Maybe what you are hearing is not a loose wrist pin.
I once had an old chevy that would 'ping' like hell
on hot dry days, but on wet/humid days would run
like a champ. My guess is that the humidity of the
air and possibly barometric pressure effects the
timing, similar to the octane rating of the fuel.
Just my guess though.

The loose wrist pin thing only applies to the old LBs that had a bushing on that end of the connecting rod. Wrist pin noise is highly unlikely with engines produced since about 1970.

The confusion in the thread you mention came about because the full model number of the mower in question was not posted originally.

Walt Conner

Depending on the model, you may have a 'V' or 'F' engine, but in the context of the question they are similar. The 'V' came on the steel-deck 'value' line, including the 10201 and 10301. The 'F' was on the premium line aluminum-deck mowers, 105xx in 1994 I think. The noises you mentioned would always be present, so whatever you heard wasn't that. They all knock and clank when turning them over and when you shut them off. Also, if it's a 'V' engined mower, you need to check every fastener immediately, starting with the muffler cover and the larger bolts under the baffle. Check engine mount bolts and also the smaller fasteners holding the sheet-metal shroud base to the engine.

I have a 'V' engine - very true it knocks and clangs on start up and shut down. Still runs like a champ. I went through all the bolts for awhile - have always been tight.

It vibrated quite a bit when I picked it up used, but I switched to a Gator blade and it is now a beast and relatively smooth running. I think my baffle plate is not working real well, because it is LOUD. Which I don't mind - the neighbors run inside when I fire up the smoke belching beast (I run extra oil to keep the 'skeeters down while mowing - and to piss off neighbors).

Good power on a light weight mower. The noise and smoke are a bonus IMHO.

Jim

Thank you for your responses.

For your information my machine is a 10420, with aluminum deck and F series engine.I will check all the fasteners.

I have become used to 4-stroke engines and the 2-stoker always seems to make a lot of strange noises by comparison.

'It vibrated quite a bit when I picked it up used'

You should try a new replacement blade on it. It also came with a mulch fan.

'I think my baffle plate is not working real well'

Most likely the stamped-steel muffler cover needs replacement. They crack at the bolt holes, distort and leave a gap around the bottom and rust out.

'For your information my machine is a 10420, with aluminum deck and F series engine.I will check all the fasteners.'

One of the best ever made. The peculiar sweet smell of grass cooking on the under-deck muffler combined with new-cut grass and burnt Lawn-Boy oil is like perfume. Then, you have the quiet 'outboard' hum to treat the ears - these things will never be known again once they're all gone. Keep it going forever.

You must be daft! I set an old Lawn boy out front with a free for parts sign on it, and it sat there for 2 weeks before somebody finally took it! And, the Honda, missing one drive wheel, that ran good last year--sat out there until i got orders from the borough to hide it somewhere, since nobody was interested in it!

After taking the muffler off of the C21ZPN that I was asking about piston slap on, I found that both engine mount bolts at the exhaust ports had backed out far enough to be rattling against the muffler. Check all your engine mounting bolts.

Hey orange; that was a good find and fix. Normally you would check these yearly when you pull the muffler cover to clean/check.

Up here in MA, Lawnboys aren't that common. I have a plain old 19" steel deck 7072 that runs on chainsaw mix and starts first pull. I got it off Craigslist free stuff. I just use it for trimming and the noise and smoke makes me smile. 2 strokes were made for pushmowers. I'm gonna run it until the engine dies.

Sounds like you'll have that 7072 forever then, cuz as long as you keep feeding them oil 2-strokes don't die. Like saxman says, that sweet combination of fresh cut grass mixed with Lawn Boy exhaust just can't be beat. I used to have a LB M series with oil injection. Was a great mower until the Mrs. backed over it in the garage. At least it died a quick death. Long live the 2 strokes!!!! Wish I had one.

" Long live the 2 strokes!!!! Wish I had one."

I know where you can get a good running 10515 for $125 plus shipping.

Walt Conner

I'd love to have it, but the wife would probably make me sleep in the garage with it. I'm only allowed 1 mower at a time. ha

@-strokes live practically forever if you use the right mix. My late '50's Jacobson is still running like new after all these years.

"@-strokes live practically forever if you use the right mix."

Until the drive system, if so equipped, breaks.

The problem today is the cost of labor and the limited avaiability and outrageous prices for many parts.

It seems like it is becoming less and less cost-effective to repair anything mechanical.

under deck muffler...Yep, I have fond memories of repairing burned spots in lawns from when I'd leave one of those old beasts running while I'd empty the bag... Apparently, hot oil-laden exhaust gasses are not turf friendly.

I have the 10302 - when I picked it up used the blade was the original LB and the mulch fan was missing. I am running a Gator now without a mulch fan, and it works great. I would recommend using the mulch fan if you are running the OEM blade. But the Gator adds enough mulching "action" by itself - I am happy with it as is.

Jim