500k2 Forks - Tips to make them work properly

[philward]

One of the area's I am unhappy with on the newly built 500k2 is the fork action. I seem to remember when I had my original new 500k1 back in 1972, it picked up minor undulations - particulary at sub 40mph speeds. I messed with fork oil but never really got it right.
I'm now finding it the same and as I ride a lot slower now, its even more irritating! It uniformily 'patters' on smooth roads (bumps in the road seem to be absorbed fine). When I lightly depress the forks, there's a slight clunking - with no damping or spring resistant and this is the same when I lift the front end off the floor and depress the bottom sliders up and down. I'm re-checking the wheel balance later today.
Any suggestions - as the 500 forks have the rod screwing into the fork cap, I'm not that well up on these type of forks.
As an aside, I've decided not to take on another project this winter and concentrate on sorting out the issues that bug me on my SOHC's - 500/750 Forks (750 is no where as bad as above issue on the 500 but still there) - I'm looking into fitting cartridge emulators to the 750 but not an option due to the rods in the forks - plus some Hagon shocks (work great on the CR750 Rep). Also going to put a starter motor conversion kit on the CR750 Rep (special mod to the narrower race alternator)
Any help from the long term 500 owner and experts appreciated!

[philward]

The stanchians where plated by Philpotts Ken - they roll them to check straightness before plating process I think

[K2-K6]

Are you certain there's sufficient oil to cover the damper valves ? And what oil do you use.

Also are you referring to "bobbing" when the front end of bike patters but without much fork movement.

[philward]

Unfortunately, I can't remember what oil is in the forks but its the same as on my 750k2 and cr Rep. Definately right amount of oil as per Honda manual. By 'patters' I mean it feels like handlebars are moving up and down all the time when on a flat surface as though the forks where reacting to ripples. When I hit a proper bump, everythig reacts fine (better than my 750 forks) - as I say, first 10mm of movement is a 'unloaded clunk'. When I sit on the bike and pull the bars up (to get to unloaded state, it clunks) - its as if that initial travel is unprung or undamped. Seem to remember that I had difficulty locating the fork top nuts (getting them to push down into the tubes to pick up thread) after I filled forks when screwed onto centre long rod (that runs from the damper to the fork nut) - even with bike jacked up with no load on the forks.

[K2-K6]

That initially sounds like a description of low threshold stiction that causes the fork to lift the bike rather than travel within themselves.

Front tire pressure can influence this as it's effectively an undamped spring and if induced by frequency that the fork can't easily respond to will show that characteristic.  Dropping the front pressure by increments of 2psi and then riding it will give some insight to this as it's latent frequency changes. 

More practical to adjust the fork response by changing the oil to something like Motul 2.5 viscosity and then ride to assess.

[philward]

Thanks, I'll give it a try

[Trigger]

I think it is the climate in Wigan compared to were the bike come from in the USA 

[philward]

I think it is the climate in Wigan compared to were the bike come from in the USA 

Hard to compare Wigan climate with anywhere never mind USA!

[philward]

That initially sounds like a description of low threshold stiction that causes the fork to lift the bike rather than travel within themselves.

Front tire pressure can influence this as it's effectively an undamped spring and if induced by frequency that the fork can't easily respond to will show that characteristic.  Dropping the front pressure by increments of 2psi and then riding it will give some insight to this as it's latent frequency changes. 

More practical to adjust the fork response by changing the oil to something like Motul 2.5 viscosity and then ride to assess.

Can you use synthetic fork oil in these old forks?

[K2-K6]

I've not encountered problems and feel it's ok.

There's different meaning to the synthetic description that is used for very different products, mainly automotive applications are compatible as compared to aircraft derivatives that are not.

[philward]

Great, thanks

[Bryanj]

Well im in warrington right now and its persisting down

[robvangulik]

Well im in warrington right now and its persisting down

Don't despair, across the Channel it's been the same, if not worse for the last week!

[Bryanj]

It was way worse going to Plymouth monday night, i had to slow down on A38 cos i couldnt see where the road/river went

[Seabeowner]

Have two 500s. One very low mileage, the other I have a couple of sets of forks for. All clunk a bit when you hoist on centre stand.
Had the forks apart on the high mileage bike recently and also compared with the spare set. Of the four fork legs I found that the damping was uneven on two of them. Used the best two and seems better. The dampers are sealed and not made to service. Anyone had one apart, presumably there is nylon ring or the like inside that could be replaced or maybe the internal bore is worn/distorted?