Stuck Blade Nut after breaking blade free with leverage bar

Nessuno · Apr 16, 2021

Restoring an old 1994 Lawn-Boy Gold-Series Model: 10520 Serial: 4901575 with a 4.5HP motor. Self-propelled model.
I know there are several threads and videos about how to remove a stuck blade nut by using impact wrench, heat, leverage bars, etc.... That isn't my problem. I did use a leverage bar, but what happened is I thought I broke the nut loose, but it appears the blade has broken loose. With the blade blocked with a piece of wood and clamp, I can use my socket wrench to spin the nut, shaft, and flywheel as one. How can I break the nut loose now? I thought about taking the gas tank and pull starter off and blocking the flywheel but am worried about breaking the fins on the flywheel. Wanted to check here first. Also thought about using a chisel to break the nut off and replace it (which I probably will do anyway). I suspect the muffler cover and/or plate-collar assembly will need replacing and are why the blade has loosened/broken from the shaft.

For those interested in the restore process: (this thing was left outside for 2 years in the upper midwest. Rusted up bad).
I've used a compression gauge with a schrader valve to test the compression to 103.
I've pulled, tested, and cleaned the spark plug. It appeared in good shape. Not too much carbon build-up.
I've pulled and cleaned the carb thoroughly. If it runs rough I may go ahead and buy a rebuild kit for it, but it passes the eye inspection.
I've pulled, cleaned, and flushed the gas tank and let it dry thoroughly. Pulled the shut-off valve and cleaned it also.
Old ignition coil (683080) was bad. No spark. Bought a cheap replacement which tested to provide spark. Will buy a more quality one in the future if I can get this bad boy running.
Cables were all seized up. Used Kreen Oil and WD40 to loosen them up. All seem operation now, but are rusty. Will replace in future as needed.
Deck needs repainting badly. Old paint is peeling off. Will get to that later.
Underside rusted up badly. Need to replace blades and clean the exhaust ports which is where I am and having the blade nut issue.

Help is appreciated.

p.s. I wasn't aware the model 10520 came with a 4.5hp. I thought it only came with a 5hp.

Nessuno · Apr 16, 2021

Been on the Internet all day trying to find out what I can. I found this from another forum posted back in 2012: "Try taking the spark plug out and stuff a length of rope into the cylinder. As you turn the nut, the rope will compress in the cylinder against the top of the piston acting as a stop, and keeps the pto shaft from turning." May give that a try tomorrow, but the idea of sticking something in the spark plug hole doesn't sit well with me.

bertsmobile1 · Apr 16, 2021

Nessuno said:
Been on the Internet all day trying to find out what I can. I found this from another forum posted back in 2012: "Try taking the spark plug out and stuff a length of rope into the cylinder. As you turn the nut, the rope will compress in the cylinder against the top of the piston acting as a stop, and keeps the pto shaft from turning." May give that a try tomorrow, but the idea of sticking something in the spark plug hole doesn't sit well with me.

The only thing you need to careful with is to make sure the con rod is at TDC.
If it is at an angle then when you apply a lot of force to the nut you can bend the con rod
Personally I would just cut it off.
If it is badly rusted then it should not be used for safety reasons so why risk the con rod.
The rope down the plug hole trick is generally used with an impact rather than a 12' long breaker bar with 10' of pipe on the end.

FuzzyDriver · Apr 16, 2021

Sounds badly galled.

I don't think there's any way I'd stuff something into the spark plug hole. I'd go after that nut a lot more. Liquid Wrench (lots of applications over several hours), propane torch, nut cracker, cut-off wheel on opposite flats to weaken it followed by chisel in the crack...

Did the nut loosen a tiny bit at first? I'm trying to picture how the blade got loose enough to turn without the nut loosening at all.

Good luck, I don't think I would put that kind of effort into a steel-deck (from your description it sounds yours is a steel deck).

Hammermechanicman · Apr 16, 2021

rope in the spark plug hole for 2 strokes has been around forever. Won't hurt anything as long as you don't get it in the ports. Old lawmboys don't have the blade adapter keyed to the crankshaft so when you break the nut loose the blade just spins. Some rope in the plug hole is the solutuon.

Nessuno · Apr 17, 2021

All good advice. Here's my plan: 1) use an impact wrench, 2) try to chisel/cut the nut off, 3) use the rope trick as a last resort. I'll tune later today or in a couple of days to let you all know how it went.

Fuzzy: I believe this 10520 Gold-Series is an 'F' engine on an aluminum deck and it has the 3-speed transmission. The deck has no rust, just peeling paint. The other parts such as cables, handles, and wheel adjustments are rusted. I didn't mention that I picked it up from one of my customers for free who said it ran well for him before just stopping (he thought it was the ignition coil). So if I can get it running with minimal cost,,,, cool. If not, I can put it up on CraigsList for parts. Speaking of which, I found a listing in my area that all kinds of LawnBoy parts for $30.00. Just from looking at the pictures, it looks like some of the parts will fit on this mower; the exhaust muffler/plate and mulch plate (I just have the bag setup at the moment) in particular. For $30.00, I think it's worth the chance.

Thanks for the help.

slomo · Apr 17, 2021

Spray it down with PB Blaster for a couple weeks prior to doing the work on it. As others said, heat and so on....... Might look into that hot wax trick too.

slomo

FuzzyDriver · Apr 17, 2021

Thanks, you had me confused when you said the underside was rusted badly. I thought that model should be aluminum, but didn't want to argue. The parts listing sounds good, where did you say you live?

Let us know how it works out!

Nessuno · Apr 17, 2021

Good news. I was about to try the hot-wax method; had my torch, candle all ready. Flipped the mower over, and verified the nut was still stuck to the shaft and noticed the square plate and collar was rotating with the shaft also. So I was able to simple grab hold of that with some channel locks and use the socket wrench to loosen the nut. It must've been starting to come loose from the leverage bar I used. After that, the mulching fan and blade came off easily. I has to use a hammer to knock the square plate loose. Had some difficulty with the 3 bolts on the triangular plate and muffler, but with the right size socket and a hammer I was able to get the socket seated properly and the socket wrench took them off without too much resistance. I proceeded to clean out the exhaust ports; I didn't think they looked bad but I am not an expert on 2-cycle. I did make sure the cylinder was covering the exhaust ports and kept a shop-vac close by. Here are some pics if you want to see what I have been dealing with. Obviously, the rusted out muffler needs replacing. It was actually clogged with grass. I'll post pics in a minute. Need to resize them; they are all high resolution.