Author Topic: Harsh Cer Forks.  (Read 23889 times)

Offline chrisk

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Re: Harsh Cer Forks.
« Reply #225 on: October 16, 2018, 22:00 »
The oranges and apples variation isn’t that great Grant.

In both cases the main objective is to keep the front wheel on the ground as much as possible, over various surface conditions.

Dampening, and rebound are adjusted to suit riders weight and basic riding position, whilst still being compliant.

Sure, the oranges have longer travel, but the basics of the fork operation are very similar to apples.

I rode my 78 DT400 2000klm on some of the worst corrugated roads in Australia, if I did this trip on my WR the trip would have been so much easier.

Frankly, I doubt very much that anyone could doctor the DT forks to react the same as the WR.

Unlike Vince, I couldn’t be bothered trying to make the standard Laverda toothpick type forks ride like a modern bike.... easier to change to something that works much better, from the get go.

Once Vince gets his forks sorted, to his liking, I doubt he’d never consider swapping them onto a Pannigale, because they work so well. Extreme example, but you know what I’m getting at.

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Offline Vince

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Re: Harsh Cer Forks.
« Reply #226 on: October 16, 2018, 23:08 »
I get fluid dynamics is complicated, get that velocity squared stuff but I am not doing the maths.All I am doing is drilling a hole as going for a ride.Or changing fork weight or height and again going for a ride.The bloody reason why this has taken so long is in both cases,Cer on the Laverda had way to hard Emulator springs when I bought it and one only High Speed compression hole.And the Maz forks on the Pantah came new with way to stiff major fork springs and  the suspension guru recommended and sold me way to stiff replacements. In both cases I spent years changing stuff with zero effects that I needed.They need to be close to correct for these adjustments that I have tried to affect them.If either of these things were correct when I first did these jobs I probably would have left them where they were. But both were supplied by the local suspension juro who does great work on modern bikes but far from that on old bikes.At no point did he suggest changing anything after follow up visits.I got 100% more info and much better advice from the Race Tech vintage bike bloke in the USA,Matt who clued me in on what was wrong in the basic fit up.

Offline Piranha Brother 2

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Re: Harsh Cer Forks.
« Reply #227 on: October 16, 2018, 23:44 »
Good on you Vince. It is fun and engaging to play with improving something - why else would we fit flat slide carbies, Jota cams and myriad other mods to our old bikes. What Cam did to his Ceris is a perfect example of improving something from stock.

When i ran 18s on my SF with 35mm Ceris and drum that later served for twin Brembos it behaved incredibly well on bumpy roads. Eventually fitted Marzocchi M1Rs but they were so poorly set up that it was a retrograde step. Troubles really started when I went to 17s (which increased tyre choices by about 5-fold) - then you get into incompatible steering geometry (rake and trail are all wrong).

Going with modern, cartridge type forks was a big improvement (as Chris K did), but again, the geometry on a frame with around 29 deg of rake and shallow offset triple clamps meant it was never quite right. Nothing dire, it still rode well on public roads of all kinds and was fine to ride at the Island, save the cornering clearance issues.  ... so the final stage is where I'm at now, redesigning the geometry. It might turn out to be a nightmare, but it might make me smile widely. Either way, I have bike #2 as the more stock fallback option.

At the end of the day it's all part of a personal journey.
What ... leave it standard??!!

Offline Dellortoman

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Re: Harsh Cer Forks.
« Reply #228 on: October 17, 2018, 00:12 »
I've also fitted damper valves to a couple of my Marzocchi forked bikes (Jota and Ducati MHR). I think the fork action was improved, but my arse isn't particularly sensitive to bumps so I'm not really sure. Maybe I need Vince to bring his calibrated arse to Tassie to evaluate the suspension on my bikes  ;D
Location: Tasmania, Approx 42°53’S 147°23’E

Offline Chris M.

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Re: Harsh Cer Forks.
« Reply #229 on: October 17, 2018, 00:42 »
Vince I love your determination but ChrisK hit the nail on the head when he said;"I couldn’t be bothered trying to make the standard Laverda toothpick type forks ride like a modern bike.... easier to change to something that works much better, from the get go."

But ...... I'm as bad as you are, installing teflon bushes into my 38mm Marzocchi forks.

I'm afraid there is no technology available that you haven't already tried that will fix your forks. The Japs discovered this in the early 80's so they introduced bushed forks which set the standard for mass produced suspension. You cannot improve your forks with out reducing sticktion.

There is a solution to all this and that's to just buy a brand new set of forks from Canada that already have teflon bushes and Maxton cartridges or buy some 38mm Cerianis with adjustable compression/preload from Hungary. No idea of the cost of the EN Products ones and I'd expect it's horrific but the Hungarian ones cost under 2 grand.

http://www.e-nproducts.com/products.php

http://www.e-nproducts.com/products.php

Offline Vince

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Re: Harsh Cer Forks.
« Reply #230 on: October 17, 2018, 00:58 »
My memory of Tassie is you dont have bumps, even the dirt was pretty smooth.Hi Chris,your bush comments are true and if your really looking at major improvements that's needed.But by then your into fork flex territory.That Kawasaki fork I fitted to that Husky replaced the std 35mm fork with 43mm ones and a much better brake. Even with the weedy drum brake on the Husky you could feel the forks bending,majorly better with the 43mm ones. Years before I did that Husky stuff I fitted some latter Yamaha forks to an XT 500 with the alloy single shock swingarm converted to twin shocks to get more suspension travel. That bit worked great but it ended up with about 150mm of trail so I got the local frame bloke to push it closer to 90mm on his Motoliner.
That was a great success,till it caught fire and burned to a crisp a few years later.Sometime around then I fitted a Ducati Parallel twin Maz disc brake frontend to my 64 Bonnie,that also worked great. So I have been doing this stuff for a while.

