Is it a 10550 with 'Easy-Stride' (Personal Pace)?

Model number is usually on a plate on rear of mower deck.
If wheels are adjusted individually just the pivot points on the adjusters need lubrication. All other parts should be clean.
A manual is available for download on the Lawnboy site.
Let us know how you come out.

Thanks for the responses. I just found a description of the problem and a solution. This forum won't let me link to that one, but but I found it by googling "Height Adj. Pin FIX". Basically you need to grind off or otherwise, remove the pin, and replace it with an appropriate bolt with the right kid of head on it. I will get around to doing this soon. In the meantime, I have a bungi cord going from one adjuster to the other--to hold them both against the mower.
I'll look again for the model number, but based on pictures, I believe mine is a 10550. It runs great! From what I've read, it is not as long lasting as other lawnboys, but it should be fine with just my own lawn for years to come.

Follow me here..lol

Remove the adjusters.

Drill out the pin that is in the adjuster to remove it. If it turns with the drill bit. Carefully grind it flush and knock it out.

The photo shows a Shoulder Stud bolt. Get one that has a shank (smooth part) the same size or slightly lager than the pin you removed.

Insert the stud with the shank toward the wheel into the adjuster. Use Red Loctite and install the nut with a flat washer on each side (sandwich the adjuster). Tighten the nut firmly.

Trim/cut the studs shoulder off a fraction of an inch longer than the original pin.

If the "pin" should ever work loose. Just use vise grips to grip the shoulder and tighten the nut up and you will be good to go again..

This is insane. I used a 10550 for years and never encountered any such problem. I cannot believe that anyone would have to replace the locking pin on the adjuster lever. Something has to be screwed up to cause this malfunction but damn if I can think of what could cause it.
Also, I don't know where you heard that a 10550 may not last as long as other Lawn-Boys, but in fact the Duraforce engine, aluminum deck and Personal Pace drive represent extreme durability in the three major components of a mower. The LB 10550 is one of the best and most durable mowers ever built. I personally do not like Personal Pace, which eventually led me to sell mine, but I wish everyone had the opportunity to experience a 10550, if for no other reason than to illustrate what was to be the high point in the evolution of the 2-cycle rotary mower.

Don't laugh, but could the spring arm assembly have been installed backwards by the previous owner?

Maybe reversed is a better word. Parts list shows a left and right rear spring arm assembly. Looks like locking pins may be in different positions.

Sorry for the late response. The issue is actually common if you google it. Try cutting and pasting my search terms into google. BTW--I finally found my model #, under the handle. It's a 10525. What year was it made and what is it worth?
thanks
Ben

1999-2000. It's very similar to the 10550 but has a completely different 3-spd drive and a different adjuster type. If you can fix it with original parts, the value would be preserved. I think its probably worth $350 or more in excellent condition (like new). If its not like new, expect less. These 3-spd transmissions are full of parts and expensive to fix. I personally would only pay half of what I could get a 10550 for because of the trans. If the wheel adjuster problem is so widespread, there probably is a Toro/Lawn-Boy part to replace it.

Out of curiosity I Googled your search terms but didn't find anything specific to lawn mowers except this thread.
Re-read your post and have a couple questions.
You said rear adjusters keep "popping out". Do you mean they are moving toward the wheels and away from the deck?
You said locking pins were loose. Do you mean they were sliding sideways in the adjusting lever?
You said you have a bungee cord holding adjusting levers against the mower. That statement leads me to believe the adjusting levers (spring arm assemblies) are bent or improperly installed.
To adjust height the adjusting levers are moved toward the wheel, moved to the desired notch and released. Spring action should hold them tight against the deck.. In fact, on my 34 year old Lawnboy it still takes a fair amount of force to move the levers toward the wheel.
I agree with Saxman. Something is wrong.

It comes up for me about halfway down the page cut and paste this into google

Height Adj. Pin FIX, L-B 1994-up S-P Gold & Comm.

The issue is that the pins are installed too loosely, or can loosen, and then are pushed to an angle--not 90 degrees, from the spring adjusters from there, over bumps, etc, the can be forced out of the holes on the deck. Then the deck can fall all the way to the ground. The solution is to either drill out and replace the pins with a suitable bolt, or pound the pins back tight, Or, as a temporary solution, a bungie from one spring to the other helps to keep the adjusters tight to the deck, so that the pins can't as easily work their way out.
The lawnmower repair guy at the shop I go to for parts says he sees this problem all the time.

OK Now I understand. Sorry to be so dense.
Have you thought of driving the pins back to the proper angle and spot welding in place?
Beats a lot of grinding or drilling and bolting.