The Old Lawnmower Club
Collection, Preservation and Display of Old Lawn Mowers
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Dennis 24" [1938] - Not the brightest spark!

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Budding Enthusiast Sat, 01/04/2023

 

I am new member to these hallowed pages. By way of introduction I have a Dennis, a JP Super and an Atco Royale B20.

Today I should like to ask a couple of questions about the Dennis, which I cannot start. The mower is a 1938 model - I believe but I hope to attach a photograph of the brass plate.

Dennis - manufacturers plate

I bought the Dennis last year, when it emerged from storage in a very nice garage after 20-25 years of rest. When the mower went into storage, I believe it was in full working order. 

Since acquiring the mower I have cleaned various elements, such as the carburettor, fuel tank and the magneto points; I have changed the oils and the spark plug. I cannot get the mower to start and I think it is because the Wico magneto is not delivering a steady stream of sparks. Would you assume from this that I should just take the magneto off the machine and get it checked or is there an alternative course of action you would recommend? 

If your response is to take the magneto off, then:

  • are there any do's and don'ts in this process? [I am sorry but I am not that technical, so these may sound like daft questions!]
  • is there anyone you can recommend for servicing Wico magnetos

Finally on the ranks of the trivial, what do I need to connect the seat to the mower? Should I just have a metal bolt and nut, or should there be a more intricate solution? [See photos]

Dennis - Seat link and back of mower

Forums

wristpin Sat, 01/04/2023

Rotate the engine with the crank and when approaching Top Dead Centre and you hear the magneto impulse trip, stop there and mark the two sides of its coupling. When you refit the mag enter it’s two pins into the coupling according to you mark.

Not sure about a “ stream of sparks” . It only needs one every other revolution of the four stroke engine. When testing, attach a spark plug to the HT lead and hold the plug against clean metal . Don’t spark the mag without it being able to discharge the spark or it may discharge internally and damage the mag’s windings / insulation.

If it’s A Wico Type A mag , One simple thing to check is that there is a strip of insulating material curled round the inside of the chamber containing the points and condenser which prevents any internal arcing from those components to the casting. Also if the mag still has one of the original metal cased condensers , the chances are that it’s past its best. It may be replaced with a modern plastic one.