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  1. One thing I have noticed is that the standard Sherpa N has a very long horizontal rear frame loop (for a dual seat). The prototype Matador, Mk1 Matador and Mk2 Matador all look like a Sherpa S frame to me because of the steep short rear frame loop. On the Miller Sherpa T prototype, the rear frame loop and shock mount area doesn't look like any of them. It's rear loop is short and steep but the tubing looks smaller diameter and the gusseting at the shock mounts is very different. The photos I'm looking at are in Bultaco Todo un mito and Don Morley Spanish trials bikes. I've also looked at two frames. A 5 speed Campera frame from 1966 which I think is an M21 and a 1963 M3 Sherpa S frame.
  2. It's fairly common practice on multiple brands of twinshock trials bikes to have the top mounts closer to the mid-line of the bike than the bottom mounts are. It was done to make the bike slimmer where it counts
  3. Yes that is great value. They are a fabulous motorbike. The ignition system is not connected to the lighting system. Each has its own stator coil in the magneto. Blowing 6V bulbs was standard back in the day for TY250A. Fitting 12V bulbs was one way to avoid it, but the lights then became dimmer. They came with no voltage regulation on the lighting circuit so as the RPM rises, the voltage rises. Nowadays there are a myriad of options for the lighting circuit on motorbikes.
  4. My memory of riding the big-wheel Beta 80 is that it was OK for me at 5'10" but I would think it might be a bit cramped for someone tall. The motor was easy to use in sections. Modern 125 two-strokes are excellent. The modern mecatechno (electric) trials bike is extremely light.
  5. I've just done a top end decoke on a friend's (low hours) 2022 TRS 300 and was astounded at how tenacious, dry and thick the carbon deposits were that completely covered both the piston crown and the inside of the head. It ranged from 0.25 to 0.5mm thick. The tenacity and hardness of the carbon in this TRS reminded me of the carbon that formed in my 1970s air-cooled two stroke enduro bikes running on 20:1 castor oil premix. Sure enough, when I then asked the owner what premix oil they use, they told me it is castor oil based. I'm accustomed to seeing soft, wet smudges of carbon that cover about 40 % of the piston crown on my 2 stroke trials bike pistons. Is using castor oil premix in modern trials bikes common practice?
  6. Piston position can be used to make timing marks and it's easy to measure through the sparkplug hole
  7. You could take the exhaust header off and measure the bore diameter through the exhaust port. The Beta 125s I've seen have a different exhaust header shape to the 200/250/270
  8. Yamaha was selling genuine spoke sets for TY250 last time I bought some. They are zinc plated. Stainless steel spoke kits for them are available from In Motion in the UK. I know you can get spokes custom made by a bloke in Brisbane. You will probably have to send him samples to copy. There are probably people all over Australia who can make spokes for you from samples. Another option that people do is to re-plate the original spokes.
  9. If its is a standard 348 engine then it is approx 310cc displacement..
  10. feetupfun

    247 bash plate

    When that casing is on a 348 motor there is a screwed plug there.
  11. There was nothing in place apart from the cable sheath to stop the wires being damaged. A common improvement for reliability was to run the wires along the top side of the mudguard.
  12. It is a modified Yamaha TY175 or TY125 frame.
  13. Another factor in rear tyre clearance is that the rear competition tyres in the 1970s were nowhere near as tall as modern competition rear tyres
  14. So here's a photo of a Spanish Betor trials shock from back then. I have no way of knowing if its actually from a model 92 or not but I do have quite a few and they all have the same length shock shaft. Some have this type of seal retainer and others have a different type of seal retainer.
  15. My memory is saying 3.25". I'll have a look to see if I have one to measure
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