tecumseh no start

[coldinbuffalo]

i have a 24 year old Toro lawn mower with tecumseh tvs 100-44015b engine. I have given it a PM every year. Put in a carb kit and float about 8 years ago. This year it ran fine until it stopped for gas and would not restart. I put in a carb kit ( consists of needle and seat and bowl gasket ). Still no start. Removed carb and double checked. Still no start. Has good spark and changed spark plug. Compression with throttle wide open is 70psi. I'm thinking that is to low. Should i look at valves and head gasket next? Looking for your advice and experience. Thanks in advance. P.S. i cleaned carb with carb spray and chased all holes with tag wire.

[KE4AVB]

Did you remove and checked the idle restrictor jet if present and also check the fuel main jet/ fuel bowl bolt if present.

Probably the best to find if it is carburetor or otherwise is introduce raw fuel directly into the cylinder or intake and then try starting. IF it starts then carb related; if no start then you need go on the cylinder and ignition problems.

[bgsengine]

Try a new plug (or two - New don't mean Good)

[bluemower]

this is an older engine. sometimes the bale cable (from the handlebar) starts sticking and the compliance switch is still closed - killing the ignition.

[Skywatcher]

Hi Buffalo

Working on a 1994 Sears lawn mower with a Tecumseh TVS120-63922K-4059A engine. The engine has compression, spark and fuel but would not start except for the occasional cough out the muffler, so suspected ignition timing out due to a sheared flywheel key. Sure enough, the flywheel had rotated almost 90º on the crankshaft. The older Tecumseh engines with the stepped flywheel key used an aluminum key and 30 foot pounds torque on the flywheel nut. Tecumseh changed to a zinc key around 2002 and increased flywheel nut torque to 40 foot pounds as the keys were shearing if the mower just hit a tuft of tough grass, yet alone a rock or tree stump. All the best,

Sky

[coldinbuffalo]

Thank you gentlemen for all your suggestions. I followed up on all of them. Of course it was the one i thought least likely. It was a partially sheared flywheel key. My daughter has been using it all season at her place so i suspect she may have hit something and when the mower stopped she assumed it was out of gas and simply refilled it. I will get the part i need tomorrow and re-assemble.

[Skywatcher]

Hi Again Buffalo

A little alteration or modification that I perform on these older Tecumseh engines if I know the mower is to be operated by a girl or older person is to retard the ignition timing by a couple of degrees for easier starting with no noticeable decrease in performance. When you look at the stepped key, there's the part that locks into the keyway in the crankshaft and the wider part that aligns the flywheel. I'll file about 1/32 of an inch from the overhang side of the wide part, install the key into the crankshaft, then turn the flywheel back against the filed edge of the key before torqueing the flywheel nut. The reports I generally get back from these customers is the engine no longer tries to kick back when they're pulling the cord to start the mower.

Any thoughts on this idea from other forum members are most welcome. All the best,

Sky

[mr-moe]

An excellent idea Sky.