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| NickG:
--- Quote ---Absolutely, they trigger off a magnet on the flywheel somewhere, and everything including pickups etc is built right onto the coil itself which is tiny. The only wire off them normally leads to the run/kill switch which just grounds the pickup out to gnd to kill the sparks. The same with briggs vertical crankshaft engines. Just a trigger spot of a magnet on the flywheel passing the coil assembly triggers the spark event. The only tolerance there is the gap between magnet and coil/pickup assembly, which also sets the timing within a narrow range. They are tiny and easily hidden and easily adapted. Another source of these is mini moto engines, chainsaw motors etc. Incidentally, smaller motorcycles and most older enduro/trials bikes are self contained flywheel magnetos too. The honda stepthru c90 wiring loom can be disconnected completely and the engine will start up. The key just providing pickup to gnd. On my sp400 enduro, it has a igniter coil and a rotating magnet on the flywheel too with cdi ignition, and that runs batteryless happily. --- End quote --- Thanks Mr Fluffy, it was my mate's mini moto engine that got me thinking but he wouldn't let me take it to bits! I was just thinking a strimmer one would be smaller but they are probably the same are they? So does that one magnet induce the current in the coil to give the spark just at the right time? Therefore doing away with points etc? The stationary engines I used to know had magnets lining the whole inside of flywheel and had points to do the timing so how do these do it with just 1 small magnet? Thanks again, will have to look into it, these can be found pretty cheaply I guess. Nick |
| John Swift:
Hi Nick , have a look here for CDI ignition system on small engines http://www.siliconchip.com.au/cms/A_110499/article.html John |
| MrFluffy:
I dont remember there needing to be a source coil to power the setup on the strimmer engines as per that article, but Ill look later at a strimmer engine I have lying round to be sure. The timing is done by a magnet passing a pickup not points nowadays and has been that case for quite some years now on the majority of small ic motors. You know you have a relic when you pop the flywheel off and see some points staring back at you :bugeye: As for price, I wouldnt pay much at all for a dead mower or strimmer engine, and 9 out of 10 times the ignition components work perfectly and the piston is smeared all over the liner inside which seems to be the common failing for these motors. Im sure a fiver would see you walk away from the tip or a garden machinery repair place with a couple of options. Ill look at that weedy engine I think I have on the shelf later for you. Hopefully find the camera to show the tiny scale of some of the components. |
| John Swift:
Hi MrFluffy , I have not looked at any small engines but think your are right I'd expect with the original magneto's have just one coil and a contact breaker John |
| NickG:
Interesting, would be good to see the photos Mr Fluffy. THanks John, looks a good article that, skimmed through it buit will have to read properly tomorrow. Nick |
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