[charlievictorbravo]

I've just moved house and the Mountfield Petrol Briggs and Stratton powered lawn mower I use on the allotment is now required to cut a lot of grass at the new house.
It has always been a difficult starter. It usually requires the plug to be removed and warmed up on the gas stove to start. Once it has started, I can stop and start it numerous times and it's not a problem.
I've just invested in a new spark plug but that has not solved the problem. When it's going, it's such as good little runner that I'm convinced that the problem is something small. For instance, I'm not convinced all those little springs on top of the carburettor are connected correctly.
Has anybody got any thoughts on possible causes?

Charlievictorbravo

[Gwiz]

It's going to be a fair bet that the carb has a fault. It is very unlikely to be the springs on the top, leave 'em be.
If you could post a picture of the engine, then I will be better able to advise you, but I would imagine that you need the carb diaphragm replaced, this is a very common problem with these engines.

[compostqueen]

I had to phone the helpline about my Briggs and Stratton mower yesterday as it won't start - then if it does happen to start after about 20 minutes of pulling my arm off, it won't restart after emptying the grass box.  I hate mowers 

[Gwiz]

I had to phone the helpline about my Briggs and Stratton mower yesterday-------I hate mowers 

I fix 'em for a living.

I hate mowers too.

[aelf]

I've been given a Briggs Classic 35 mower (because it wasn't working - been rusting in a garage for years). Turned it into a project to do with my lad and we stripped it, cleaned everything and rebuilt it. got it started after several attempts and now it's running great! 

Very simple engine - great for teaching the basics 

[charlievictorbravo]

I've tried twice to send further responses with photos but neither seems to have got through so I'll forget about the pictures - my camera seems to produce pix that are too big for the forum!

I took Gwiz's initial advice and replaced the diaphragm with part no 795083 but that did not solve the cold starting issue - I eventually started the beast by warming the plug.

Could this be an ignition problem? I've tried to check for a spark but I found I need to do it in the dark with an extra two hands and I'm not convinced I was getting a HEALTHY spark.

The B & S model number of the engine is 10D902, type 0111B1, code 02051855

Any suggestions?

Charlievictorbravo

[aelf]

You have probably done most of this but:

Is the air filter clean? I would also check that the magneto is set with the correct air gap, the springs are not fouled and that the engine governor is moving freely. If that doesn't work, my next thing would be to strip the carb down completely and clean it thoroughly, checking the O ring is good and then reassemble (greasing all joints and seals). If that doesn't fix it, I would take the head off and clean off any build-up of muck, checking that the valves are not fouled, fit a new gasket (if the old one is damaged). Is your fuel old? After that, I'm running out of ideas 

[Gwiz]

Did you clean the filter on the pick up tube while you had it apart? It's a very fine filter that blocks up quite easily.
As Aelf suggests, make sure you have the correct air gap between the flywheel and the arms of the coil, make sure the magnets on the flywheel aren't rusty

[compostqueen]

Mine is at the menders. The first thing he did was check the petrol tank and said he could see muck floating in it. I couldn't see anything though  :blink: