April 21, 20233 yr I bought a new chain and sprocket kit for for my TL250 but no spacer was available for the rear sprocket. I can make one but am seeing only two ways, neither of which is highly desirable. See picture 1. -If I mount spacer to hub and then sprocket to spacer, I will have to open up holes in the freshly anodized sprocket for nut clearance for the spacer to hub attachment. -IF I could find longer studs, I could use them and basically sandwich a spacer between sprocket and hub. However, I suspect that studs that have been in place for 1/2 century will not come out easily. What have others done? Pictures? The sprocket is supposed to be a TL125 sprocket but has an undercut on the back side. Does anyone know what that is for? Sprocket at required spacing https://ibb.co/tXpwXfJ Back side of sprocket https://ibb.co/FgMt0nQ
April 22, 20233 yr If you can get the studs out you can use countersunk head screws instead and sandwich the spacer
April 22, 20233 yr I've had excellent luck getting studs out of aluminum. The coefficient of thermal expansion for aluminum is roughly twice that of steel. Using this fact, I heat the aluminum with a propane torch. Then I apply a penetrating oil (like PB Blaster) while still hot where it can seep in. Depending on the level of corrosion involved, sometimes waiting is necessary and sometimes more than one application will be required. Removing the studs while hot is helpful. This even works for a steel/steel thread like a spoke and nipple. Obtaining longer studs is very doable. But you may have to resort to getting them out of China via eBay or AliExpress.
April 22, 20233 yr Author I already had some PB blaster on the threads overnight. With some heat form a MAP torch, they came out OK without a lot of fuss. I was surprised.
April 22, 20233 yr Congratulations. Should have mentioned that the heat also degrades any locking agent that was present. I recommend using Red Loctite when installing new studs.
May 30, 20233 yr Howdy... Did you ever find an alternate solution for fitment ? A block of some sort ? Also looks like C/S sprockets are hard to come by as well. Anyone know where to find one ? Thanks... BB Edited May 31, 20233 yr by RobbRoy Additional info request
June 1, 20233 yr Author I made one out of aluminium. The sprocket was a Talon supposedly for a TL125. It was not totally flat so had sort of a groove on one side. I'm really curious what that groove is for on the 125. A drawing is attached. I did add a 45 degree chamfer on the hub side. A custom sprocket company may also be able to help. https://sprocketspecialists.com/product/rear-sprocket/ sprocket spacer.pdf Edited June 1, 20233 yr by mcman56 add detail
June 2, 20233 yr On 6/1/2023 at 7:00 AM, mcman56 said: I made one out of aluminium. The sprocket was a Talon supposedly for a TL125. It was not totally flat so had sort of a groove on one side. I'm really curious what that groove is for on the 125. A drawing is attached. I did add a 45 degree chamfer on the hub side. A custom sprocket company may also be able to help. https://sprocketspecialists.com/product/rear-sprocket/ sprocket spacer.pdf 108.09 kB · 4 downloads Thanks Dan ! That helps a lot, but my ANSI dimensioning skills are lost somewhere in the grey matter... Does the 1.771 dimension enough to get the true position of the distance between the holes ? I'm not a machinist, but seems you might need both ? ..or is it self-defining in some way I do not understand ? Might you have the TALON P/N for the 1-2-5 sprocket ? Thanks again !
June 2, 20233 yr Author The drawing is not to GD&T standards but implies a circular hole pattern with a 1.771" radius and holes every 90 degrees to match the stud locations....if that makes sense. You could probably make a simpler spacer but I tend to over design. The sprocket got thin at the groove area and I wanted to support it well. If the groove was faced away from the hub, a simple flat spacer would work but you would need washers or something similar in that groove. I'm really curious what the groove is for on the 125. Could Honda sell some kind of lock washer part that fits in there? I got the chain and sprocket kit from TY Trials. Pricing was quite good but for some reason was shipped 2 day to the US which almost doubled the price. TR216 60 428 was the rear. TG314 12T (428) was the front. From what I can tell the front was a special order because that P/N is normally a 520 chain. They show a spacer as unavailable on their web site. Speed and Sport in the US also showed a spacer listed as unavailable. If I were to do it again, I would consider a 520 chain. I saw at least one sprocket company on line that still sells 12T sprockets for the 1976 XL250. They could probably supply a rear sprocket with the correct number of teeth that would be flat so the groove would not have to be considered. I'm guessing they do spacers also. sprocket with groove https://www.tytrials.com/trailandtrialsuk/prod_49834-Rear-Sprocket-TL125-60t.html
June 3, 20233 yr Not going to a 520 ( at least on the 250 ) was confusing to me as well.... I have communicated with a gal at Talon and sent some info to the custom sprocket folks. Yes... The 1.171 / 90* defines the true position dimension. I did talk to Matt @ S&S previously. No suggestions. So much for easy fixes to make a play bike... Thanks again for the help !
June 4, 20233 yr Author I did notice that quite a few 15 mm spacers are sold for car wheels. Could any of them be small enough to modify? You could probably use something much less robust than what I did. IIRC the TL250 sprocket mounting studs are 10 mm. Modern trials bikes use 6 mm.
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