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Collection, Preservation and Display of Old Lawn Mowers

Hello from Denmark



i purchased an old Suffolk Demon Deluxe last year.It´s running really well.But this year oil is runing out of the hole where you put

the oil in(sorry i don´t know the technical description)

Any ideas how to solve it?

Also i would like to know if somebody could tell me from which year it is. I can´t find to much information about the demon.More for the Punch.

Greetings from Denmark


Bjorn Fri, 25/05/2018


yes i found the manual allready, thank you.But could not find anything about the oil problem.


wristpin Fri, 25/05/2018

Your oil problem.



Crankcase breather in the valve chest ( below the inlet and exhaust manifolds) gummed up

Worn piston rings and may be the cylinder bore as well

wristpin Fri, 25/05/2018

The oil drain is in the lower sump just below the filler. Looks as though it has been fitted with an internal hexagon plug ( needs an Allen Key)

The crankcase breather is relatively easy to remove and clean, I will post some images later.

Piston and rings - complete engine strip down.

Bjorn Fri, 25/05/2018

Thanks a lot for the help.

I thought so that it was the hexagon plug but my problem is that its worn out.any trick to remove it?

Solved it. It was not much oil coming out, around 100 ml.


wristpin Sat, 26/05/2018

Crankcase breather.

The purpose of the breather valve is to allow air to be expelled from the crankcase when the piston descends. On the upward stroke of the piston, the valve shuts and a small negative pressure is created in the crankcase which helps to keep it oil tight.

The moving part of the valve is a small paxolin disc that "floats" in the alloy body  - up to vent and down to seal.

What goes wrong. The valve can gum up with dirty oil. The disc and its seat in the valve body can wear and not seal. Turning the disc over so that the unworn face is against the body can improve things.

The valve is held in place by a spring located by the stud that holds the cover on.

Valve components, retaining spring, cap, paxolin disc, valve body and fibre sealing washer 



Bjorn Sat, 26/05/2018

Thanks a lot wristpin.I changed it now.Need to buy oil tomorrow..then i will see if the problem is fixed.

Bjorn Sun, 27/05/2018

Ok was testing it today, no oil spill. Thank you.

Another question,is there a grassbox for this model?

wristpin Sun, 27/05/2018

Worth putting a Wanted ad on this forum, otherwise keep an eye on auction sites. Not too difficult to make one especially if another OLC member has one and will post some decent profile images with measurements.

gtc Mon, 28/05/2018

Additionally, you could consider joining the OLM Club itself. The mailed-out quarterly newsletter Grassbox will reach many more mower enthusiasts than come onto this forum, so a Wanted ad in that could bear fruit.

wristpin Tue, 29/05/2018

While looking for something else I've just come across a 19" Demon De Luxe parts list and there, right at the end of the listing is "Grass Catcher (not illustrated)" L7696

So that answers your question - there was one!

Bjorn Wed, 30/05/2018

That´s good to know.I found this on ebay.It could be the fitting grass catcher.It´s on a Mark II