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TomC

Driveshaft Repair with Jury-Rigged Onan P220 Repwr

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TomC
Need Immediate Help. Issue: How best should the motor be sitting for best alignment of the drive shaft? I bought an AC 919H with a 48" deck both in great shape with new front tires for $500 (happy dance). It had been repowered with a 20HP Onan P220 that runs strong with no smoke and has good compression. I quickly found out why the good deal when the fiberglass driveshaft coupler disintegrated shortly after purchase. I should get some photos posted of the total jury-rigged cluster of a driveshaft install that the guy did to get it out the door. I just didn't think to look there. Allow me to list the infractions: * - The rubber compression coupling and the adapter plate assembly were reversed (I'm not kidding) - Rubber on the motor. * - The adapter plate ass'y holes had been drilled out over-sized for no apparent reason and it was bent. * - He had used different length bolts for opposing holes * - Most of the bolts were way too long (inches) * - Because nothing fit, he used (again, not kidding) no less than 17 EXTRA washers and over-sized bolts to fill all the gaps in the bolted connections. It was a crime against humanity. I'm really surprised it lasted as long as it did and didn't cause irreparable damage when it went (I shut 'er down fast and had to push the beast). I'm also glad the AC frame housing is about 1/4-inch thick there since right above that coupling resides my most important "parts", doncha know. But I digress. On the to problem. I got all the right parts delivered (yay! for Jack's Small Engines) and got ready to install. One thing I noticed was that the original drive shaft sat higher than my stock AC 916H, putting a bit more misalignment/torque on the driveshaft. I also noticed that he had shimmed up the motor (again, more washers) for no apparent reason. My repair manuals say nothing of shimming the motor up but I'm not a repower expert (though I may soon be with the 916H). Should the motor be shimmed? Flat on the deck? Shimmed up in the front only to help shaft alignment (seem to recall this is a "no")? Anyway, I throw myself on this knowledge center for recommendations about how to best approach this (and any other insights short of "get a new motor"). I need the tractor working for hay rides at our yearly Halloween festival. Thanks, Tom

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goatfarmer
I repowered a 3410 with a newer Briggs 11hp. I had to raise the motor about 3/4". Raising the motor with shims shouldn't be a problem.

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Nuzzy
Oooooff... B) At least the fiber disc choose to come apart now rather than when a bunch of people were around expecting a fun hayride! When I did my diesel repower of my 912, I got lucky and didn't have to shim at all. I did have to make a new coupler between the flywheel and fiber disc, but it was a straight shot. I'd get your drive shaft about where you know it should be and held temporarily in place. Then start eyeballing things and seeing how far out of alignment that particular motor is, and if there are angles between the motor and shaft that need correcting. I agree, shims should be problem if they are done correctly.

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TomC
This was the problem. The guy had put the shims in for no apparent reason. If anything, the motor is already a bit on the high side. I wonder if its okay to just shim the front up a bit to fine tune the alignment. Its too bad they didn't design these like other vehicles, with nice universal joints at both ends (like some of the nice repower sites have).

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Brettw
On a 919 I am not sure there even should be a fiberglass disc / driveshaft coupler. I believe that tractor should have the rubber coupler? Your jury rigging may have started there, if I am thinking along the correct lines?

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HubbardRA
Do not shim just the front! The engine crankshaft must remain parallel to the BGB shaft. Let the flexdisks do their job. There should not be any problems as long as you do not put tension on the flexdisk when you bolt them up. Release the set screws in the BGB yoke to let is float while tightening up the driveshaft bolts.

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TomC
Figured I post an update, it looks like this may have to be a new engine approach (but I haven't yet made that commitment). I got all the correct replacement parts, and the driveshaft assembly is around an inch too short with the motor back as far as it can go. Short of fabricating some robust spacer, I don't see how it will work. Open to suggestions though!

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Brettw
I just did a repower on a 7119 and had to measure to the center of the driveshaft from the frame pan where it bolts down to get the correct motor. It is approximately 6-1/4" to the center of the driveshaft measured from the mounting surface.

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PhanDad
Depending on engine there are different length driveshafts. What length driveshaft do you need? Maybe on is available, or you could have the exisiting one lengthend.

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Brettw
The old single cylinder engines driveshafts were a tad longer than the twins. About an inch I believe. I am sure some of us here have driveshafts, so place a wanted in the classifieds perhaps?

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