Is 150 PSI a Good Compression Number?

[MonkeyCam]

This is not twitter.
Long posts with lots of information is soooooo much better than a short post with not enough information.
First of all does the mower have a throttle & choke or just a throttle ?
If it is the latter you are most likely going past the full throttle position and engaging the choke.
What you describe is exactly what happens when the choke is engaged.
Also check that the cable has not come loose in the anchor point and engaging the choke .
You can slip your finger in the carb throat and check the throttle butterfly for movement when you move the throttle.

Double check the valve lash .
Remember the grub screw is the lock nut and the big nut is the adjuster.
It is not a good system & I oft have to do it several times to get it right.
While the rocker cover is off check the movement of the valves.
They should both sit at the same height above the floor of the head ( nice mix up there isn't it ) and move the same amount.
If not one of the cam lobes could very well be worn.
The cam fitted to inteks is not particularly any better than it needed to be and some wear quite badly, particularly if the DPO ran the mower across slopes which causes reduced lubrication of the cam.
Pull the exhaust off and check for carbon blockage and bugs / rodents etc reducing the flow thus choking the engine

The mower’s throttle lever has the following 4 settings in this order:

Turtle
Icon that looks like a piston inside of an engine
Rabbit
Choke

The lever doesn’t click into each position; it’s a smooth transition from one end to the other.

With a flashlight I can look into the carb and see the butterfly move when I move the throttle lever, but it only closes when I get to the far end (choke position). It almost immediately opens when I go back the other way, but other than that it doesn’t seem to move at all throughout the rest of the lever’s range of motion.

You kind of lost me with that talk about valve lash and grub screw. That’s a little over the head of this newbie. :ashamed: Like I said earlier, I found out I had a valve problem early on when the starter rope was really hard to pull. I adjusted the valves, which solved that problem, but I’m hesitant to try anything more advanced than that.

I removed the muffler and used a flashlight to check for obstructions, but I didn’t see anything.

 

[bertsmobile1]

So how did you adjust the valves ?

 

[MonkeyCam]

So how did you adjust the valves ?

Long story short, I watched a bunch of YT videos.

 

[bertsmobile1]

No How did YOU adjust the valves, what tools in what places and what did you set them to.
have you rechecked them ?
Even old hands get it wrong now & then.
When the rocker cover was off did you check the operation of the valves ?
They should sit at the same heights when closed and move in the same amount when the cam pushes on the pushrod.
Did you pull the pushrods & check that they were strait ?
The alloy rod wears where it passes through the plastic guide so should be turned over when ever you do the valve lash ad tosses when the waisting gets excessive.

 

[MonkeyCam]

No How did YOU adjust the valves, what tools in what places and what did you set them to.
have you rechecked them ?
Even old hands get it wrong now & then.
When the rocker cover was off did you check the operation of the valves ?
They should sit at the same heights when closed and move in the same amount when the cam pushes on the pushrod.
Did you pull the pushrods & check that they were strait ?
The alloy rod wears where it passes through the plastic guide so should be turned over when ever you do the valve lash ad tosses when the waisting gets excessive.

I looked up the valve clearance specs. for my engine (.006 in. for exhaust & .004 in. for intake) & then put it at TDC on the compression stroke before I adjusted them. I was, of course, watching the valves while I was getting the engine to TDC, & they looked like they were working properly, at least to my inexperienced eye. Next, I loosened the rocker nut then used a feeler gauge while adjusting the rocker screw. I had a helper (my 12-yr.-old daughter :smile tighten the nut while I held the screw stationary w/ one hand & kept the feeler gauge inserted w/ the other. I did both valves the same way. I didn't pull the pushrods. I guess I need to re-check the valve clearance & take a closer look at the pushrods & valve operation.

So you don't think it's a carb issue?

 

[bertsmobile1]

That is the problem most have when adjusting small engines .
You set the gap by moving the nut
You lock the nut in position by turning the screw in the middle of the nut.
They will be still wrong.