Triggered by the never ending story about the Vincent standard damper I got curious about the report of very stiff Konis. So I looked inside two NOS adjustable type Konis I got from the Spares Co 30 years ago - and was not impressed by the seals inside. The dust wiper seals were allright but the hydraulic seals were just punched out rubber material, compressed by the top ring nut for sealing the contents. So no surprise that the damper had a tough feel way too stiff from that type of "seal" . So instead went for real polyurethane hydraulic u-cup seals , no question about o-rings for rod seals certainly.
Konis are wellknown for stiff compression forces, extension setting is easy to dial with the classic bottom key for preloading the extension valve from light to very strong. No big deal but the compression setting had to be worked on , basically set by a stainless spring steel wave washer acting on the extension valve. I took the washer out for testing with 1 mm gap in the set but this gets you a few mm of backlash so in again but I hammered the wave washer for a lot less preload on extension valve. For oil fill I used HLP 10 hydraulic oil as you don´t want oil foam forming in hydraulics, would be cathastrophic in hydraulic machinery. You fill up oil till no backlash in full stroke from air is noticable and then a bit more. There will be some volume of air certainly but not critical here in standard mounting condition on the bike. Same with the original damper, some air inside is required .
So my conclusion, once you changed these rubber seals for real u-cup types by fabricating an alu adapter bush to go in the big ring nut and another wiper seal in the brass top nut you just do a bit of hammering the wave washer to your liking and the Koni should do nicely on your Vincent for decades.
In my eyes the main flaw of the original Vincent damper are the o-ring seals acting on some soft steel piston rods - no durable combination. We had endless measurements here of components to four figures but no hardness numbers of the rod. Not surprising the leaking calamity then, you will not find any shock absorbers or teleforks since mid-fifties with non-hardchromed piston rods or stanchions - not for good looks or rustprevention, but for protection from scoring, like with hydraulic machinery with their cylinders. So simple action on the original damper: Get u-cup seals and have the rod hardchromed or copy it from cheap hardchromed piston rod material. But yes, you still have the same damping for compression and extension, Vincents were still stuck in their friction damper thinking at their time - not my choice .
Vic
old Koni seals:
wave washer left, fat spring for extension preload:
u-cup seal in alu bush, blue dust wiper in brass top nut :
assembled Koni top, below a Hagon piston:
Konis are wellknown for stiff compression forces, extension setting is easy to dial with the classic bottom key for preloading the extension valve from light to very strong. No big deal but the compression setting had to be worked on , basically set by a stainless spring steel wave washer acting on the extension valve. I took the washer out for testing with 1 mm gap in the set but this gets you a few mm of backlash so in again but I hammered the wave washer for a lot less preload on extension valve. For oil fill I used HLP 10 hydraulic oil as you don´t want oil foam forming in hydraulics, would be cathastrophic in hydraulic machinery. You fill up oil till no backlash in full stroke from air is noticable and then a bit more. There will be some volume of air certainly but not critical here in standard mounting condition on the bike. Same with the original damper, some air inside is required .
So my conclusion, once you changed these rubber seals for real u-cup types by fabricating an alu adapter bush to go in the big ring nut and another wiper seal in the brass top nut you just do a bit of hammering the wave washer to your liking and the Koni should do nicely on your Vincent for decades.
In my eyes the main flaw of the original Vincent damper are the o-ring seals acting on some soft steel piston rods - no durable combination. We had endless measurements here of components to four figures but no hardness numbers of the rod. Not surprising the leaking calamity then, you will not find any shock absorbers or teleforks since mid-fifties with non-hardchromed piston rods or stanchions - not for good looks or rustprevention, but for protection from scoring, like with hydraulic machinery with their cylinders. So simple action on the original damper: Get u-cup seals and have the rod hardchromed or copy it from cheap hardchromed piston rod material. But yes, you still have the same damping for compression and extension, Vincents were still stuck in their friction damper thinking at their time - not my choice .
Vic
old Koni seals:
wave washer left, fat spring for extension preload:
u-cup seal in alu bush, blue dust wiper in brass top nut :
assembled Koni top, below a Hagon piston: