May 23, 20197 yr Bit late on parade, but your OP asked what is the width of various tyres... So I got the Micrometer out.. Pirelli MT43 275x21 74.1 mm Michelin Trials Light 80x100 78.7mm Dunlop Tr Universal 275x21 68.9mm RG Arron 275x21 67.9mm So if you really need a narrow tyre, then the old 275x21 is about 10mm less than the new 800x100 types. They used to be just either 275 or 300 many years ago. …. Is that an expansion chamber I see on that bike, will make for interesting riding in some sections...! .
May 24, 20197 yr Author Rim pic below. I's a DID rim. So are the "speedo drive lugs" right near the axle on the side away from the brake drum? 3 little tabs that stick out just a little? Did a little painting of the frame today. It's supposed to rain for 3 days starting tomorrow, so I had to get that going. Handlebar risers just need longer bolts to finish up.
May 24, 20197 yr 5 hours ago, Tillerman6 said: So are the "speedo drive lugs" right near the axle on the side away from the brake drum? 3 little tabs that stick out just a little? That's them yes those three little lugs. The speedo drive casing normally fits between the hub and the fork leg. It's a good design because you can take the wheel and backing plate away from the bike easily without having to undo the speedo cable. The speedo drive and cable can just hang there waiting for reassembly. I've been trying to take some rim stamping photos of my mystery wheel but my phone battery went flat. Photos coming later
May 24, 20197 yr Author 3 hours ago, feetupfun said: That's them yes those three little lugs. The speedo drive casing normally fits between the hub and the fork leg. It's a good design because you can take the wheel and backing plate away from the bike easily without having to undo the speedo cable. The speedo drive and cable can just hang there waiting for reassembly. I've been trying to take some rim stamping photos of my mystery wheel but my phone battery went flat. Photos coming later While we are on the subject of tracing parts back to their parent machines, I remembered that I had a "Yamaha Cross reference Index file on my computer. I can't seem to get it to copy and send to the Trials Central website, but I'm working on that. I think everyone that has an old Yamaha should have that information available. It's really just a list of the first 3 digits of the Yamaha part numbers and a "Tag" name for each one. The first 3 digits are code for the original bike that the parts were built for. Other bikes use the same parts later on, but having the 3 digit code on a part tells you what other bike the parts were originally used on. That way you can look up that year and model on Ebay or whatever under the original year and model and possibly find your missing parts that way. For instance, the part numbers beginning with 434 were TY parts. My brake shoes off the front wheel were 322 which was from an RT2 MR ( maybe a street bike?) I used Windows Photo Viewer to open these. Hope this helps! I will keep trying.
May 25, 20197 yr Yes that is a cool way to help ID Yamaha parts if they have the prefix on them. That list can also be found using google. I was told by a Yamaha dealer that there is a system that records each time someone asks for a Yamaha part that is "no longer available" and once enough people have asked, they start making them again. I suspect that TY175 kickstart levers might be one such part that they now sell. That prefix on your brake shoes doesn't help much with identifying your backing plate though because many Yamahas models use that same pattern of brake shoe. Edited May 25, 20197 yr by feetupfun
May 25, 20197 yr Photos of my mystery wheel. In the photos it is holding up the front end of a derelict TY175JC Edited May 25, 20197 yr by feetupfun
May 25, 20197 yr This brake plate came with the mystery wheel. The arm on it in the photos is TY175. I use this backing plate when I'm machining TY twinshock front wheel brake shoes because it doesn't have the arm sticking out like a TY twinshock backing plate does. Edited May 25, 20197 yr by feetupfun
May 25, 20197 yr TY twinshock front backing plate vs MX YZ 125 backing plate. Both use 110mm brake shoes
May 25, 20197 yr Author Feetupfun, I think actually I like the MX/YZ backing plates better since I'm not running a speedo. They sure made a lot of different versions over the years! Those shoes of yours marked 401 are from a MX 125 originally and you could look for more shoes on Ebay or whatever from that bike and that's how I got my new shoes that are on my bike now. They were brand new and not all that expensive on Ebay. They were not 401 series but something close. I checked out the Racetech Gold fork valves and looks like they don't make a version that will fit the 75 DT 250 B/C forks. I think the do make something for the MX/YZ forks in some years. So are you machining down the new shoes to fit the drum housings better, or you have found a source of brake shoe material and scrape off the old ones and somehow attach the new ones yourself? If I get rich I could email Race Tech and see if they could send me a set of valves that had not been sized for another application. Possibly I could thread them and adapt them to my forks? Do they go inside the forks or sit on top?