Offline AndyW

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Re: Harsh Cer Forks.
« Reply #231 on: October 17, 2018, 04:00 »
I fitted some latter Yamaha forks to an XT 500 with the alloy single shock swingarm converted to twin shocks to get more suspension travel.
A mono-shock  T500? That would be a rare beast indeed Vince, are you sure you don’t mean that the other way around?
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Offline Vince

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Re: Harsh Cer Forks.
« Reply #232 on: October 17, 2018, 04:30 »
I bought the whole rolling chassis off a later model 250 Yamaha 2 stroke, it was a single shock bike so I got some alloy welding done for twin shocks and fitted some piggyback Husky shocks I had acquired. So that was an XT 500 with 280mm of suspension travel,better than the 100mm it came with.The fire happened because the XT tank had vertical fuel taps and if you put it on the ground it would take a core sample of dirt that would end up in the needle and seat. Discovered that after the fire.
There was 10 blokes on that ride and when the fire started all 10 tried to bury the bike in the soft dirt it was on.Zero chance of putting it out,the fuel in the tank ended up boiling off and the cap was like an Oxi torch. Sad end to a great bike. BTW you should have seen how hard I was watching those swingarm shock mounts at first, just a bit scary doing small jumps at first. It was fine, no bending or cracking. I was a bit more crazy back then.Fun job to do




Offline Vince

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Re: Harsh Cer Forks.
« Reply #233 on: November 13, 2018, 20:27 »
I was pretty happy with the forks on The Snowy Ride,there are 2 more things I want to try but not at the moment. The shocks, Icons are something that needs work. We did a shocker, get it of a road called The Olympic Way, in my case it felt like someone was lining up and kicking me square up the arse ever second. Bang Bang Bang.Only one other bloke said the same and that confused me as usual but with some thought as usual its on comparing Oranges with oranges, more Laverda orange references. For a start I weigh a lot more that everyone expect a very tall bloke and his bike has the later moved forward upper shock mounts, when that was done in the 70s in the off road world it was called layed down the shocks, it gives a more compliant ride as I think the forces move more freely on the racked angle. Must be the reason why Laverda did it plus it was a stronger arrangement mounted between the joining of frame rails.The only other bike similar to mine was ridden by a much lighter bloke, 75 to 80 kg compared to my 125kg.My issue with Icons is they have a huge bump stop that makes feeling the shock bottom hard to notice plus they do multi rate springs that firm up when getting to the end of travel. My little trick to identify whats happening is to push this bump stop down the shock shaft and see how much sag it has and what travel is being used.I couldn't do this on the ride as the soft panniers where in the way but I could jack up the preload and I did. Now preload usually has a minimal effect on spring rate, except with these multi rate springs it closes up the soft end of the spring and you lose compliance and that's exactly what happened.I did take some of the harsh big hits away but I then could feel ever tiny small hit, and also it jacked the rear a bit and made the bike a touch nervous, especially in the corrugated dirt bit we did. My bike has 20mm longer shock tops anyway, available from Icon as a spare part and added a few years back as I mainly do tight roads and that and the forks through the trees lightens the steering a lot and I like that.So this added preload at the rear plus Marty's replacement wheel with the std aspect rear tyre, 90 section as opposed to my usual 70 raised the rear just enough to add this nervousness in the loose gravel section. Still rideable and fine mostly but noticeable. Had me on tippy toes with the thickly padded touring dual seat plus air hawk. Anyway cut to the point, I am ordering the next hardest springs from Icon and I hope I can borrow a spring compressor from someone to swop them out and we will see if its helps with compliance on the more local shit roads and we have plenty of those.

Offline motoddrob

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Re: Harsh Cer Forks.
« Reply #234 on: November 14, 2018, 00:03 »
I'm not so sure about Ikon shocks these days given the choices available today. They're 70s technology.
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Davo

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Re: Harsh Cer Forks.
« Reply #235 on: November 14, 2018, 05:26 »
My Maxton shocks are great.

Offline Vince

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Re: Harsh Cer Forks.
« Reply #236 on: November 14, 2018, 06:30 »
Icon do an alloy body version for $600, the springs are $80 or so.

Offline Tippie

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Re: Harsh Cer Forks.
« Reply #237 on: November 14, 2018, 06:48 »
My Maxton shocks are great.+++++
With all your suspension work Vince, getting the correct weight springs is the absolute start point.
I used to change springs for two up touring (probably the two of us combined weighed your 125kg!), was brilliant, bike behaved like it had no passenger, totally different to the alternative of jacked up preload bottoming out all the time.
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Offline motoddrob

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Re: Harsh Cer Forks.
« Reply #238 on: November 14, 2018, 06:52 »
Alloy body but with 70s technology?? or have they caught up?
I do have a set on the SFC
If I was to buy something today I'd probably look at
Gazi or YSS or cashed up Ohlins or Maxtons
Have to admit to being slightly cynical to Ikons.
Last dealings left an unpleasant taste!
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Davo

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Re: Harsh Cer Forks.
« Reply #239 on: November 14, 2018, 06:54 »
If you are keen on antique tech Vince I have a set of Konis you can have.