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SWM 125 Alpaca ignition problem.


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I have just finished a touch up of a total wreck and tried to roll start it today. It seems like the spark, which is healthy
fires way too early. It just dead stop the engine from turning with a pffff sound. I mean a spark something like in the middle of the compression phase.

The vertical line with a yellow dab of paint lines up with the cylinder when piston in TDC and the line is in the middle of the hole on the stator cover
when I remove the plastic plug about where I figure the timing should be.

I know nothing or very little of these bikes but I do think that the Bosch 12v 55w system with a flywheel facing outwards, and the stator in the cover is OEM?
All colours on the connector to the coil are correct as the marking on the connector.

Any ideas?


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  • 1 month later...
On 2/9/2022 at 10:34 AM, turbohead said:

Not a bad touch-up! However, what about the engine while out of the frame? Was it taken apart for an internal "touch-up", too...?

(det finns några intressanta fallgropar när det gäller gamla Rotax-motorer)

I had actually two unrelated problems. The first was the trigger that was damaged and caused the spark to fire when it wasn't supposed to. Another stator plate fixed that. The second problem that showed up then was the completely wrong timing of the rotary valve. I did set it correctly ant the bike is running fine.

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And about the engine. There were no play on the connecting rod or crank bearings. Everything turned nicely and all gears worked, so I just rebuilt the top end. The clutch side was assembled but when removing the clutch in order to reach the rotary valve I noticed that the "klåpare" had been there as well. It's all sorted out now.

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