Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

I have a snowblower with a TEC 7-hp over head valve engine that pulls the pull cord like it has a broken fly wheel  key.  I have seen this on many lawnmowers but never on a snowblower  engine. The engine runs nice once started. Is this possible.

It does sound like you have a timing issue.  Have no idea if it's the flywheel key but it sounds like it might have something to do with alignment of the flywheel magnets/ignition coil.  Doesn't that engine have a compression release mechanism?   

Yes is possible.  I had a problem with the pull start on my 2006 Ariens 11528LE (Tecumseh OHV engine) immediately after I bought it.  The cord would pull halfway out then snap back with enough force to break off the bottom of the handle.  I was literally left holding the other half of the handle.  Call Ariens and they said it was a Tecumseh warranty issue and to call them.  Took it to an authorized Tecumseh dealer.  It took them forever to fix it because they had to consult with Tecumseh for direction.  This was back when Tecumseh was still around.

To your question though...before I got it fixed I began using the electric start and once the engine was running it worked flawlessly.  But even after running it for a while if I would would shut it off and then try to restart it using the pull cord it would snap back on me.  The Tecumseh shop never explained to be what was broke, but they did fix it...knock wood it's been fine ever since. 

Could be a flywheel key.  Maybe previous owner ran into something and stalled the engine.  How do the impeller and augers look?

If there's no unintentional misalignment, it almost seems like Tecumseh timed the engine(s) with too much advance which will deliver more torque at lower rpms. 

Paul7 wrote:
Paul you described it perfectly that is what is happening wish the guys told you what the fix was. I will look at the flywheel key.

Check the Valve Clearance....

        Most likely the valves are too loose...   If they get too loose the Compression release lobe on the cam will not have any affect and the engine will snap back the pull rope on the compression stroke......  Seen it a million times,   it is really bad on the Vangard OHV engines Briggs has,  but not uncommon on the Tec Engine  too... 

Let me know what you find...

Good Luck,

Friiy

friiy wrote:
You were correct after adjusting the valves all is well. Thanks for the input.

Were the valves loose or tight?  

Generally, I like to keep valves adjusted to the loose side of the adjustment specifications.  As valve lash gets tighter, it tends to be more of a problem than a valve lash that's a bit on the loose side.   Loose valves will always close but tight valves will not.  

Borat ------     When the valves heat up and the clearance tightens the motor will be easier to start. (compression release will engage slightly).... 

      Anything that is overhead valve is prone to this problem,   I would always check valve lash on something with this problem before checking the flywheel key on anything with a belt PTO..

Friiy

friiy wrote:
I agree that it will be easier to turn over because the valves aren't completely closing if the lash is too tight.   The down side of that is the valve never completely close thus allowing a portion of the combustion process (flame/gases) to escape causing excessive heat and damaging valves.   In some circumstances, if the valve lash is tight enough to compromise compression too much, the engine may be difficult to start.