SOHC.co.uk Forums > CB500/550
What do we see here?
K2-K6:
To describe the joints, the rubber composite design (it doesn't need to control geometry here as the swingarm does that) is relatively cheap way of making a joint that can't rattle over time as the rubber flexibility keeps it quiet but allows limited movement.
The centre bore is usually clamped between the shock (at the bottom) with that part not moving at all in relation to the shock. As the suspension moves, the rubber twists (inner and outer metal parts of the bush move separately) with the rubber accounting for all the movement needed through suspension travel. The inner doesn't move on the securing bolt (it would be better engineering practice to have no threads there as you indicate) but with the bush clamped against the shock forks it shouldn't matter much.
It's a double shear joint, the push and pull forces are taken by both ends of the bolt (it would be very very hard to break the bolt in this design) also it makes no rotation torque on the bolt and so will not come loose even without securing washers etc. In reality you could almost put it there with your fingers and it should be safe.
The top mount is just the opposite in how the centre bush is now on the frame, with the outer on the shock. Same deal force plane though. The top pivot is long and passing through two frame wall sections usually to give support for the one sided design else it would bend that mount if just sticking out from a single piece of metal. This one will more or less work without the security nut/bolt as all of the suspension load is taken by the main spindle not the bolt.
philward:
Always facinating to hear an engineering perspective on something we just take for granted Nigel. Never thought about the top mounting spindle going through 2 walls of the frame but when reading about it, makes complete sense.
deltarider:
--- Quote from: K2-K6 on March 30, 2022, 12:40:15 PM ---[...] it would be better engineering practice to have no threads there as you indicate but with the bush clamped against the shock forks it shouldn't matter much [...]
--- End quote ---
It seems I am not particularly lucky with these breast bolts. BTW, is that the correct word in English? Please, allow me a sidestep. Below a pic of another breast bolt, the one that is supposed to hold the kick arm in place. Already in 1980, when I acquired my bike, it was wobbly and now this is what the shaft looks like. Needless to say the kick arm slips. If any of you has a tip to improvise something... Suggestions in the international forum were not useful. It's a known CB500 problem; many suffer from it. I hope to find a solution without having to replace the shaft.
Oddjob:
We call those shouldered bolts, a bolt are those which are partially threaded, like a shouldered bolt, setbolts are fully threaded.
Never had a 500 kickstart slip, I'd just replace the kick start shaft myself, if the knurls are worn you'll never get it to tighten properly again.
K2-K6:
As above, with shaft worn it's difficult to get a good solution.
Something that's possible to help (this is quite common in moto-X bikes with kickstart used alot) using a black (engineering) allen/socket bolt, plus a washer under the head and grease on the bolt threads. It can let you tighten the kickstart the most possible to clamp it with the teeth available.
They are the strongest bolt and not plated, so will rust and need to be covered in grease after installation. If that bolt can't clamp it, then it's absolutely a new shaft as this will take more torque than any other generally available bolt.
[ Guests cannot view attachments ]
This type of bolt.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version