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Old 09-09-2009, 08:38 AM
Fabian Fabian is offline
Join Date: Sep 2009
Location: Australia - Melbourne
Posts: 168
Default Blue wire to black wire nightmare


Name is Fabian

Just want to introduce myself to the members and ask a technicial question to help solve my electrical problem on a Chinese 66cc 2-stroke.


This is a bit long winded and encaptulates a very frustrating 2 days of transfering every single electrical part from one engine with known good electrics to a new engine in step by step stages, only to achieve absolutely nothing and not solve the problem.

Here it goes.

Basically the engine only runs when the blue wire is connected to the black wire and the black to the blue wire.
If i run blue wire to blue wire and black wire to black wire, the motor does not run at all, BUT, when the sparkplug is removed from the cylinder head and resting on one of the cooling fins, it sparks just beautifully.
I have tried 3 different sparkplugs with the same result.
I have removed the magneto from the previous engine and installed it on the current engine and have also installed a brand new CDI unit but the problem is still the same.
Only runs when blue wire is connected to black wire and it constantly misfires when it runs and has no power and doesn't want to idle.
I've cleaned out the carby, cleaned the air filter and installed a new fuel filter just to be sure and disconnected the white kill switch wire and flipped the magnet over and back again, but the problem still remains.

During the day, and by chance, someone rode up my street with a Chinese 2-stroke motor on their bike and they had the blue wire connected to the blue wire, so i have no idea as to why my current setup does not run properly and fails to run at all with blue wire and black wires connected to each other.

I thought of the magnet not being aligned correctly on the new engine but it is in the same position as the old engine.
This is the replacement engine for the one that had the bottom end bearing problem.
That engine ran perfectly so i used it as a guide to check the indexing of the magnet on the new engine.
With blue connected to black the engine runs very poorly, makes no power, misfires and won't idle

The old engine has the keyway facing just infront of the bolt/screw that sits just ahead of the rear cooling fins on the barrel and the new engine has the magnet aligned exactly the same, although i have not taken the nut and spring washer off the crankshaft to see if the magnet has been installed without a woodruff key and reversed 180 degrees.

I have not installed the magnet or removed the magnet from the engine.
I can just see the keyway and with engine at top dead centre the keyway is at about the 1 oclock position and the magnet keyway lines up with where the crankshaft keyway would be on the old engine.
At top dead centre, the old engine and the new engine had the magnet in exactly the same position at top dead centre.

Photos attached of magneto, magnet and blue wire connected to black wire

This problem is driving me to the brink of despair

Attached Images Blue wire connected to black wire.
Magnet orientation in relation to crankshaft at top dead centre.

Pic attached of magnet orientation when flipped over and located on crankshaft keyway with piston at top dead centre.
Compare this pic to the other pic of magnet in the original position when located on the crankshaft keyway.

I've yet to flip the magnet over on the new motor to see if this solves the problem of a non running motor when blue wires and black wires are connected to each other.

I'm out of ideas if this does not solve the problem.


I've flipped the magnet over and the motor runs with blue wire to blue wire and black wire to black wire, but still makes no power, misfires and won't idle - feels like it runs worse than before.
It won't run at all with black wire connected to blue wire and black wire connected to blue wire.
I even connected white wire to blue wire and blue wire to black wire but it did not run at all.
After that the motor does not run with wires connected either way.
With sparkplug removed from cylinder and resting on cylinder head, the spark is weak and intermittent.

For gods sake, will someone give an answer to this god dammed son of a B****H, piece of garbage engine.

I can't take any more of this frustration, considering i've tried ever god dammed possible combination and nothing works.

This is driving me insane

I've flipped the magnet back over to the original side; the way it was installed on the engine from the factory.

The engine runs the same as before, with blue wire connected to black wire and black wire to blue wire, but just as before, it misfires, has no power and won't idle.

Every single possible combination of options has been tried, unless there is one that i've missed.

Why did the previous engines electrics work perfectly and even with the electrics from the old motor installed on the new motor does the new motor not want to run properly.

It defies understanding.

I am at a total loss to even understand what is going on, since the other engine ran perfectly.

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