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Tractorholic
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I bought a couple MF-7s last fall. One ran, one didn't. The running tractor had been repowered to a larger Tecumseh flat head engine--they had to cut out the hood on the left side to do it, but I couldn't find a model number.

I changed the oil and put fresh gas in the repowered tractor and let my mom use it to mow her lawn around the house. She really likes it, it's small and has a sharp turning radius, and she can get to places on her lawn that her big GT18 can't. But the engine is tired--after running for about 30 minutes it doesn't want to run anymore. It also had a crack in the gas tank that left a mess on the ground whenever we parked it...

I could never get the other MF-7 to start--it gets spark, but when it's turning with the plug in it pauses for a moment every second turn--I tried all the usual things--cleaned the carb, put carb cleaner down the spark plug hole, etc. but no go... I even pulled the flywheel and cleaned and set the points.

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So, I finally decided to repower at least one of them.

I considered using one of the Chinese Clones, but I thought the 6.5 hp might not have enough torque, and the 9 hp models at HF didn't have electric start. Home Depot sells some Chinese closes as well as eBay, but I was generally looking at over $350 by the time I paid for freight, etc.

I finally found a brand new, never used Tecumseh OHM-9 OHV engine on a local classifieds. The guy wanted $200--a reasonable price I felt. I went over to look at it and took measurements--crankshaft diameter was correct (1"), mounting holes in the same place; heigth and width were okay... so I bought it.

I got it home, and discovered a few things..

1. The big wrap around gas tank stuck out too far on the left side; ditto for the square plastic air cleaner. The exhaust was okay as far as size, but it would have exited under the hood... not a good idea.
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2. The battery can be put back in it's original place, but there's no place for a fuel tank. One option for the battery would be to put it at the front of the engine below the carburetor. I know batteries give off explosive hydrogen gas when charging... does anyone know if this location would be a problem?

3. If I can't put the battery in front of the engine, it will have to share space with the fuel tank... The little red half gallon tank I used to break in the engine will just barely fit under the hood, leaving about 4 inches to one side--maybe enough room to put in a motorcycle-sized battery... whaddya think??

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Regards,

Utah Smitty
 

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Proud to be Deplorable
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Smitty, I think the best place for the battery would be up by the tank. Less because of gasses, and more because of heat buildup right in against the block like it would have to be if it was up front.

As for capacity, a mc battery should have more umph than needed, the Tecumseh should have compression release anyways.

The exhaust reroute should be pretty easy... If the block is threaded. If not, you'll need to make an adapter to get to standard pipe.

Good find on the engine, I'm sure it'll do Mom a good job.
 

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Nice find on the engine Smitty. It's hard to find good vertical cylinder horizontal shaft engines these days. The new ones tend to be the Honda style slant cylinder arrangement which is a totally different shape than what is needed. I have an MF8 that need an engine as well. There are a lot of cheap snowblowers around this time of year that are a good source of 8 and 10hp Tec hm engines. I bought one the other day for 100$ with a nice non smoking hm80 on it. Good luck on the re power.
 

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Tractorholic
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Well, I got the exhaust adapter made and put a can-type muffler on it. Here's how it looked before:

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The original muffler openings were toward the grill and I didn't like the exhaust exiting under the hood. I decided to make an adapter and put a 1" screw on muffler out the side.

I started by making a flange for the exhaust port out of 1/4" HR plate. I have a 1" metal hole saw, so it was faster than drilling a bunch of holes in a circle, breaking out the middle, then filing it smooth (which is what I did on my first attempt before I remembered the hole saw!!)

I laid out all the holes first, then drilled pilot holes for the hole saw drill bit, and the two bolt holes.

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I also had originally planned to use just a 1" nipple cut off at one end so it was only about 1/2" long, but it was too short and didn't leave enough room to put the bolts in.

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I beveled the the hole so that it lined up exactly with the 1" pipe, then tacked it on the inside to hold it while I welded the outside.

