Bradocross Posted February 4, 2023 Report Share Posted February 4, 2023 I have no manual and plan to take my forks apart, clean them and then install the new "Magical" fork springs and adjusters that I just received from France. Does anyone know what the original spec. is for the amount of, or level for, the forks on this bike? I'm assuming that the spec. for oil weight is10w30 or 10wt (I'm 130lbs so a light rider)? The springs and adjusters did not come with any info. so I'm assuming that I set the adjuster length so that the combination of the adjusters and the new springs match the length of stock springs? Thanks for your help. Quote Link to comment Share on other sites More sharing options...
Bradocross Posted February 4, 2023 Author Report Share Posted February 4, 2023 PS. When I say "adjusters" I mean the required spacer for the progressive fork spring and not the cool "preload Adjustable Fork Caps" that are on back order. Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 4, 2023 Report Share Posted February 4, 2023 If you are using Magical springs with original damper rods, for your weight, 10 weight fork oil should be OK. You didn't mention buying the aluminium damper rods so I'm assuming you are going to use the originals. To start with, set the total Magical spring+spacer length the same as the original spring + spacer length. That will be a few less mm preload than original because your original springs will have sagged a bit over time. For reference, standard A model fork spring free length is 400mm. When you have done that, measure the sag with you aboard and adjust the preload until you get about 60mm sag with you with all your weight on the pegs. Once you have set the preload, go for test rides to see if you want to change to 15 weight oil. Standard TY250 forks have very light damping so I wouldn't go below 10 weight fork oil. If your forks have the drain holes on the sides (early A model) then the standard oil quantity is 175 ml per leg. If your forks have the drain screws at the back (everything after early A model) then the standard oil quantity is 162 ml per leg. The two types of forks have different design (different volume) damper rods. 1 Quote Link to comment Share on other sites More sharing options...
majesty Posted February 4, 2023 Report Share Posted February 4, 2023 If you need a service manual, PM me your direct e mail address and I can send you one 😑 Quote Link to comment Share on other sites More sharing options...
Bradocross Posted February 4, 2023 Author Report Share Posted February 4, 2023 Yes, I'm sticking with the stock dampening rods and my drain screws are on the rear of the fork legs so I should assume these forks are from a later model ('76 or '77 in the U.S.?). So please correct me if I'm wrong in doing the following: Referring to the diagram below, I should be removing the stock springs (#9), the stock spring seats (#11) and the stock spacers (#12) and replacing those with the new progressive springs and Magical adjustable spacer. Everything else (stock) will remain. You recommended that I, "....set the total Magical spring+spacer length the same as the original spring + spacer length". I should ignore the length of my sagging springs and use 400mm as the measurement of the original spring in your formula. When setting the sag are you referring to the difference between the handlebar height and ground when the bike is resting and when I'm on the bike? Or are you referring to the amount of fork travel down the fork stanchion tube between the bike resting and me sitting on the bike (sorry, I'm a newbie). You mentioned that the dampening rods are different in the later models. I've been thru all the parts diagrams and noticed that the springs, rods and tubes are the same part number throughout the 1970s in the U.S. I've also been told that the diagrams are wrong as they all depict the drain screws on the side which confirms they are wrong. Thank you for all your help Quote Link to comment Share on other sites More sharing options...
