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Strange but true


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Places I would check are the weld joining the shifter pawl mechanism to the shifter shaft, and the centrifugal auto compression release on the camshaft. Look for hairline cracks in the welding, put a bit of stress on the joint to see if a crack opens up. When I bought my bike the compression release was not functioning, a burr had developed on the flyweight component that prevented the small spring from returning it to the cranking speed position. As well take a close look at the condition of the O-ring that fits to the small spigot behind the oil filter compartment, it forms a seal to the right side crankcase. Mine had a slight tear, so I carefully beveled the mating hole in the right crankcase with a countersink to ease the insertion of the spigot. New seals might be another idea. The Jitsie flywheel puller did a good job for me.

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  • 2 weeks later...

Got the puller and the flywheel is off. Came off with an alarming snap and I thought, for a few seconds, I had done some major damage. But all OK.

Spoke to Beta about getting the cases apart. Asked about the special splitting tool, but they did not have one, and had never sold one. Suggested the cases could be split by severe bashing with a copper mallet.

I didn't have the nerve for this, and, as a moderate bashing with a plastic mallet had no effect, fabricated a splitter from 5mm plate as per the picture in the manual.

This worked fine but it still took considerable pressure to pull the cases apart. Still, now have a bespoke crankcase splitter for the 4T, which other TC members would be welcome to borrow.

With the cases apart the cause of my problem was evident.; two broken dogs on the sliding 2nd/3rd gear on the mainshaft.

Have ordered this from Beta along with a new water pump shaft.

As everything else looks OK I am just going to replace all the gaskets and seals that have been disturbed.

Then just go to get it all back together, but that should be the easy bit!


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  • 2 weeks later...

Finally managed to get everything back together.  Engine runs sweetly and all gears engage - success!

Lessons learnt:

  • Beta manual is excellent and takes you through every stage. Only thing I struggled with was getting the chain off the camshaft. Best to remove the snap ring from the chain side bearing and slip the bearing off the shaft.  With the water pump shaft removed, the cam drops just enough to get the chain off.  Assembly is the reverse but you may need to jiggle the "hanging" water pump drive cog with a small screwdriver to get it in the correct position, for inserting the shaft.
  • Water pump shaft can be unscrewed with an adjustable spanner, so no need for the special tool.  The way its arranged I would think it is possible to replace the pump shaft without disturbing the engine.
  • Crankcase splitting tool makes things much easier.
  • Beta UK are excellent for parts put their prices are eye-watering.  The parts manual has sizes for bearings and seals so cheaper to get these elsewhere.  Case and cylinder gaskets are metal, and £40 each. I would consider reusing all but the head gasket if I was on a budget.
  • Moisture had got in under the stator cover and rusted one of the screws of the water pump cover.  Had to drill and use an extractor to remove.  I will be keeping an eye on this and drying regularly in the future.
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