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As you can see, my welds are always neat and tidy... NOT!!
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The bolt holes are pretty close to the port opening, so I ended up having to use socket head screws on them.
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Here's the end result:

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I used copper-based anti-seize on all the threaded parts as it's good to 1800 degrees. As you can see, it clears the lower edge of the hood, but doesn't project too far out and risk burning someone.

Now I have to figure out how to adapt the air cleaner. The factory model juts out to far on the side and keeps the grill from being installed... Even with it off, the bore to the carb is pretty close to the inside of the grill--there's a couple screws sticking through the grill that make it more challenging as well. I thought of making another adapter and putting a round air filter on it in front of the engine, but things are a bit tight and I'd have to put a 90 degree bend...

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Anyway, any suggestions are sincerely appreciated...

Utah Smitty
 

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Tractorholic
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What are you going to do with the old engine Utah? I need the bracket on the the top that holds the throttle cable all the carb linkage, rods and govener rod ect. May be interested in the shroud also. If you want to part out some of the old engine give me a shout thru e-mail here on the sight.
 

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What are you going to do with the old engine Utah? I need the bracket on the the top that holds the throttle cable all the carb linkage, rods and govener rod ect. May be interested in the shroud also. If you want to part out some of the old engine give me a shout thru e-mail here on the sight.
I'm in need of the linkage from the governor arm to the carb if you're interested in parting this engine out. I need everything but the bracket that's welded to the tinwork. Screws, brackets, linkage, springs and all.

New member here, great place from what I've seen so far.

Thanks

Mike
 

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Tractorholic
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Well, I've moved along on the repower... finally got the airfilter situation solved by making an adapter flange for the carb with a piece of 1" ID pipe welded to it, then used an elbow on a 1" Diam. radiator hose to mount the aircleaner up above the carburetor.

Now my problem is hooking up the electrical. The new engine is an OHM 90 with electric (12V) start. There is a kill switch on the fan shroud, and a 4 position spade-type connector with two wires--red and green, running from the back of the shroud by the starter. I started the engine and tried to measure the voltage from the wires but only got a couple volts when measuring DC, and about 26 volts measuring AC.

Does anyone know what the voltage output on this engine is and how I would adapt it to the MF7 wiring harness? The engine is a Tecumseh OHM 90 222302A--I'm kinda stuck...

Thanks,

US
 

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Ask Pat (Amigatec)! He helped Ray with his Cummins thread!
 
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Tractorholic
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On my Tecumseh "Formula" engine, the two wires appear to be for a remote kill switch. I think I used the green wire to go to the ignition switch which grounds out to the frame to kill the ignition. It also appears that if the red and green wires are shorted, then it also kills the engine. I THINK that if there is any charging coil it outputs to where the battery cable wires onto the engine. I do remember making the same tests you did because those wires appear to match the the original engine wiring harness. I got pretty much the results you did, and when I hooked those wires to my voltage regulator, the engine ran VERY rough, which it had not before.
 
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Tractorholic
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Discussion Starter · #11 ·
On my Tecumseh "Formula" engine, the two wires appear to be for a remote kill switch. I think I used the green wire to go to the ignition switch which grounds out to the frame to kill the ignition. It also appears that if the red and green wires are shorted, then it also kills the engine. I THINK that if there is any charging coil it outputs to where the battery cable wires onto the engine. I do remember making the same tests you did because those wires appear to match the the original engine wiring harness. I got pretty much the results you did, and when I hooked those wires to my voltage regulator, the engine ran VERY rough, which it had not before.
I think I got it figured out...

The green wire is to kill the magneto like you said, the other wire goes to the battery post on the solenoid to charge the battery, etc. According to the Tecumseh Service Manual (which I found under the Manuals Section) the alternator has to have battery voltage to work.

I removed the fan housing, and discovered that there are also 2 yellow wires that go to a rectifier-- only the red wire comes out. I figure if I hook the green up to the "D" Terminal and the Red to the Battery side of the starter solenoid, I can probably bypass the Voltage regulator altogether... we'll see.
 

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Tractorholic
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Discussion Starter · #12 ·
Another question, which actually applies to all belt drive situations. There are a number of metal "fingers" approx. 3/16" diameter that are placed over a pulley, etc. Are these just to keep the belt from slipping off?

