175TS Fork Strip Question

[Samurai]

Hi Aaron, good points well made.

I appreciate that just because something is currently fitted doesn't mean it was like that originally. I've worked on enough modern bikes to know that situation occurs on bikes much younger than 60 years old

I'll look into the hard split ring which seems sensible. I can't see why someone would go to the trouble of carefully machining a grove for something that was never there just for the hell of it though?

Things may become more apparent when I strip the other leg this weekend and see it the internals match.

Cheers,

Jason

[Samurai]

Hi Buster,

Thanks for confirming the O-ring on the top fork caps, much appreciated. I thought there should be as most other forks I've worked on have them.

Cheers,

Jason.

[Samurai]

Ok, a bit of an update in the forks, following some quality garage time yesterday

After cleaning all the moly grease from the components, I believe that Aaron was quite correct about the damper piston having had work to it. By the look of the newness and lack of wear marks, together with the fact that it appears to be made of alloy, it seems like the previous owner had new piston s machined specifically, probably to replace the worn out originals.

Part of that conversation seems to be the deliberate and very precise machining of a 24x17x3.5mm O-ring seat. The new O-rings fit precisely and a test fit show that they seem to provide a seal, whilst still allowing the rid to slide freely, without undue resistance.

I fully appreciate the fact that, as Aaron correctly points out, that the seal should really be made of some PTFE-type material, but it does not seem to have been designed for such and also, I've been unable to find any piston seals that dimension anyway, probably for the same reason.

I'm guessing that whoever made the pistons decided that the o-rings should be sacrificial to prevent wear on the alloy and machined them deliberately for that purpose. Why they didn't use steel or such, to replicate the seemingly solid originals, I have no idea though?

This leaves me with little option (short of paying out for reproduction or secondhand dampers), but to re-assemble and see how it goes. This time filling the forks with oil first though! Never having ridden a 60 year old Duke, I'd not got any experience to compare the ride with and thought that 'they're all like that sir' . . .

I had originally bought the bike as an unfinished project, with the rolling chassis and tinware all painted and mostly together. Having been concentrating on the full engine rebuild and rewiring and keen to try it out, I kind of buried my head in the sand and stupidly made the assumption that the assembled forks had actually been filled with oil and not just hurriedly assembled for sale, as appears to be the case Hey-ho, should have known better really . . .

On the plus side, I did check the forks for straightness and can find no gaps at all when I roll them together. I'll keep you all updated on progress once I've reassembled them.

Thanks for all the help and advice so far guys

[ranton_rambler]

This is what my damper pistons look like - just a bit of turned steel pegged onto the rod. I don't think they will make a great seal to the inside of the stanchions.

DSCF5535small.jpg

[Samurai]

Just to finish up this thread and to bring you up to date on progress.

I stripped, cleaned and reassembled the forks with 110 ml of 10w fork oil (using new O-rings in the seemingly specially machined replacement damper crown!) and all now seems well with the fork action.

Having now discovered that whoever had been inside last, had just rebuilt them with a liberal coating of Moly grease and no actual oil, I can say that the cause of the forks jamming in the compressed position was a result of the lack of damping allowing the stanchions to compress so far inside the slider's, that the slightly larger upper section of the 30mm lower legs, ended up sticking in top of the slider.

Having nothing to compare them with, the only thing I don't know is if the actual stanchions are original 30mm ones, or whether they are 31.5mm ones that someone has turned down the lower part to fit inside the early 30mm slider's?

Does anybody know if the 30mm forks were actually 30mm diameter for their whole length?

The ride from the forks is now more inline with what I would have expected their action to be like, although I may experiment with slightly less oil (100 millilitres as opposed to the max 110), or possibly drops the weight to 7.5w, as if anything the damping feels a bit on the firm side for such a light bike.

Again, I'm always interested to hear from those with more experience of these bikes!

Now, off to fix the snapped clutch cable, will this never end?