1985 Bobcat 743 Rebuild

1985 Bobcat 743 Rebuild

Postby Tony » Fri Apr 25, 2014 12:11 pm

I bought a "lightly" (2300 hours) used 743 (serial 5019-M-12xxx) at an equipment auction mainly for use around the house. Based on loose web research, it seems to be a 1985 vintage and I've been assuming it is a Kubota engine (based on looks and color). The manual seems to indicate that only a Kubota went in the 743, while the 742 got the Mitsubishi. Until I pull it out, I won't know for sure I guess. It came with one accessory (backhoe), so I'm hoping to locate a loader bucket for a good price. I have a pallet fork setup from a forklift I plan to fab up as a bobtach accessory. Maybe get an auger some day.

Before picture:

[center]Image[/center]

Anyway, the plan is to strip it down as much as possible (without getting too anal) and sandblasting/repainting everything. Sticker kits are available on eBay for a reasonable price. I'll probably get a portable media blasting setup from Harbor Freight, something like this would probably work. I don't need to take the whole thing down to metal, just remove a layer of grime and rough the paint to get good adhesion on my repaint. Any suggestions on blasting media? Sand, Aluminum Oxide, Walnut shell, glass? What about paint and method? I was going to use the highest grade of rattle can I can get. Something with a rock hard finish and high durability. Is that asking too much from a rattle can? Should I consider wheeling the chassis down to the local autobody shop and having them hit it a couple coats of auto paint?

I'm going by the Bobcat place in the morning to pickup a full set of filters (air, oil, hydraulic). Probably use Rotella oil for both engine and hydraulic. Manual suggests 10w-30 or 10w-40 for hydraulic. I'll probably use 10w-40 for both (engine and hydraulic). Manual says 9 quarts for the engine and 6 gallons for the hydraulics. This model seems to indicate a chaincase and I'm sure its probably never been replaced. That's another 32 quarts. I assume 10w-40 will work there as well.

First effort is to get it running smoother. It started with great effort then died almost right away. When I went around to pour some fresh fuel in I noticed it had no gas cap. Good chance the tank (and now the injection system) is full of water. So now I have to find a gas tank drain (or removal) method and sort that out. Manual shows how to bleed the fuel system, but not remove the tank.
Last edited by Tony on Tue Sep 09, 2014 8:38 am, edited 1 time in total.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Fri Apr 25, 2014 5:41 pm

I managed to get by the Bobcat place Wednesday and picked up all the parts and fluids to get the engine humming along.

[center]Image[/center]

I also managed to get my cab tilted back and saw I have the mark of the "hidden filter".

[center]Image[/center]

I got my gas tank removed, cleaned, and put back in place. Put a couple gallons of fresh diesel in and it started right up and runs wonderfully! Smooth, quiet, no smoke at all.

While it was on the trailer, I was going to maneuver around and attach the backhoe to the bobtach. It was removed before being loaded on the trailer. While I was navigating, I suddenly heard a huge racket under the seat, like ball bearings in a blender, and I no longer had hydraulics. So I dropped the rpms and pulled the shutoff. I don't see any fluids leaking, so I suspect my output spline on the engine gave out or slipped off the main pump input. I guess that's my next step. Read up on how that gets fixed. Most likely I'll be pulling the engine out. I may wait on the oil change and coolant flush until that's done. I would likely lose both in the removal.

While I was down, I went ahead and started pulling components off to prepare for re-painting. I removed the right-side rear backhoe stabilzer fine, but when removing the left-side one, the tensioning bolt broke. I wasn't using a breaker bar or anything, just a plain ol' short open face wrench. Must have been fatigued with rust.

[center]Image[/center]

Anyone have a spare one laying around for cheap?
Last edited by Tony on Tue Sep 09, 2014 10:25 am, edited 1 time in total.
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Re: 1981 Bobcat 743 Rebuild

Postby wbecker » Sat Apr 26, 2014 7:47 pm

Sounds like you might have a broken Universal Joint. It's between the engine and the hydrostatic pump.
I just pulled my engine to replace a rusted out hydraulic tube and found my U Joint in critical condition.
How do I add a picture? I tried, upload attachment, tried to add the picture and got message that it's too big, but I had it resized to 800X600, ?
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Mon Apr 28, 2014 7:48 am

Thanks for the response!

wbecker wrote:Sounds like you might have a broken Universal Joint. It's between the engine and the hydrostatic pump.