Also, when I ran the engine on the other frame I had, it took a long time for the transaxle pulley to quit spinning after I put the clutch in... is there something that helps to slow this down, or is it just because the tranny is worn and everything's loose?

Thanks in advance...
 

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Tractorholic
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Hi Smitty,
On my MF 8, the fingers seem to serve two functions. One is to help hold the belt in place, but the other is to help stop the belt. I found that if I tweaked the guide finger on my idler/clutch pulley so that it engaged the belt when the idler wheel loosens the belt, then the whole assembly stopped much faster.
 
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Discussion Starter · #14 ·
Thanks, Howard... I wondered if they worked like that--I'll have to finesse the one on the idler clutch pulley. It looks like if it was a little to the rear, it wouldn't drag when the transaxle was engaged, but would tend to snub the belt when the clutch was pushed in.

Regards,

Steve
 

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Tractorholic
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Well, I hooked up the wires from the engine to the harness and everything works fine. I hooked the green wire to the "S" on the key switch. It connects to ground when the key is off, which grounds the magneto and stops the engine. I hooked the red wire to the battery side of the solenoid, which supplies nominal 12V to charge the battery.

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The magneto on the engine had to have current from a battery, etc., before it would generate power.

Thanks for all the input on this...

I've continued to work on the tractor and will post pics shortly.
 

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Discussion Starter · #16 ·
Well, I've pretty much got the repower done. I test mowed my lawn last night and it appeared to work fine, except the engine only runs at one speed, regardless of where I put the throttle lever. It's moving the lever on the engine, but the governor holds it in one place... I'll have to look into that a little more.

One picture I didn't show previously was the running of the extended oil drain lines.

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After I got it bolted down on the tractor I discovered I really didn't need the two elbows--I could have just run the 1/4" pipe straight from the engine to the front, then elbow it down and cap it.... oh well!!

Anyway. After I got the charging circuit hooked up, I went to work on mounting the fuel tank, battery, and air cleaner--pretty much in that order.

I decided to use the OEM tank but mount it up where the battery used to go. There's just enough room to clear the hood.

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I measured the from the inside of the grill to the front of the engine--enough room for a lawn and garden type battery with about 1 1/2 inches to spare. I figured if I made something to help isolate the battery from engine heat, I could probably use it there.

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So, I started in earnest on the fuel tank. I used the original straps, and the original shutoff valve. I bolted a couple pieces of 1 1/2 x 3/16" angle onto each side of the battery box for a "shelf" for the fuel tank. I used a piece of corrugated plastic from a yard sign as the shelf--it will also help insulate against heat. I had to notch out one shelf to allow for the shutoff valve.

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I mounted the tank and hooked it up, then fired up the engine using the pull starter-- SUCCESS!!

On to the air cleaner assembly.

The original air cleaner was too big and interfered with the mounting of the grill--even with the POs butchering job...The muffler just barely fit under the hood, but the exhaust exited to the front of the engine--putting a lot of hot exhaust under the hood.

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The hood also interfered with the engine shroud--fortunately the previous owner solved that problem for me by notching the hood.

For the air cleaner, I used 4 1/2" electrical cover plates to "sandwich" the air cleaner between them. The air cleaner is a 5" diameter unit I picked up from the local O'Reilly Auto Parts (Formerly Schucks/Kragen/Checker). I think it cost about $6.00. I found a 1" ID radiator hose with an elbow in it to make the bend from the horizontal inlet to the carb to the vertical inlet to the air cleaner.

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I measured for clearance for the sealing part of the air filter, and cut a hole in one of the plates, then welded a 1" diameter pipe onto it. I drilled two 1/4" holes in the plate just a little offset from the center of the air filter, and bolted two pieces of 1/4" all-thread to the plate.

I drilled two corresponding holes in the other plate for the top piece and my air filter assembly was complete.

I had intended to have the aircleaner sit horizontally and above the carburetor. However, the edge of the air cleaner interfered with the edge of the hood. I could have just tilted it over, but it looked real tacky, plus I didn't have something I could brace it with. I set it aside to work on something else while my mind ruminated on the problem...

