Can't start old Tecumseh HM-80

[weebl]

At the end of summer/early fall, I picked up an old snowblower with a Tecumseh HM-80 engine (4 cycle L head). It was a neglected machine, but I got it cheap, and the engine ran. It took a few tries to get it going, but it would fire up fine. I already cleaned out the engine with several oil changes, and it now has GC in it. It is also sporting a new spark plug (old one was actually different than spec, but wasn't anything more than normally worn).

Now that it's winter, it won't start. First issue seems to be the recoil mechanism. It won't rewind fully, so I can't ever get enough rope to pull to start it successfully. I took that part off this evening, and tried what is called a drill start (look it up on Youtube). The drills I tried weren't the most powerful around, and I also didn't spend too much time trying the start, but it still won't go. Relatively mild today - 0C/32F. When doing this, the engine sounds like it's sputtering, almost firing when I turn it, but it never really catches.

I plan on fixing the non rewinding recoil and trying that (but may not have luck starting I suspect).

Where do I try my search for the problem next? (Fuel is fresh and with stabilizer added)

 

[crazyoildude]

try cleaning the spark plug after you test for spark

 

[Craig in Canada]

I have a 1986 Toro with an HM80. These machines are really sensitive about the carb. It'll clog with deposits even while running Sta-bil if you look at it funny.

Have you pulled the carb to inspect and clean? Have you started from factory settings to try to tune it? Any signs of float problems (fuel dribbling out an air vent in the carb body)?

Grab a copy of this to help you out: L-Head service manual

 

[dwendt44]

What Craig said. You can likely get it to pop off with a shot of
starting fluid. If it surges the least little bit, it's definitely the carb.
There is a small low speed jet that really likes to get plugged up.

 

[01rangerxl]

I think the bolt for the float bowl has some small passages in it...some are between threads and can be hard to see. Clean all of these out with a small piece of wire and clean the carb up with some carb cleaner or Deep Creep. Maybe go ahead and replace the gaskets for the bolt and float bowl too.

 

[jdh]

i have a 5.5 tecumseh snow king and it is very sensitive to carb settings and the slightest piece of crud will make it not run. thouroly clean the carb and the tank try bb's for the tank they work great. you may have 2 repeat this a couple times to get them clean. after that get it started and mess with the carb adjustments until u get it running smooth, my snow blower was sitting for 2 or 3 years and i got it running in tiptop shape with the above method so good luck!!

 

[Craig in Canada]

...and don't forget that you'll need to re-tune the carb in the target temperature range, and that the main needle needs to be set under HEAVY LOAD, not just set for "full speed".

When not under load the actual throttle plate isn't open very far so it's not actually using the main jet. Under load the governor opens the throttle plate and the main jet actually gets used.

Whenever we get our first deep, heavy snow each season I take a screwdriver out with me and tweak the main screw a little while blowing (after everything's all warmed up). Don't forget your ear protection

 

[weebl]

Originally Posted By: jdh
try bb's for the tank they work great.


Pardon my ignorance, but what are bb's?

 

[MolaKule]

My experience is almost exactly what jbl stated, as I too received my Tecumseh powered MTD secondhanded. It was given to me with no oil changes and a dried up and varnished tank.

Also try a new spark plug in it. A Quick-Start spark plug really helped improve my cold weather starting.

And make sure the squirter bulb is not broken and leaking air.

 

[jdh]

Originally Posted By: weebl
Originally Posted By: jdh
try bb's for the tank they work great.


Pardon my ignorance, but what are bb's?



bb's from a bb gun