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Discussion Starter · #1 ·
I picked this thing up from my recently deceased grandfather's estate before everything goes to the auction, along with a Lawn Boy 5237 and a Murray 20.

Started working on it tonight. Didn't have spark so I started to pull the coil then saw that the wire coming from it went under the flywheel, meaning points under there. After cleaning them with emery cloth and putting it all back together I had spark. Thought for sure I could get it to run for a bit by pouring a little gas in the carb but no. It was spitting gas back out, and I could hear air hissing out of the carb on the comp stroke.

Then I put my hand over the mangled exhaust pipe (someone tried to remove it and now there's just a little nub so that's gonna be fun) and I could feel air coming out 2 different times per cycle so probably needs the valves lapped. Hopefully. Well I don't have a spring compressor or my valve lapping stuff here so that will have to wait, but it's pretty good progress for a couple hours on a Monday night.

Well anyway, here's some pictures, didn't see anything like it on an image search:
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That looks a lot like a Yazoo 24" cut high wheel self propelled walk behind mower that I used to have, only the roller drive system was in front of the rear tires.

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'81 Gravely tractor, 50's 60's 70's 80's 90's Gravely tractors Various Honda Power equipment
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It mite have tight valve clearance that need to be adjusted plus re-lap of the valves.
Those engine parts are hard to find now with the PTO drive like you have.
Do away with the points and install the electronic ignition, either a module kit or change the igntion coil.
Those old Hahn Eclipse were good on hills with their rear wheel drive traction when they are working right.
I have the one that drives the wheel axle instead of the 'Scrub Drive' so it doesn't wear the tires down and has excellent traction for steep hills.
 

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Discussion Starter · #4 ·
It mite have tight valve clearance that need to be adjusted plus re-lap of the valves.
Yes that's probably more likely why both valves aren't fully seating and I'll be doing that at the same time as lapping. At the very least it's an easy thing to check

Do away with the points and install the electronic ignition, either a module kit or change the igntion coil.
I did this on my 16hp cast iron Briggs single cyl, how do I know which one to get for this engine? The flywheel is a much smaller diameter so probably not the same one obviously
 

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Discussion Starter · #5 ·
That looks a lot like a Yazoo 24" cut high wheel self propelled walk behind mower that I used to have, only the roller drive system was in front of the rear tires.

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Yeah it does kinda look like the early Yazoos with the large diameter rear wheels. I'm surprised that I can't find any pictures of other Hahn mowers that look like this thing. When I really get into it I'll be on the lookout for a model number tag or something.
 

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'81 Gravely tractor, 50's 60's 70's 80's 90's Gravely tractors Various Honda Power equipment
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If you use the module kit you can use the same flywheel. The flywheel would only be needed in some cases when you install the different Magnatron electronic coil.
On yours, you might just need the coil. The only wire you would use would be the kill switch wire. Disconnect the point wire and let them go.
 

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Discussion Starter · #7 ·
This morning I had a little bit of time before going to work and decided to work on this a little more. First off the intake valve clearance was .009" and the exhaust was .010", both a thou over max respectively. So I went ahead and dropped the valves to have a look.
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The sealing surfaces were pretty rough so I just buzzed over them quickly with a wire wheel, I will lap them later but for now I just want to hear this run.
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And after a quick wire wheeling of the seats I popped the valves back in and did a compression test, 65psi. Not great but it should still run. Still wouldn't start. When I was cleaning the points they would barely open when turning the crank. I should have known that the gap would be way bigger than that but I just wasn't thinking clearly, thought maybe they were supposed to be like that. Well the spec is .020" so now I'm thinking if I just adjust that out to spec that it'll probably run at that point. Eventually I'll definitely do the points eliminator one way or the other but again, for now I just want to make sure it runs decently. Just a quick update
 

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'81 Gravely tractor, 50's 60's 70's 80's 90's Gravely tractors Various Honda Power equipment
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You might have to throw some new gaskets in the carb to fuel tank mount, clean it and you might be running again as long as you have spark again. Clean up the valves and adjust the clearance while you have it apart. Good luck with it and let us know.
 

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Discussion Starter · #9 ·
Still can't figure this out. I opened the points gap to .020" and figured with 70psi compression (now), and presumably (but probably not) good spark, it should at least start on a splash of gas, then I can move on to this carb/gas tank combo thing and get it sorted out. But no. It just didn't make sense. I pulled the plug and laid it against the head and it had what looked like good blue spark to me, and yet wet gas was coming out of the exhaust port.

Spark, fuel, compression, even the valves appeared to be timed correctly when I was turning it over with the head off. But then, as I keep pulling it in vain, here and there it would sound like it wanted to start. Then for some unknown reason, it did. And somewhat reliably too on its own fuel. I adjusted the carb a little and it ran a little better yet.

