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feetupfun

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About feetupfun

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  • Bike
    1963 to 1981

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    Gladstone Australia
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  1. feetupfun

    Choosing a new front tire.

    Here is the forks page from the TY250A parts book. The graphic artist who drew the anti-topping spring has drawn it to be about 100mm long when in reality the anti-topping spring is only about 25mm long. I'm talking about the spring that is shown fitted below the piston of the damper rod (item number eight)
  2. feetupfun

    Choosing a new front tire.

    I didn't say to buy a trials bike. That was someone else. The TY250 parts book does show two springs but they really only came with one main fork spring. I'll have a look at the parts book tonight and that will remind me of what you are looking at. Many people have said the same thing as you previously about the parts book. Yes TY250 fork springs for 34mm Kayaba forks will fit in 34mm Kayaba MX YZ forks. You would need to make custom length preload spacers. Trivia fact No 1 - you can fit Race Tech Gold Valves designed for MX YZ DT 34mm forks in 34mm TY250 forks. You say your forks are similar but not identical to 1975 YZ250. What do you see that is different? Trivia fact No 2 - if you have a look at photos of some of the early prototype bikes that Mick Andrews rode while developing the TY250 you will see what looks like your front hub and fork sliders in use - straight out of the Yamaha parts bin.
  3. feetupfun

    Mar engine weight

    You could use a plank as a balance beam, put the motor at one end and add mass (water in a bucket that has litres marked on it) to the other end. Measure the distances from the fulcrum and multiply the distances by their mass to give you the mass of the motor. Motor mass x distance to fulcrum = mass of water x distance to fulcrum Motor mass = mass of water x distance from bucket to fulcrum / distance from motor to fulcrum
  4. feetupfun

    Choosing a new front tire.

    From what I've read, he's got a TY250 twinshock that has the trail riding kit that was available from Yamaha (and popular in the USA) when they were new. It sounds like someone has fitted a YZ 250/360 or MX 250/360 front end from the mid 1970s to the TY.
  5. feetupfun

    Choosing a new front tire.

    The writing on your MX YZ forks is not TYB, it's KYB, which is the company that made forks for Yamaha at the time. KYB is the trademark for Kayaba. Yes you will need to have the fork tubes sticking out the top for it to steer properly. Yes it is best to leave the springs out when testing fork travel. Those Falcon shocks are a good length if you are not lowering the footpegs. Original shock length was 325mm. The ground clearance with those Falcon shocks will be fine. Set the sag with you aboard to 40-50mm. If you want more ground clearance you can fit longer shocks but with longer shocks, standard position footpegs will be too high for the bike to handle well with you standing up. 15WT oil in MX YZ forks may be too heavy damping for a trials bike but try it first. It is easy to replace. The MX YZ springs will probably be too stiff for trials riding but try it first and you can fit TY springs later if you need to. The top hat washers should sit on the top ends of the fork springs. Yamaha use that sort of washer so that the cylindrical preload spacer that usually fits above it can be made very thin-walled yet not slip past the end of the spring.
  6. feetupfun

    Choosing a new front tire.

    Your triple clamps are TY Yamaha. Your fork sliders are MX or YZ Yamaha and your brake backing plate is MX or YZ Yamaha. The lines on the fork tubes are there as a reference for where to clamp them on the bike that they originally came from. If they are longer tubes than TY250A then they are not TY250B, because all the TY250 twinshocks have the same length fork tubes. I would expect that the fork tubes are also off a MX or YZ Yamaha. To maintain the standard TY steering geometry you should set the tubes so that the axle is in the same position as it would be with TY forks. If the travel of your forks is longer than TY forks you may need to fit travel limiting spacers to the damper rods, to avoid the mudguard or tyre hitting the lower triple clamp.
  7. hello,im looking for help figuring out how to fix my 348 trial kick start issue....it kicks through like mush,like its not properly ingaging.when i got it a few months ago ,i cleaned the carb and got it going.even then about every third or forth kick would not engage ,just kinda mush through the kick.now thats all it does....even though i have installed a new clutch,cable,and original type levers,and a new 10mil plunger......someone else had this problem on here,did he ever find the solution?.....im using amsoil 80 dirt clutch oil in the clutch..the new clutch is a TJT it comes with two more plates than the original montesa pack,so i left them out.......some one really otta write a book on these things.

     

    1. Show previous comments  1 more
    2. montesa 348 kick trouble

      montesa 348 kick trouble

      hi,thanks for responding .the original clutch plates are not all flat.i put them on a plate of glass and some wobbled/did not lay flat.so i put a new set in-(tjt plates).i put the same number of new plates in that i took out(i never thought to measure thickness of cluch pack ,old and new,to compare).i orderd new springs as well,but did not install them because my old springs are 2ml longer and quite a bit thicker,so i figuerd they are stronger.i just replaced the clutch two days ago.the new 10ml plunger is to long it seems,because i cant get the new clutch cable to have any free play at all,so i disconnected the cable to try an start the bike..whith the cable disconnected,the plunger has free play/is not engaged....(i will make a longer cable)(the old plunger was warn down to a nub,way past its best before date)the 3 leg clutch depressor was warn in a couple ml in a messy way,from the mushrooming of the plunger so i sanded it smooth and polished it to a mirror finnish...the kick still acts the same way.it does not engage properly.its like theres no compresion....well,almost none...the new clutch ,grabed good,when i put it in gear,just rolling it in the garage...............what to do hmmmm?

    3. feetupfun

      feetupfun

      I suggest again to measure the height of the new and the old plate packs. I suspect that it will be shorter than what came out.

    4. montesa 348 kick trouble

      montesa 348 kick trouble

      ok ill do that and let you know how it goes

      thankyou

  8. A very hot exhaust header and poor running can be caused by the ignition timing being set too late
  9. feetupfun

    Rim tape removal

    smells nice too
  10. feetupfun

    Choosing a new front tire.

    From what you have written it sounds like you have non-standard forks, so to know how high you can have the mudguard above the tyre, you will need to test where the tyre OD is with the forks fully compressed. Standard TY250 forks don't have much room between the tyre and the lower triple clamp and yours with different forks might have even less.
  11. feetupfun

    Rim tape removal

    I've not seen a front wheel rim tape glued on. Do you know why it had been glued?
  12. feetupfun

    Bolt on footrests

    On my SM TY175 pegs, the holes for the pivot pin elongated. I do weigh 95 kg though. I welded on some thick washers and they have been OK since.
  13. feetupfun

    Bolt on footrests

    reminds me of: Hey. You. Get offa my cloud
  14. feetupfun

    Clutch on my OSSA MAR gets stuck every winter

    If spring steel yields over a long time period when loaded below it's yield stress limit, then yes. Bear in mind that clutch springs only carry slightly more load when the lever is in than when it is out, so it probably doesn't make much difference to how long the springs last storing the bike that way.
  15. feetupfun

    Hi, looking for advise on buying an Alpina project

    Some (not many) MK4 Matador components are shared with Alpina and Frontera. I would say they are no more or less valuable than any other early 1970s Bultaco.
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