sad bunch of damage, but I might mention this: in 1972 (when my 750K2 was but 9 months in my hands) I was hit from behind on the right-side exhaust pipes by a Suzuki GT750 waterbike rider going nearly 50 MPH: I had just [been] stopped to avoid hitting the train (which he did). This pushed the right side of the frame forward about 1/4" (also bending the engine mount bolts and aiming the 2 right mufflers at the sky to do it), which became a little over 3/8" when I pulled the engine later. This made the swingarm pivot to the right about 1/2" from the bike's centerline.

With the engine out and the front of the frame lashed to the floor-mounted tire-mounting machine in the shop, and 3 guys (all 3 bigger than me) with thick water pipes (I think 2") we were able to get the misalignment a little bit over-corrected by pulling the right side of the frame back via the passenger footpeg mount (which also hangs the mufflers, hence the bend). When all was put back together, I have to run the left-side chain adjuster about 1/10 turn (distance) more than the right to make the wheels parallel (they are offset about 1/8", rear to the left).

That was over 150k miles ago. Although I see a small difference in the rear-wheel's wear pattern on the left side of the rear tire, this hasn't otherwise made the bike cantankerous to ride since then - although it has made the bike like certain tire tread patterns more than others: it REQUIRES a central groove (at least as much as the ones found in the Avon Roadriders) for good high-speed stability. It carries a Vetter fairing all the time, too. The bike handles well all over the Rockies, although I haven't raced it [as much] since the accident.

How did you deal with sprocket misalignment or is 1/8th inch acceptable tolerance?

I debated making some custom spacers to correct my sprocket alignment but decided to source a new swingarm as the safer option..

The sprocket misalignment issue of the CB750 at high throttle openings taught Honda a great deal about sprocket tech, circa 1970s. The results of it were: all Honda's [own] sprockets received tapered tooth tips (on the sides of the teeth, halfway down the tooth) on both front and rear sprockets, to deal with chassis misalignments under heavy throttle. While it was a taciturn admission that the early 750 frames were...a little soft...it ended up delivering up to 5% more HP to the rear wheels of all of the SOHC4 bikes first, then all Honda's chain-driven bikes after about 1980. Soon after, Suzuki (and eventually Kawasaki) did the same with their branded sprockets. The result was greatly increased chain life (so long as they were not O-ring chains) and power transfer.

Some of these details are disclosed in My CB750 Book: there was, for the 750 in particular, additional base-circle changes to the rear sprockets, along with shortening of the tooth tips on all sprockets (by 2mm). For my part on those bikes I 'touched' in those days, i ground many, many sprockets for those owners who wanted to "try this tech out", and no one was ever disappointed: the biggest surprise to some was how much longer the sprockets lasted: not intuitive when you're shortening tooth tips, but physics don't lie. It also helped with slightly loose and misaligned swingarms.

[rosewood]

After some research I found a couple of places south of where I live that could help correct the frame. The closest to me was a guy who had adapted a car chassis jig to accept motorbikes. It looked like a decent hi tech setup with electronic measuring read outs..He was the more expensive option but also closer for convenience. I still needed to finish the front end which involved tapered steering head bearings and rebuilding the front forks. My fork stanchions had seen better days and had worn through the chrome plating. After dismantling I found both stanchions bent probably another casualty from the front end collision. I found cruzin image offered these for a 550f which were different to other 550/500  models. He had blocked me after questioning the piston ring kits so I had a colleague purchase from ebay on my behalf. I gave the fork lowers a quick polish and rebuilt them which went smoothly, also turned up some replacement top fork nuts to replace my rusted chrome ones. Installed on the bike it was a roller again and I loaded it up to get the frame sorted, it was an expensive exercise but at least I had confidence the frame was as it should be..