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.

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.

I adjusted the valves to the Tec specs at .004  They were both loose

Ive experienced this numerours times with Honda engines on cement mixxers and power washers. Many times it would pull back so hard one time spraining my wrist. Many other times shattering the plastic t-handle. I was told by the repair shop that there was too much carbon build-up on the piston. Not sure if its true or not.

stresst wrote:
The 1st thing I would do is check the valve adjustment before anything else. Not sure but I think Honda says to check the valves after 30 hours of running time and then 100 hours after that. You as a user should always change the oil every 40 hours and make sure you install a new air filter at least every 12 months in your case maybe sooner due to the cement blowing around the engine.

stresst wrote:
It happened to me just as you described...with the plastic t-handle breaking in half.  It was with a brand new Tec 11.5hp OHV so no carbon build-up.

friiy wrote:

   If I understand the above right  the sparkplug wire can be removed and pullback will still happen.  That pullback would be from compression only. 

   It's been a few months since this happend and I just got to the engine today.  I think it was probably pulling back for both reasons, compression and timing.  I could pull the cord with no gas or spark and get pullback but at times I would get a fire can pullback.

   The valves were .011 intake and 0 exhaust.  They got set at .005.  Pulling was then normal with the plug wire out.  I thought I was in there.  With gas and spark connected it was hard to fire but when it did it always was a single put and pullback.  So I think the compression pullback was cured but the timing pullback still there.  I'll probably pull the covers tonight. 

   If I did not read your prior post I would have bypassed the valves and gone right for the flywheel key.  If it's not the key I'll be lost as I'm pretty sure this thing has SSI.