Hard to start Briggs Hanging up on compression

[RMR]

Briggs single cyl 20hp 331877 2371 G5 2015 model. Maybe 100hrs on the clock. It wants to hang upon the compression stroke on about 3 out of 5 starts.

-Good hot battery 12.7v at solenoid Battery under seat, (solenoid on firewall close to engine) Voltage drops to 7.8v at starter under load when it hangs up. Even piggy backed another battery in parallel.

-Ran ground from battery straight to block--- No change

-Tried a new solenoid---No change

-I've adjusted both valves to .005.--- No change

Should I go tighter on the valves? I've done that trick in the past with only 50/50 luck.

[bgsengine]

Compression test - you may have a failed camshaft - ACR lobe worn off.

[KE4AVB]

Being a 330000 series more likely the ACR on the camshaft is broken in several pieces. This 793880 camshaft commonly fails this way. When inside make sure you recover all the broken pieces and inspect especially the governor/oil slinger for damage.

//Added Info\\
Also is easy to check for without opening the engine other than the valve cover. The ACR bump is on the intake valve which is furtherest away from the flywheel. You should see a slight movement right before TDC compression if the ACR is working.

[38racing]

Not sure on 33 series but 31 series is .003-.005 on intake so you might want to try the .003 when you are checking for the bump.

[KE4AVB]

Technical Specifications

Model Series 3318
Displacement 540
Oil Capacity 48 oz (1.4 l)
Valve Configuration OHV
Flywheel Torque 110 lb/ft (149.0 Nm)
Governor Arm Torque 40 lb/in (4.5 Nm)
Carb Mount 70 lb/in (8.0 Nm)
Plug Gap 0.03 in (0.75 mm)
Intake Valve .003-.005 in (.08-.13 mm)
Exhaust Valve .005-.007 in (.13-.18 mm)
Idle Speed 1750
Air Gap .010-.014 in (.25-.36 mm)
Flywheel Puller Part 19203
Flywheel Holder Part 19433
Connecting Rod Torque 150 lb/in (17.0 Nm)
Sump Torque 220 lb/in (25.0 Nm)
Head Torque 250 lb/in (28.0 Nm)

[hanz63]

One other thing to add should you have a failed cam- open it up before ordering parts. When that little arm /spring comes off real damage can be done inside. Like 20% of them that I open have cracked blocks or oil pan damage.

[bgsengine]

Not sure on 33 series but 31 series is .003-.005 on intake so you might want to try the .003 when you are checking for the bump.

What I do is set valve clearance and then leave feeler gauge (or just stick a business card in there) and then roll engine backwards from valve clearance setting position (1/4" ATDC) and feel for the ACR bump on intake. if it ain't there. that's probably where the issue lies. if it is there, valves are already set so close it up and try again. 'nother thing to watch for, might just be a failing starter top end bearing (starter draw bench test should show that, though but not everybody has the DC shunt or Amp Clamp to use..)

[Arkie]

Not sure on 33 series but 31 series is .003-.005 on intake so you might want to try the .003 when you are checking for the bump.

What I do is set valve clearance and then leave feeler gauge (or just stick a business card in there) and then roll engine backwards from valve clearance setting position (1/4" ATDC) and feel for the ACR bump on intake. if it ain't there. that's probably where the issue lies. if it is there, valves are already set so close it up and try again. 'nother thing to watch for, might just be a failing starter top end bearing (starter draw bench test should show that, though but not everybody has the DC shunt or Amp Clamp to use..)

If you see the compression release bump and still no go here is a guy with similar issue video. (some other tips at the end of the video)
I've seen a starter just weak enough to cause such, (knowing that the battery is Ok) sometimes the upper bushing has side movement, the brushes worn down, sometimes even a worn out Bendix gear with a bad tooth. I've had real good luck with DBelectrical's starters as replacements.

https://www.youtube.com/watch?v=ZpUnDGkEmI0

[38racing]

I had a thread going here on all the things I tried for the
cranking issues on my friend's ariens. Last summer I found the starter top bearing gone as mentioned above. Replaced starter and haven't seen the mower for this summer.

[RMR]

I checked compression last night. 175psi. So there is my issue. I'll pull the valve cover again and check the acrv function tomorrow before I tear it apart.