OLD POST I KNOW BUT... I recently did the 144cc big bore to my TL125. Works great, but not sure I'd go through all the problems again BUT what a difference it made. Now it's making me wonder about the addition of more flywheel weight. I had a friend at a bike shop long ago that would measure id/od and use a sleeve from car engine, cut them to width, freeze the flywheel and heat the sleeve, put them together and produce a heavier flywheel. It worked but you were limited without machining to what ever weight you got, that was it. It worked on small MX 2 strokes to make them ridable for kids. Has anybody tried something like this????
Slow process but my 75 TL125 is taking shape. It was a barn find for sure based on the condition it was in. It now has the 144cc big bore, "EVERYTHING" else needed cleaning, rust removed, replaced or rebuilt. Not in stock trim but hopefully a fun rider.
In going through old posts about TY175 forks I came across a post you had about 175 vs 250 TY forks. I have a 75 TY175B, do you know of stiffer springs that would fit? You mentioned TM125, TY250 are too large to fit the stock 175 forks correct? I know a full swap 175 to 250 would be best but for know maybe just springs will have to do. 190lbs with gear, additional 1 inch of preload currently.
Thank you, Rod
TM125 springs will fit in TY175 forks but were too stiff for me on initial compression. They are straight rate springs. TY175 springs have a soft initial spring rate which suits trials riding.
Other than TM125 springs I didn't try any others in TY175 tubes.
If you have an extra inch of preload over standard you have probably reduced the available fork travel by allowing the springs to coil bind before all the fork travel is achieved.
TY250 springs are too big in diameter to fit TY175 tubes.
If bottoming out is your issue, I hope you have tried using heavier oil.
190 pounds rider is not that heavy for using TY175 springs. I suggest you see how sacked out your springs are and if they are sacked out, get some good standard TY175 springs and set the preload to around 25mm and use heavy grade fork oil.
What is your actual preload dimension? What fork oil are you using? What is the free length of your springs? Are you sure you actually have TY175 springs in there?