Will 15w be really horrible? /furtive glance at quantity of 15w in shed...
It would be a bit OTT, I think. The forks actually aren't soft: just oversprung and under-damped. 10w might be better.
Get some ATF (Automatic Transmission Fluid) - it'll do for the vast majority of 70/80s mass produced machines.
You'd think so, but with the hard springing you wind up with something that hardly moves. I tried 12w in mine: it wasn't a success.
When faced with 70s UJM forks all I've ever done is a couple 2p's under the fork caps and the appropriate amount of ATF.
Oh yes, I forgot about the 2p pieces. I used that dodge on a CB550 when I put a full Rickman fairing on it.
That is the sort of experience I needed to hear about before trying it myself really I have plenty ATF. Might even have some 2p's.
I really don't think that the 2ps would make any appreciable difference in the 400. As I said, I used them on a 550. That was because the added weight of the fairing was making the forks sag a bit. Heavier oil *will* improve the damping, yes, but you'll get forks like those on my Ducati - not much cop on anything other than smooth surfaces. Basically, you're dealing with a fork design that is well over 30 years old. If you really wanted to make a difference to it, you'd take it to Maxton or somewhere and get it revalved: that's the only way to effect a noticeable improvement. Incidentally, the front forks on the 400 are exactly the same units as you'll find on the CB250G5, CB360, CJ250/360 except that the damping internals are revised. The stanchions and lower legs are the same (well, they matt-blacked them on the CJs). Well, the whole front end is more or less the same: 18" front wheel, same front brake, front mudguard. CJs used a different front mudguard. Incidentally, if you need a rear carrier for the 400 (and they are the proverbial rocking horse shit), a rack for a 250/360 uses the same fixing points and bolts straight on. So buying a totally dead 250 for £50, if it has a rack on it, is a Good Idea.
I wasn't looking for an improvement as such. I had just acquired a few bottles of 15w so was wondering which bike I could use it in The fork oil hasn't been changed for a while, the seals are weeping and one of the lowers needs changing. It has a crack near the top where someone has made a mess of changing the seals That's handy to know. Cheers.
