Won't Spin Past Compression Stroke

[Johner]

Model 33R777
Type 0003 G1
Code 190214ZD
Single cylinder.

Will not spin past compression stroke.
Battery measures 12.8 v. Starter is new (and all this was tried with 2 used starters as well, so 3 different starters).
Battery connections cleaned, starter relay connections cleaned.
Battery voltage measures 12.7 all the way to the starter; battery, starter relay input, starter relay output, starter lug.
Remover spark plug, spins like crazy.
Attached car battery. Will not spin past compression stroke. Remove spark plug. Spins like crazy.
Attach compression gauge, struggles with partial spins, but got 100 psi , so it may register more if the engine could spin enough to give a good test.
So, why, if all parameters measure good, will the starter not get past compression?
Thank you,'
J

If you look at the cylinder you will see ridges in the wall. The piston is cocking and jams. Have experienced this on a 2 cycle.

 

[andy spence]

Hi Andy,

I remember those early "easy spin cams" but I also recall they sacrificed engine torque for easier starting.

From the sound of it, this would make a fixed permanent compression release.

I'm curious to see this design proposal, can you provide a picture example? How does this set screw affect the tappet face?

Next one that I will post a pic
The tappet ic much harder than the screw but the screw only proudest only .012 -.013 and rounded very smooth. It is a finan fix and works great

 

[bitdemon]

Why does a compression release exist? For the weak human pulling the cord. No engine equipped with a starter should ever require a compression release.

And no amount of adjustment of the valves will fix a worn compression release cam lobe. Drain your oil and look for sparklies. May be worse than you think.

Ha! Reminds me of my minibike days from decades ago. Minibike had a 4HP or so B&S engine, and the 'approved' hot-up procedure (I read about it in a magazine) was to tighten up the governor spring a little, drill a smallish hole in the big-end for better splash lubrication, and off-hand grind the compression-relief lump off the heel of the cam. Yep, it was way harder to pull to start with the end result I had to re-rope the pull starter many times - became an expert at that in time!