10 HP Tecumseh will not start

Ariens 924117-1024 Snow King snow blower
Tecumseh OHSK100 221608C
carb - mfg. # - 5144 svc. # - 640169
series 3 emissions type - not adjustable

History - Reliable work horse for many years. Occasional oil changes.
First major storm this year, Feb. 2015, started losing power under load. Became unusable.

Compression test showed about 60psi.

Cylinder bleed test indicated rings could be the problem

Replaced piston rings. Compression test showed mid 90's psi.

Would not start. When trying to start, would get an occasional pop. Noticed flame exiting exhaust port (exhaust manifold and muffler removed).

Performed bleed down test. Indicated leakage at exhaust port.

Removed and dismantled carb. No obvious issues.

Removed and lapped exhaust valve.

When put back together, compression test showed near 135 psi.

What would be good range of compression for this engine?

Gapped the coil to specs and confirmed good spark.

Still wouldn't start. Same symptom as before. Occasional firing.

Dismantled carb again. Checked float clearance and ensured that the hinge clip was facing in the correct direction.
Do not seem to be any blockages.
Float bowl is filling when gas line connected.
Primer is working.

Still wouldn't start. Spark plug is wet. Seems that some fuel is making it into chamber.

I am now stuck. Done everything I can think of. I just don't know if the fuel mixture from the carb is correct.

I am thinking of buying a new carburetor.

Any suggestions?

Thanks.

Larry

 

If it is a overhead valve and they are not adjusted right they won't crank. I forget one way if it backfires through the carb it is the timing, I it backfires through the exhaust it is the fireing I think thats right.

 

It should start with 135 #s of compression. Make sure the flywheel key is OK since that is a timing concern. Probably it's just flooded. That usually happens when things don't start right off.

I'd shut off all gas and empty the carb bowl. Then with full choke/no throttle spin it over a couple of times to get all the gas out of the carb circuits. Then full throttle/no choke/spark plug out spin it over five or ten times. Then spoon a little gas down the plug hole, stick the plug back in it and with full throttle/no choke see if it will try to start. It may take a few pulls. If does, turn the gas back on and with half choke, half throttle it should take off.

 

I assume you have checked for spark at the plug?

Since you had the engine apart are you certain you got the timing correct?

 

marbobj,

Flywheel key is good. Followed your recommendations. The engine has an electric starter motor so I use that when turning the engine. The engine seemed to fire more consistently but still wouldn't run on its own. After multiple attempts I checked compression again multiple times and got some inconsistent results. I think something is wrong down in the inards again. I will tear it all apart and start from ground zero again.

Thanks for your input.

Larry

 

Pilot Dane,

I have good spark. Gapped the coil and tested the plug. Had the flywheel off and the key looks to be in good shape.

Larry

 

But are you certain the timing cam to crank inside the case is correct?

 

Are you sure your valve clearances are OK?

Steve

 

Timing cam to crank inside the case is correct. I do have a question, though. What is the function of the spring loaded gizmo riding just behind the cam gear? Is it used to control the exhaust valve when starting the engine?

TIA.

Larry

 

I do believe valve clearances are good. I gapped them with feeler gauge and also performed multiple adjustments when doing pressure tests.

 

I ordered valve spring compression tool part # 19063. Turns out that this is not the correct tool for the OHV engine. I have found 2 tools listed for OHV Tecumseh. Anybody know which is the correct one for the OHSK100 engine?

670315A Tecumseh Valve Spring Compressor Tool for OVM Ovxl OHV TVT Engines 670315A New | eBay

670237A Tecumseh - OHV Valve Spring Compressor Tool 670237A

Larry

 

I use a tool that looks like this and it works with both side and overhead valve engines. A nice feature is that you can screw it down and you have both your hands free.

 

Pilot Dane,

That is the 19063 tool. Can't get a grip on the bottom of the spring using that tool on the OHSK100.