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Carb settings for a Suffolk Super Colt (Zenith Carb)?

I've just brought an old Suffolk Super Colt. It's been stood all
winter outside but after a little coaxing, I managed to get it to fire.
It won't run for any length of time, though, so I stripped the carb down
for a clean. It all looked in good shape, but the engine still won't
run properly. While I had the carb apart, I also took of the cylinder
head and cleaned that up and re-seated the valves. Does anyone know
what the carb needle valve settings should be? Also what does the Air
needle valve do and what is the setting for that?
Or any ideas on hy it won't run properly? It will start on the first
pull but then dies after about 5 to 10 seconds. If I open the choke,
it won't run at all. If I'm quick enough and manage to put it into
drive during the first 5 to 10 seconds then it picks up and runs for 30
seconds to a minute and cuts grass! The lawn is going to take a long
time to cut if I have to keep restarting it evey minute!! Any ideas??

Pete Warburton
April 2008

Zenith Garden Tools, Lawn Mowers

i got mine mower off my free cycle (yahoo) site,the guy i got it from,said it was about 45 years old,but i think its more like 10 years old,as it looks as good as new,paint is like new,no rust any wear,but its in gear all the the time,even when the its on idle,it goes off all by its self ?

hairy dave
June 2016

could be e85 fuel

petrol
September 2011

try screwing the two mixster scrowes right the way in then 2.5 terns out then fine ajust so it revs the hiust.

tom rudd
August 2011

Regarding flooding problem.

This can be caused by the float having a leak(replace), a faulty gasket (replace), a blockage (clean carb), or a slight bend in the tip of the float needle (replace float).

I have it on good authority from on old guy who has been repairing them for 20 odd years, that it is not possible to repair the float or needle, they aren't expensive so buy a new one.

Budgie
August 2011

You may already know this but just in case you don't, or for others who are not aware of it.

Do not use old stored fuel as it goes off and can cause running problems,
Before you put the mower away for the winter, empty the fuel tank and carb so that you have a fresh start with new fuel in the spring.

Budgie
August 2011

The lever on the bottom is the choke ( air intake ), and should be in the horizontal position ( closed ) when starting from cold, once started it should be moved gradually to the down position ( open ).
When restarting after the engine has been warmed up, it can be started in the open position.

Budgie
August 2011

Somebody has suggested to open the mixture screw to get an initial setting which is quite right, but remember that to get the mixture spot on the best method is to look at the colour of the spark plug.
If the plug looks black then there is not enough air, and if white (or grey) too much air. One point to remember here is check the air filter first. Its a waste of time messing with the mixture if the air filter is dirty and blocked. With the sponge type you can wash them in washing up liquid or they are cheap enough to replace.
Another sign with the mixture is: Weak = cutting out, and Rich = hunting (hunting is where the mower revs up and down on its own)
Have fun!

Adrian
June 2011

I had a similar problem. I cleaned all the carb, jets etc and still the problem remained. Finally I checked the fuel tank and realised there is a filter which was clogged with rust etc in the fuel tank (the filter is part of the fuel tap. Once cleaned the Suffolk Punch has run like a little bird.

Hope this is of use

Steve
October 2010

Hi I had lots of problems with the zenith carb so after seeing a video on youtube I replaced with a mini motto carb and its now working without problems. Very easy mod I just had to make the screw holes bigger on the manifold buy using a hacksaw and cutting in from the outer part.

stevie
April 2010

Main jet screw in, then open one and a half turns, Idle jet screw in then open three quarters of a turn

Whinewizard
November 2009

i have recently aquired the same mower and had the same problems. i now have the mower running reasonably well but can not get it to idle without stalling. first off i replaced the float and resealed the gasket on the carb, the float was 2 pound from local lawn mower shop. old floats wear and move on the shaft setting them to high.

jambazil
June 2009

DONT BLOW WITH PNEUMATIC AIR WITH HIGH PRESURE IN A SUFFOLK CARBURATOR WHEN THEN HE IS BROKEN

tom
June 2009

I have a suffolk engine and i blow with pneumatic air in the sprower of the carburator and afther that my engine wouldn't run i have got to buy a new sprower

tom
June 2009

I have just had my carb apart to try to clean up for new season and after putting it back together is won't stop overflowing. I have no idea why, it seems to be something to do with float but cannot understand it. Wife not amused as it is her pride and joy. Any ideas what I might have done wrong?

Scott
April 2009

I have the same problem,but now mine wont run at all-roughly in what position should the horizontal screw be?this is the first trouble i have had for 25 years,I blew out the carb and cleaned around the float but lost then found the mixture jet and forgot how many turns. is it richer further in?

harry
March 2009

I have a similar mower with a Zenith carb. It's a Suffolk Punch - so that information will prove very useful to me as was having problems today.

Can you confirm what position the lever at the bottom should be in - I presume for starting it should be fully open, but when should I back it off a bit (the mower dies when I close it, which I presume it more or less the point)?

Robin
May 2008

The top screw (vertically downwards) is the idle mixture - turn fully in then back out 1 1/4 turns. The bigger screw on the side (horizontal) is the main mixture...get the engine running then on full throttle turn it out until the engine just starts to falter - maybe with a bit of black smoke - then gently turn it in until the engine runs smoothly.

John
April 2008