That's kinda what I was thinking as well.

How do I add a picture? I tried, upload attachment, tried to add the picture and got message that it's too big, but I had it resized to 800X600, ?

It'd be great to see your picture. I think there is a 2MB per attachment limit. Is the picture larger than that?
Last edited by Tony on Tue Sep 09, 2014 10:26 am, edited 1 time in total.
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Re: 1981 Bobcat 743 Rebuild

Postby wbecker » Mon Apr 28, 2014 8:17 am

I tried again, no message but still no picture, it's only 158KB. What do I do?
What I did is click upload attachments/browse, found the picture/clicked add the file, nothing happens.
Bill
Attachments
U Joint.JPG
U Joint.JPG (156.91 KiB) Viewed 25464 times
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Re: 1981 Bobcat 743 Rebuild

Postby wbecker » Mon Apr 28, 2014 8:28 am

Well, I see it worked.
I removed the engine to replace a leaking hydraulic tube that is in front of the engine, the tube was rusted out.
That's how I found the U Joint was bad.
Attachments
IMG_9798 (Copy).JPG
IMG_9798 (Copy).JPG (114.86 KiB) Viewed 25464 times
IMG_9803 (Copy).JPG
IMG_9803 (Copy).JPG (169.98 KiB) Viewed 25464 times
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Tue Apr 29, 2014 1:14 pm

Excellent reference pictures wbecker! Thanks for posting them.

I'm hoping my Bobcat isn't that rough in that area. Looks like yours sat outside and was run hard.

Once I clear enough room in my shop, and get my engine crane out of the back, I'll get things moving along. The engine removal procedure looks very straight-forward.
Last edited by Tony on Tue Sep 09, 2014 10:26 am, edited 1 time in total.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Tue Apr 29, 2014 2:32 pm

HanSolo wrote:Here's an idea of what a broken u-joint did to my 843... Image


Based strictly on sound, I wouldn't be surprised if I don't have the same situation. I'm thinking my u-joint shrapneled and it's bouncing around inside my fan cage.
Last edited by Tony on Tue Sep 09, 2014 10:26 am, edited 1 time in total.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Tue Apr 29, 2014 2:41 pm

antfarmer2 wrote:You can get the ujoints from loadersourceparts for a hundred bucks but watch the bolts I had to get four shorter ones to keep it from binding easy to miss make sure you use blue locktight good time to pull the rad and oil cooler to clean and makes it a one man job to put the engine back to line up ujoints pull the shroud for cleaning and cheak metal lines I replaced the two that cross at the bottom and the one in the shroud they will bite you latter

Good suggestions. My local Bobcat dealer said the u-joint from them is about $100, but they have to order it. I'm waiting on a call back for that pricing.

antfarmer2 wrote:you can try it your way but I have done it and gave you my best advice it's not that hard and you can take out the rad oil cooler and steel bracket with muffler out in one piece but there are two nut's kind of hidden on either side to the cab then you can take apart for cleaning and get a cherry picker in there then put the engine back in by yourself

I always like to look at all the angles. Your suggestion of removing the engine seems to be the best choice. Besides, I should check other things while I'm digging around under the hood.

antfarmer2 wrote:the other way is to lay on the hydro pump and guide the ujoints on while someone else pushing the engine in while crushing your hand

:lol: That's the way I usually do things. Whatever will generate the most pain or expense for me... sometimes both.
Last edited by Tony on Tue Sep 09, 2014 10:26 am, edited 1 time in total.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Thu May 01, 2014 7:38 am

HanSolo wrote:In my case the damage was contained to the flywheel fan blades, the shroud and one metal hydro line. And the input shaft on the rear pump was broken. I was lucky shrapnel didn't penetrate the cooling coils.

Image

Image

Image

Image
Last edited by Tony on Tue Sep 09, 2014 10:27 am, edited 1 time in total.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Tue May 27, 2014 10:22 am

I finally had a chance to spend some more time on my Bobcat.