Bradocross Posted February 5, 2023 Author Report Share Posted February 5, 2023 Majesty kindly provided me with a service manual and parts list for the TYA. These documents include a completely different diagram of the forks that do not include a spring seat or a spacer (see below). The Magical springs are 443mm long. I just pulled my forks apart and discovered that my fork springs are 450mm long. This looks similar to the service manual diagram than the online parts diagram as it does not have a spacer but, unlike the service manual diagram, it does have the spring seat and a second small spring on the dampen rod. There appears to be some extra pieces below the piston not shown in any of the diagrams so I'm now wondering why these parts diagrams are different and why neither matches what If got inside my forks (see picture below). Are these TY forks? Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 5, 2023 Report Share Posted February 5, 2023 (edited) 1 hour ago, Bradocross said: Majesty kindly provided me with a service manual and parts list for the TYA. These documents include a completely different diagram of the forks that do not include a spring seat or a spacer (see below). The Magical springs are 443mm long. I just pulled my forks apart and discovered that my fork springs are 450mm long. This looks similar to the service manual diagram than the online parts diagram as it does not have a spacer but, unlike the service manual diagram, it does have the spring seat and a second small spring on the dampen rod. There appears to be some extra pieces below the piston not shown in any of the diagrams so I'm now wondering why these parts diagrams are different and why neither matches what If got inside my forks (see picture below). Are these TY forks? Your photo shows TY250A forks apart from the fork spring which is single rate and longer than standard. The standard spring is dual rate, thinner wire, shorter and the ends are tapered on the OD. The spring in your photo looks like what I bought from B&J Racing about 15 years ago to try in a TY250. The B&J set I bought were exactly the right length to use without any preload spacers. In my opinion, the Magical springs provide a superior action for most riders compared to both standard springs and the B&J Racing springs. The parts diagram you said is from "Majesty" is not showing TY250A forks. It is from the TY250 Owners Manual but sadly is not what TY250 forks look like. The TY250 fork diagram from the TY250 parts book also has a few mistakes which can cause confusion. Your forks in your photo look standard except for the fork spring. Edited February 5, 2023 by feetupfun Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 5, 2023 Report Share Posted February 5, 2023 John Cane has a reference photo on his website showing TY250 fork internals which might help you. https://www.tytrials.com/trailandtrialsuk/cat_88541-Front-Forks.html Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 5, 2023 Report Share Posted February 5, 2023 Measure the sag on the fork tubes. The zero position for fork sag is with the front tyre off the ground. Your damper rods are early TY250A (welded-on bottom end). Later TY250 damper rods have the bottom end reduced diameter section made using a swaging process. Yamaha commonly change the design of something but retain the same part number if the two designs are interchangeable. Yamaha didn't make TY250 forks. They were made by Kayaba to Yamaha specs. Kayaba changed the design of TY250 twinshock forks in many ways between the first and the last version but they are functionally the same and the parts are inter-changable. Quote Link to comment Share on other sites More sharing options...
Bradocross Posted February 5, 2023 Author Report Share Posted February 5, 2023 I compared the configuration of the forks components in the forks I pulled apart to the photo of John Cane's dampening rod. Apparently the last person who worked on these forks put them together backwards. The top photo (below) shows the parts assembly order on the dampening rods I took out of both fork legs. I reassembled the correct way after viewing John Cane's (bottom photo). I've got the magical and adjustable spacers in both forks and now have them back on the bike. I was surprised that I was able to put the fork caps on with the new spacer added but it worked. I've got the spacers adjusted to the minimum length and I'll have someone help set the sag when out riding. I'm curious about the sag starting point you mentioned (60mm). That's more than a third of the entire travel length of these forks (178mm). That seems a bit steep for sag. I may have to remove the spacers and even then I don't think I can get that much sag with me on the bike. Thank you again for all your help and support. Quote Link to comment Share on other sites More sharing options...
feetupfun Posted February 6, 2023 Report Share Posted February 6, 2023 5 hours ago, Bradocross said: I compared the configuration of the forks components in the forks I pulled apart to the photo of John Cane's dampening rod. Apparently the last person who worked on these forks put them together backwards. The top photo (below) shows the parts assembly order on the dampening rods I took out of both fork legs. I reassembled the correct way after viewing John Cane's (bottom photo). I've got the magical and adjustable spacers in both forks and now have them back on the bike. I was surprised that I was able to put the fork caps on with the new spacer added but it worked. I've got the spacers adjusted to the minimum length and I'll have someone help set the sag when out riding. I'm curious about the sag starting point you mentioned (60mm). That's more than a third of the entire travel length of these forks (178mm). That seems a bit steep for sag. I may have to remove the spacers and even then I don't think I can get that much sag with me on the bike. Thank you again for all your help and support. As for John Cane's photo, yes he put it there because it's easy to get it wrong. It's no surprise that people get it wrong with the available parts diagrams being so incorrect. Did you compare the length of the spring+spacer that went in compared with what came out? Quote Link to comment Share on other sites More sharing options...
Bradocross Posted February 6, 2023 Author Report Share Posted February 6, 2023 The springs that came out were 450mm with no spacer. What went in was 463mm: springs were 443mm and spacer was 20mm (minimum setting). 1 Quote Link to comment Share on other sites More sharing options...
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