Tecumseh mower troubleshooting

[bsr]

Hi All

You helped me source a replacement air filter for my mower last year... unfortunately it's still playing up.

It now runs for about 30 seconds, then slows, hunts and eventually stalls. If I leave it for 30 minutes without cranking it will then start again. This makes me think fuel starvation but I have no idea really... any thoughts? It could be something to do with the old air filter breaking up and being sucked through the engine.

It's a Golf HBL Mower, Tecumseh BVS143 engine, Dellorto FHC 2013A Carb. I've never worked on a small engine before (have done simple car stuff like servicing and brakes) so would appreciate any suggestions on troubleshooting.

Also, is it worth doing anything? I'm happy to give it a go but the mower is 20 years old and has had nothing except annual oil changes and cleaning the plug... knowing my luck I'll probably break all the hoses, gaskets etc and have to spend more than the mower's worth replacing them.

Thanks in advance


bsr

 

[Burnerman]

Hell thats an old 'un
Scratch the memory cell......the fuel inlet banjo (called because of the shape).....undo the centre bolt and there's a filter inside. Make sure its clean.
At the same time, see that theres a good supply of juice running out of the banjo.....old metal tanks rust inside.
Then - float chamber off, inspect for rust in the hollow inside.
Pop out the float pin and remove the float and the needle jet for cleaning with aerosol carb cleaner.
Undo the main jet, and remove the other emulsion tube above it (some carbs have this in one long bit). Squirt carb cleaner through every orifice and if you have an air line, so much the better.
Look at the end of the carb throat - air cleaner side. See the small hole to the side? Thats the air bleed for the pilot screw which allows the engine to run slowly......if there is a spring loaded pilot screw, take it out and flush clean - reinstall one turn out from fully in.
Nowt the matter with the old Tecumseh motor... a bit smoky and clanky maybe but they go for ages!
(If none of this makes any sense, post a pic of the carb if you can).
John

 

[Mursal]

As above and try it without the air filter

 

[bsr]

Thanks. Carb pics below.

Do I need to buy a servicing kit (£10) or should the gaskets be OK?
http://www.dellorto.co.uk/merchandise/products.asp?CategoryID=22&PartsectionID=134

View media item 74316 View media item 74317

 

[Burnerman]

You can normally get by with just the gaskets at either end - it depends on whats available and how quickly you can get the bits, really......the outside of the carb needs a really good clean before you get the spanners out - use an aerosol carb cleaner with toluene.
Just for info - the screw in the centre of the pic is the idle mixture screw. Count how many turns to fully in for reference for the rebuild.
Enjoy - don't worry about poking fuse wire and the like through the jet holes to help clear them - it doesn't do any harm.
John

 

[bsr]

It's not helped

Carb stripped down (it was nice and clean inside except for some varnish on the bottom of the bowl).

Mower still doesn't run - very hard to start and then only runs slowly for a few seconds before stopping.

Spark plug is very oily but sparks well against the mower chassis. Mower oil level is fine.

Any ideas?

 

[Burnerman]

When it does run, does it chuff any smoke?
If it doesn't, does it improve if the engine is choked?
A new plug would be a good move!
John
I'll just edit this one.....plug out and turn the engine over smartly. Does it shoot any old fuel out of the plug hole?
John

 

[bsr]

I've tried on and off choke - doesn't start either way.

There was smoke on starting but not now - it doesn't get up to normal speed before stopping, just chugs for a few seconds then dies.

No fuel came out when I cranked to check the plug was sparking, I'll check again tomorrow.

OK, I'll try and find a new plug. I thought if the old one was sparking and I cleaned it then it would be OK?

 

[Burnerman]

9 times out of 10 thats correct - but it has to be ruled out.
It does sound like a carb problem but they are reasonably foolproof, if you are happy with the work you have done on it.
Are you happy about removing the flywheel on the engine - just to check for a sheared woodruff key?
John

 

[Mursal]

Would you try a small amount of neat petrol in the manifold (carburetor) just to see if it starts/runs differently? Be careful and only do it outside have something to put the flame out if it ignites.

Could you have an air leak between the carburetor and engine?

 

[bsr]

Hi Mursal

Could I check what you mean? You want me to take a teaspoon of petrol and put it in the inlet manifold, and then crank the engine?

There is definetly fuel in the carb bowl - I've checked using the drain plug.

No fluids come out of the plug hole when cranking.

Will try and check the woodruff key, but I don't have a bearing puller. Can I do it without?

 

[Burnerman]

I'll take you through the symptoms first, and then you can decide whether to venture further.
With a sheared flywheel key, the engine will fire once or twice - may even backfire - but it won't run. Often people think, well keep on pulling the starter and it will get there.....
Anyway, loosen the flywheel nut (jam the flywheel but dont fracture the cooling fins), put some wedges under the flywheel to lever it upwards and give the nut a sharp crack with a hammer. Don't overdo it and the flywheel should come free.
I don't know if your engine is so old as to have contact breaker points but if it does, this is the time to check them, so post back.
John

 

[Mursal]

Sorry for the delayed reply, just a teaspoon in, to see if it runs differently for you? Rev up, then stop, hopefully ..........

 

[bsr]

Hello

Thank you very much for your thoughts so far.

• New spark plug - no effect
• Petrol into carb intake manifold - no effect
• Woodruff key - looks fine, see pic

Points - not sure what to check - see pic. I guess the magnet bit spins around, and causes a pulse in the box which travels down the wire to the plug? Either way the plug is sparking...

View media item 74736 View media item 74735

 

[Burnerman]

Dammit that all seems to be in order
You are correct - the magnets in the flywheel induce a current in the igniter which produces high tension at the spark plug. All seems to be ok there from what you say, but its difficult to check the igniter under load - an in line neon indicator is a help there.
So.....when you try to start the engine, does the governor mechanism hold the carb on full throttle? It should do.
John