I had some pits on my NC30 forks and found that TNK supply "equivalent" replacement tubes.

Rebuilding the forks with the new TNK stanchions revealed an issue. They have a plastic bush insert that is not wide enough for the fork piston to go through. There is no corresponding part in the original Honda fork tube. For the record, the piston has an outer diameter of 22.5mm. I'm having a think about it, but just using a dremel to grind away the plastic bit seems like it should work as long as every tiniest piece of dirt & plastic is removed (lots and lots of flushing and cleaning).

Anyone see any reason this won't work?

Have you been in contact with the supplier before hacking them up? Perhaps they sent the wrong tube?

There was a little screw up with delivery/order dates earlier in the process and I'd rather leave them alone if I can. My impression was that the UK importer was doing the best job they could on relatively little information, just relying on TNK to give them the right stuff. This isn't ideal, but I don't want to be sending stuff back (to Italy?) that I've had for weeks if not months and already partially assembled. What I'd really like is a way of making it work without needing to rejoin the 2-36 week lottery that is international shipping.

It's just dawned on me.

What year is your NC30?

There are two different types of forks on the NC30 and they both use different sets of tubes...

I nearly brought a pair of spotless new old stock in the box Honda fork tubes about a month ago, only 40quid! >.<

Should have had them now I think about it.

It's a later model Japanese import, declared manufactured 1991.
My understanding was that the earlier nc30s had a smaller piston & maybe a longer tube.
I'm guessing that the oil is squirting around in the same ways & any differences should be possible to dial out with thinner oil if it's a bit more restrictive.

squaredoffagain wrote:It's a later model Japanese import, declared manufactured 1991.
My understanding was that the earlier nc30s had a smaller piston & maybe a longer tube.
I'm guessing that the oil is squirting around in the same ways & any differences should be possible to dial out with thinner oil if it's a bit more restrictive.

The function of the early and late forks is fundamentally different.

One is a damper rod fork - the central rod has orifices..lol - they are immersed in the oil at the bottom of the fork.

Later are a cartridge fork - they have the gubbins inside a cartridge (funnily)

Totally different ideas for working the damping and not cross compatible.

squaredoffagain wrote:It's a later model Japanese import, declared manufactured 1991.
My understanding was that the earlier nc30s had a smaller piston & maybe a longer tube.
I'm guessing that the oil is squirting around in the same ways & any differences should be possible to dial out with thinner oil if it's a bit more restrictive.

Ok ignore that anyway as many of the imports have been crashed / rebuilt or just generally messed about with.

Both are 41mm forks but the tubes are not compatible, the holes at the bottom are in different places which affects the dampinging.

Early forks have only a silver screw on the top which adjusts preload.

Later forks have a silver screw with a smaller brass screw inset.

The old forks are stripped down so a little more reading shows me they are certainly damping rod internals. The original stantions have two holes about 3 inches from the bottom. The replacements have 4 holes closer to the bottom.

Maybe that plastic thing is what the cartridge is supposed to sit on?

Hope not. A query has gone back to them.

Was there only one version of the damping rod internal? I could imagine an earlier one having a slimmer profile perhaps.

It's a complete bitsa. It had new-style fork tops on old style fork internals that I've mistakenly bought new style tubes for.

The search for a compatible cartridge, to make it all modern, has begun.

[edit: subsequent research suggests I was wrong about this and that I have late model internals from the original forks, but the new tubes I got are for the early internals and there's nothing I can do but change the tubes for the right late-model ones or convert to damping rod/damping rod+gold-valves if I want to use the TNK tubes]

squaredoffagain wrote:It's a complete bitsa. It had new-style fork tops on old style fork internals that I've mistakenly bought new style tubes for.

The search for a compatible cartridge, to make it all modern, has begun.

wow.

so the little brass clicky wasnt screwed into the cartrdige then and was doing nothing! preload would be off too with the different caps I think.. crazy.

I got a copmlete set of non leaking later type NC30 forks and yolks for 30 quid the other day. Dont even need new stantions.

Im sure youll find something :)