jawa no spark?

George Smith /

Alright I have a 76 Jawa 40 with no spark, It has what appears to be a replacement coil, I honestly think the wiring is just wrong, anyone have a wiring diagram or advice

Re: jawa no spark?

I just bought a moped like that and i have the exact same problem. I think its the black box

Re: jawa no spark?

there's one Jawa manual HERE There's some small amount of wiring info near the end.

Evidently the "black box" unit is often suspected of failure .. but the wiring itself is confusing so who realy knows what's up.. ("Search" this forum for related threads.)

First thing i'd check for is faults or corrosion in and around any switches / wires /connectors that are meant to kill the spark.. like a Kill switch or a keyed Ignition switch.

it might be wise to check all safety-related bulbs like tail and brake lamps and replace any broken ones. They are sometimes part of the ignition circuit on some bikes.

Unless one is on hand, last resort would be to track down a known good, working black box Ignition unit and swap.. i'd want to believe any Jawa CDI unit would work until proven otherwise..

Re: jawa no spark?

George Smith /

hmm no luck there....as I dont have one of those black boxes like in the diagram, but it did give me an idea for testing the ignition coil...could i just use a 6v battery to test the coil itself then from there find out if the generator is the culprit?

Re: jawa no spark?

Do you mean you have a points/condenser type ignition? .. a set of points that open and close by a cam on the crankshaft's end, mounted on the "stator" inside the magneto?

Re: jawa no spark?

George Smith /

would appear that way

Re: jawa no spark?

Regarding testing the coil, i'm slightly guessing here, but afaik, the black boxes only replace the points and condenser.. So, otherwise the magneto acts like any other ignition.

If so, the spinning magneto will still generate and deliver energy to the ignition coil's primary winding. And a battery would not be needed to test the coil.

Set a volt meter to it's highest range, connect the meter's + lead to the coil's negative connection, and then ground the meter's negative lead. Kick the engine over and a high voltage should show on the meter.

(It would be at this point that the black box would take over, chop this primary voltage and thus time delivery of the spark to the plug).

If the meter shows voltage it says that the magneto and ignition coil are ok ..

(BUT, i admit i'm not sure about it.. There could be more to it and this test might be inconclusive. No primary coil voltage might be due to trouble with the electronics in the box.)

Re: jawa no spark?

oops.. i posted too soon.. you got points and a condenser? in your profile the bike is a "1976 Jawa Transistor 40" .. wonder what the transistor thing is about if it's not a transistorized ignition..

Well.. anyway.. my next step would be to isolate the basic ignition components from the rest of the wiring and switches. Disconnect everything else.. (Imagine substituting a spinning magneto for the battery in this pic) Then check for spark at the spark plug.. remove the plug and ground it's base to the engine block and kick the engine over.

Re: jawa no spark?

Re: jawa no spark?

and that page leads to THIS page where a little more info can be salvaged..

Re: jawa no spark?

George Smith /

well this wiring diagram is exactly what i have on the bike even though it's a jawa 40, btw the bike is a jawa 40 not a jawa transistor 40 which people have been scratching their heads over everytime i ask about it lol http://www.jawamoped.com/html/28_wiring.html so that helps a lot, i should be able to get somewhere with that :)

Re: jawa no spark?

I have a jawa 207 that has been sitting for a while. I think it need s a new thyristor or 6vbattery. The piston sounds dry. I have a very weak spark only felt if you hold the wire when turning it over.

I am so desperate. it just sounds like its not getting spark. The magnito is gennerating because i have been shocked by it. all the bulbs are working and i set upbike like the wiring diagram I have for it.

nate

Re: jawa no spark?

George Smith /

well i did it....it's got spark and fired up.....here is what the prob was....

the person sold me an engine that had spark but was believed to not be running due to low compression....well it was the opposite had good compression and no fire, the ignition coil on it was for a motor with the thyrstor ignition....which the person replace the old tranzimo coil with....thus no spark...as they had no thyrster module, i was able to get it running using an old tranzimo coil from a dead motor i had. btw the tranzimo coils would make getting these jawas with thyrstorzs alot easier as they seem to be pretty cut and dry :)

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