Toro Tecumseh Lost Compression; found a screw

nbpt100 said:
I would run it until it does not function to your needs. You can put straight 40 weight in the engine and it may slow down any oil burn and give a bit more compression. You seem to indicate it was fine (or good enough) until this abruptly happened. If you have or can borrow a leak down tester you can get an idea of where the engine compression stands. Those Tecumseh's used on Toro's were pretty well made. Like an LEV115 or 120? They have an oil pump system that lubes the cams. Good Luck.
Click to expand...
yes, it's LEV120.
 
I did not take a picture of the cylinder bore... will do so when I get a new head gasket. The cylinder is aluminum. BTW, just learnt that the engine (or most small manual start engines?) has a "compression release" mechanism which helps manual pull-start. Maybe this explains the lower resistance when turning the flywheel by hand.
 
The compression should be about 60 if it is healthy. Since it starts and is 24 years old, whatever it has is good enough.
 
Resistance depends on the HP of the engine. Is it a 4, 5, 6, etc. That valve looked sickly anyway. I don't think there was much left in it before the screw got jammed in it. As for the RTV black, that color is normally used for oil ( valve cover gaskets, oil pan gaskets, etc ). I wouldn't worry about piston scoring, you got bigger fish to fry. All, in all, you did a great job. But, a valve not seating correctly, you're losing compression. Don't let the grass get out of control, and you should be ok ( less strain on engine). You're Upstate NY, grass growing should slow down in July-August, then pick up fast from Sept.-Oct.. Might last. All depends on how much grass you're cutting ??? BTW, if you're going to do anything, just buy a tube of RTV Grey for the head gasket if it starts leaking. Please lemme know how much grass are you cutttin. That's the key to all of this.
 
I forgot, wouldn't hurt to start looking for July 4th sales online. I got a rider delivered for free from Walmart ! That was 50% off too. Hate for you to be stuck in the middle of mowing season without a back up machine
 
If it were me, I would keep my eye out for a used similar Toro with the LEV 120. Maybe one with an ugly deck but good running engine. You can do an engine swap in short time. You also may be able to put a Briggs Quantum engine on that deck as well. You just need to make sure the blade ends up in the correct position. Do not assume it will. If it is self propelled it adds to the complications of fitting the pulley and blade adapter. Which may make this engine an incredible long shot to easily pull off. You will need to take careful measurements. A great engine and plenty of parts availability.

From what you said about the valve appearing bent, I would be more concerned about that than anything. The seat may be damaged too. If it turns out to not be so bad you may want to put the right head gasket in. I am not sure how long the Black RTV will hold up. It is an interesting experiment. The High Temp Red or High temp Copper may be a better option should you revisit it. Nothing is as good as just using the right gasket and be done.

Here is a gasket for a LEV120. It is a little more than the cost of High Temp copper gasket maker.. I found this in a 30 seconds. If you invest more time than me you may find it cheaper..... but confirm it is the right one for you. Best of luck.

https://www.ebay.com/itm/2840687830...bRXJuWqBLlQJBJUXEcySxukR48Y=|tkp:BFBMpNmGv_hl
 
Bad timing....I threw out about 8 trash picked / re-built machines in Oct 2024. I'd say 6 of them were Tecumseh. All of them push mowers with bags ( That's when I got the rider ). As I got older, I couldn't push cut the grass anymore. ( 3/4 acre), so out they went. I had you're engines and plenty of spare parts. You're upstate NY, I'm top end Westchester County NY, next stop would be Fishkill. You could have ransacked my shed for whatever you wanted, free. I'm so sorry :)
 
windeye said:
Thanks for all the ideas and suggestions. The screw was indeed on the butterfly. The plate fell off and got stuck in the intake. Put it back with loctite. De-carboned the piston top and the intake valve with brush and throttle cleaner. The intake valve still sit a bit cockeyed; can't adjust it to be 100% anways, so did not test it for leaks. I also can't find head gasket, my local Toro dealer does not have it, their suppliers don't have it. I smeared some Permatex Ultra Black on the old gasket, and torqued the head back on per the procedure and spec in service manual. Rotating the fly wheel by hand, there is some resistance but not much, thinking this is the end of it. Later on, when I put everything together, and pulled the string to start, the compression resistance felt OK, and it actually started. So I finished mowing the rest of the yard. No idea how long the Ultra Black will last. Before I go buy a head gasket, question: how much resistance of compression should be when turning the flywheel by hand? Oh, there was some scoring on the top end of the cylinder wall, but nothing major.
Click to expand...
If you want to get parts, I have found this site is good for those long discontinued items.

https://www.jonesfarmsupply.com/
 
windeye said:
Am mowing today, and toward the end of it, the mower lost compression completely. Now this mower has been with me for 24 years since new, never had a compression problem. Just oil changes and spark plugs etc. I am thinking to junk it simply because it has been so long. But then curiosity got the best of me, and I started to take it apart based on what I think might be wrong.

I first suspected valve springs, so took the valve cover off, and found the intake valve does not return properly. See video [here]of the bottom valve. When the push rod retracts, the valve seat does not follow all the way, leaving a gap. The exhaust valve is good. The spring on the intake seems to be OK.

Then I thought I had to take the head off, and I did, and saw the intake valve hang. What the heck?! Upon close inspection, I found a screw stuck in between valve and the seat. Picture below.

It's getting dark, and I am being attacked by the mosquitos, so I'll check further tomorrow. But where could the screw be possibly come from? Any thoughts, anyone? Thanks.

View attachment 287225
Click to expand...
Not to healthy looking this poor thing. I guess its scrap.
 
Seen this before. Small screw stuck on the intake valve/seat. It came from the carburetor's choke plate. Check the carb for a missing screw on the choke. Supposed to be 2 of them there. It's salvageable if you want to install an Amazon cheapo carb, ( or find a similiar screw to replace the one that backed out ). Remove the screw, clean up the intake valve and seat the best you could, and you can probably re-use the head gasket.... I've done this before. Used some high heat RTV on the head gasket, and slapped it together. Didn't even torque the head bolts, just tightened them up good..... I let the RTV set up overnight, and the machine ran fine the next day. You're choice if you want to mess with it any furthur, or junk it. Please let us know what you're decision is. That Tecumseh is a great engine, you'll never find a new mower built that well again. I have 3 or 4 of those old flathead Tecumseh mowers that I trash picked. Thru a carb on them, and they run great.
 
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