Sovereign XSZ40 Lawn Mower Starts then Stops

[yottie]

Mower starts, runs for 10 seconds, stops. Have checked plug and filter, fuel is fresh...help please! (ps has been spitting now and then recently during operation)

 

[Burnerman]

If the engine has been popping back through the air cleaner then it's often a sign of weak fuel mixture - which needs a carb strip down to access and clean all of the fine brass jets.
However, it's also indicative of spark plug issues so treat it to a new one......particularly if it's a BPR6ES or equivalent.
John

 

[yottie]

Thanks B, am waiting for a QJ19LM to arrive shortly.
Had a look at taking the carb off to investigate jets etc, it looked a bit techy.
Am used to SUs etc, are these similar, it would be useful if there was a workshop manual otl., can't find one in Google.?

 

[Burnerman]

In comparison with the SU carb, they have no similarities operating wise, however the fuel level is still regulated by a plastic float and needle valve, and this allows fuel through a main jet, through an emulsion tube above that and then into the Venturi.
The slow running jet bypasses all of this, and looking at the end of the carb Venturi you can see a small drilling where it gulps it's air.
Absolutely nothing to be afraid of taking these things to bits, just don't lose anything and careful with any gaskets!
You'll need a can of carb cleaner standing by though, and compressed air is a real boon.
John

 

[yottie]

Thanks again B. OK it's Bank Holiday, went out this morning, traffic was horrific, thought right will have a real go at that carb.
Hoisted the machine onto the pic-nic table and worked sitting down and comfortable.
Took pix before I dismantled, air cleaner off (the dog can now see the rabbit!)
Things looked clearer now.
Thought I'd start by undoing hose from tank.
Having got this off thought "I wonder"
Using a shower head extension fitted over carb inlet and blew vigorously, restricted at first then...geronimo (I hoped) it seems easier to blow.
Put everything back together and....started first pull and kept going!
Will try it on grass tomorrow, it can't have really been all it was could it??

 

[Burnerman]

If it was the fuel inlet you blew down, you may have cleared a blockage at the needle valve......if it was a blast of air down the carb Venturi, I'd doubt it!
Post back after you've given the machine some work?
John

 

[yottie]

OK. after DIY "air compressor" machine started at second pull and carried on! Cut a large area without any problem.
It would seem to have been a blockage at the needle valve??
Either way a can of carb cleaner is ebaying its way here and will strip carb down later
ps: still an occasional spit back.
again,many thanks for help

 

[Nige F]

Re occasional spit/miss. I wouldn't worry too much if it still does that after your clean with carb spray. Mine does that - I reckon it's endemic with small Sidevalve engines and the new 'orrible unleaded petrol