Qualcast Punch LRP

[superluke2]

I have a qualcast punch petrol mower, final supply of lead replacement petrol about to run out. Will need to run it now on unleaded. Anyone know if it will need any adjustment.

[R Tallentire]

Hi Superluke2

If your Suffolk has the old cast iron engine, it should have leaded fuel, but in the old car world it has been found that over the years the lead got beaten into the valves and seats so valve recession is not as big a problem as expected.  As all side valve engines are low compression the octane rating of unleaded is more than high enough, so ignition timing does not need to be changed. I have been using a cast iron Suffolk on unleaded since four star became difficult to get, with no ill effects yet. Aluminium engines have hard valve seat inserts so were already suitable for unleaded fuel.

Regards, Richard

[superluke2]

Thanks for that Richard it is the old cast engine. Machine has done me 20yrs + so it doesn't owe me anything.  My dad had one and it is still going after 40yrs.

[Gwiz]

I totally agree with Richard.
I've been repairing horticultural equipment for over twenty years, and have never encountered a problem with the valve seats.
The only problem we did encounter, in the early stages of the change over from leaded to unleaded, was that a lot of engines stopped working because the unleaded loosened the carbon build up in the combustion chamber, and that stopped the engines from working.
If that happens, simply decoke the engine.