03-19-2017, 03:01 AM #1
Spacers to re set magnets in a small engine flywheel
Anyone who has ever owned a machine with a small engine mounted on it knows that they can become tenacious if not downright cantankerous.
A friend of mine made the 75 mile trip to my place Friday to see if I could help him get his 1990 Toro Proline 48" walk behind mower running.
He had replaced the spark plug, the air filter flushed out the fuel tank put on a new fuel filter changed the oil, and greased it where needed but the thing simply would not start no matter what he tried.
So first things first I pulled the plug and checked the compression this was fine next I put a screwdriver in the plug wire and held it the stem of the blade very near the engine. NOTHING, so I grabbed the blade to see how big of a shock I would get. Not even enough to make me twitch.
Time to pull the cowl and check the IGN. module and flywheel.
Just as I figured there was a heavy coating of rust on the magnets and the laminates of the module. A few minutes of cleaning with emory cloth had these shinning. Checked the spark again without replacing the cowl the battery was low but still turned the engine without the plug installed. This time I felt what I figured should be a powerful enough shock to make a spark I put the plug on the wire and held it to the side of the engine.
NOPE! so I used the screwdriver again. YEP plenty of spark must be a bad plug even though new. 45 minute to town and back with a new plug, checked it and had a spark. Installed it used jumper cables and a jumper battery the thing started right up but the electric blade clutch would not engage
Since it is supposed to receive it's power from the engine this meant a problem with the under the flywheel generator
I pulled the flywheel and found all 6 magnets stuck to the stator and not on the flywheel. Luckily the bond holding them to the flywheel had failed on all of them and none were broken just some small chips out of a couple of them.
So by now it is Saturday afternoon and the True value in the nearest town has already closed so this meant an hours drive one way to TSC because I didn't have any 2 part epoxy on hand.
I made these spacers out of an old mud flap to equally space the magnets inside of the flywheel.
I used the end of 1 magnet to check the other five to make sure I had then all arranged in a north south configuration then epoxied each of them to the inside of the flywheel after a couple hours cure time we re installed everything and started the 14 HP Kohler again this time I just used the pull rope and only had to pull it twice. The blade clutch engaged when he turned on the switch just like it should. Ready for 0ne more year's worth of mowing 20 lawns a week. Next weekend he will probably haul his 56" mower over because the blade clutch has stopped working on it as well
I told him to please not tell anyone who got his mower running because when it comes to small engines I try to not know anything about them.
03-19-2017, 11:43 AM #2
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So true about "when it comes to small engines I try to not know anything about them" but we end up fixing them anyway. That is the situation with my 10HP Patriot wood chipper for chipping up to 3" diameter tree cuttings. I keep it ready for use for brush clearing to reduce the wildfire fire risks from dry brush. The chipper is stored and used from a flat soil area cut into my lower slope on the property. I keep the machine covered from the elements but the exposure takes its toll on the Tecumseh engine and chipper parts. Fixing the machine in the field without a workbench is a pain and usually end up repairing/replacing more than necessary before finding the root cause.
Thanks for the step-by-step thinking that went into your repair.
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03-19-2017, 01:25 PM #3
Paul at first I thought about simply posting the pic of the spacers and a couple sentences of what they were used for but then I thought someone else may encounter a similar problem so why not create a blow by blow explanation of how I came to need them in the first place, hoping that my rather lengthy diatribe may be of some benefit to someone else.
My father had the philosophy that almost any engine could be made to run and all of it's componentry could be repaired with a little patience but he drew the line on small engines. He used to say if God had meant for them to exist he would have made them with more than 1 cylinder. This coming from a guy who quite literally could diagnose almost any problem in a vehicle's engine just by hearing a vehicle pass by his shop from 50 yards away, and almost tell the year and make of a vehicle by sound alone without looking up and seeing it. Being legally blind it wouldn't do him any good to look at a passing car or truck anyway
03-21-2017, 06:44 AM #4
03-21-2017, 11:13 PM #5
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Thanks for the "blow-by-blow", Frank. Who knows how many of these small engines have been scrapped because the "mechanic" failed to apply rigorous fault-finding methodology, and just kept changing components without verifying they were the cause of the problem, or stopped looking when the next problem surfaced. When confronted with the displaced magnets, most would have said: "You need a new flywheel!" I also understand that these small engines are produced in such quantities and so cheaply that very often the labour time to properly identify and perform each repair condemns them to the "beyond economical repair" pile.
Slightly off the original topic, but your father's compensation for what most would regard as a crippling disability reminds me of my wife's step-grandfather. He earned his living as a horticulturist specialising in grass turf for golf courses, bowling greens and cricket pitches, yet he was colour-blind! He claimed it was an advantage enabling him to see fungi and other defects that normally-sighted people missed.
I also remember a maintenance foreman on a Urea plant which had a massive 200-bar 5-stage reciprocating CO2 compressor. Despite the high ambient noise levels, he would stand on the compressor deck, then say to the chargehand: "Have a look at no.2 inlet valves." Sure enough, there was just the slightest evidence of deterioration, and he had identified it well before it showed up on the interstage pressure gauges.
Once again, thanks
03-22-2017, 12:20 AM #6
Russell, I've encountered displaced magnets in the flywheels before and they are usually reduced to giblets. or at best maybe as many as 3 of them will still be attached while the others have been ground down to pixie dust or will lock up the crank or destroy the stater. On the rare instance where all of them are un bonded it is a simple fix just as I described.
Yes the cost of labor for repairing small engines or just about anything now days can be prohibitive
04-18-2017, 12:08 AM #7
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