Another problem I had is that the choke lever on the carb stuck way out to the left side of the engine.

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The previous owner had already butchered the left side of the grill to make room for the H80 engine he used to replace the original H70. I bought a longer cable to go from the dash lever to the choke, with the cable housing running along the left side of the engine, and shortened the lever and redrilled the hole two different times, but I still couldn't open the choke lever.

I finally re-routed the cable along the right side and front of the engine, and cut off the first bend of the choke lever and redrilled it. Now it works!!

I had to make a bracket to hold the clamp--fortunately there is a strategically-located bolt that held on the original muffler guard in just about the right place.

Now back to the air cleaner housing. I was concerned that the metal of the cover plates might be a little thin, so I bought two more plates and started looking for a spot welder to double them up on each side--thus making them stiffer.

I had seen the spot welders at Harbor Freight, but wasn't too impressed with them. The biggest problem I saw was that the tips were really sloppy and didn't line up with each other. However, I had read some good reviews on this forum and elsewhere, and they were on sale at HF so I decided to buy one. Just as I was about to leave for the store, something prompted me to look in the local online classified ads. Lo and behold!! Someone had a 110V version for sale in practically new condition for $60--about a third of the sale price at the store.

He was an hour away, but I jumped in the truck and beat feet to his home. Turns out he had a business building hydrogen generators and had bought the welder for some fixturing he had. He had some neat products, many of which were in production... for use in automotive and home generator applications... cool!! but I digress.

I got the welder home, and it had the same problem with the arms and tips having too much slop in them... I finally found a cheap solution for this, which I'll share in another post.

After welding the stiffener plates I felt much better about the air cleaner housing though it was a bit heavy.

I finally decided to mount it with the filter in a vertical position. This required finding yet another radiator hose with a right hand elbow and a "zag" in it to place it above the engine... for those of you that don't know, a "zag" is a technical term for the second half of a "zig-zag". ;o}

I still needed to brace it with something. I had some heavy gauge (16 ga or so) galvanized steel, so I sketched out a bracket that would attach the the side of the grill on one side, using two existing carriage bolts. The other side bolted to the bottom plate of the air cleaner.

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To bend the bracket, I used a nifty little tool that I bought at Harbor Freight years ago. It's like a press brake die, but has an angle bracket with magnets that attaches to a large vise. You position your part between the two dies and turn the vise handle in... Mine is 6" wide, and made from two 3" segments. I believe you can get wider units as well...

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An added benefit was that the bracket also acts as a heat shield for the air cleaner and the top of the battery.

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In mounting the battery, I used a piece of 1/2" CDX plywood and covered it with yet another piece of corrugated plastic. I ran two pieces of all-thread along each side, and secured the battery to the wood with a piece of angle under the wood. The wooden platform also bolts to the center bolt by the grill... it appears pretty sturdy--time will tell.

I bought a piece of 6 ga electrical wiring for the positive battery cable. I routed it to the battery terminal of the start solenoid--using plastic wire loom where it runs close to the engine block. A piece of corrugated plastic placed vertically between the battery and engine helps insulate the battery from engine heat.

I put the grill and hood on the frame--it fits close enough that the hood latch works...

Not especially pretty, but definitely functional...

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I love the sharp turns and easy handling of these little machines... I only wish I had a hydrostatic drive rather than the manual transaxle, but it will do nicely just the same.

Regards,

Utah Smitty
 

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Wow, US! A lot going on in that post! Glad you found the hose with the "zag", I usually find the "zig" and it won't work.
 
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Tractorholic
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Discussion Starter · #18 ·
Wow, US! A lot going on in that post! Glad you found the hose with the "zag", I usually find the "zig" and it won't work.
LOL!!

Well, I'm glad it's done. Now mom can mow her lawn with it instead of the big Sear GT18 she has...

Thanks for you insights and help.

US
 

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If Mom's happy, everybody's happy! Did you get the throttle figured out?
 

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Excellent! Those little tractors are great, very nimble as you say. My biggest problem is getting my long, heavy self folded up on the seat!
 
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