Topic: Swingarm Bushings - Nylatron

[Hwmetzger]

I've currently got a CB750K7 torn down in preparation for powdercoating. In the process I discovered that the stock swingarm collar is seized to the original phenolic bushings and had to press out the collar. Collar and bushings are both shot. I've ordered an early NOS collar (the kind with the grease grooves) and found a good swingarm bolt with the grease fittings on each end.

My plan was to machine a set of bushings from either 348 or 841 Bronze, however I've got a stick of Nylatron sitting in the shop right now.

Any opinions on using this for bushings instead of Bronze? I've made bushings from it before for farm equipment and industrial machinery, but never for a motorcycle.

[BenelliSEI]

Go for it! I’ve made them out of a piece of similar stuff. Delrin? A white plastic often used for the same type of farm and conveyor fittings. Held up fine. The challenge is to get the “hats” you make snug enough in the swing arm that they only rotate on the collar, and not in the swingarm. I think I actually glued them inplace the last time. Still no play or wear, after a few seasons........ easy to check occasionally, when you put the bike on the centre stand.

[Hwmetzger]

After doing some research and looking over engineering data, Nylatron looks like a great material for this application.... except for one thing.

Apparently Nylatron can absorb up to 7% of its weight in water, and expand up to 2% dimensionally. Given that the bushing would exist a few inches above the road surface, I feel this is a poor application for Nylatron since it will get wet.

[david 750f]

I used the 841 “sintered bronze”, it is an oil impregnated bronze. (Also known as Oilite). Excellent for swingarm bushings, machines easily.

[lrutt]

Bronze for me if I was making one. Go with what I know.

[Tracksnblades1]

Which type of the many nylatrons are you comparing to your brass selection.
Remember those nylatron nylon rear sprockets they made back in the early 80's...?
👍

[Jerry Rxman Griffin aka MuthaF'er]

And you can get bronze bushings for around $20 from the right places. KenoshaKid???

[DaveBarbier]

And you can get bronze bushings for around $20 from the right places. KenoshaKid???

Yup, they fit well in my 550. eBay is where he sells.

Also if you’re going to machine oilite, Tubalcain says not to ream it as it glazes the surface and seals it so it doesn’t lube as it’s supposed to.

[Radski]

I've currently got a CB750K7 torn down in preparation for powdercoating. In the process I discovered that the stock swingarm collar is seized to the original phenolic bushings and had to press out the collar. Collar and bushings are both shot. I've ordered an early NOS collar (the kind with the grease grooves) and found a good swingarm bolt with the grease fittings on each end.

My plan was to machine a set of bushings from either 348 or 841 Bronze, however I've got a stick of Nylatron sitting in the shop right now.

Any opinions on using this for bushings instead of Bronze? I've made bushings from it before for farm equipment and industrial machinery, but never for a motorcycle.

Question... typically is the swingarm bolt always a #$%*ter to get out of a '77 CB750K? Mine seems stuck too and with my limited knowledge, with what you said happened to yours, is the same thing happening to mine? Or are they supposed to come out like the other years? free and easy

[HondaMan]

Nylatron is not strong enough for these swingarms. Honda proved that in 1979 when they tried it on the DOHC CB750, which handled poorly right from the showroom floor. The next year they went to phenolic, then sintered metal bushings, then roller bearing types by 1983.

Use either 841 bronze or 660 bronze for these swingarms. The shock loads to the bushing exceed 12,000 PSI with one rider aboard and more than 18,000 PSI when 2-up (and I often 2-upped with 600 lb payloads on mine, but with SAE 660 bronze bushings aboard). The Nylatron deforms and recovers once or twice with loads this high, but then it begins to migrate away from the high-pressure zones. The used ones from the DOHC bikes looked like someone machined the hole off-center after about 5000 miles, and they were cracked on the thin sides.

[Hwmetzger]

And you can get bronze bushings for around $20 from the right places. KenoshaKid???

I know the dimensions of the collars have changed through the various production runs, I'd prefer to make my own so I know they're the right size.

Question... typically is the swingarm bolt always a #$%*ter to get out of a '77 CB750K? Mine seems stuck too and with my limited knowledge, with what you said happened to yours, is the same thing happening to mine? Or are they supposed to come out like the other years? free and easy

The bolt was pretty easy to get out. Just a light tap with a hammer to get it moving and I could easily pull it out with my hand.

Nylatron is not strong enough for these swingarms. Honda proved that in 1979 when they tried it on the DOHC CB750, which handled poorly right from the showroom floor. The next year they went to phenolic, then sintered metal bushings, then roller bearing types by 1983.

Use either 841 bronze or 660 bronze for these swingarms. The shock loads to the bushing exceed 12,000 PSI with one rider aboard and more than 18,000 PSI when 2-up (and I often 2-upped with 600 lb payloads on mine, but with SAE 660 bronze bushings aboard). The Nylatron deforms and recovers once or twice with loads this high, but then it begins to migrate away from the high-pressure zones. The used ones from the DOHC bikes looked like someone machined the hole off-center after about 5000 miles, and they were cracked on the thin sides.

I knew the stress concentration was fairly high on the bushing, but didn't think it was that high. That would definitely move the FoS to below 1, especially with a dynamic shock loading in that range.

I thought it was worth asking since I already had some Nylatron on hand. Looks like I'll be picking up a stick of 841 or 660 soon.