Help to identify and set-up forks

[Skunk]

I've fitted new forks to the bucket but need to set them up. As I don't know what they are now (brand, model, oil weight, etc) what's the best 'baseline' to start from? ie what weight should I start with (I'm guessing 10w) and how much (no idea but was going to start with the same about that comes out)?

Anyone got 'expert' opinions?

Here's some pics, the brakes are RG50, the wheel AR125, the bike AX100 and I think the forks might be Honda...

[Robert Taylor]

I've fitted new forks to the bucket but need to set them up. As I don't know what they are now (brand, model, oil weight, etc) what's the best 'baseline' to start from? ie what weight should I start with (I'm guessing 10w) and how much (no idea but was going to start with the same about that comes out)?

Anyone got 'expert' opinions?

Here's some pics, the brakes are RG50, the wheel AR125, the bike AX100 and I think the forks might be Honda...

Irrespective of what they have come out of these damper rod forks are all very similiar in function.

We have all been guilty for many years of fitting firmer springs to hold these sorts of fork up in their stroke. Whilst it is true that many of these forks are undersprung it is also because at low velocity fork movements there is very very little hydraulic control. But when you hit something abrupt the ''fixed orifice'' holes in the damper rods ''choke off'' in flow rate meaning that manifests itself as a jackhammer feel through the bars. I.e no low speed damping and too much high speed damping.

The very best money you can first spend on those forks is to fit a set of emulators ( with appropriate rate and preload of the high speed poppet springs ) These will, if fitted proffessionally by a technician intimate with how they work and are tuned provide an enormous improvement. I.e The bike will ride higher in its stroke ( and more compliantly ) and will not viciously and unsettlingly dive through its stroke when you hit the brakes. More sidegrip, more rider feel and confidence, easier on the tyres.

It will liberate you from having to use overfirm springs that will exacerbate the abrupt compliance harshness. Avoid beleiving the cheapskate suggestions of just adding longer preload spacers to the existing springs, this is not 1970! Over preloading will actually make the forks feel harsh. Appropriately preloaded, firmer springs ( correct for you ) will actually feel more compliant at the top of their stroke but will resist brake dive better.

With emulators installed I would start with an oil level of 160mm, this might be a little low but if you have some veterinary syringes to hand it is always easier to add oil than take it away.

Also bear in mind that firmer springs ( apples for apples, same manufacturer / series, length and diameter ) will displace more oil than softer springs when installed. That because the wire is thicker etc. That is why many racing fork manufacturers will specify the oil level ( and therefore trapped air spring volume ) with the fork springs installed.

Isnt it sad that to this day many motorcycles have 1950's technology damper rod forks standard? Not everything is going forward, in spite of what the marketing types would have many beleive.

[Skunk]

Thanks for the reply Robert. I've been reading your suspension thread with interest...

As this is a bucket and I'm not the best rider I hesitate to ask this - what sort of money is involved in what you're suggesting?

I think it would be outside the 'budget' of this bike ($1200 total so far including the rebuilt engine). However I know full well the benefit of a functioning suspension.

What information would you need to get 'appropriate rate and preload of the high speed poppet springs'?

To be honest I had thought of just getting some progressive springs with the correct rate. Or a front end that has more travel available. This one only has 80mm available which unfortunately (for my budget) is not enough I feel.

[Robert Taylor]

Thanks for the reply Robert. I've been reading your suspension thread with interest...

As this is a bucket and I'm not the best rider I hesitate to ask this - what sort of money is involved in what you're suggesting?

I think it would be outside the 'budget' of this bike ($1200 total so far including the rebuilt engine). However I know full well the benefit of a functioning suspension.

What information would you need to get 'appropriate rate and preload of the high speed poppet springs'?

To be honest I had thought of just getting some progressive springs with the correct rate. Or a front end that has more travel available. This one only has 80mm available which unfortunately (for my budget) is not enough I feel.

PM me for pricing, I dont wish to invite any ''parasites'' who would possibly turn this into a ''dutch auction'' Suffice to say there is a lot of added value with the way we set up emulators.

Progressive springs are like pouring salt on the wound!!!!!!!!!! Again I stress that a good part of the issue is hydraulics, too soft during initial low fork velocity movements and too firm during latter high velocity fork movements. Fitting progressive springs is just going to give you more of the same! Sometimes you can get away with the stock springs ( unless your personal stats are ''challenging'' ) just by sorting out the number one problem, the hydraulic action. Very end of stroke progressivity for bottoming out resistance is fine tuned by the oil level / trapped air volume. At least that way you have flexibility.

Just today I took an order for emulators and linear springs. The guy had beleived the sales blurb for the progressive springs ( that he also waited a month for ) and is one very unhappy customer.

[k14]

Come on skunk, surely you're not actually going to spend money on bucket suspension

Just do what I did in my CB forks, put 30w harley fork oil in there. I think I even saw them move once

[Skunk]

Yep, I'm looking at spending money on it AGAIN!

Mr Robert Taylor has come up with a very good option that doesn't cost too much (but still far more than I would normally spend).

It's currently got 20w in there and it bottoms out with just a firm push. I think it would need 50w.