Lost spark

[Ruralrider01]

I was taking a new build on a good long test ride I was riding for about 2hrs without issues when all of a sudden my engine died. The engine was not getting spark so I checked all connections to ignition box which were good I also disconnected the kill switch cuz I heard a faulty switch will prevent it from running but no success. Is it possible the Chinese ignition box is junk? If so does anyone know where I can order a quality replacement? Thnx

 

[Greg58]

Welcome to the forum, you can find the coil and cdi from a lot of the vendors on the sides of the forum. You can also get them on eBay. If you have a multimeter you can test both to see which is at fault. The link below tells how.

http://motorbicycling.com/showthread.php?t=35090

 

[crassius]

just had 2 CDIs fail after a few minutes right out of the box - I doubt there is a quality replacement anywhere, so keep a spare on hand

 

[biknut]

I was taking a new build on a good long test ride I was riding for about 2hrs without issues when all of a sudden my engine died. The engine was not getting spark so I checked all connections to ignition box which were good I also disconnected the kill switch cuz I heard a faulty switch will prevent it from running but no success. Is it possible the Chinese ignition box is junk? If so does anyone know where I can order a quality replacement? Thnx

The most common failure in the ignition system is the magneto coil. You can troubleshoot it by unhooking it and ohm out the coil. You should read about 350 ohm, give or take a few.

The cdi box is a lot less likely to fail.

 

[Ruralrider01]

Thanks guys this has been really helpful

 

[mrfubs]

if your grounds have not changed and your spark plug is not black and nasty and your not using a chinese junk plug then its 1 of 2 things its either the cdi or its the magneto and the magneto rarely fails

 

[maniac57]

if your grounds have not changed and your spark plug is not black and nasty and your not using a chinese junk plug then its 1 of 2 things its either the cdi or its the magneto and the magneto rarely fails

Actually it's just the opposite. The engine mounted coil fails FAR more often than the CDI box.
But both can be a problem so check both if possible.
Out of maybe 250 chinadoll spark failures I've seen, the engine coil was at fault probably 80% of the time.

 

[BobbyT]

Actually it's just the opposite. The engine mounted coil fails FAR more often than the CDI box.
But both can be a problem so check both if possible.
Out of maybe 250 chinadoll spark failures I've seen, the engine coil was at fault probably 80% of the time.

I agree the mag fails more often,can't hurt to keep a CDI and mag on hand incase you need one.

 

[Ruralrider01]

I did the tests with my multimeter and my magneto is the problem. Thanks again for the awesome forum it's been a real help all throughout my first build

 

[Will122391]

Very common problem. Use some sealant and seal up all the holes near the magneto to assist in "waterproofing" it. My coil hasn't failed since I did that

 

[Kioshk]

Agreed: be sure to have a spare coil on hand (I keep one in my kit; you don't want it on your bench when it blows 5 miles from home). Also pay close attention to clean grounds and waterproofing.

 

[KCvale]

... its 1 of 2 things its either the cdi or its the magneto and the magneto rarely fails

That depends on the magneto, the new mags have no white wire and a better blue wire winding.

The Mags with a white wire have a coil tab soldered to the metal housing for engine ground, if you run these things too hot the weak solder can let the ground tab come free.
No ground to the spark plug, no spark.

Just Ohm for a dead short between the black wire and a head bolt.
If it's an open it's usually the ground tab.

One last critical thing...
Magnets can and do fail, just had to replace one in a new engine last month.
A weak magnet won't create enough current in the magneto to generate a big enough pulse for the CDI to create a spark.

One sure sign you have a weak magnet is when you replace the magneto.
If you can just hold it place with one hand and put all 4 bolts in it's weak, you have to fight that magneto around to get one bolt in, then fight to get another in if it's good.