I got everything ready to pull the engine, disconnected all tubes, wires, and linkages, but I couldn't loosen the engine mounting nuts. I first tried a big breaker bar, but that didn't budge them. I grabbed my crappy air impact wrench, but even that wouldn't budge them. The next step is to borrow (or buy) a better impact wrench. Mine only does 250 ft/lbs, which I would have thought to be adequate. I might try putting a torch on the bolt, but that might be tough without heating the nut. I would just trailer the whole mess down to the Bobcat place, but I'd really like to clean out the engine bay while the engine is out. If I have the shop do it, they aren't going to bother.
Last edited by Tony on Tue Sep 09, 2014 10:18 am, edited 1 time in total.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Mon Jun 02, 2014 10:49 am

Okay, had another chance to dig into my Bobcat. I upgraded my impact wrench to a 700 ft/lb model and the engine mounting nuts came right off. In fact, the impact didn't seem to have much of an issue at all. I got the engine pulled out and sitting on one of my lift table carts. It's very dirty in the photos, but I've since pressure washed it and it looks great...

[center]Image[/center]

It turns out my yoke joints are in great shape. They move freely with no play or grinding. However, the splines in the yoke are about as smooth as you can imagine...

[center]Image[/center]

I'm not even sure how they got this bad. After the Bobcat starting slipping, it's like it was run for lengths of time just to round things off nicely. The spline adapter on the hydraulic pump is just as bad...

[center]Image[/center]

I pulled my yoke off so I could bring it to the Bobcat dealer in case they have a question regarding shape, size, whatever. I was going to pull my spline adapter as well, but I wasn't sure how to get it off. I assumed it was simply a "sleeve" that went over another splined shaft with a single bolt in the center that holds it on, but I couldn't seem to budge it. I couldn't get a good grip on it, so maybe it's just wedged on there well. Maybe I just need to get more aggressive with a gear puller or something.

I'll go by the Bobcat dealer today to get pricing information. I hope that piece isn't expensive.
Last edited by Tony on Mon Oct 06, 2014 7:31 am, edited 2 times in total.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Mon Jun 02, 2014 11:06 am

antfarmer2 wrote:You can get the ujoints from loadersourceparts for a hundred bucks

I was able to Google for them... I assume you mean http://www.loaderpartssource.com/


watch the bolts I had to get four shorter ones to keep it from binding easy to miss make sure you use blue locktight

I intended to use the original four bolts. They appear to be in fine shape. Is there a reason I shouldn't?


good time to pull the rad and oil cooler to clean and makes it a one man job to put the engine back

I probably need to pull the radiator anyway as it looks like the fan has been slinging a mixture of grease and dirt for years and the fins are pretty clogged.


I replaced the two that cross at the bottom and the one in the shroud they will bite you latter

Mine look fine. Do they get fatigued with no outward signs?
Last edited by Tony on Tue Sep 09, 2014 10:19 am, edited 1 time in total.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Mon Jun 02, 2014 11:15 am

I am having problems posting a reply to the other forum. This is what I get:

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I guess I'll be replying on this forum for the time being.
Last edited by Tony on Tue Sep 09, 2014 10:19 am, edited 1 time in total.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Mon Jun 02, 2014 11:16 am

Tony wrote:
antfarmer2 wrote:You can get the ujoints from loadersourceparts for a hundred bucks

I was able to Google for them... I assume you mean http://www.loaderpartssource.com

I searched their site, by search engine and just flipping through a bunch of pages, but couldn't locate the yoke part I need.

According to the service manual, I think I need part 7106572 (was 6558924). I'll confirm this with the dealer later.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Mon Jun 02, 2014 1:19 pm

I was able to get by the dealer just now. Unfortunately, they are giving me a price of $300+ for just the end piece of the yoke "assembly"... the part with the splines. I'd have to reuse the rest of my yoke, which is fine as it doesn't seem real worn.

The spline adapter on the hydraulic pump is only $45.

I'll try to source these parts for a more reasonable cost, if possible.
Last edited by Tony on Tue Sep 09, 2014 10:20 am, edited 1 time in total.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Tue Jun 03, 2014 10:23 am

Tazza wrote:Sadly you have little choice, i don't know where to get these parts other than the stealer.

As for the part on the pump, it's a taper lock, remove the bolt. Get a 2 or better yet, 3 leg puller. You may need to grind the feet a little to get them behind the adaptor. Tighten it up and give the forcing bolt of the puller a good whack and hopefully it will free its self.

