Jawa Transistor with no power?

I recently ended up with a jawa transistor 40, I know everyone on here tends to give the Soviet bikes a bad rap but I thought I was up for a challenge. Anyway when I first got the bike pedalling would result in the lights flickering and the engine starting to turn over without sparking.

After researching online and doing some multimeter testing I decided that the big red "tranzimo" unit was toast. I picked up the newer Hungarian unit and matching stator ring off from treats and swapped them. Now when I either pedal or hook up the generator to a drill I get no lights and no power off the magneto.

Any Jawa experts have any ideas? I'm contemplating just making an e-bike out of it.


Re: Jawa Transistor with no power?

Thyristor ignitions on those Czech bikes are troublesome. You can swap out the black box for a generic Asian CDI and keep using the trigger from the stock ignition as well as the magneto.

Re: Jawa Transistor with no power?

theres a tutorial in the wiki to make our own transistor. I have done that with alotta success, it's pretty easy and very satisfying.

Double check wiring, maybe the coil is bad, those things need an odd voltage coil I think but usually the universal ones cover it.

theres a great printable writeup on jawa electrics here:


Re: Jawa Transistor with no power?

Found the picture for the Asian hack of the thyristor...


...unvalidated though so someone will have to gamble the 10$ for the pocket bike AC CDI box to find out...

Re: Jawa Transistor with no power?

The Hungarian unit probably wasn't grounded properly. Also change your spark plug cap. I want a transistor frame. My frame requires insurance in ny.

Re: Jawa Transistor with no power?

Would this work? Only $12 plus shipping.

https://www.jawashop.com/thyristor_z942/ (edited)

Re: Jawa Transistor with no power?

Re: Jawa Transistor with no power?

These are the replacement parts that I ordered and installed


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