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DanG

Anyone know about spark plugs and engines?

3 posts in this topic

I have an issue with a second monkey bike I bought in that it won't run, although it did for about 10 seconds.

I have compression and new fuel....

Spark is the issue.

The plug is newish, and here lies the issue I think. I have taken it out and kicked the engine over without it touching and no spark.

Touching the metal ring / thread to the case, no spark.

Holding the plug 2mm off the case there is a strong spark between case and ring AND also a spark across the plug gap as there should be.

I am guessing this is the issue, and that possibly the plug is earthing before spark gets to the gap.

Can this happen? Any ideas? Bit baffled at the moment.

Cheers

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The sparkplug needs to be touching the side of the engine so the circuit is competed (as it would be if screwed into the head) & then when you kick it over you should get a spark.

Have you checked the gap is correct (although if new should be about correct) & if used what is the condition/colour of the plug - for a 2 stroke should be about the colour of a digestive biscuit ?

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Try twisting the ht cap a half turn- cheaper machines have a ht cap that is simply screwed on to the ht lead and is a common break point.

Also dip the plug in petrol and clean with a fine wire brush, set the gap on the plug to about 22 with feeler gauge (or roughly the thickness of your thumb nail).

A good test is to put your fore finger in the cap (rather than the plug) and attempt to start- if the coil works and power is being sent you will get a 'little' jolt.

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