TL125 /Koni rear shock spring rate?

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Jools
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Re: TL125 /Koni rear shock spring rate?

Postby Jools » Sat Dec 19, 2015 11:59 am

The thing is with the damping, the Konis are rebuildable, and I'd bet the seals etc are still available -maybe from Ikon, so I don't see that it would be a major drama to re-valve for lighter damping to suit lighter springs. (I've done it with front forks but not rears - it can't be too hard eh?)
I'll advertise TY175 springs wanted now!
Thanks again for your help David.
-Jools



David Lahey
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Re: TL125 /Koni rear shock spring rate?

Postby David Lahey » Sat Dec 19, 2015 1:02 pm

Sorry to dampen your enthusiasm, but I don't think seals to fit the old style KONIs are available, or maybe I should say that they became no longer available as a spare part in the late 1980s. You can buy modern KONI/IKON seals but they are different (and not interchangable). Last time I tried to buy the old style seals was in the early 2000s.

You could modify the sealing arrangement and inner tube retaining method in the old KONIs to allow you to use some other shaft seal that was the right size for the shaft, but that machining work would cost lots and you would still have the KONI damping.
KONIs use an interesting design where the underside of the seal sits on a belled washer on top of a spring, that rests against the inner damping tube end cap. This holds the tube down and the seal up, and allows the seal to move a bit if needed. New seal housings would be needed (maybe someone is making them - I haven't heard of anyone though)

If you do find anyone selling seals to suit old KONIs please post it up because the old KONIs do go well on trail and MX bikes of their era.


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Jools
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Re: TL125 /Koni rear shock spring rate?

Postby Jools » Sat Dec 19, 2015 1:14 pm

Mmmm, the plot thickens!
I do have a lathe, but it's a Seneca, about 100 years old, and I wouldn't trust it for fine tolerance work.
(But I do have a good mate who owes me, and who has a lathe)
:lol:



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Re: TL125 /Koni rear shock spring rate?

Postby David Lahey » Sat Dec 19, 2015 1:42 pm

All this stuff about old shockies had me looking further in the shed and I found a couple of relevant things

One was a shockie I'm pretty sure is TY250. The spring has the same diameter wire and coil diameter as for the TY175, but has one less coil (14) which puts the rate at 45 lb/inch

The other thing I found was a set of old KONIs I had rebuilt professionally (by RAD) in the early 2000s to use on a Cota 348. The seals appear to be the new type KONI seals, and they are held in seal retainers that were supplied by the shockie rebuilder. I don't know if they modified the old seal retainers or were able to buy new seal retainers that suit the old shocks and the new seals, but they look new. I remember those shocks had a very dead action so I didn't compete with them. That same bike is nice to ride with 1970s Boge Mullholland trials shocks, better with 1980s Marzocchi trials shocks, better with 1990s Falcon Trials shocks and still better with mid-2000s Falcon trials shocks


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Re: TL125 /Koni rear shock spring rate?

Postby David Lahey » Sat Dec 19, 2015 1:49 pm

Jools wrote:Mmmm, the plot thickens!
I do have a lathe, but it's a Seneca, about 100 years old, and I wouldn't trust it for fine tolerance work.
(But I do have a good mate who owes me, and who has a lathe)
:lol:

Sounds good. Mine is old too but not that old. It is a 3 1/2 inch swing Myford and I guess it would be from the 1940s. The motor starting coil failed about 10 years ago and that is the only thing that has ever stopped it (it now has a 35 year old motor scavenged from a drill press)


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Re: TL125 /Koni rear shock spring rate?

Postby David Lahey » Sat Dec 19, 2015 2:24 pm

Here is a photo showing the old and new style KONI seals and an old seal retainer
Attachments
IMAG3175[1].jpg
IMAG3175[1].jpg (2.09 MiB) Viewed 14626 times


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Jools
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Re: TL125 /Koni rear shock spring rate?

Postby Jools » Sat Dec 19, 2015 2:51 pm

Yer a wonderful man David!!! All good info thanks. I do also have a mate who has CNC facilities, who can machine a piece of aluminium thin enough that you can see through it! (I know that sounds apocryphal, but it's not, I've seen it). He builds RC jet turbine engines for fun amongst other things.
And here's the thing... I value his skills and machinery so much that I've never actually asked him to any machining for me... almost as if I'm waiting for the REAL job from HELL before I exploit the friendship!

That's handy to know about the 45lb TY250 spring, that opens up the potential supply chain!

"I remember those shocks had a very dead action so I didn't compete with them".
"dead action". -That sounds like over-damped and undersprung?

We have to bear in mind here that all this is for a TL125. Like, it's not serious comp riding, just for bopping about on my 30 acres of Wombat state forest gullies, and helping my grandson getinto trials. I just want something basically functional. (I know... wiseguys will be replying, "just get TY!" (Well I probably would if I could find a half decent one for a decent price!)

:wink:



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Re: TL125 /Koni rear shock spring rate?

Postby David Lahey » Sat Dec 19, 2015 3:46 pm

Yes I'm not surprised about machining aluminium so thin you can see through it. Chip packets and decorative helium balloons have a layer of aluminium deposited on the plastic to make the plastic less gas permeable and it is quite easy to see through it.
Dead damping for me means there is too much rebound damping for getting lift when jumping up or over something. It can also mean that the rear suspension packs down when compressions are close together in time. A typical place for this to cause a problem in trials is when riding a rocky creek bed. It is in the relationship between the spring rate and the rebound damping that problems arise. Trials bikes benefit from a low spring rate to make them easy to ride slowly, but shockies like KONIs are made for use with stiff springs.

Yes for what your TL is going to be used for, the KONIs should be fine


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Re: TL125 /Koni rear shock spring rate?

Postby Jools » Sat Jan 09, 2016 10:35 am

An update on this. Thanks to Terry (Katostrom) who very kindly gave me a pair of TY shocks/springs for my experiment.
All that was needed to fit the TY springs to the Konis was a spacer/packer 35mm long to compensate for the shorter TY spring. My temporary measure was to use a poly pipe (Black) hose fitting - (I think it's for 1 1/4" pipe). This is a perfect fit over the Koni body, and although cosmetically challenged, (a nice aluminium ring would look pretty) the poly will probably stay there!
Yes it's overdamped, but certainly the lighter springing is a big improvement over the oversprung Koni and also the shagged original TL damper.
There's a weight cost, the Koni is 500g heavier than the TY. I used the Koni top spring seat which allows the thinner gauge TY spring to float about a tad, - be easy to make a ring to fix this
So thanks for your input lads.

Image



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Re: TL125 /Koni rear shock spring rate?

Postby David Lahey » Sat Jan 09, 2016 12:59 pm

Thanks for showing us that Jools, good to see you sorted those Konis


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