Tecumseh Engined Mower

[Dave54]

Nice day down here, and Mrs Dave54 was using the ride on mower to cut the grass. I thought I'd do the odd bits that I usually do with the brush cutter, and had a sudden thought about the Tecumseh engined walk behind mower that belonged to my late mother in law.
So I dug it out from the back of the shed, thinking to myself "Waste of time, it hasn't been used for at least 5 years". So there was oil that appeared to be oily and reasonably clean. Petrol long gone of course. Tipped some petrol in, pumped the bulb. Pulled and I thought it fired. Pulled again, and sure enough it ran! I had to pump the bulb a bit to keep it going at first, but it settled down to a nice rattle, and I proceeded to cut the bits of grass.
Now I know the oil needs changing, and I know I'm going to have to de-gunk the carb, because it sometimes takes it on itself to stop, which I'd assume is crepe in the carb, and it seems a bit down on power sometimes, OK at others.
One thing I'd like to know though, and the point of all this. I've had the carb apart before several years ago to try to cure the hunting problem the engine developed. It cured it for a bit and then it came back.
Any ideas what's causing the hunting please? It's very pronounced, on then off.

 

[Nige F]

As soon as you said pump the bulb I knew it would be a sod running It'll be the diaphragm in the carb body needs replacing.

 

[Dave54]

Ta! I'll have a look see which one it is and try to get one.

 

[Burnerman]

Is this the one with the black priming bulb on the side of the carb, and a plastic clip on air filter top, paper element inside, Dave? The fuel tank on the back of the motor?
John

 

[Dave54]

Yes John it is. Its a red bulb on the side FWIW, but otherwise as you say.

 

[Burnerman]

So the fuel is a gravity feed into a round float chamber, I guess. Clamp off the fuel pipe and......
Basically its carb off for a stripdown......float bowl off (mark its orientation if it has a bump on the bottom), float pin pulled clear which will release the float complete with its needle.
Use carb cleaner if you can to blow out the airways after removing the main jet which should come with the emulsion tube above it - thats the one that gives most aggro.
Looking at the main choke inlet, if there's a small hole to one side of the main choke that's the pilot air bleed - that needs to be clear, but not all carbs have that.
Basically when the engine hunts, its mixture is weak and it starts to slow down. The governor senses this and opens the throttle to speed things up again, so its constantly revving then slowing.
You've got things right when the engine will tick over slowly, often enough!
(There may be a fine gauze filter in the tank just above the fuel outlet, if there's no filter in the line.....it can't be removed and fuel should flow from the tank really freely.)
John

 

[Dave54]

That's it exactly John. I did pull the carb off, but it's years ago as I said. Can't remember much about it. I'll give it a degunk and blow it out. Check the fuel is getting through, although that filter in the tank looks clean. Thanks for the advice.
Surprised really that it stated and ran at all after that time!

 

[Burnerman]

A pleasure Dave.....is there a pilot mixture screw on that carb, or just a throttle stop?
Another thing - sometimes the O ring that seals the carb to the inlet stub goes AWOL or splits......just check that one as you don't want air leaks there.
John

 

[Dave54]

Not 100% sure without looking. Which will be in the next day or two now. IIRC though, there are no adjustments apart from the throttle stop. Your description above is just what I wanted. Pulled plenty of carbs apart in the past, and I've got air and carb cleaner to clean it out but they're fiddly little burgers on those mowers, and it's worth knowing any wrinkles there might be. Thanks again!

 

[Burnerman]

Pleasure! This emulsion tube I'm on about may come out with the main jet......failing that, a bump on the main jet stalk may dislodge it - they are all different.
You can see the top of this tube down the main choke, in brass. If it doesn't want to shift, then all you can do is to spray in the carb cleaner.
Hope you get somewhere! I'm not even sure if Tecumseh are still in production....very similar to Briggs, but no parts are interchangeable.
A useful site is GHS Ltd for pattern bits.
John

 

[Dave54]

No, I don't know whether they're still made. The mower was one from Argos IIRC, they were on offer, and as MILs machine was knacked, we got that. Must be 10 years ago. She was still mowing her several, largish lawns at nearly 80 years old. I used to go and do them sometimes, but she didn't like me doing them really.
I'll give it a go and see. Basically it's a good machine, so it can do the bits around here hopefully.
Again thanks for the info, and the site for the bits.

 

[Dave54]

Just to report back, the mower is a Lawnchief 460, which is basically an Electrolux U 46 PD. Carburetor as you described John, normal small carb with throttle butterfly, and with fixed brass emulsion tube (according to uTube the brass ones are fixed, plastic removable). Soaked the lot in cleaner, there was enough lacquer in the float bowl for a 1960s beauty competition, blew everything out with air, and it appears to be clear. Put it back together. Bolt and nut to attach the carb nearest the cylinder is fiddly but just "do-able" Started and ran much better but still hunting. Bit of adjustment to the bent wire clamped under a screw which serves as a throttle stop, and it's running nice and smoothly. Thanks!

 

[Burnerman]

Nice one Dave
Its worth checking the head bolts on these as the gasket squashes a bit, and at the same time blowing the crap away from the cylinder fins.....prevents localised overheating.
John

 

[Dave54]

I'll do that John. No idea what the head torque is supposed to be I suppose? Got to change oil and sharpen the blade yet anyway. Wheels are a bit wobbly, I might pull them and see if they will bush with a bit of tube. Depends how I feel really. Do too much to it, and it'll feel spoiled and will throw a wobbly!

 

[Burnerman]

I don't know the torque setting Dave but usually a tweak with a 1/2" AF socket does it......may not need it, of course.
John