Tecumseh engine backfiring...

[Hammack_Welding]

Guys I have an old welder with a Tecumseh HH140 motor that I just can't seem to get straightened out. It has been sitting up several years under my shelter because I just did not use it anymore. It was running fine when it was put up. I pulled it out and started fixing it back up because it was the welder that dad gave me when I started business years ago. Anyway the gas tank had rusted out so I built a new one. Then I pulled the carb and cleaned and rebuilt it. Also rebuilt the fuel pump, and replaced the fuel lines. Put a new battery in it and as soon as fuel reached the carb she fired up and started running. The problem is it has almost a constant backfiring out of the exhaust. It's not a loud hard pop, but you can tell that is what's going on. It's not surging, or cutting off, and will start and stop fine. I just can't seem to get it to run as smooth as it should. I'm starting to think I may need to lap the valves, but before I do that I thought I would see if anyone here works on these things and could offer a suggestion. Any help would be appreciated. ~Jackson

[kolot]

Check the point gap or might have a dry rotted insulation on the plug wire, run it at night in the dark see if you see it arcing to ground, that would cause a misfire, if it's old it could very well be.

[denrep]

Hammack - Could be a valve sealing issue, but I'm putting my money on carbon build-up. You could de-carbon by dribbling water into the carb at fast idle. See if that simple step improves things.

Good Luck

[Hammack_Welding]

No, wires leaking fire anywhere. Denrep, I had some seafoam spray, and fired it up today, and sprayed it in the carb as it was running to cut the carbon. It blew a little white smoke for a bit, and I switched it off and let it sit as the instructions stated. I let it sit for a little while, and fired it back up now the motor starts hard, but once it does finally start it will run nice and smooth as it should until you take the choke off then it dies. So now that the backfiring has stopped the engine will not run without the choke on.... I hate a dang tecumseh...

[denrep]

Probably picked up a "slug" in the idle circuit.
Back the idle screw off, rev the engine and then "gag it" down hard with a rag to induce very high vacuum throughout the carb; that'll probably clear it. Don't forget to readjust idle mixture.

Good Luck

[Hammack_Welding]

Well, I'm making some progress. I took the carb off and checked everything again to make sure it was spotless. Put it back on fired it up and same thing. It runs only on choke, and at mid level RPM. This little welder doesn't have an idler on it so it is at speed all the time. I just happened to look down and noticed that I had not put the vacuum line back on the fuel pump. Figured that might be my problem so I put it back on, and no change. So now I am wondering if the fuel pump is pumping. Sure enough I take it off and find that it isn't. So now I will pull it off, and go back thru it again tomorrow and hopefully that solves the problem.

[smokin_dodge]

If it only runs on choke, then it sounds like a fuel issue.

I would strip the carb and soak it or blast it thoroughly, drain the entire fuel system and run some good clean gas through it (or appropriate cleaner)

One quick test you can do is install a quick connect where the spark plug is and put 100PSI in the cylinder. This will quickly tell you if you have a leak somewhere. While the cylinder is pressurized, rotate the engine through its strokes and see if you have any leaks other than your intake and exhaust stroke.

One thing i used to do to test valve seats was to pressurize the engine block, then tap on the valves with a dead blow multiple times and release the air pressure. Doing this multiple times will tell you if your valves seats or alignment is off.

[mwshaw]

Make sure you are completely diassembling the carb, a lot of people don't remove the high speed jet that is inside the body of the carb in the same hole the high speed needle and bowl nut screw into. Those clog up on the little passages between the threaded parts of the shaft. Very small openings that are hard to clear out. A tag wire off a paper tag is about the size of the opening. Much smaller than 1/16"drill bit.

[mla2ofus]

Originally Posted by mwshaw

Make sure you are completely diassembling the carb, a lot of people don't remove the high speed jet that is inside the body of the carb in the same hole the high speed needle and bowl nut screw into. Those clog up on the little passages between the threaded parts of the shaft. Very small openings that are hard to clear out. A tag wire off a paper tag is about the size of the opening. Much smaller than 1/16"drill bit.

That's another good use I've found for a tip drill set. I just use the shank end to ensure not reaming a passage.
Mike

[smokin_dodge]

If you find yourself cleaning a number of carbs a year, you can invest in a bucket of parts cleaner. I used to work with a guy who rebuilt old motorcycles who used to just submerge the whole carb. He would take the seals out of them if they had bowls and use a cleaner like this

http://www.berrymanproducts.com/Default.aspx?tabid=146

[lamename]

Your pilot circuit is clogged.

[Hammack_Welding]

Ok, I am making progress, but I've now gotten to the point I refuse to let this dang thing beat me even if I have to throw a new motor on it.... Instead of rebuilding this pump again, I picked up a plastic Briggs and Stratton vacuum pump for $20 since it was half the price of the kit to fix the other one I figured I would try it. Hooked it up and the motor started perfectly, but no matter what I did I still could not get it to stop running lean. Well, I was working on it the other day, and dad came by and told me that he had bought a new carb for it a few years ago, and never installed it. I looked for it in the shop, and finally found it still in the box. I put it on the motor, and started it up and it ran pretty good with no back firing. However the motor seems to be running a tad rich. Also once you load the motor suddenly the motor will bog and dies. Once it starts to bog the carb immediately starts to flood, and it will also flood the second you switch off the motor. When I say flood I mean it literally a small stream running out the throat of the carb. As long as the motor is running with no load placed on it I see no signs of flooding. This new carb is a Walbro "WGH" and is different than the original one, but it is the correct replacement as the original is no longer made. Now I am attempting to find adjustment procedures for it with no luck. This carb has a fixed main jet so there is no screw in the middle of the bowl. There is two adjustment screws on the side of this carb which I have not found yet what they are for. I am guessing the flooding is coming from float being out of adjustment? Any suggestions as to what to look for on this flooding? I am about ready to go order me a new motor and use this one for target practice. Thanks for the advice.

[Rog02]

The needle closest to the mounting flange is the idle mixture adjustment. The needle in the mid section of the venturi is the power (high speed) mixture adjustment.

Parts diagram for a typical WHG carb
http://wem.walbro.com/walbro/product...yName=TECUMSEH

[Patrick lang]

I have a 5hp Tecumseh Power Sport, Horizontal Shaft (Model: OH195EA) for a gokart. I can not get it running anymore but i back fires sometimes when i pull the pull cord. I cleaned the carburator, new floater, new bowl gasket, new floater pin, new Air Filter, clean gas tank, clean head and valves, new spark plug, but when i was cleaning the carburetor their was a Fuel Well spacer in it. I went to buy a new one and the guy said it did not need one because the tube inside was metal, but it came with one and it had a bolt with a spring pin in it. Should i buy the Fuel Well Spacer and try it or is their another problem??? Im getting agrivated withthis engine bc its been a month since it has last run. I have a youtube video under (pat14lang). Any advice? Message patrick.lang2013@me.com or comment the video online please. Thank you