[Problem Need Help] Garelli Mosquito 39B No Spark


New Member
Local time
4:00 AM
Jul 21, 2008
Dear friends,
Now I have chance to upload the Garelli Mosquito 39B pictures. This is 2-strokes 38CC, which is run good in the around 1950-1960. But then lost and forgotten in the garage, until now I found and try ro restore it. Probably last time before I, someone has try to restore/modification it. So, when I find it just found 2 cables came out from the magneto. But all other part (carburetor and cable, piston, engine mounting,bike frame etc in good condition).

Main problem is there is NO SPARK to ignite the sparkplug and just found 2 wires tangle from the magneto it's useless for me, leaving a question where should I get to start from. Coz I dont have too much experience on engine (esp electricity), may know the principle but the practise..NILL :confused:

I believe the first step is try to get some spark , later step to add fuel/air mixture to make this running again.

So attch is some pictures of the motobike. Originally it has no battery (accu) and ON/OFF switch. Only a cylinder compression release valve on the engine which is push to open during initial starting pedal and after gain some speed (for spark) then close the valve to start the compression. To shut off the engine, just open the valve again to leak the compression. There is spring lever to disconect the engine from tire and back to normal bike

I have conduct some test using Voltmeter set to AC measurement
1. When I measure the 2 cables (vice versa between those 2) and pedaling, it oscillate between 40-50V AC, more faster pedalling then bigger the reading
2. When 1 cables measure (vice versa between those 2) and 1 terminmal attch to body, pedalling, just gain 7-10V.
3. Do you think this is a AC Magneto generator ? Trying to measure 2 cables using DC measurement but can not get the reading.
4. Actually what current is enter the sparkplug, AC or DC current ?

That's it I'm dead blind... :eek:

Pls kindly give your opinion, if u may having this situation :p. I heard there is a chance to modification using CDI (not to use platina again) to increase the AC voltage. What if just feed those 50V AC to CDI unit to generate spark? Is it possible just plug those 2 cables to simple CDI unit ?

Thak you guys sorry for my bad English


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When it comes to vintage motorbikes I've never seen before, you can bet I'll be of no help. But I have to wonder if those two wires connect somewhere in the area you refer to as the platina. I see screws at the 9 and 3 o'clock positions. Have you tried connecting the wires to those screws?
just a guess, ,,,, I think the 2 wires from the engine need to go to an ignition coil....then to the spark plug.
Dear KilroyCD/srdavo,
Thank you so much for your warm advice !
Yes actually originally electricity from magneto will pass this platina and end up to sparkplug, using original wire. But due some problem on the platina magneto, then I rewound the magneto coil. But I can not get the original size of thin wire copper, at that old time they using so thin wire, so it can generate more electricty.

So, I ended with those 2 AC cables with voltage around 40-50V

What if, I feed this cable to regulator/rectifier to produce stable 12V DC
Then after that using 12V DC I feed to DC CDI unit to generate bigger spark

In your free opinion is it possible to do such modern modificaion ?

Thank you much for your advice !
Nothing's impossible. You will need to reduce the voltage so the CDI doesn't burn out. If converted, it sounds very much like the ingition system will be much like that on the 2-stroke engines a great many of our members ride.
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Dear KilroyCD,
Yeah thak you so much for your advice.
I read about this Whizzer in this forum a lot.
I wonder if this kind of motor also using CDI or just direct fm magneto to coil?
And what kind voltage did the magneto provide ?
Thank you so much
Dear Friends,
Thank you so much for your suggestion. After working for almost 1 month, the restoration is complete and Mosquito is back on and runninh happily again on the street. It's almost 40 years of hibernation in our garage. The solution is just to feed the cable (AC power) from the magneto to simple AC CDI unit then IGNITION COIL & SPARKPLUG. After repair the tank (which is very rusty & dirty) and search for correct oil-gasoline composition, the engine can run easily now. Here attch for some picture.



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Thanks... Ater browsing and searching, if I can conclude...
What I'm think is in State that there is not too much European moped left compare in British/France etc.
But you guys just prefer old big motorcycle, since you already have your own brand, which is Harled Davidson... ??
But I must admit in the State you have more old classic card than in Europe, it means US and Europe have it's own market...

Thank you,
Very nice bike. great job with the electrical problem too. I wish I could have helped with some answers for you.