# 10.5hp Yardworks wont start



## machine4321 (Jan 7, 2017)

Hey all, Ive been browsing for a week tryign to get this figured out. I have a 10.5hp tecumseh HMSK105 that I got for free. Its been sitting for a couple years.

I have drained old gas (It was green lol) replaced main fuel line, new plug and pulled carb apart. I havent rebuilt it yet. Compression on about 4 pulls was 65 (cold ) So I figure its worth putting some cash into. I did replace the throttle control as it was seized up.

I did get it to run once by dumping fuel in the chamber but it was lean and muffler got red pretty quick so I shut it down. Since then it hasnt ran. Ive clean the low speed jet, main jet, vent on side of carb, verified float position, bowl gasket looks pretty new(no chunks ect falling off). I couldnt get the emulsion tube out but confirmed that liquid passes through.

Plug is wet, primer fills bowl very quick and fuel leaks out the carb opening if not careful.
I have spark (felt it by mistake lol) but im not sure if its strong enough. Its more on the orange side and not blue. but I have no idea if thats enough. I will check air gaps and flywheel stuff when I have a chance. Im stumped, this is my first go at a small engine but I am skilled at automobile engines. Ive done alot of EFI tuning in the past but carbs are new to me . Any other thoughts or things to check? My back is toast from all the snow this year.

Oh and the electric start, does it need to be grounded or anything? It doesnt do anything when plugged in, not a peep. Id like to get it working. on a side note the wiring on this has been messed with. there is a 2 conductor wire thats cut near where the fule line runs. not sure if this was for the light or something. I didnt worry to much about it as it has ran in the past and I have spark. Ground out coil and spark goes away.

Thanks again


----------



## machine4321 (Jan 7, 2017)

I will take a video tonight of the spark to let you guys see it.


----------



## e.fisher26 (Nov 6, 2016)

Weak spark may be coil, or just clean the magnets on flywheel (older engines have points behind flywheel). Did u rebuild carb with kit or just clean whats there? Theres welch plugs that need to be removed with small gas passages behind them. Kits have new welch plugs. Ive used a few new no name replacement carbs off ebay that worked great for me, and they come with adjustable jets. The cut wires you see are probably for a light. Ground wires for shut down are usually green and by the carb.


-efisher-


----------



## Motor City (Jan 6, 2014)

You would probably be best to get a new carb. As for the starter. Sometimes the gear kind of gets stuck on the shaft. You will have to take it off and free up the gear on the shaft. I usually put a light grease on it. If the starter doesn't do anything at all. Plug it in and push the button and tap the motor with a hammer, it may have stuck a bit, from sitting.


----------



## machine4321 (Jan 7, 2017)

I cleaned what was there, I didnt take the plug out. I have found a carb on ebay for 20bucks CAD so I may try that out. It does have a coil so I guess thats my next step. I will check the magnets ect and air gap. Wierd thing is it did run that one time lol 

Thanks for the pointers.


----------



## e.fisher26 (Nov 6, 2016)

Of its a coil id put that on bottom of list, try to get a carb with the adjustable bowl jet. Make sure you use the same hole for the linkage.


-efisher-


----------



## Motor City (Jan 6, 2014)

machine4321 said:


> I cleaned what was there, I didnt take the plug out. I have found a carb on ebay for 20bucks CAD so I may try that out. It does have a coil so I guess thats my next step. I will check the magnets ect and air gap. Wierd thing is it did run that one time lol
> 
> Thanks for the pointers.


Did you actually check for spark? Pull the plug and put the plug back into the plug wire. And lay the plug on the head and pull it over, and check for spark. Make sure the throttle lever is in the run position.


----------



## Blosumsno (Dec 7, 2016)

As Motor City said but I'd like to add make sure the head or whatever you lay the plug on has no oxidation or paint. Weak spark can also be caused by a coil, as others said above, with shorted turn(s) or moisture in the winding. Also if there's a ground wire coming from the coil to some part of the block make sure that connection is clean, some coils are grounded through the core or frame via the mounting bolts so cleaning this area may help.

A good spark should jump a gap well beyond that of a spark plug. I use a spark tester Mine is an older version of this one. This video shows well how much of a gap it should jump: 




Good luck


----------



## RIT333 (Feb 6, 2014)

Harbor Freight has a nice $5 Spark Plug tester that light up with spark, and it turns it into a one person job.

Nifty.

Inline Ignition Spark Checker


----------



## e.fisher26 (Nov 6, 2016)

I have that tester, works good



-efisher-


----------



## Blosumsno (Dec 7, 2016)

I like it because you can use it while running the engine and it's easy to catch misfires.


----------



## Blosumsno (Dec 7, 2016)

RIT333 said:


> Harbor Freight has a nice $5 Spark Plug tester that light up with spark, and it turns it into a one person job.
> 
> Nifty.
> 
> Inline Ignition Spark Checker


Sure is cheaper than the oem ones.

Found Oregon makes a Briggs clone inexpensively too: Briggs and Stratton 19051 19368 Spark Tester - outdoorpowerdeals


----------



## machine4321 (Jan 7, 2017)

Hey, I cleaned the magnet (alot of rust) The coil is in rough shape, the plates that wrap around the coil are starting to separate and there must be corosion in the coil as the ground tab is rusted clean off the coil. so no shut down. But I may have found a bad head gasket. When I did my comp check it was cold of course, I pulled untill the gauge stopped climbing and it settled around 70psi I think.

Today when I put gas directly in the plug opening I get some combustion but im noticing smoke puffing out around the engine (near gas tank). I thought maybe muffler gasket was toast and pushing smoke back around the cooling fins. I removed the muffler and put a few more drop in the opeing and still getting smoke from around the head. 

I guess a head gasket should be a pretty easy swap on these?


----------



## machine4321 (Jan 7, 2017)

Well...lol When I went to remove the gas tank to replace the line I went to the 2 head bolts that double as mounts for the tank. When I realized they were something different I wen tto tighten them and noticed that something wasnt right and I thought they were stripped. Im pretty sure I ran the motor after that and that would explain the red hot muffler and sparks ect. The head gasket was leaking at these 2 bolts and noticed a difference right away...how ever I think running the motor did more damage to the gasket as I still hear some puffing from behind the shield by the oil filler.

So either way I need a coil and a gasket to move on to the carb.


----------



## e.fisher26 (Nov 6, 2016)

Head comes off, clean both surfaces, look for cracks and replace gasket. Need inch pound torque wench for head bolts, i dont know what the number is off the top of my head.


-efisher-


----------



## Motor City (Jan 6, 2014)

The torque is 200in/Lbs. Tighten them in 3 steps. And google the tightening sequence.Get your self a new coil and your back in business. To gap for the coil to flywheel, use a business card between the two, and tighten it down.


----------



## machine4321 (Jan 7, 2017)

Thanks, I think my torque wrench fits in that range.


----------



## machine4321 (Jan 7, 2017)

Well good news. She runs. First pull. Old carb and old coil are still on but new headgasket was the trick. I did clean the carb and airgapped coil/sanded magnet. It does shake around a lot but the deck bolts may need to be tightened. Still need a coil for grounding and carb is only 16bucks so I will get that when it's back in stock.


----------

