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1928 Moto-Mower


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#16 jtrojek OFFLINE  

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Posted September 14, 2016 - 06:49 PM

I had five minutes so I ran out to the garage today. Doug, I grabbed that picture of that little bracket for you. I then got the flywheel off and was able to take a look at the magneto. The points are dirty and not very well aligned. I guess I'll clean the points, try to align t points better and gap it. It also looks like someone was doing something or other in there at some point. I should do something about that electrical tape. Does anyone see anything that is definitely not right? Given the way other things were put together incorrectly, I wouldn't be surprised if something is wonky here too. What's that flat looking pin for that I'm pointing at? I want to make sure everything at least looks good before I put it back together and check for spark. I want to take this apart as few times as possible so any insight/advice would be appreciated.

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#17 DougT ONLINE  

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Posted September 14, 2016 - 07:34 PM

The points look they have too much gap for sure. the tape doesn't scare me, just make sure the wire isn't grounded out where it goes around the insulated point piece. You could ohm check the secondary side of the coil. You should get something in the 5-10K ohm range.  You would have to remove the condenser wire to test the primary side of the coil. With the points open it should read around 1.4 ohms. If you get down around .7-.8 you will have problems. If you are pointing at the pin that holds the point spring, that is its only function.



#18 jimmy G OFFLINE  

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Posted September 15, 2016 - 12:20 AM

I think that tab is for holding the points straight wile tightening (looks like someone didn't use it) I'd look close at that solder joint

#19 jtrojek OFFLINE  

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Posted September 17, 2016 - 01:48 PM

Thanks for all your advice so far. Today I filed the points, cleaned them and gapped them. Now I have a strong, healthy spark. I just have to pick up a new spark plug wire end, clean the carb, finish re-routing the throttle cable and linkage, and properly mount the decompression valve bracket. I'm getting there. Regardless, today I was happy just to see a good spark. Now it' back to family time.

#20 crittersf1 OFFLINE  

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Posted October 05, 2016 - 02:59 PM

Tom & Jerry used to chase each other around with one of those


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#21 jtrojek OFFLINE  

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Posted October 10, 2016 - 03:39 PM

I think a Tom and Jerry Moto-Mower chase sounds like a great idea for a display at the shows. Your comment made my day. I finally cleaned the carb and got it back together. I gave it a yank and it started on the first pull. It ran okay, but not right, and I noticed some other things that may explain why. First, that nut would appear to keep the decompression valve from being decompressed (see picture). Maybe that's for good reason, maybe not. Given the other things on the mower that were assembled wrong, would I be running any risks if I took that nut out of there to see what happens? Now that I reoriented the little bracket over the pin for the valve, I'd like to be able to use the decompression pin to shut the engine down, which if I understand it correctly is what I'm supposed to do. Is this reasonable? Am I missing something? Should I be aware of something before trying it? Second, when it was running, it looked like fuel was spraying back out the carb where the air filter should be. Also, after it ran for 20 seconds or so, it started smoking somewhere around the spark plug, almost seeping from somewhere around there but I can't tell where. Then, I was looking in the manual and saw that the valve clearnce nut needs to be adjusted so there's a little play between it and the lifter. I think there's way too much clearance on the engine, if that's the case. There must be 1/8"-1/4" clearance (see picture). I suppose this means that the exhaust valve is not opening all the way. Is that probably true? If that's true, is that likely why I had exhaust seeping from somewhere or other that wasn't the muffler, because it couldn't escape properly? Is it also possible that the fuel (or whatever it was) being blown back out the carb air intake was due to the exhaust finding another place to escape? I've never had an engine designed like this before and have a lot to learn, so I'm just guessing. Feel free to laugh at me if my theories are completely out to lunch. Should I then set the clearance so there's just a little play and see what happens? I don't want to wreck something if I can help it, much like the decompression valve. Lastly, how do you properly adjust the nuts on the springs that go from the driveshaft to the sprocket (see picture)? How tight should they be? After cutting two feet of lawn they let out and it didn't drive. I assume there's a proper tension that they should be adjusted to, probably something more than finger tight (which is what they were, probably not even) Well, those are my next three questions. I think it will run well though once I get this figured out. It has good compression and wants to go. Just needs a few more bugs ironed out. So far I'm pleased though.

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#22 DougT ONLINE  

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Posted October 10, 2016 - 10:53 PM

The nut on top of the valve cage is wrong. Seems there should be a heavy seat washer in there. The parts breakdown should show it. You need something to spread the force across the cage instead of having the decomp bolt pressing right on the center of the cage. That bolt has to have enough force to make the cage seal but not so much that the yoke breaks. (common mistake, tight's tight and too tight's broke) I can't remember for sure but it seems there should be copper sealing rings on the top and bottom of the valve assy itself. If compression is bypassing the valve it will spit back through the carb. Seems most of these do spit a little. It doesn't take much to push the decomp pin down. Make sure that lever doesn't hold the pin down a little.

 

The exhaust valve should close just as the piston passes TDC. You can use a plastic carb clean snout or something similar to feel the piston through the plug hole. I use the valve adjustment to fine tune that. As long as you've got some gap and the valve closes right, you should be OK. The intake valve is operated by engine vacuum so exhaust pressure in the cylinder is more likely to keep the valve from opening right than to let pressure out the intake. Another thing I've run into with these engines is the the exhaust valve spring will get weak or loose as the valve sits deeper in the seat and it will let the valve float when the engine is running. Take a screwdriver and hold pressure down on the valve with it running and see if it makes a difference. A sloppy valve guide can also let exhaust smoke out.

 

The spring loaded bolts are a slipper clutch in case something gets caught in the reel. If you are going to use the mower, they should be on the stiff side. If it's just for show maybe a little looser would be safer. don't think I've ever seen a manual for the mower with any kind of a spec. Seems that they were wired to keep them from backing out. Do the bolt heads have holes drilled in them?






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