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Collection, Preservation and Display of Old Lawn Mowers

Suffolk Punch 43S setup

Good evening all,

I've just become the proud owner of an old Suffolk Punch 43S and have been giving it some TLC that it hasn't seen in a while.  Overall it seems in good condition considering the age - the clutch for the roller works and, when I can get it to idle, the cutting cylinder doesn't rotate. The engine started after an oil check, petrol, full choke and a few pulls but was a bit lumpy and not really controllable. 

Last weekend I dismantled and cleaned out the carb and replaced the air filter.  No particular issues that I noticed.   I didn't take out or adjust the jets at all.   Afterwards it ran much better - but now I have a larger problem with control!   When I move the throttle lever, the wire moves the regulator lever; when the engine revs highly the regulator moves the spindle as expected.  However, none of this seems to move the throttle valve and, even when I move the throttle valve manually, it does not control the engine speed.  When the throttle valve is at idle, the engine is still fast and the cylinder is engaged.   The other problem is that when I move the throttle lever to stop, it carries on (fast) and the only way to stop is to shut off the fuel.  Even when the throttle is at low/stop, the valve still wants to remain open but when forced to the idle setting, it slows but not to idle.

I can't help feeling that it is just a matter of adjustment to get this working properly but I am afraid that I don't know the settings to set it back to.  I enclose a few pictures of the suspect areas in case they show that a crucial spring (or whatever) is missing. Any advice gratefully received.




wristpin Tue, 21/07/2020

First you need to understand that the handle mounted throttle control only pulls ;  the return action is provided by that large hairpin spring . When you move the throttle lever past slow to stop, that spring should pull the link on the end of the cable to touch the cut out terminal on the back of the throttle plate - the opposite side to where that thin black kill  wire terminates. 

Looks like that area could do with a good clean up, so make sure that the throttle cable is free moving and the link is earthing out the kill wire . It may even be that sorting that issue, improves the throttle response.

kingswindsor Wed, 22/07/2020

Many thanks Wristpin,

I'll give the area a good clean up and take it from there.  The parts do move at the moment but its obviously not right and a clean should help free things up.   I'll make a point of checking why the kill switch is not connecting at the same time and we will see if it helps the throttle response.  A good job for the weekend.