TY250 Fork Improvement

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TriCub
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Re: TY250 Fork Improvement

Postby TriCub » Tue Jul 01, 2014 10:23 pm

Seems odd that the KT has smaller porting on the top of the damper than at the bottom. The TY isn't a lot better as all the oil has to go through both sets of hole on compression and the smaller is going to control the damping. Perhaps an increase in the top holes would be a good place to start before any porting will have an effect.



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Kombivan
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Re: TY250 Fork Improvement

Postby Kombivan » Wed Jul 02, 2014 2:45 am

I hear the two stage springs are the go.



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Re: TY250 Fork Improvement

Postby Stanm » Tue Jun 16, 2015 7:57 pm

Hi
I finally got around to doing a bit of fork work.
I purchased a set of magical springs and that in it self was a feat. Another story. These springs are longer than the standard springs and don't require any spacer.
The the spring also takes up more air volume so to get the same air gap you need less oil.

I settled on 170ml oil 60%atf and 40 %10/30.
I also did what I have seem recommended many times. I block off one of the 2mm dia rebound damping holes in each damper rod.

This has resulted in some improvement and the best all round performance yet. Saying that on big downs they still feels a bit hash

Any body had any progress?? with emulators??etc

Cheers



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Re: TY250 Fork Improvement

Postby David Lahey » Tue Jun 16, 2015 9:18 pm

yes I've been trying a few things over the past month
The bike is my 250 Godden Majesty and it has standard TY250 fork springs with the preload set at 35mm. I put gold valves in them a while back, using the gold valve springs that came fitted to the valves, which I had assumed were the right ones for TY250 forks. This involves cutting off the top end of the damper rod spring seat and drilling extra holes in the bottom end of the damper rod. The intention of the gold valves is that all the compression damping is managed by the gold valve rather than by the compression damping holes in the damper rod.
With those gold valve springs I ended up reducing the gold valve spring preload until it was zero, and that felt pretty good. A while later I rode Greg Harding's Fantic 240 and wanted to get those TY250 forks even better.
About a month ago I checked the other springs in the gold valve packet and noticed that there was a pair of springs that were softer than the ones in the bike so gave them a go. First off I tried one turn of spring preload and rode a wet rocky trial and they were very supple and felt magic on really slippery stuff, but would bottom out more than ideal on sharp hits. I considered fitting some stiffer fork springs, but decided instead to increase the pre-load on the gold valve springs to 2 turns. I then tested it at Classic Dirt 11 at Conondale on some seriously rocky rooty stuff and they still have good suppleness and are now much more resistant to bottoming. I'm thinking they might even benefit from going to 1.5 turns preload from 2, but will ride the next trial with them at 2 turns before changing anything


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Re: TY250 Fork Improvement

Postby Stanm » Wed Jun 17, 2015 8:08 pm

Hi David
In my other Comp TY I have standard springs with from memory 45mm preload spacer that is down about 10mm from standard.
I use a bit more oil 195ml and this performs OK. However i tend to like to ride the other bike.
In saying this I have ridden a TY now for 10 years and you get used to the bike and develop a lot of strength and resilience. New rider and modern rider don't think my Ty's are anything special.
My son is am A grader an I ask him to comment on the two setups and he says they are both OK. So I am still scratching my head!!!
However I am not unhappy with my current setup but as we all know there is always that little improvement that we would all like.

Look forward to other comments.



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Re: TY250 Fork Improvement

Postby David Lahey » Wed Jun 17, 2015 8:34 pm

Funny you say that about your other TY. I also ride a TY250A and find switching between it and the Majesty quite a revelation. After spending so many hours trying different setups in the forks on the Majesty, I can jump on the TY250A and be pleasantly surprised at how nice its (completely standard) front end feels. Maybe its just that there is less weight on the front end of the TY250A, but it steers like a dream and the forks behave themselves on everything except big front-down landings where they bottom a bit too easily.


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Re: TY250 Fork Improvement

Postby TriCub » Thu Jun 18, 2015 9:45 am

David Lahey wrote:Funny you say that about your other TY. I also ride a TY250A and find switching between it and the Majesty quite a revelation. After spending so many hours trying different setups in the forks on the Majesty, I can jump on the TY250A and be pleasantly surprised at how nice its (completely standard) front end feels. Maybe its just that there is less weight on the front end of the TY250A, but it steers like a dream and the forks behave themselves on everything except big front-down landings where they bottom a bit too easily.


Have you tried a dual rate spring and a longer bottoming cone in a stock set?



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Re: TY250 Fork Improvement

Postby David Lahey » Thu Jun 18, 2015 7:28 pm

TriCub wrote:
David Lahey wrote:Funny you say that about your other TY. I also ride a TY250A and find switching between it and the Majesty quite a revelation. After spending so many hours trying different setups in the forks on the Majesty, I can jump on the TY250A and be pleasantly surprised at how nice its (completely standard) front end feels. Maybe its just that there is less weight on the front end of the TY250A, but it steers like a dream and the forks behave themselves on everything except big front-down landings where they bottom a bit too easily.


Have you tried a dual rate spring and a longer bottoming cone in a stock set?

Standard TY250 springs are dual rate, and you can always increase the overall spring rate by running more oil. I've tried that and it does work and I've arrived at a really good spring rate in the Majesty TY250 forks by doing that. I just haven't ever fiddled with the TY250A forks. While the Ty250A forks do bottom now and then, they never give a shock to the hands, so I'm happy letting them bottom in their nice soft way. I would think that trying longer bottoming cones would mean lots of hours of pulling the bottoms off the forks, doing some lathe work and putting them back together again, trying different designs. Thats a lot of time commitment


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Re: TY250 Fork Improvement

Postby Stanm » Sat Jun 20, 2015 9:17 am

Hey Tricub
How would u do the the bottoming cone set? I have a set of DT forks that came with a ty and I have examined these and found that the cone set is larger. They come out with a circlip so I believe you could swap them but as they are longer you would need a spacer tube. This could howerever interfere with the piston on the damper rod. Not sure?? That is something i have thought of and would be worth a try.
This is another subject I have been thinking about. Using DT fork tubes but i was thinking how I could use fit the original cone set. But as you point out I could try with the larger ones. Thanks I have another job follow. I will let you know how I go.
My last comment I mentioned I am still scratching my head. But I was thinking my set up cannot be that bad as my son won the A grade two day Twinshock last year against at least one expert and other A grade riders on one of my Comp TYs.

Cheers



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Re: TY250 Fork Improvement

Postby TriCub » Sat Jun 20, 2015 9:13 pm

To get a longer bottoming cone you have to machine the bottom of the fork tube to allow the valve to fit further up into the tube and fit a spacer. This can then let you have a longer taper to get a more progressive increase in damping before bottoming. Doing this will reduce the travel or the top out length of the forks but it can be corrected by spacing the damper rod further out of the bottoming cone and fitting a longer bolt. This will in turn bump up the spring pre load a little as well.
All quite straight forward if you have a good machine shop but probably easier to control bottoming by adding more oil to the piont where the reduction in internal volume close to bottoming causes quite an increase in air pressure within the fork. Heavier spring can help as well , I used MX springs in my Sherpa to help keep the forks from bottoming on long down hill sections.




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