Wiring in a petrol hedge trimmer

[Spoonie]

I realised as I started to type this post that I should have been more specific with the title of my last post, as I'll be asking for a LOT of help with that particular hedge trimmer (an Echo HCR 171ES) over the coming weeks and months I suspect! So I thought I'd start this post off with a bit of background, to give my posts some context. I'm someone with no background in any of this stuff - I've done lots of general DIY around the home and garden, but I work in an office, and don't know much at all about mechanics or machinery and decided I'd like to change that. So I figured that the best way was to pick up some old two-stroke machines (a couple of strimmers, a hedge trimmer and a water pump of all things!) and watch tonnes of videos and ask lots of questions (hence my arrival here!) and try to learn how they work, how they're put together, how to fix them, etc! So on that basis, please forgive any questions which seem basic or obvious; it's just how I learn

Anyway, I was gifted the Echo hedge trimmer for free with the instructions 'it doesn't work and we're not sure why but we have some new stuff so you can have this one!' Today's question, or theme, is about the electrics that make up a hedge trimmer/strimmer, etc. The Echo has two wires which run through the plastic conduit from the handle to the body, along side the throttle wire. As far as I understand it, these effectively create a circuit which allows the unit to function, and when you turn the unit off, that breaks the circuit, which stops the spark plug from sparking, thereby stopping the engine (please correct me if that's wrong!)

One of the two wires has a female spade connector on the end which clips onto the body of the engine. The other, however, is broken. It has both a clean break and then a badly frayed bit, a little further along from it. I recognise that one option would be to replace the whole wiring harness from the handle (and I've contacted a dealer to get a price for that, along with some other bits), but I presume that'd be epensive and I'm keen to understand how else I could overcome this. My thinking was that I could cut the wire further back (to remove the frayed section and then replace the missing piece with a short piece of wire, and crimp it on at one end, then add male and female spade connectors at the other end (just after the clean break, the wire has a pair of these before it meets the body, presumable so the wiring harness can be detached). I have a few questions tho:

1. Does the above plan sound sensible? It makes sense in my head, but is that what a competent repairer would do?
2. What sort of wire would I need for this and where would I get it? I'm capable with a soldering iron, crimpers, heat shrink etc, but the wire itself I'm not really sure on.

Again, any thoughts or help wouldbe much appreciated!

[Mick]

The Echo has two wires which run through the plastic conduit from the handle to the body, along side the throttle wire. As far as I understand it, these effectively create a circuit which allows the unit to function, and when you turn the unit off, that breaks the circuit, which stops the spark plug from sparking, thereby stopping the engine (please correct me if that's wrong!)

I'll come back to the rest of your post later, but this bit you are indeed wrong.   What the wires do in this case is stay open circuit while the engine is switched on, and when you want to switch the machine off the wires  take the connection on the coil to earth, that kills the spark. 

So basically without those wires connected to the machine it should run, but you won't be able to turn it off.

[Spoonie]

That's helpful, thank you!

[Mick]

That's helpful, thank you!

You're welcome.

Now I forgot to come back and reply to the rest of your question, so you've probably worked it all out now.  But yes any suitable wire will do as long as it's flexible enough. Just find something of similar size and splice it in where necessary, heatshrink the joins to stop it shorting anywhere, you should be good to go.

[Spoonie]

Thank you! Yep - have gone for exactly that approach, so that'll be me one step closer! Dismantled, cleaned and sharpened the blades tonight, made a gasket for the gearbox last night and have a couple of other bits to do and then I should be ready to put it all back together and see what it does!