So then I mowed my postage stamp front yard with it, it did ok. Looks pretty good despite the blade not being freshly sharpened.

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But when I took it next door to some taller grass it struggled a lot. Ok fair enough, it's only 3.5hp. So I took it to some not quite as tall grass to try to get video of it mowing, it wouldn't even stay running when I engaged the blades.

At this point I think maybe it's got a weak coil? So top priority will be the electronic ignition, then I need to resolve the muffler problem and concentrate on fuelling. Maybe I'll even give it a paint job at some point.

Oh and I never did test the self propelled system on it, next time.
 

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Glad you were able to get it going,Looks like a pretty cool machine.Did you happen to look for a model number on it?
-Nate
 

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Discussion Starter · #13 ·
And no I haven't found anything yet, once I gave up tonight I went ahead and sorted out the Murray 20 to give to my mom. It was revving to the moon, turned out the throttle was just stuck. Runs really well.
 

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Discussion Starter · #14 ·
I got a little more free time this morning so I lapped the valves and checked the clearance, now they're both at the maximum spec.

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Compression is now 60psi. The head gasket is in decent shape but when you look inside the cylinder there's some carbon that goes below the top ring line, which I'm assuming means the top ring is either broken or stuck. So I guess I'm gonna pull this thing and tear it down to check on that, see if I can find some rings and gaskets and just do a quickie "rebuild" on it.

On the plus side I did extract what was left of the muffler pipe and have an NOS one on the way, along with a magnetron coil.

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I got a little more free time this morning so I lapped the valves and checked the clearance, now they're both at the maximum spec.

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Compression is now 60psi. The head gasket is in decent shape but when you look inside the cylinder there's some carbon that goes below the top ring line, which I'm assuming means the top ring is either broken or stuck. So I guess I'm gonna pull this thing and tear it down to check on that, see if I can find some rings and gaskets and just do a quickie "rebuild" on it.

On the plus side I did extract what was left of the muffler pipe and have an NOS one on the way, along with a magnetron coil.

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My neighbors had one of those and it lasted a pretty long time which if you knew the boys using it was a testament to how tough they are built!
 

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Discussion Starter · #16 ·
Well this escalated quickly
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The rings were fine though the gaps are a little big: top .030", middle .032", oil control .062". Once I had the engine removed and could get a good look at it it became apparent that the carbon I thought I was seeing was actually what looks like cylinder warpage or something. Looks like high spots where the bolts are. Or idk, I don't really know what to make of it. I couldn't even get the piston to come out from the top, the skirt is too big for some reason.

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Discussion Starter · #17 · (Edited)
I worked on this cylinder for a little bit tonight, just trying to roughly true it up. As I suspected, the top was all warped into a weird shape and there are some deep scores.

This shows how bad the ridge was and the initial high and low spots:
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At this point I've got it down to these 2 low spots and a couple pretty bad scores that I'm not sure are gonna come out:
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I'm gonna have to see what size piston/ring sets are still available for these. But I'm pretty happy with this progress.
 

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Are you using a spring-based hone doing that? If so, know they don't work great if the cylinder is out of round at all, as they take metal off all the way around (which you don't want) rather than just off the high-spots (which is desired). It needs to be done on a boring machine to get the cylinder round and even from top to bottom.
 

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Those shiny warped spots are 'Hot Spots' right in an area common with clogged cooling fins that usually cause that in those areas where the shiny spots are in the cylinder.
Then you figure how old that engine is and how long it was run with the clogged cooling fins to cause that. That mower was popular 40 plus years ago. That unit could be going on close to 50 years in age by now, I have a couple of them from new. They just sit in the garage now.
That engine used the camshaft driven PTO to drive the wheels. They haven't been produced in decades plus being the 'L' head engine, you can tell it is old and getting new parts for them will not be that easy due to its age.
I rebuilt one 15 years ago, the parts were hard to get then. I ran it for a few years and when it died, I just left it sit and let one of my older Honda's take its place.
They did have excellent traction for the steep hills I have, that's why I liked it.
The old Hahn Eclipse mowers were tied in with Gravely back in the 60's and early 70's, Gravely dealerships used to sell them.
The Hahn Eclipse mowers I have, have the Gravely name stamped on them with the Hahn name.
They were a good tough mower that were built to last and take a lot of abuse.
 

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Discussion Starter · #20 ·
Are you using a spring-based hone doing that? If so, know they don't work great if the cylinder is out of round at all, as they take metal off all the way around (which you don't want) rather than just off the high-spots (which is desired). It needs to be done on a boring machine to get the cylinder round and even from top to bottom.
Yes I'm using one of those spring ones with the 3 stones. I'm just trying to clean it up, I'll check it with a bore gauge and make sure it's not too bad before proceeding.
 
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