Small Engine Carb Issue

Czech · Jun 13, 2011

So I've been trouble shooting a Tecumseh 6.5 HP LEV 120 carb issue for months (years?), it's on a lawn mower. One last post before it either goes to the shop, I buy a brand new pre-assembled carb, or I spill a lot of gas on the hot muffler.

What it's doing: Runs but misses a lot. If a well running motor sounds like 'da da da da da da da da da', this sounds like 'da da da dadada da da dadada da da dadadaaa da da'.

What I've done: Carb kit last year, just did another kit because I felt like it. I did check all orfices and jets and such, replaced the straw along with o-rings, float good and sitting pretty. Replaced the coil with new, I had a feeling it was electrical becasue my first carb kit didn't work. New plug. Fresh fuel, unless it is in the tank there is no apparent fuel filter. New air finter. I noted that when sprayed with carb cleaner while running, if sprayed directly onto the top of the butterfly where the linkage goes, it kills. That tells me there is a good leak there by the oil pad, but not sure if that's the problem or if the kits come with replacement parts for that. I wonder if I spray the muffler if it will ignite? Just fantasizing again....

Thoughts gang?

It runs well enough to get the job done, but darn it I don't want the funny sounding mower in the hood!

CJ-SR4ever · Jun 13, 2011

How does the gas line look? I had to replace the gas line on my mower. it had alot of cracks in it and was not keeping a good prime and ran rough and would stall out. Is there a shut off valve that may be malfunctioning? Do you have any adjustment set screws on the new carb?

Czech · Jun 13, 2011

Fuel supply looks good from what I can tell, no shut off, main lined to the tank. I did not buy a new carb yet (stress yet!), there really isn't any set screws at all on either old or new. The low speed in one that cranks all the way in and stays there and gets capped so you don't adjust, the main is the typcial float bowl nut that get seated all the way into the bottom of the bowl.

PJF1313 · Jun 13, 2011

You said that your replaced the coil already. Could it not be gapped right with the flywheel - too much gap, causing a weak spark? Or the gap on the new plug?

CJ-SR4ever · Jun 13, 2011

I have had many issues with carbs that have floats. The metal floats are the worst. Just the slightest pin hole in the float will mess things up. if the float gets gas in it, it pulls the needle valve down and just floods the engine. Im not a big fan of Techumseh.

Reggie Dunlap · Jun 13, 2011

Carb problems most likely due to ethanol in fuel, which also degrades rubber fuel lines... Use Stabil fuel stabilizer once you get it fixed.

mjbrown · Jun 14, 2011

Czech said:
So I've been trouble shooting a Tecumseh 6.5 HP LEV 120 carb issue for months (years?), it's on a lawn mower. One last post before it either goes to the shop, I buy a brand new pre-assembled carb, or I spill a lot of gas on the hot muffler.

What it's doing: Runs but misses a lot. If a well running motor sounds like 'da da da da da da da da da', this sounds like 'da da da dadada da da dadada da da dadadaaa da da'.

What I've done: Carb kit last year, just did another kit because I felt like it. I did check all orfices and jets and such, replaced the straw along with o-rings, float good and sitting pretty. Replaced the coil with new, I had a feeling it was electrical becasue my first carb kit didn't work. New plug. Fresh fuel, unless it is in the tank there is no apparent fuel filter. New air finter. I noted that when sprayed with carb cleaner while running, if sprayed directly onto the top of the butterfly where the linkage goes, it kills. That tells me there is a good leak there by the oil pad, but not sure if that's the problem or if the kits come with replacement parts for that. I wonder if I spray the muffler if it will ignite? Just fantasizing again....

Thoughts gang?

It runs well enough to get the job done, but darn it I don't want the funny sounding mower in the hood!

Czech...
before you buy that new carb, does the carb have a rubber hose/tube running from the side of the carb, to a flat rectangular shaped plate on the crankcase? if it does, check that tube for a split...this a fuel pump so to speak,that works off the vaccum of the crankcase. i just worked on my dads wheelhorse rider w/ a 10 hp briggs,and it was acting the same as you describe. sure enough, that tube had a split in it, and was causing a vacum leak..i am no small engine pro, just putting it out there, trying to help

mike

gfreek · Jun 14, 2011

While its running does it improve or get worse when gas is squirted into carb or the primer is pushed?? Another thought is have you checked the flywheel key?? If its sheared or partially sheared the spark timing will be off.

maverick06 · Jun 14, 2011

I just disassembled the carb on my chipper yesterday and got it running. The needles had some buildup on them, make sure they look clean and are smooth. Perhaps its a leaky gasket aft of the carb.

The metal floats are terrible. If they slosh around they are nearly trash. You can try to get the gas out and solder them/coat in model airplane glue, both are more patched than anything else. Also, make sure all the ports are cleared, The carb I have had a lot of very tiny ports you would never see if you didnt know what you were looking for.

I also tossed the whole thing in my ultrasonic cleaner (about $25 from harbor freight). That really pulled off some nasty stuff! I will probably end up having to buy a new carb off of ebay ~$40. Its safer than buing the rebuild kit for this one.

