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sd267 04-19-2009 05:42 AM

small engine carb trouble
Morning, Ihave a 12HP Tecumseh lawnmower engine thats bolted to an older Craftsman tractor. Its dumping fuel out the throat of the carb (horizontally mounted). I changed the needle and seat think that was it but still no fix. The float looks to be in one piece and theres no obvious signs of the float itself filling up with fuel. Any suggestions? Also the bowl is "stepped" for lack of a better explaination. Meaning it has a small shallow end and then a deeper part. I'm pretty sure its right but just to confirm the shallow end goes underneath the hinged part of the float. Right? Thanks in advance. Scott

frazierdavidson 04-30-2009 01:25 PM

I would think that somehow the float is maybe sticking and holding the needle valve off of the seat. I would make sure the float moves freely and isn't binding. If the float is metal, you can shake it and listen for any fuel sloshing inside.. Personally, I think small engine carburators are so simple that they're complicated !!! No good reason why they shouldn't work !!!

Grampa Bud 04-30-2009 02:39 PM

Is this happening right after winter storage? You changed the needle and seat; are they new or parts laying around the shop? What about the needle for the float? Is it just brass or is it brass with a neoprene tip? If you had the float needle out you can pump a shot of high pressure air back through the fuel passage that will usually clear out debris and gum from storage. Any time you take the float out of the carb you should check your float level adjustment after putting it back in. The flat top of the float should be level with the bowl mounting boss on the carb; or maybe a degree lower. Hold the float up very gently so as not to damage the seat or needle. I think you will find your problem in one of these places.

mausie 05-05-2013 09:36 PM

My two stroke carb. primer bubble is still drawing air after a rebuild kit. I have made sure the system is sealed also.Do you have any suggestions?

Grampa Bud 05-06-2013 06:46 AM

Small engine carb trouble
Mausie your problem is mostly found on older 2-stroke engines. You say the primer bubble is sucking air. One reason could be that the fuel line from the carb may be old and cracked inside the tank thus allowing air into the line. There should be a "klunk" filter on the end of the fuel line in the tank as well. It serves two purposes: (1) It keeps any debris in the tank from getting into the fuel line and (2) It holds the pick-up end of the fuel line under the level of the fuel so no air, just fuel, can enter the line. The fuel/air mixture is made up at/in the carb; not before. Good Luck! :thumbsup:

rkingndayton 05-06-2013 07:58 AM

When I was younger and had no money, we would always quickly boil our carbs and then douse them with WD-40 immediately after removing from the water. I'm sure that's not "recommended", but it solved most carb issues that we had.

Of course, the mowers were always freebies from relatives, so there was nothing to lose......proceed at your own risk if you try this "rig"!

mausie 05-15-2013 08:12 PM

[QUOTE=Grampa Bud;1173596] I ruled that out by replacing the feul lines then taking another line and hooking it to the feul intake then sticking the other end in a container of fuel, still with the same result. When you replace the piece of celaphane piece that is in the carb rebuild kit with the valven flaps on it is there any special care you have to do to it ?

RWolff 05-15-2013 10:09 PM


Originally Posted by rkingndayton (Post 1173620)
When I was younger and had no money, we would always quickly boil our carbs and then douse them with WD-40 immediately after removing from the water. I'm sure that's not "recommended", but it solved most carb issues that we had.

You VOIDED the warrantee doing that!!!!! LOL :laughing:

Well my thoughts on Tecumseh and Briggs engines to begin with is- I consider them to be disposable junk, I don't think I've seen one yet, even brand new that runs smooth and evenly without surging and falling back constantly.
I have a 49 cc scooter I ride daily, aftermarket carbs for these engines are under $40 to buy new usually, sometimes it's better just to replace the carb than trying to mess with it, especially if it has age, wear and tear, clogs etc., you wind up with a worn butterfly valve or the float is leaking, the needle is worn and leaking, by the time you take it out, take it all apart and mess with it, and try to rebuild it with a kit etc., you could have a brand new replacement already in and running and know it should be good.

If you can get a replacement and the price isn't bad, it might be worth doing that than dinking around with the old one.

A new carb might run approx 50-80 dollars & a rebuild kit is approx $12, but then there's your time and all that too.

mj12 05-17-2013 06:29 AM

My last rebuild kit was around 20 dollars, found the whole carb online for 13 plus shipping. I bought the rebuild kit locally, ended up having half a day in that carb fixing what others had done over the years.

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