ATCO Medium Weight Mower (PROBLEM!!!!)

[vhgmcbuddy]

Hello all
I own an ATCO Medium Weight 2 stroke 14″ cylinder mower dating from 1935.
When I kick start (using a lodge C3 spark plug) it starts first time every time.
If I leave the throttle lever down low and just let the mower tick over it is fine.
But as soon as I rev the mower up on the throttle, it goes out of control.
It gets louder and louder and louder, it jusk keeps revving faster and faster and faster until is sounds like it is going to explode.
Does anyone here know what might be going on here.
Any ideas or information on what may be the cause, will be greatly appreciated.
Many thanks.
Daniel

I will try to put some images on so you can see the mower for model identification.

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[wristpin]

Nice images. Looks as though it’s just been restored, has it run “normally” before or is this its first outing with you? Are you sure that this is not the normal behaviour of an ungoverned two stroke? I’ve got a couple of machines with similar engines and if the throttles are opened more than about 1/3rd I have to run after them!
I think that the easy starting rules out air leaks on the induction side or crank case so perhaps you could try richening the mixture a bit – raising the needle in the throttle slide.
After that I’m at a loss as what to suggest.

[vhgmcbuddy]

I may be wrong with this suggestion , but could it be possible that the slide return spring is so weak that when the engine is running it gradualy alters the slide to full throttle on its own ?????

[enginear]

As WP say’s about an ungoverned engine yes this is normal, put the machine into work cutting grass and the rpm would drop pretty quick then you will find that you would need to open the throttle to get it to cut, the heavier the work the more the throttle need’s to be opened, if the engine was a four stroke doing the same work it would be governed and the throttle would open it’s self dependent on initial throttle setting when under load, when not under load the rpm would be limited by the govenor, which you engine has not got hence the rpm get’s fairly high, the torque figure is higher at a lower rpm on the four stroke and it is normally quieter as well, because it can be run at a lower rpm figure.

[vhgmcbuddy]

Thankyou for all your messages. I will look into all the suggested ideas and reply to you after. I restored this mower to as near original as I could. I even went to the effort of having the original paint replicated to the perfect atco green of the 1930s era. The decals or labels whatever you want to call them, I had made for me locally as well. This mower has been in our family for the full 78 years of its life and the only mower we have owned as well. Better than the modern lot that goes wrong all the time. All we are missing is the grass box that my great grandad who is “103” says was (lost in WWII) somehow.
if anyone can post an image of what it looks like that will make my day.
I thought it needed restoring, it was looking a bit worn out.
Many thanks.
Daniel

[vhgmcbuddy]

hi hope you get one as its a nagging problem I have as well. I have a ransomes mk 2 that needs a box and I have been looking for three years. not wanting to sound out of order and I hope you have a sense of humour but,could it have been turned upside down and used as an Anderson shelter ?

[Author]

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