Scooter dies at random  By  arron (Read 4,846 times)

Dies No Throttle=Spark
I just installed a Red Coil, the Boot doesn't fit as tight as I would like, The Cooling Fan Blows Loose the Plug Boot and she dies as you Described. I would search in the ignition system.

So, Aaron.  There must be a harbor freight not too far away.

The have a spark tester - it's an inline thing, only about $5.  You pull the wire off the spark plug and attach the other end of the tester to the now-empty spark plug.  The tester has a clear plastic body, and once you start (or try to start) the scoot it will light up each time there is a spark.  IF there is a spark.  Sort of an end-to-end tester for the whole ignition system - not perfect, but a great first step.  Suggest you grab one.

Or, if you happen to have an old induction timing light you can do the same by putting the clamp around the spark plug wire and see if the timing light flashes.

I have good spark whenever I test, but the problem is that the failure is happening at speed and then clears up once I come to a stop. The scoot turns right back over first try every time, but then will die again, sometimes right away, sometimes I make it all the way home. But the loss of power always happens while moving, never while standing still or at idle.

Not sure how fuel gets to the carb for your scoot, but it seems like restricted fuel flow could be a cause too. Enough gets to the bowl to keep it running when demand for fuel is low, but on acceleration/at speed it can use it up faster than it can replace it. So naturally then it will sputter and/or die. Blocked fuel line/filter, intermittent fuel pump (if it uses one) or even possibly the float bowl valve is closing too soon so that there is not enough fuel for higher demand.

It's just a maybe... if you don't find anything electrical going wrong. But I tend to agree with rcq92130 on some ignition fault; because of the suddenness and randomness of the symptoms.

The bog down noise I think is just the noise from air being sucked into the carb since you probably open the throttle up wide. But the usual engine running noise is not there so intake noise is what you hear.

Yep, one other thing.

I had an almost identical problem. Thought it was a failing coil, so I bought a new coil/plug wire from GY6Racing (the best supplier!). When I went to install the new coil I discovered the spade connectors to the coil were not tight but had loosened up over time. At speed there just wasn't enough of a connection to support the current to the coil. Just tightening the connectors would have solved the problem, though the cheap $10 new coil was hardly a wasted investment.

That black box is the CDI - basically a simple computer that controls when the coil sparks.  Unlikely it has failed ... BUT ...

You should definately change it out for a better one (that one looks OEM).  The replacements remove the RPM limit and also vary when in the engine's cycle the spark happens so you get better power out of the engine.  Higher performance replacements are inexpensive.  The tricky part is this:

Most of the replacements are called "advanced angle" CDIs.  These work OK at speed but create problems starting that might even be damaging to the scooter.  These are different than the GOOD ones which are called "advancing angle" CDIs (not advanCED, but advanCING) which vary when the spar occurs --- standard timing at low RPMs, varied for performance at higher RPMs.  These eliminate the starting problem et give the better performance.

I only know of one supplier of advancing angle CDIs, but fortunately he is a member of this bard (and a top notch supplier).  Contact him under the ID "tvnacman" (real name John).  Many or most here have bought from him; no complaints I know of.