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Young Buck
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1,611 Posts
Discussion Starter #1
Today after work I picked up 5! M series Lawn-Boys. All need work but my goal is to build one great runner. I should have enough parts, other than good wheels, and 4 of the 5 turn over and have compression. the one that doesn't is a 10201 that was tor apart and rusted to death in the bore. the deck on it is the second nicest, so it may be a doner if I can get two set up. Of course I buy the odd man out lawn-boy it seems, with the oil injection which seems cool but I have no idea how it works. I am going to try to get one running in some capacity tomorrow morning. My fist question is are they supposed to lock up when rolling backwards? I wouldn't think so but have had mowers like that before. and what are the major need t knows of this engine? Hopefully I can get educated and have a good running mower.

Models and serial numbers closest to farthest:

1. Model M21BMRA first canidate
Serial: J052B0257

2. Model: M21BMRB missing recoil
Serial: K176C0205

3. Model: M21BMRC missing recoil
Serial: k066A0016

4. Model: M21BMR
Serial: H208B0188

5. Model: 10591 motors junk
Serial:5901636

6. Model: 10201 Silver Series, needs coil apparently
Serial:3912164

3 of them are missing one or both drive wheels, but Hopefully I can put some commercial wheels I found on eBay on my runner.

Thanks For looking!
 

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Young Buck
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1,611 Posts
Discussion Starter #2
GOt one running (sorta) today. It surges and smokes like crazy. I think the block is full of oil from sitting. Is this normal when they sit forever. when I had the carb off I looked in and the cylinder may have been a bit scored. if so its Sad since it looks so nice on the outside.
 

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Young Buck
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1,611 Posts
Discussion Starter #3
Help me with my new M series Please!

I think Im gonna need help building this franken M series, Just a manual or where I can get on cheap would be nice. one I found on ebay was $45.00. The one I got running got ran for an hour today and will not stop smoking. also don't know if I got the crab clean enough as it has lots of very small orifices and it is surging a lot and doesn't want to stay revved up with the blade and drive engaged. I just know nothing about these engines other than basic 2 stroke principle.

Thanks,

Eric
 

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Not 100% sure this is the issue, but I've heard of problems with the oil valve on that black plate between the carb and the block. Over time those have failed and it will then let too much oil in and cause the smoking. I thought I read about some people cleaning those with success, but I haven't done it myself.
 

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You should be able to find manual on line. You probably should have posted this in the regular walk behind section That's where most of the LB guys hang out. The 10591 has the best transmission and it will fit any of your models. It uses the standard toro rear wheel clutch and the wheels are readily available for cheap. But you have 4 of the regular Tuf Torq's so one way or the other you should be good!

On the oil issue, you can unplug the oil tank and just use 50:1 premix if you want. The oil valve is cheap from Toro though. I used a small shot of Sea Foam in my oil and eventually cleared it up?

Good luck and post photos. I bet you already know this but these are some of the best mowers going for quality of cut. It leaves behind some beautiful cut grass.
 

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Young Buck
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1,611 Posts
Discussion Starter #6
Thanks for the notes on the oil valve. Is it just a little ball valve in the brass tube through the plate?
 

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Young Buck
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1,611 Posts
Discussion Starter #7
So I am planning to hone one of the blocks and install new rings, and was wondering what Kind of sealant I should use. I think I have some Permatex ultra grey in my toolbox. would that work? I think i used it on a Honda valve cover with good results. also any rebuild tips on these would be good. I took the junk motor I had apart, and was pleased with how easy it was. It had a badly scored cylinder on the exhaust side, and the rings were fused to the piston. any carb cleaning tips for these mikuni carbs would be good too. I dont think I got the first one clean enough.
 

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Young Buck
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1,611 Posts
Discussion Starter #8
SO i got the Franken-M together today. IT has the deck and mounting plate off a 10590, the main engine components came of the third one i tore down looking for a good piston and bore, and the tins and the rest are a hodge podge of the best condition parts I could find on the other mowers. Had to make my own head gasket out of FelPro 2499 material as I couldn't find a new one except for one in the uk. So far so good. I had cleaned worked and polished the intake port, exhaust port, and head on wed. making sure not to change the port dimensions going into the bore. I only took out the casting imperfections I could get with my Dremel. I couldn't really get down into the transfer ports, so i didn't try. Thurs. I put the crank in the block with new bearings, new rings on the like new piston I found inside and cleaned up, and a load of white lithium grease on the oil pump gears. Today I painted the muffler I had previously burned all the carbon out of, and I assembled the mounting plate and BBC twice as I forgot to put the belt on the first time. from there it went together like cake. Took it out into the yard, which was wet from light rain, and started up second pull. Runs pretty good. cut the wet grass great once I slowed down from 3rd to 2nd, Need to adjust the idle screw as it surges, and also surges a bit without load. I did have to remove the governor arm, and even though I tried to match where it was I may need to pull the blade and put the tach on it I am running 50:1 premix for the first tank till the oilier catches up. any tips on carburetor tuning for these?
 

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JD318
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990 Posts
Wow, 5 M-series!!! What a haul!
I've only ever SEEN 1 M-series in my life that I bought off a guy, and then resold to clear out space in my garage. Never did get her running.
Good Luck--looks like fun.:thThumbsU
 
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