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I have a B&S Model 331777 for my Craftsman 917.28822. I noticed the other day that it was running a little rough, mostly at full throttle. Power would dip from time to time. I took off the valve cover, pulled the spark plug, and rotated the crack shaft both lifters moved but the intake was barely moving compared to the exhaust. I checked the lift rods and they were fine. I also checked the gap thinking this was the original issue and they both still seemed fine. My only guess is the intake came lob wore down but I can't imagine that's really the issue so I'm looking for more plausible ideas before I open the thing up.

Thanks in advance.

Adjust valves engine cold: Intake valves .003 - .005 / Exhaust valves: .005 - .007
Follow procedure above for adjusting valves, best illustration for B&S Twin Cylinder Engines on youtube.

Let me ask a dumb question. You saying the rocker furtherest away from flywheel is barely moving?

The cam lobes are only induction hardened so the hard facing is about 0.002" thick
It does not take much in the way of dust or grit in the oil to grind through it
Once the hard facing is breeched the cam lobe will wear round quite quickly .
Every now & then I see one like that.
However much more common is the inlet valve guide shifting in the head due to over heating .
The valves springs & guides are identical so should sit at the same heights off the floor of the rocker housing .
At the firing position the rockers should be parallel to each other .

It more likely the op is referring to the exhaust valve rocker. The 31 and 33 series will run with the exhaust valve barely opening. Take the air cleaner filter and they will sound like there is no muffler. I have exhaust lobe worn nearly round. This week I had one that sounded like but it was not a worn lobe but a rocker stud backed nearly all the way out. It had over 1/2 inch of clearance.

From what you are saying you have a worn out cam lobe on the intake valve. You can check the clearance on the valves and when the lobe is worn out it won't effect the clearance. Since there is no wear on that portion of the cam since there is no pressure on it from the valve spring.

seems along with the ACR issues on the cams, i see several with rounded exhaust lobes...

A lot of these junk built up from segments camshafts had cam lobes which were not properly hardened. This was never a problem with the one pc. forged steel camshafts used for years by B&S. But they no doubt save a few cents with these plus they get a lot from selling replacements.
Walt Conner

It would cost a lot more to forge the cams and a lot more material.

hlw49 said:

It would cost a lot more to forge the cams and a lot more material.

Click to expand...

I doubt it would cost all that much more when they already had the equipment and the one item verses inventorying 4 different items to make a segmented camshaft. The big savings was having it made in China with Chinese quality.
Walt Conner

7counting the compression release. Fly weight pin and spring.

I was assuming those would be there guardless of forged or segmented.
Walt Conner

Actually it costs a lot more to make a one piece forged camshaft than to make a built up one
The price would be least double if not more
A forged crankshaft in a motorcycle accounts for a touch more than 1/2 the entire cost of making the engine
This no doubt is why Kohler switched from a forged crank in the Command series to a cast malleable iron crank in the Courage series .
And once you start down the high volume low margin road there is no turning back till you get to the end , bankrupt .
So halving the cost price of a million cams is significant
Add to this B & S most likely buy the cams in so it is a case of he who supplies the best price gets the order
When B & S were a manufacturer rather than just an assembler then the cost of tooling comes into play
Once they become a bought in item it is the problem for the supplier not the purchaser

Sorry for taking so long to get back to you all. The grass was starting to slow its growth and so I was using my walk behind to take care of the areas that are still green (and get a bit of well-needed exercise)
So, the one that isn't moving much is on top and I expect it to be the exhaust, NOT the Intake that was incorrectly mentioned previously...and @StarTech caught . I took my digital calipers to try to get an idea of how much they open.
Exhaust:
Low: 25.91 mm
High: 27.31 mm
The valve opens approx 1.4 mm

Intake:
Low: 27.40 mm
High: 31.85 mm
The valve opens approx 4.45 mm

Now, I guess it's possible that the intake and exhaust don't open the same amount and this fact is making me think this is the reason why power is dipping from time to time but.

Firstly valve lift is not a good measure unless you set all of the valve lashes identical
Resting ( fully closed ) height is what you measure to verify that the valves are seating properly & the valve guides have not shifted
You slip the rockers off the pushrods then rotate the engine to check cam lift to verify that the cam lobes are OK
AFAIK all mower engines use the same valve lift & same valve lengths so your measurements if they are correct show a cooked engine with soft heads that have allowed the guides to shift
SO it is off with the heads to check them properly .

With both rocker set at zero clearance both rockers movement should be the same as the cam lobes are identical.
This zero clearance is when the valves are closed. But with the rocker clearance being at .003-.005 IN and .005-.007 EX they should be nearly identical with setting at zero; unless, you just want be nit picking.

Now back to my Strawberry/Kiwi drink and the party.

Looked up the engine service manual to see what the valve lift would be and Briggs did not give it. Looked up a similar Kohler engine. Lift is is 8.9 mm or .350 thousandths. So if the lift would be similar yours has about half what it should be.