May 25, 20197 yr 41 minutes ago, Tillerman6 said: Feetupfun, I think actually I like the MX/YZ backing plates better since I'm not running a speedo. They sure made a lot of different versions over the years! Those shoes of yours marked 401 are from a MX 125 originally and you could look for more shoes on Ebay or whatever from that bike and that's how I got my new shoes that are on my bike now. They were brand new and not all that expensive on Ebay. They were not 401 series but something close. I checked out the Racetech Gold fork valves and looks like they don't make a version that will fit the 75 DT 250 B/C forks. I think the do make something for the MX/YZ forks in some years. So are you machining down the new shoes to fit the drum housings better, or you have found a source of brake shoe material and scrape off the old ones and somehow attach the new ones yourself? If I get rich I could email Race Tech and see if they could send me a set of valves that had not been sized for another application. Possibly I could thread them and adapt them to my forks? Do they go inside the forks or sit on top? Yes your magnesium MX/YZ/IT backing plate is cool and most importantly the brake torque slot matches the lug on your fork leg. I get my brake shoes relined with oversize thickness linings and then mount the shoes on a backing plate and machine the linings to suit the diameter of the drum they are going into, using a lathe. Most of the brake drums in my trials bike hubs have either been remachined at least once or are worn and need remachining so buying brake shoes with standard linings is not an option. Racetech do make gold valves to suit 34mm DT forks, but they don't list them as such in their on-line catalogue, nor do they list gold valves for 34mm TY250 forks. I bought the gold valves they list for 34mm YZ MX forks and used them on TY250 forks. The Racetech website explains where they sit and how they work. You do need to machine the end of the damper rods and drill extra holes in the damper rods to fit gold valves. Then buy much stiffer fork springs and spend about 20 hours getting the setup working well.
May 26, 20197 yr Author Had a frustrating morning this morning as the seals I bought on Amazon did not fit the fork tubes. The fitment list said they would work, but did not. And they want about 40.00 US for each seal if you buy OEM seals from Yamaha 584-23145-50-00 for the 75 DT250. So I am trying a set from All Balls. For 30 bucks you get 2 seals and 2 dust covers. Hope they fit. I almost wrecked one of my fork sliders trying to get the first ones installed. It had a steel outer ring and it was .006" too big for the fork slider GRRRRRRRRRRRRRRRR! So it's going back. Live and learn. The next ones do not have the steel ring on the OD, so if they don't fit at least it will not damage the inside of the tube.
June 16, 20197 yr Author Well, more seal problems- the All Balls seals jammed half way into the seats on the fork tubes and had to be removed. I made a male plug the same size as the fork tube and plugged up the bottom end with a threaded thick aluminum washer. this lead out to another washer on the outside bottom end and another nut. this sealed up the bottom end and I poured the fork leg full of water. Then with the fork tube in special jaws on the vise I put the male plug thru the seal and it rested on the water inside the tube. the seal kept the water inside when I hit the top of the plug with a hammer. After a few whacks with a 5 pound mallet, the seal was pushed out from the inside by the hydraulic pressure. There was still some damage to the outside of the seal, but the fork tube did not get any scratches from a wrench or screwdriver this way. Now I am wondering if I can grind down the seals to a more reasonable diameter. The fork tubes are 45.999mm on the ID or 1.810" but the seals are .012" oversize or 1.822". Any ideas? I know they are supposed to be tight, but the seals are not just rubber. Has any of you guys ever run into this problem before?
June 17, 20197 yr Consider a set of SKF seals instead? They keep getting the best reviews from my friends and fellow riders. Just a thought.
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