Anyone know about magnetos? Friends old Honda rotovator has been lying idle for about two years and was working Ok when laid up. It is not showing a spark now, I've checked the "dead mans handle" and that's OK, plug lead and cap look to be OK, checked plug is OK (sparks on mine), so what could be wrong? Do they have points? I thought magnetos were almost indestructible.
For those that don't know what the hell I'm on about...
could be the points if its got em
IIRC the windings fail through age on this type of thing, You'll probably have to get the magneto rewound or replaced.
I had a brand new dynamo unused which sat in a box for years but when I trid to put it to use it had died because the windings had deteriorated with age even though it was unused.
My bike magneto did the same thing and needed replacing, its the shellac coating that breaks down and then the current leaks and ends up duff.
For this reason alone is why you won't find magnetos or dynamos on the shelf especially for vintage vehicles has these would have to be rewound to order or exchanged.
Steve.
It could be the winding but I would look at the points first. These are usually under a cover at the opposite end to the drive shaft to the magneto. These could be stuck, dirty or oily. JD
I'll have another look and see if I can see a removable cover, hadn't noticed one or I would have been in there poking around. Lets hope it is just stuck/rusty points or whatever. Getting the thing off, it's on the same shaft as the starting pull thingy, and then rewound sounds like it could be expensive if we can find someone local that does that sort of thing. Thanks to all those that have replied.
If it is flywheel magneto the situation is different (the "old" made me not consider that). If using a magnet incorporated into a flywheel it will either use an integrated electronic box, in which case it is a repair by replacement - and the cost will often be higher than the machine is worth, or there will be a set of points somewhere, often behind the flywheel, or operated by a pushrod and easy to get at, plus a wound unit close to the flywheel with the plug lead coming out of it (these rarely give trouble). JD
Not had one since the one on my AJS some 35 years ago!
You could have a word with the chaps at uk.rec.stationary engines, they talk of rewinding magnetos from time to time.
Another solution mentioned is a thing called an "atom" electronic conversion which gets good reviews.
I think a kludge is to forget the magneto, use a battery (which will need recharging each time) and attach the atom in place of the points and a car coil.
AJH
Hi Bob
In my experience this is a common prblem with agricultural devices which have been left lying in the shed all winter. I don't know the Honda but I occessionally have the same problem with my rotovator and mower. The problem for me has always been that the points are actuated by a little push rod on a cam and when it was previously stopped, the push rod was fully extended. When the engine is next turned over it cannot free the push rod because its already at its further extent of travel, therefore no spark because no make and break at the points.. WD40 or similar works, BUT you have to get to it first.
Usually the magneto is under the flywheel and getting that B****d off is what takes all the time. Now for the secret.. The trick is to undo and remove the nut that holds the flywheel in place. Then take two hammers of as near equal weight as you can, about half a pound will do, and tap on opposite sides of the fywheel at the same time. If you get them tap in sync the flywheel will jump of the taper. Be very careful, if its held in pace by a Woodruff key,not to lose the little blighter. Now you should see a cover under which lurks the points and other gubbins.
Clean out the spiders etc., and give the push rod a squirt of magic juice and then re assemble as they say in all the best manuals. Don't knacker the key putting it back in the taper!!
Once you are practised at this you can do it in ten minutes.
Best of luck
That sounds more like what I've seen, the plug lead does appear to come from behind where a flywheel should be, not the front of the Magneto as it did in my 1946 Norton Model 18, but then that was a separate unit and it had points. Friends away for a week so I can't get to check it all out until his return but thank you everyone I knew someone would point me in the right direction.
Geoff wrote
Thanks Geoff, will have a go at it next week when friends back from Hols.
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