Tecumseh carburettor puzzle

[JohnFW1]

Hi, my lovely Qualcast mower was NOT lovingly decommissioned in the autumn. It always starts first pull. But this season it stops again after a few seconds and can only be encouraged to run with excess choke. I disconnected the wire linkage and removed the carb to clean it but could only find one brass nut under the float chamber. I unscrewed it and blew through the holes - replaced it and reconnected everything. Now the mower starts first pull - but if I open the throttle even a tiny bit the engine races. What has gone wrong? And how do I properly dismantle the carb?

 

[Burnerman]

Tecumseh often use Dellorto carbs, and a pic could well help here but if you have the float chamber off then you need to remove the float and needle by pulling the pin out and making sure all is clean there. In the central part of the casting lurks another brass jet called the emulsion tube - this map be screwed in place or it could just fall out by tapping the carb body. Either way, make sure all of the tiny holes are clear.
Its really essential to use compressed air or an aerosol carb cleaner here. As for the engine speed racing, are you sure you put the linkages back in the original place?
John [/wiki]

 

[JohnFW1]

Tecumseh often use Dellorto carbs, and a pic could well help here but if you have the float chamber off then you need to remove the float and needle by pulling the pin out and making sure all is clean there. In the central part of the casting lurks another brass jet called the emulsion tube - this map be screwed in place or it could just fall out by tapping the carb body. Either way, make sure all of the tiny holes are clear.
Its really essential to use compressed air or an aerosol carb cleaner here. As for the engine speed racing, are you sure you put the linkages back in the original place?
John [/wiki]

Too dark tonight - will photo carb tomorrow. Thanks for prompt response!

 

[JohnFW1]

Tecumseh often use Dellorto carbs, and a pic could well help here but if you have the float chamber off then you need to remove the float and needle by pulling the pin out and making sure all is clean there. In the central part of the casting lurks another brass jet called the emulsion tube - this map be screwed in place or it could just fall out by tapping the carb body. Either way, make sure all of the tiny holes are clear.
Its really essential to use compressed air or an aerosol carb cleaner here. As for the engine speed racing, are you sure you put the linkages back in the original place?
John [/wiki]

Too dark tonight - will photo carb tomorrow. Thanks for prompt response!

Hi again,
Photos I have - but I'm a real novice with forums - how can I attach my two photos?

OK I think I have it - here goes

 

[Mursal]

I don't do photos on this forum

But, I think you will have to click Upload Pictures (center top, then down a bit)
Then make a new album and save images to that.

To be honest, you'd probably have the lawn cut, quicker ..............

 

[Burnerman]

See the spring loaded pip on the bottom of the float bowl? Pressing that up allows you to see if petrol is flowing through the needle valve ok.
Now, the jets you need to check are above the central bolt (which could be a jet in itself if its drilled). With the carb on the bench the emulsion tube should fall out with a sharp tap. Squirt carb cleaner through the small hole at the end of the venturi to clear it.
Be lucky! You cant do any real damage with care.
John

 

[JohnFW1]

See the spring loaded pip on the bottom of the float bowl? Pressing that up allows you to see if petrol is flowing through the needle valve ok.
Now, the jets you need to check are above the central bolt (which could be a jet in itself if its drilled). With the carb on the bench the emulsion tube should fall out with a sharp tap. Squirt carb cleaner through the small hole at the end of the venturi to clear it.
Be lucky! You cant do any real damage with care.
John

Thanks Burnerman! When I took the carb off to investigate the only bolt I could see was the one you can just see peeping out under the float chamber bowl. When I undid it only the bolt + jet came out. Should the bowl also drop? Also did you check second pic and if so does linkage reassembly look OK?
Kind regards - John

 

[Burnerman]

Yes John with the central bolt out the float bowl will come free - try not to split the gasket!
Afraid I cant see the linkage clearly but it should be free to move. With the engine off, the governor mechanism should hold the throttle butterfly fully open.
John

 

[JohnFW1]

Yes John with the central bolt out the float bowl will come free - try not to split the gasket!
Afraid I cant see the linkage clearly but it should be free to move. With the engine off, the governor mechanism should hold the throttle butterfly fully open.
John

Hi - I finally took the carb off again and this time dropped the bowl and float etc. In the centre - right under the screwed in tube/jet there is I think a really tiny O ring or other piece of polymer/rubber like material. But it fell apart. I think I need to concede defeat!!! Not sure which model the carb is. I found "5148 D OU" stamped on the flange of the casting. Does that help me at all?
John

 

[Burnerman]

Aha - if this is the bit I'm thinking of.....
You removed the float bowl, the float after pulling the pin out, and the stubby pointed needle valve came with it - right?
That tiny 'o' ring is vital - its the needle seal and the carb will flood without it.....it often falls out of its housing and most people don't know its there - its usually red or green.
Easy enough to get though, from Briggsbits or suchlike.
If this isn't the item, give us a pic!
John

 

[JohnFW1]

Aha - if this is the bit I'm thinking of.....
You removed the float bowl, the float after pulling the pin out, and the stubby pointed needle valve came with it - right?
That tiny 'o' ring is vital - its the needle seal and the carb will flood without it.....it often falls out of its housing and most people don't know its there - its usually red or green.
Easy enough to get though, from Briggsbits or suchlike.
If this isn't the item, give us a pic!
John

Err - no. You are right about the stubby needle thing - quite a shock when it fell right out! No - I am referring to the bolt/jet thingy that you undo to get the bowl off. Deep down inside there was something I took to be gunge = but it wasn't - and it came out in pieces. Will try to get some close up pics but just off to bed now.....

 

[Burnerman]

Ok, no worries then (to be fair, I only thought it was Briggs carbs that had the neoprene nedle valve seal, and not all of them anyway!)
Look for: The brass bolt, a fibre washer, then the float bowl.
I do think, at the moment, its compressed rust in the bottom of the bolt, but interested to see!
John