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TY250 Forks on TL125
Posted October 19, 2006 - 01:44 PM
Posted October 19, 2006 - 03:40 PM
The option I chose was to modify the frame where a triangular piece is cut out of the frame behind and below the steering stem, the frame is heated and bent rearward to close the gap thus reducing the steering stem angle. My wheelbase was reduced approximately 2-1/2 to 3 inches. The bike now steers like a TY175 and I use all stock components. The only drawback I have experienced so far is a situation where dropping into a shallow narrow gully the forks wanted to fold under rather than compress. This was because the front wheel was touching the uphill side before I had completed the downhill side. Other than that I am happy with the mod.
The following quote is from the TL125 Home Page.
As mentioned earlier TL has a tendency to "fall into a turn", i.e. in tighter turns the bike wants to increase the steering angle and one has to hold back against the bars. During turning the bike is also very sensitive to obstacles, and has quite a bit of "bump steer". These handling characteristics are probably a combination of "tall" triple clamp (ie. one where fork tube plane is offset substantially from the steering stem), high rake angle and relatively high center of gravity and foot peg location.
I been experimenting with various modifications to alleviate this problem while still keeping the bike in AHRMA "modern classics" class. Easiest improvement is raising the fork tubes up in the triple clamps. Raising the tubes (ie. tubes sticking up from the top triple clamp) just 10mm to 20mm (1/2" to 3/4") makes a difference and doesn't reduce ground clearance to any noticeable effect. The next step is changing the rear shocks for longer units. Original Honda units are 14 1/2" long (370mm), I have swapped them for 15 1/4" (390mm) Works Shocks units from B&J Racing. These modifications together changed the measured rake from 28.5 degrees to about 25 degrees (note: these were measured so they may not be absolutely correct, however the decrease in rake is about 3 to 3.5 degrees).
To address the triple clamp offset issue I actually changed the whole front end for a unit from mid 70s Yamaha TY250. TY forks are slightly shorter than TL, so they had the same effect as raising TL forks in the clamps.
Of course I'd like to hear from anyone who might have tinkered with the TL frame geometry etc."
Posted October 19, 2006 - 11:28 PM