Suffolk Super Punch 17 inch Slow Running

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peternsomerset
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Suffolk Super Punch 17 inch Slow Running

HI,

I have a Super Punch with a 75cc engine "Bullet" type exhaust and a rear serrated split roller which I was told was made in the mid fifties.

Over the years I have had problems with this and other mowers in that with the throttle flap completely shut it revs too high, yet years ago I remember I could stall the engine by shutting the flap.

I now have a collection of carbs, some of which have worn flap rods which I thought was causing the problem but my present on is quite well fitting.  I have also fitted new gaskets to the manifold and each end to the manifold extension tube (sorry if terminology is wrong). I have perviously cleaned the carb and replaced the float chamber gasket.

The engine runs OK but just a bit fast but it would be nice to resolve the problem and any advice appreciated.

Thanks

Peter H

 

 

 

wristpin
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“Worn flap rods”. Would they

“Worn flap rods”. Would they be the thin wire governor links or the shafts running through the body of the carbs with the throttle butterfly’s screwed to them? If the latter some of your problem will be that the  shaft and butterfly don’t fully close and don’t reliably close to the same position, and that the engine will be drawing in air from around the spindle , upsetting the mixture. 

Back in the day a couple of after market firms marketed replacement spindles that overcame some of the spindle wear and also had a better fitting for the original peened retention of the operating crank. If you are lucky you may find that the likes of Jon Cruse at the Hailsham Mower Centre may still have one but otherwise you will need to find someone with the necessary skills and equipment to make a new spindle and may be re-bush the carburettor body.

peternsomerset
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Hi,

Hi,

The answer is the shaft in the carburettor.  In the past I had hand made a shaft but it was very difficult to get the flap and lever to be at the correct angle to one another!

The basic question I have is,  on a good carb,  if the flap is closed as far as it can be against the carb barrel,  should the engine always stop?

(I do realise that there is a small flat edge on the side of the butterfly)

BTW I have never figured out how to set the governor spring as it never seems to make a difference!

Regards

Peter H

 

     

wristpin
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With the butterfly fully

With the butterfly fully closed , in theory the air supply is shut off and it should stop but as the fuel side of the slow running system is independent of the main jet and also draws its air from above the closed butterfly it’s quite possible that there’s is enough leakage to allow it to run.

peternsomerset
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Thanks for clarification, 

Thanks for clarification,  you confirmed my thoughts,  I will have another try at slowing it down if it gets too fast!

FWIW I relocated the diaphragm as a spigot was missing (bought another Jon Cruse to fit later) and the engine seems to run much better!

Thanks

Regards

 

 

   

wristpin
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FWIW I relocated the

FWIW I relocated the diaphragm as a spigot was missing (bought another Jon Cruse to fit later) and the engine seems to run much better!

FWIW ???   and what diaphragm ? You've completely lost me!! We are talking about a Zenith carburettor?

hortimech
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FWIW is For What Its Worth ;-

FWIW is For What Its Worth ;-)

But I am with Wristpin here, just where do you fit a diaphragm to a Zenith carb ???