Think I have a valve leak

[Stephen Newell]

I'm working on a 6hp Tecumsen engine on a log splitter. Last year I had difficulty getting it started. It would start but as soon as the prime gas was gone it would quit. I took it to a shop and I believe they worked on the fuel system however when I got it back it was difficult to start but would run. Still it lacked about half the power it once did. Now this weekend I got it out to use and again it will only run until the prime gas is gone. What do you guys think.

 

[Steve@Advance]

Sounds like a clogged carb.

Take the carb apart, clean out the main jet with a stiff wire or torch tip cleaner. The dried fuel residue has to be scraped out, carb spray and blowing will give a false clear, there may still be residue stuck inside the jet, making it too lean to run.

 

[gab]

More than likely if it has an adjustable main jet it's plugged, has one or two tiny holes in it.

 

[Stephen Newell]

Last year I did take the carb apart and put it in a can of Chem-dip and cleaned it. When it didn't do anything for it I took it to a small engine repair shop and they only made it marginally better. I guess I could try it again.

 

[Bruce(OR)]

All good ideas and info.
I have a log splitter that sat with gas in it for a year. I got it fired on ether and kept lightly spraying it until the fresh gas in the tank had a chance to work it's way into and through the carb.
With yours I would be tempted to make run and placing hand over the air inlet, allow your fingers to spread open to allow air in just enough to keep it running.
Yes, a good chance you will foul the plug. Do it again and you might be able to clear the jet without having to tear it down.

 

[Stephen Newell]

Last year when I finished with the splitter I ran it until it ran out of gas. The year before when the problem started I had left gas in it for a year and it went bad. This year even though I've been spraying starting fluid in it it's not helping. It won't run for more than a second.

The plug shouldn't be fouled, the shop that worked on it last year put a new one in it.

 

[Stephen Newell]

I came up with a better plan for the carb, I found a new one on ebay for 18 bucks so I ordered it. Apparently neither myself or the lawn mower shop is qualified to clean the old carb. I certainly couldn't see any trace of dried gas in it.

 

[Bruce(OR)]

The new plug is good possibly until you choke the engine with your hand in order to get reverse airflow in the carb in order to attempt to clear the jet.
That trick can result in stalling the engine and fouling the plug. Not enough air and way too much gas.
Pull the plug and dry it off.
Propane torch,
Bic Lighter,
Wipe with a rag and air dry,
Starter fluid on the plug that will also evaporate are just a few ideas on drying a spark plug.

 

[Janicholson]

It sounds like the carb is just running on the verge of lean. Use number drills to enlarge the main hole (one size). Jim

 

[Jerrycpp]

Sounds like the carb is the problem, as others have noted. I had the same problem; a new $15 carburetor fixed it. Plus, the new carb had adjustable main and idle jets. Using non-ethanol gas will prevent this problem, or, run the system dry when shutting it down.

 

[caterpillar guy]

Connect the hoses to the tractor remotes and junk the gas engine. Will run fine then.

 

[Geo-TH,In]

I hate Tecumseh engines. Either the carb leaked gas or they were impossible to start.
That said, I have a 10 hp tecumseh on a rider and installed a gas solenoid to stop the leaky carb. It starts fine.

Do a compression test. I have seen valve seat recession on the old flat heat engines.

If you think you have a carb issue, check out Amazon for a new cheap carb.

Engine will run for a short time. Heat expands the valve stem and engine loses compression.
Check valve clearance.

 

[UncleTom]

Those tehcumsehs get hard to start if they have points in them. They get worn and out of adjustment. I just worked on one yesterday. It had spark but weak. I pulled the fly wheel and used 600 grit and put a finish on both sides of the points contacts. Re set them at .020 and now it starts first pull. Its not always the carb when spark is intermittent.

 

[Stephen Newell]

Thanks for that. If the new carb doesn't work I will try that.

 

[560Dennis]

I got Tecumseh on the 40year old ariens snowblower ,they are very reliable . Prime it ,choke it ,two pulls and its going ,go to half choke and out of the shed , open choke
You might want to check compression. If low ,remove head. Inspected valves
I think the valves could use a hand lap job . How old is it ?
Grind stem on exhaust and intake.

 

[Stephen Newell]

It may be around 25 years old. I only use it to split a couple cords per winter and didn't ever have any problem until the summer of 2020 when I left the gas in it from the winter before. Since I worked on the carb and had a lawnmower shop work on the carb too I just wondered if I had one of the valves not closing well enough to draw gas in the engine. I've taken the carb apart again since I started this thread and cleaned it again and there is no change. I ordered a new carb for it and if that doesn't fix it I will look to the valves.

 

[560Dennis]

I would say , since it was the carburetor had that white crusty crud closed down the main jet it ran lean .
Interesting if new carburetor does it ?
Keep us posted !

 

[Stephen Newell]

There was never anything in the carb which looked like it caused any problem. There wasn't any white crust and all of the openings and jets looked clear. Still since the gas had that stink that bad gas has I soaked the carb in a dip solution and then blew it out with carb and choke cleaner. The new carb was only 18 bucks so worth a try. Will have to wait until I get it.

 

[Stephen Newell]

You guys were right, the new carb got it running. It wasn't a direct replacement, the new carb didn't have a choke at all on it however it started easily. Still there was a part missing. I think the lawnmower shop lost a linkage for the throttle control is the main reason it was underpowered. Don't know what was there originally but I folded a piece of stiff wire sort of like a paper clip and I was able to control the RPM.

 

[guido]

(quoted from post at 03:08:23 11/21/22) I'm working on a 6hp Tecumsen engine on a log splitter. Last year I had difficulty getting it started. It would start but as soon as the prime gas was gone it would quit. I took it to a shop and I believe they worked on the fuel system however when I got it back it was difficult to start but would run. Still it lacked about half the power it once did. Now this weekend I got it out to use and again it will only run until the prime gas is gone. What do you guys think.

Must be common for that poce to be missing.

This one is missing too. It looks like the picture?

 

[Stephen Newell]

That piece I had but the lever where you change the engine speed did nothing. I made a hook to go between the throttle and the lever. Without it the engine would stay at idle.

 

[tperson]

I agree, carb problems. Personally, here's what I'd do:

1) buy a new Harbor Freight 212 Predator engine. $119 today for cyber monday (https://www.harborfreight.com/search?q=212%20predator%20engine)

2) stop down at the local airport and buy some aviation fuel. Yeah, it's expensive...like 2x pump gas but:
- it never varnishes since it doesn't have the olifins or polyfins (sp?)
- has 98% the same energy as regular gasoline so there's no reason to re-jet
- by law, cannot contain ethanol
- you're only going to use a few gallons of it a year and it's cheap insurance.

I switched all my small 2-stroke stuff to av-gas 5-7(?) years ago and couldn't be happier...everything starts when I pull the rope, no carb trouble. In fact, my ice auger has had the same tank of gas in it for 3 years...still starts. My recommendation, however, would be to NOT run it in an EFI engine. The O2 sensors won't like the lead...or so I've been told.

There's little in life more aggravating than a recoil-start engine that refuses to start.

Tom