While you have it off, you may want to replace the seal behind there. If the old one looks leak free, you can leave it alone, but this is your call. I got a seal kit cheaply from metro fluid power (pumps motors valves). The guy i used to deal with doesn't seem to be there any more though, Steve smith.

Thanks for the response. I guess I'll go ahead and order from the dealer.

I'll hit it with my 3 leg puller tonight. I think there's plenty of space behind the spline to get my puller feet in there.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Tue Jun 03, 2014 3:46 pm

By the way, the current part numbers are 6562960 for the yoke end piece (just the splined end piece) and 7106572 for the splined adapter that goes on the hydraulic pump.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Thu Jun 05, 2014 8:35 am

My puller gets under the spline adapter fine, but I tightened the puller until I ran out of elbow power and it didn't pop off. I dosed the inside of the adapter with WD40, plus a little on the key-way shaft (behind the adapter) and left it overnight, under tension. Hoping the WD40 will work its way between the adapter and the key-way and it'll pop itself off. I tried whacking it on all sides with a sledge, lightly as to not damage the key-way shaft.

As for the seal, the parts explosion doesn't show a seal, the Bobcat dealer doesn't know of a seal, and I can see what might be a seal, but not for sure. I may have to just take the chance that the seal is fine. I presume if it doesn't look all chewed up, it's probably okay.

I placed the order with the dealer for the parts I need. Should be in today. I'll try to get things put back together this weekend and see what I get. I'll probably just use pure water in the cooling system in case I have to pull the engine again. I'll probably go ahead and change the engine oil and filter as that doesn't seem to be involved in the engine removal process.
Last edited by Tony on Tue Sep 09, 2014 10:20 am, edited 1 time in total.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Fri Jun 06, 2014 12:06 pm

Well, things are not going well. “Tapped” the puller a few times and ended up breaking the puller.

[center]Image[/center]

Splined adapter is still firmly in place. I'll have to resort to Plan D... which I haven't formulated yet. Maybe put some heat to it. If I do that, I'll be sure to pull the shaft seal before. I'd rather not melt the seal to the shaft. I wonder how much heat is going to be transmitted deep into the pump assembly and what else could get screwed up. I suspect this adapter has been in place for 30+ years. It's had a long time to secure itself to that shaft.

I did pick up my new parts yesterday.

[center]Image[/center]

[center]Image[/center]

[center]Image[/center]

[center]Image[/center]

I can now see the fairly extreme taper on the adapter. Maybe a solid hit on the end will break the fusion to the shaft and I can use another puller to get it off.

Oh, my dealer said my price on the seal would be about $35. They said it'd be cheaper to take the seal down to the local gasket and seal shop and see if they have a match.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Mon Jun 09, 2014 6:21 pm

This weekend I was sitting there staring at my adapter, willing it to come off, when I considered just cutting a groove down one side and cracking it off. The metal looks like it would crack easily if I got a good start on it. The one thing I was afraid of is what happens if the new adapter is wrong or something? I hate starting down a path of no return. Cutting that old adapter off would be such a path. One thing I did try was sliding the new yoke onto the old adapter and it fits great with no play. I briefly considered going with it, but I haven't come this far to turn around now.

On another note, pulling the shroud off won't be an easy task... not at all. There are two nuts/bolts against the “firewall”, one is WAY behind the air cleaner (which I'd probably have to take off to get to), then there are on the front side near the muffler (no problem there), then the one in the bottom (no problem there), then finally two more - one on each side - of the shroud that looks like the nuts that hold the hydraulic fluid cooler in place. The lines going to the cooler run through a hole in the shroud, which means I'd have to take the lines off the cooler to get the shroud out.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Mon Jun 30, 2014 11:24 am

I have my 743 all back together, but when I went to print out the picture(s) of the wiring (I always take pictures of my engine compartment before disassembly), the close-up wiring photos for the solenode and starter connections were corrupt. I have a little Sony point-and-shoot that I use for this type of work, but every once in a while a photo I take will save to the memory stick in a corrupted state. I don't notice it until I go back to look at it. The camera doesn't give me an error when it saves it.

Anyway, I asked OldMachinist for a copy of his 743 wiring schematics, but he hasn't responded yet, so if anyone has a PDF laying around, I'd appreciate a link. Google searches have taken me on a 30 minute tour of spam sites, but no usable information found (except the thread here that I mention above).

