Won't Spin Past Compression Stroke

[JDusza]

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

 

[slomo]

Perform valve adjustment.

Load test the battery with a carbon pile tester. I see you sub'd in a car battery with no luck. Points to valves out of spec.

Check and clean all grounds. Grounds are the most overlooked cable on mowers.

What is the voltage AT the starter, while cranking?

 

[slomo]

So, why, if all parameters measure good, will the starter not get past compression?

Probably using a car compression tester on a small engine (gives you inaccurate readings) and valves are out of spec. Dynamic compression too high.

 

[JDusza]

Thank you for the input. I guess I have to look at valves.
I can't say i understand the failure yet though as the cylinder is a closed can if the rings are good and the valves seat.
So how can compression be too high? If the valves don't seat won't that yield a loss in compression?
Are we saying the exhaust valve is stuck closed?
Thank you.
J

 

[slomo]

Read up on dynamic compression.

 

[JDusza]

I found something on the net about a valve release system built into the cam shaft that relieves a bit of pressure so the starter can spin. The failure led to metal pieces in the sump and the need to replace the cam shaft.
Could this be my issue?
J

 

[ILENGINE]

I found something on the net about a valve release system built into the cam shaft that relieves a bit of pressure so the starter can spin. The failure led to metal pieces in the sump and the need to replace the cam shaft.
Could this be my issue?
J

Yes, but the valves need to be properly set within tolerance to make the final decision if the compression release has failed. But don't wait too long to find out, because Briggs has a common issue of backordering the camshaft, and some of the warehouses are getting low on inventory.

 

[Tiger Small Engine]

I found something on the net about a valve release system built into the cam shaft that relieves a bit of pressure so the starter can spin. The failure led to metal pieces in the sump and the need to replace the cam shaft.
Could this be my issue?
J

Step 1). Load test battery and clean and tighten all connections.
Step 2). Check valve clearance and adjust as needed.
Step 3). Listen, learn, and don’t overthink things.

 

[Auto Doc's]

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

As these engine run, the moving valve parts wear a small fraction of an amount and the valve lash open up too much, which makes compression higher. With higher compression, the engine becomes harder to start, especially cold.

Valve adjustment is not and over complex task, you just have to take your time and double check the adjustments.

Here is a video about the valve adjustment process. This adjustment should be checked once per year before getting into the heavy cutting season. Adjust only with engine cold.

B - Search Videos

www.bing.com

 

[Forest#2]

The compression release is on the intake valve.
It dumps some compression when the piston is just before TDC if the intake valve lash is .003-.005 with the piston 1/4 inch past TDC. .003 slowly turn the engine on the compression stroke and just before TDC you should see the intake valve stem just slightly bump towards open then re-close just before TDC. If you do not see this bump up the compression release on the camshaft might be bad.
Lot of information on-line about compression release on the single cylinder Briggs Intek engines and failure of the compression release and how to adjust the valves to get a compression release.
If the valve lash is at .003 and it still won't crank through insert a .002 feeler gauge under the rocker arm so as to take the lash to .001 and test crank.

Ignore compression readings for now.