Relections on a 78 TS250 rebuild

Forums Technical Two Stroke: Hints and Tips Relections on a 78 TS250 rebuild

  • This topic has 8 replies, 7 voices, and was last updated 7 years ago by Anonymous.
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    • #4769

      Not much traffic on here, so I will reflect how my rebuild is going, hopefully to get some response.
      I am an Mz newbie and have bought a 20 year stored 1 previous owner Supa 5 with 14000 miles on it. Its been stored in a non dry state, so has corrosion, hence the rebuild.
      Previous owner advised it has lost 3rd gear, is this common?
      Well I had it home at 1pm, and it was a nearly bare half rolling frame at 5pm, same day.
      Barrel was corroded on, but tapped off, think the bore and piston will clean up.
      Little end worn, so Burwins for new parts.
      Front wheel stripped and cleaned last night. Quickly down to original alloy and looking good. Tyre perished so new matching front bought from ebay.
      New cables, footrest and chain case rubbers bought.
      It came with a spare engine with a top end stripped off, so may just drop that straight in. Found you need tools to strip the cases, and haven’t found the engineering drawings to make my own on line. Today, I’m going to clean the road grime off the frame ready for paint. May brush it, haven’t decided.
      Oh, and what a mess inside the petrol tank. The oil measuring cup had corroded to nothing and its taken 15 petrol flushes, 10 with 200 nuts/bolts in, to get a start at it becoming clean. Petrol tap was that clogged the ports needed redrilling

    • #4770
      Mike Dalton

      Hi, mike here. Am in a similar position. TS250 (85) in garage awaiting attention. Have had some pratice. Just finished the rebiuld on TS125.Got the special tools for the strip,bought vernier gauge and made timing light and its rides great. No heat in garage so waiting for it to warm up before starting on 250.

    • #4785
      A A A Dummy

      Re Petrol tank I would recommend POR 15 (the kit) it comes with an acid etch which neutralises the left over rust and a cleaning agent (rather like alloy wheel cleaner) cost £40 but you will have a robust clean tank afterwards that will take modern ethanol fuel without any problems to the coating.. I have done 3 tanks without any problems. If you are organised the prep and the POR 15 can be used in a couple of tanks if you get the 485 ml can of the stuff. I have a running TS250 with 20,000 on the clock. Re gearbox I find the SAE70/90 oil silky smooth. Many years ago I had the same problem with 3rd gear. Maybe earlier models had a weakness in the selection dog as I had to replace mine several times (just a thought) GOOD LUCK

    • #4789
      Peter Fielding

      Welcome to the club Jon, sadly the web site is slow to take off but there are a few of us participating. 3rd gear problems seemed to be more common with the ETZ models which use the same gear assembly and it was popularly attributed to wear in the MZ machinery which produced the selector drum, there are many articles on the subject in the Hints & tips booklets which are available from Regalia. Supa5s did not often suffer from this problem in there early days and I wonder if your engine was made towards the end of the Supa5’s life (around 81/82 though many were not registered in the Uk until much later).

      I spent some time recently wrestling with a rogue gearbox and leant a few new things along the way so I kept a diary of my experiences. let me know when you get to the stage of tackling your engine/gearbox and I will tell you how to download a copy if you are interested.

      The engineering drawings for the Supa5 engine are in the workshop manual but really all you need is a good quality clutch puller and the bridge used to separate the crank cases. Go for the puller advertised as workshop quality, the smaller cheaper ones will eventually let you down and never ever try pulling the clutch with a 3 legged puller.If you really want to make your own, I can scan and email the drawings.


    • #4816

      Thanks Mike , Stuart and Peter, its great to know I am not alone…
      The project is slowly coming together. (my slowly may be a bit quicker than some, I measure progress in days, not weeks)
      The rolling chassis is complete, ish. Not concours, but, heh, its an Mz, designed to be used not worshipped.
      Tank, yes, I have heard POR15 is good. Being a cheapskate and never ever following an ‘easy path’ I am still keen to try and achieve a clean enough to use steel tank. Without additives. Couldn’t believe the gunk I got out initially, its still coming out rusty after 15 flushes. Amount of fuel I have waisted I could have bought a new tank. Live and learn.
      Engine going back together next. S/H bore, plus 1/2mm. corroded piston scotch brighted, new ebay rings. If this is ok it will be a result.
      Otherwise a rebore and +1mm
      Going to take a flyer and try and use the second spare bottom end, as is. What could possibly go wrong?
      Easy enough to drop the lump back out for a proper rebuild later.
      Michlein M38 NOS arrived for the front. Good lord a 2.5 looks skinny. Too small I know, but I wanted M38 both ends and the rear is new.
      Brake shoes both ends half worn so not expecting the stoppers to stop.
      Looking forward to see what electrics I have.
      Its all a bit of an adventure.
      Best way to learn, making mistakes as you go.

    • #4878
      Mark Bagshaw

      I’ve used washing soda [cheap as chips from Morrisons]& battery charger to get all crap from my tanks then just finish off with some cheap acid cleaner from ‘ARCO’

    • #4879

      Thanks, care to elaborate? Battery charger?

    • #4902
      Bernard Lumb

      Do a search on electrolytic rust removal.
      I used it on an ETZ tank and it worked well.
      Make sure you get the connections the right way round.

    • #5626

      So where are we now Jon ?
      Rollin I hope.

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