For those keeping tabs on my progress, I got the yoke re-assembled...
Image

... and after using a metal cutting wheel on my Rotozip to cut a slit about halfway down the side of the spline adaptor and hit it, several times, with a cold chisel. It finally split and peeled a chunk off the top edge...
Image

Do you think it came off then? Nope! That thing refused to come off the shaft. I whacked it several times with a 4 pound sledge being careful not to damage my pump shaft as I don't know how well supported it is (bearings and such). Eventually I was able to get it off...
Image

With the old adaptor off, the new one went right on, and I was able to put the engine back in (by myself), using a little ingenuity and luck. I pushed the engine in until the yoke was hitting against the adaptor. I then turned the engine (using a big pipe wrench on the "auxillary" shaft sticking out the back) until the yoke adaptor would stay somewhat horizontal by itself. I pushed on the engine until the yoke went over the end of the adaptor, then a series of small turns on the engine, pushing, more turning, pushing, until it slid on completely. Re-attached all hoses, wires, exhaust, etc. That's when I discovered my photo of the wiring connections for the battery, solenod, and starter was useless. This is what I have now...
Image

Using common mechanical sense, you would normally wire the battery lead to one side of the solenod, the starter to the other, then a smaller wire from the ignition. But there seems to be a wire from one side of one solenod (a smaller wire) going to the "S" on the starter and a larger wire going to the other side of the same solenod. There's an "R" terminal (reverse?) on the starter, but appears unused. The second solenod doesn't seem to be connected to the starter. The terminals on the solenods don't look freshly used, so I don't think I pulled any wires off the solenods themselves, only off the engine/starter. I'm thinking the second solenod could be for the glow plugs as that would be a pretty big load for a simple ignition switch.
Last edited by Tony on Tue Sep 09, 2014 10:22 am, edited 2 times in total.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Tue Jul 22, 2014 7:56 am

Well, the final wiring was easier than expected. Apparently the starter has a built-in relay, so the hot wire from the battery goes straight to the starter post. The orange wire that shares the post on the starter with the hot wire must just feed voltage back into the system for various other purposes. It also seems to carry the output of the alternator to recharge the battery.

Now that everything is hooked up, time to test fire! It's been a while since the ol' gal ran, so it took some cranking. The smallish battery I bought for it wasn't up to the task, so I jumped it with my truck. With that, and a little shot of ether, the engine turned right up and runs smooth as silk. The main pump is quiet with no squealing. Good sign. I operated the bucket curl and the Bobtach plate tilts back and forth. Yeah! I operated the arm lift, but the arm went up about 6 inches and stopped. Went back down again, but now it won't go more than a couple inches. I was leary to operate the drive motors as it's still sitting on the trailer. I cautiously operated the levers, but it appears the drive motors aren't moving the unit. Next thing to address :roll:

I am going to move forward with the 773 refurb until I can make some time to fix the 743.
Last edited by Tony on Tue Sep 09, 2014 10:23 am, edited 1 time in total.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Tue Sep 02, 2014 1:30 pm

Hit a stopping point on the 773, so I went back to the 743. I purchased and installed a new brass filter along with the spin-off hydraulic filter I had purchased some time back. After replacing those, and topping off the fluid reservoir, the ol' 743 works great! Drives, spins, lifts, tilts. It's a little lazy on the arm lift above the halfway point, but that may be due to hydraulic fluid infused with water. It really should be changed, but I'll save that for the new owner. I've spent too much time on this as it is.

Final touch was paint, stickers, and a new seat, which I was able to finish up this weekend.

Before paint, but after sandblasting or flap disking a few spots. I wanted to sandblast the entire project, but I ran out of media and couldn't find suitable media to finish. The flap disk worked okay, but was a bit aggressive in spots.

Image

Image

Image

Image

After paint, decals, and new seat.

Image

Image

Image

Image

Should be on the market later today.
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Re: 1985 Bobcat 743 Rebuild

Postby Tony » Mon Oct 06, 2014 7:35 am

The Bobcat sold within the first two weeks. Nice couple from the area bought it to work around their yard.

Congratulations to the new owners on a fine little Bobcat!
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