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Bush Hog JBI Alterations

2K views 0 replies 1 participant last post by  olcowhand 
#1 · (Edited by Moderator)
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This is around a 1972 Bush Hog JBI. It started life with a 14hp Briggs, but OE engine was gone and I decided to boost the power just a tad.

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Here she is as I bought her, w/12hp Briggs installed. I also altered/added a few other items. It could come equipped with optional rear power-take-off, but unfortunately, this one has none. 3 point lift was standard. I got the belly mower deck, but opted not to use it, as it is rusted through very bad, plus my mods prevented it. This is the only garden tractor I have seen that your feet fit inside the dash tower. The left pedal was to engage the front pto to the mower deck. It will serve a different purpose before I'm done. Right pedal is hydro control, plus a lever on right fender box will also control the hydro.

First item of business was an engine upgrade. I had a Wisconsin TJD engine off a Yazoo mower I bought off ebay for only $100. The engine had a fresh rebuild, new pistons, rings, and rods. She ran like new. The engine barely fits, even with notching the frame a bit on the right side for flywheel cover clearance, but she ended up fitting like a glove.

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The Wisconsin's stator was burned out & expensive to replace. I opted to add a small Honda car alternator I found at a small junkyard up the road. $20 for the alternator with built in regulator, so about $150 less than new OE stator & regulator. I had to machine a cast pulley to fit the shaft as the Honda used a serpentine pulley. Then I had to machine a pulley off an MTD mower deck, then drill & tap holes in the cast double pulley on the Wisconsin so I could bolt the MTD pulley to it. Mounted the alternator outboard to a bracket I welded to the frame rail. Works great & is a 40 amp alternator for more power.

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Next came adding a rear power takeoff. I had to build from scratch the entire shaft system. I had a pulley that matched the double pulley in the above right pic. So I had to put together a bracket to bolt two pillow blocked bearings to hold the stub shaft with the matching pulley mounted on it.

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I already had a used universal joint for the lower shaft (above pic), so then bought rectangular shafting & shaft tube from TSC, plus the rear universal joint to build the rest of the shaft to go back to the reversing gearbox at the back. I ended up with severe run-out of the shaft at higher speeds, so had to put a bearing midway back to prevent the run-out. The rectangular bearings are not available, so had to machine a steel bushing to fit snug on the shaft, weld to the shaft, then use a std pillow block bearing for support.

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With the engine rotation, direction of rotation wouldn't match for my Massey tiller I wanted to use with this tractor, so had to scrounge up a reversing gearbox. A guy on Machinebuilders.net had a gearbox he had offered to another guy a few days before. I asked him if the guy took him up on it & he hadn't. He then said he'd take $20 plus shipping! I even told him it was worth way beyond that price but he didn't care....said he got it cheap, so he'd pass it on. So I said ship that thing & used Paypal to send him payment plus shipping, and I added extra. It worked perfectly! I had a part of a pto output shaft, so I cut it to length, the cut a keyway, I slipped into keyed hold in lower part of gearbox. The input on the gearbox was a 1" keyed stub shaft, which the rear pto shaft's universal slips right on.

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Notice the removable hitch.

Left pic below...needed to re-weld and add gussets as this was a weak spot. Center pic is where I had to torch hole to mount the gearbox. Last pic shows reinforcement added to where rear lift cylinder attaches. Mount plate had been pulled back at least 1 inch.

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So it's time to build belt engagement parts for the rear pto. The left pedal used to engage the front pto that drove the mid mount belly mower, and since I removed the front shaft assembly, I used the cable from that pedal to engage the rear pto belts. In the pic, the cable isn't installed yet, but the cable comes out of the front of dash tower, then around the pulley mounted to chassis rail, then over to the tension pulley arm. The foot pedal has a factory lock to hold it down. You fully press the pedal down, pull what looks like a choke cable on dash, then the lock is disengaged & allows the pedal to come up, allowing cable to slack & tightening the belts. This works great because to quickly turn tiller off momentarily, you just press the pedal...no need to lock, then let off pedal & till away.

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The steering column top plastic bushing was completely

shot, worn too much for a bushing insert, so I turned one from aluminum,then inserted a bushing.
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In stock form, the fuel tank sat behind the grill, but with this huge engine, it had to be relocated. The right fender box WAS the battery box, but the fuel tank was a better fit in the right box than the left, so moved battery to left box & put the fuel tank in the right side. I also use an electric fuel pump mounted under the dash.

You can see the battery cables snaking up through the pipe. This box swivels out for easy entry to the tractor seat, so the pipe made a perfect way to run the cables.

One fender box lid was missing, so I made one to match.

In the first pic below, you can also see the controls for throttle, hydro, and 3 point lift.

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I also had to raise the hood & dash to give clearance for this engine's spark plugs. You can see in following pic that I simply needed to drill a higher set of holes to raise the dash assembly. The same worked on the hood with the grill.

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The taller engine also raised the driveshaft to where I had to torch out a slot for driveshaft to clear the tunnel at the floorboard. I fashioned a cover to conceal this, but no pic of that.

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I believe I've covered most of the mods now, so on to the painting. I used Massey Red, with acrylic enamel "Wet Look" hardener. Black is just std enamel with hardener also. Didn't take pics of black parts.

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Here she is with new tires all around and new paint, plus the decals I made myself. I love this tractor! The exhaust is stainless milk pipe with a baffle slipped in, and sounds awesome! I do plan to do one more thing later....add power steering, but that can (has to) wait.

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