Spray the thing down with carb cleaner too, who knows what bits of crud that might disolve. You are fighting about 3 dirt molecules here, they are hard to find.

Czech · Jun 14, 2011

Thanks gang! Great feedback as usual. So out of everything above, I have not looked at the crank case vent at all, that's something I need to check. The gap on the coil is good, it was misbehaving in the exact same fashion before I did that, but there is some assumption on this as I just eye balled it. It does have strong spark. As far as the rebuild goes, I work in a lab so follow that protocol when cleaning, it looked like I was doing surgery. Everything was cleaned and then sprayed off again right before assembly. Did not check the flywheel but will do so, I guess I thought if it was running somewhat it would not be that but this is why I posted (feedback). Always Seafoam! Jeez I hate the etoh, stuff is really hard on everything.

gfreek · Jun 14, 2011

The flywheel key will partially shear or fully upon sudden blade impact with a solid object, rock, tree root, pipe etc. You should be able to remove the flywheel nut and cup & see.

DriveByWire · Jun 14, 2011

What's the exhaust look like when it's running? Is there dark smoke coming out as if it's overly rich? How does the tip of the spark plug look?

Czech · Jun 14, 2011

Plug looks pretty darn good and exhaust is clear, no obvious signs of being rich at all!

Hogwildz · Jun 14, 2011

Check the exhaust for a spark arrestor, that may be clogged. They are usually just a screen that gets carbon build up on them.

Czech · Jun 14, 2011

That's a good one too, Hog, forgot about it. Man I sure love this forum to bounce stuff off of, good bunch of folks here.

mjbrown · Jun 19, 2011

mjbrown65 said:
Czech said:

So I've been trouble shooting a Tecumseh 6.5 HP LEV 120 carb issue for months (years?), it's on a lawn mower. One last post before it either goes to the shop, I buy a brand new pre-assembled carb, or I spill a lot of gas on the hot muffler.

What it's doing: Runs but misses a lot. If a well running motor sounds like 'da da da da da da da da da', this sounds like 'da da da dadada da da dadada da da dadadaaa da da'.

What I've done: Carb kit last year, just did another kit because I felt like it. I did check all orfices and jets and such, replaced the straw along with o-rings, float good and sitting pretty. Replaced the coil with new, I had a feeling it was electrical becasue my first carb kit didn't work. New plug. Fresh fuel, unless it is in the tank there is no apparent fuel filter. New air finter. I noted that when sprayed with carb cleaner while running, if sprayed directly onto the top of the butterfly where the linkage goes, it kills. That tells me there is a good leak there by the oil pad, but not sure if that's the problem or if the kits come with replacement parts for that. I wonder if I spray the muffler if it will ignite? Just fantasizing again....

Thoughts gang?

It runs well enough to get the job done, but darn it I don't want the funny sounding mower in the hood!

Click to expand...

Czech...
before you buy that new carb, does the carb have a rubber hose/tube running from the side of the carb, to a flat rectangular shaped plate on the crankcase? if it does, check that tube for a split...this a fuel pump so to speak,that works off the vaccum of the crankcase. i just worked on my dads wheelhorse rider w/ a 10 hp briggs,and it was acting the same as you describe. sure enough, that tube had a split in it, and was causing a vacum leak..i am no small engine pro, just putting it out there, trying to help

mike

just ran into this again today with walmart weedeater push mower...b/s engine.
dad was frustrated and going to send a 1 yr old push mower to the scrap yard. i pushed the primer bulb 3-4 times and pulled starter rope, motor ran in just the primer gas and died. i took the breather off and pulled the rubber tube off the carb connecting to the crankcase. i twisted the rubber tube slightly , and sure enough, there it was. just a slight crack in the tube, and it allows air. went home to my own scrap pile,and looked at a couple of mowers, found what i was looking for and went back to dads. put everything back together and TA-DA! saved a brand new mower from certain death.
dad sure is greatful he got a kid who learned from him NOT to throw everything away, "cuz you never know when you might need something from it"...LOL

heat seeker · Jun 20, 2011

Great job saving it from the scrap heap! It's a shame when something useful is tossed because of a small problem.

Czech · Jun 20, 2011

Ok gang, I'm really thinking about the startig fluid and muffler deal, that bad. I tore down the carb again this past weekend, all looked good from what I can see but I did replace the butterfly shaft washers and such. Also checked the breather hose, that idea sounded so darn good but alas, I cannot find any cracks. Also tore the muffler off and hit that with compressed air just for good measure, fly wheel key looks fine. I's still convinced it is carb related so I did order a whole new carb, yeah, I'm that frustrated. If that works, at least I'll have an extra parts around if needed, always the optimist! If I get this sucker running nice again, she's getting new wheels (pnuematic) and a paint job complete with racing stripes!

CJ-SR4ever · Jun 20, 2011

Sounds good! Don't forget to install the car horn from " The Dukes of Hazzard" ;-)

Czech · Jun 28, 2011

New pre-asssembled carb, better but still not great, misses at idle but not under load. Any thoughts on the governor? Just tossing out ideas.....

Small Engine Carb Issue

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