I have a Mountfield SP470 with a Briggs & Stratton 35 SprintClassic 2.6kW motor model 10D902 type 0153. On trying to start it for the first time this year it seems to start but runs for only 1 or 2 seconds. It appears to be burning the fuel I primed it with but then cutting out.

I changed the spark plug as it appeared slightly corroded but it did not help.

I added a spoon of fuel directly into the spark plug hole and started the machine and it seemed to run for pretty much the same length of time as when I primed it.

I suspected a fuel delivery problem so I removed the air filter, primed it and started it and it did the same but I noticed there is a small black tube running into where air filter sits and I guess this is where the fuel comes in? If it is nothing was coming in through here which would explain why it cuts out.

Interestingly if I prime 3x and then start the machine and then continue to force fuel into the machine by continually pressing the prime bulb the motor keeps running until I stop priming.

I did leave the old fuel in the fuel tank over winter so I suspect it has gone off and blocked something.

What can I remove, check and or clean to try and get it working again?

Thanks for any replies in advance.

Aaron Gale.

Aaron Gale, April 2008

As The carb on this engine uses a diaphragm, i suspect this is the problem. Briggs and Stratton recommend this is changed every 18 months. The diaphragm is situated between the carb and the fuel tank, which you need to seperate. The diaphragm and replacement gasket only cost a few quid(got mine off ebay).

Hope this helps

Paul

Paul, May 2008

Hi, thanks for your replies. I ended up taking the engine apart as far as I could cleaning up and then reassembling with the same result. I noticed during dissasembly that the black thing isn't a fuel line. The fuel tank was clean of debris and no water in the fuel. I found somewhere to service it for £49+parts which seems reasonable compared to one place that wanted £139+parts!

Aaron Galw, April 2008

Check that there is no water in the bottom of the tank. Water works as well as a cork when it comes to fuel blockages. This is supported by the fact that you found the spark plug to be corroded.

phil_saunders@bigfoot.com

Phil Saunders, April 2008

The black tube that you mention is actually a crankcase breather, and no fuel comes from there. If the carburettor sits on top of the fuel tank there is a chance that the dip pipes - which draw the fuel up to the carb - have got some debris in the filters at their ends.

John, April 2008