Sometimes has spark but sometimes doesnt.

A

AnotherWebUser

New Member
Me and my friend have put together an 80cc MB, and for a day or two it was running great, then it stopped starting, so we tested for spark and had nothing, replaced it with an ngk and it was running perfect again. The day after replacing the spark plug and after riding about a little we were having problems again, it was misfiring badly and after riding about 30m it stopped. We tried for another 5 or 10 mins to start it but it wasn't happening, so we walked it home. We got home about 15 minutes later and after a couple attempts it started, at first still misfiring a little but then it went away and was back to normal. Now 2 days later we are having the same problem with no spark, it misfired a bunch, enough to move you before stopping but now not much, occasionally it fires once or twice but won't start. Any ideas?
 
Ok so just after posting this it started running again and got me all the way home, but there's a chance its going to do this again. Could it be overheating? Or maybe a faulty cdi or mag? But I can't really understand why it only stops working sometimes.
 
Ither to much oil in your gas as venice said or no spark from crappy China magneto ,I suggest this magneto and spark coil personally

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BBR Tuning High Performance 2-stroke Super Magneto

Tired of getting a weak, inconsistent spark? With the BBR Tuning High Performance 2-stroke Super Magneto your spark issues are soon a thing of the past. More powerful than your stock magneto, the Super Magneto will make sure the spark you get is strong and your CDI keeps getting that spark more...
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BBR Tuning Volt Master High Performance Racing CDI (Stage 1)

Tired of your engine not starting every time you need it to? Need a more consistent spark than that stock CDI's giving you? Increase your spark and finally fix the timing issue most CDI's have with the BBR Tuning Volt Master High Performance Racing CDI (Stage 1). The reason most engines don't...
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I had a look at them but the mag is out of stock, and because I'm in the UK shipping costs more than the coil. Does anyone know where you can get these parts in the UK?
 
Doesnt look like they have the ones with the red wire and a bit larger copper coil, but you do have a source for the standard parts that may get you up and going reliably again.

Be sure and double check all the connections and where wires are soldered to magneto.

a bad soldier could cause your troubles.

hope this helps
 
Try running it without the air filter for a day or two... that will lean out your fuel mixture a bit.
If that fixes the problem?, you just need to install a slightly smaller jet in the carb (& re-install the air filter).
 
Get a bikeberry mag and cdi dude they great, also tip (Sand the bottom of the magneto contacts on the engine as well)
 
I have some serious doubt that it's your ignition coil... (either they work or they don't).
In all my years working on these, I've don't recall ever seeing one that worked 'on & off' (unless you have a bad wire connection somewhere).

What you're describing sounds like a wet spark plug because you can't see the spark travelling though the liquid on the plug (instead of it jumping the air gap)... & then when the liquid dries up the spark is back.

Maybe your problem is something as simple as the choke lever being slightly on?
Or maybe the wires (or kill switch) are grounding to the bike somewhere??
 
Venice Motor Bikes said:
I have some serious doubt that it's your ignition coil... (either they work or they don't).
In all my years working on these, I've don't recall ever seeing one that worked 'on & off' (unless you have a bad wire connection somewhere).

What you're describing sounds like a wet spark plug because you can't see the spark travelling though the liquid on the plug (instead of it jumping the air gap)... & then when the liquid dries up the spark is back.

Maybe your problem is something as simple as the choke lever being slightly on?
Or maybe the wires (or kill switch) are grounding to the bike somewhere??
Click to expand...
Those are some good ideas, ill check it out, it hasn't happened again yet but next time I'll take out the plug and see if its wet. The choke definitely hasn't been on though I have checked that. Also kill switch is disconnected but ill make sure none of the other wires are grounded on the frame as they are zip tied down.
 
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