How to test if a spark is strong enough?
Discussion
A friend is rebuilding a 50cc bike. When cranked there is a spark but I want to be able to confirm the spark is strong enough.
The gap is 1mm. We have found some literature that suggests if it is strong enough, it should be able to cross a 7mm gap.
I don't think opening the gap out to 7mm is feasible but we could give it a try.
Spark plug testers are ten a penny but most only show that there is a spark but not the strength of it. What methods are there to do this test?
Thanks
The gap is 1mm. We have found some literature that suggests if it is strong enough, it should be able to cross a 7mm gap.
I don't think opening the gap out to 7mm is feasible but we could give it a try.
Spark plug testers are ten a penny but most only show that there is a spark but not the strength of it. What methods are there to do this test?
Thanks
You need a tester like this. Yes, this is on the US Amazon, but you can see how it works. Basically there is a threaded adjuster so you can see how far the spark 'jumps'.
https://www.amazon.com/Tester-Adjustable-Ignition-...
https://www.amazon.com/Tester-Adjustable-Ignition-...
geeman237 said:
You need a tester like this. Yes, this is on the US Amazon, but you can see how it works. Basically there is a threaded adjuster so you can see how far the spark 'jumps'.
https://www.amazon.com/Tester-Adjustable-Ignition-...
Thanks that looks like it would do the job.https://www.amazon.com/Tester-Adjustable-Ignition-...
In the interim, in absence of such at tool, I've instructed my friend to put 2 nails 7mm apart in a block of wood. Then wire them to the plug lead and the earth and give it a go...
paintman said:
Is this an 'out of curiosity' thing or does the bike not start?
The bike doesn't start. It's an old 50cc Derbi two stroke that my friend bought as a pile of bits. He's already spent a load of time on it. He gave up about 6 months ago. I'm trying to help him now, we are going back to basics and working through it one step at a time.The ignition is very similar to Piaggio and Vespa bikes of that era & uses a Hall Effect sensor. It looks like the orientation of everything is correct for the timing to be OK. Once we confirm that the spark is strong enough, we'll look at the carb - the first step will be to take the vacuum fuel feed out of the equation. The carb is a chinese copy...
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