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Suffolk Super Punch Starting Problem

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peternsomerset Thu, 30/03/2023

I was half way through mowing the lawn for the first time this year with my 1953 17 inch mower and it stopped and ATM am not sure if its petrol or spark or both!

I have done some checks as follows and will be buying a new plug and supressor:

Cleaned out carburettor

Removed filter and fuel come out from bottom inlet if cranked hard but spark plug seems dry!

There is a reasonable spark

I have an old car pressure gauge and it gives about 50 lbs/square inch

I did leave some petrol in the tank over winter! but cleaning the carb made no difference. 

I will clean everything again later but would appreciate any suggestions as it does not even try to fire ATM.

Thanks for your time

Peter H

Forums

wristpin Thu, 30/03/2023

Presume that you have the cast iron SIF engine with the Zenith up draught carburettor.

Get an aerosol of carb cleaner or flammable maintenance spray ( not All is flammable)  , pull off the air filter and spray up the throat of the carb and see if it fires . One or two fires would suggest  that more carb cleaning is required. Try the same thing with a direct squirt into the cylinder via the spark plug orifice. If you get no suggestion of the spray being ignited , it would seem that the spark is either too weak or not arriving where needed.

A rough and ready spark test.Remove the plug cap/connector from the lead , hold the lead end about 6 mm from bare metal and see whether the spark will jump that gap . If you get a decent spark there, try a new connector and plug. If an engine of that age is on its original points and condenser , it may be worth cleaning the points and fitting a new condenser. Condensers do tend to weaken with age.

I’ve never seen a compression figure published , but if you can feel a lump when you pull the rope  it should be ok but on an engine of that age, a top end overhaul may be useful.

 

peternsomerset Fri, 31/03/2023

Thanks for the info I have just had time to read it and the engine is a 75cc cast iron.

I bought a plug and cap fitted them and it now runs.  I mowed the lawn and suspect it was the cap as the copper loop was loose.

There was a spark but am fairly sure it would no jump 6mm so will do that test as soon as it stops raining!

I think I changed the capacitor a couple of years ago but will also check the gap and clean them.

Regards