B7100 cam plug low oil pressure and dynamo bearing replacement

The problem of the B7100 front cam oil galley plug dislodging and causing oil pressure low enough that the oil pressure light comes on, has been covered by several threads on this forum and others on the internet.

The symptoms in this situation was an oil light that would come on after the oil got hot. Revving the engine would cause enough pressure to turn it off again. I found out about this fix only because of the internet forums, which I am thankful for.

I am in the process of this repair now. This thread will describe my repair. I am also including a DIY on replacing the dynamo/alternator bearings, since that is a recommended corollary repair.

The first step is to remove the hood by pulling the clips out of the hood pivot bolts. Then drain the radiator and remove it (good time to clean the chaff out of the fins). Disconnect the air cleaner and exhaust bracket from the timing cover.

The oil does not need to be drained at this time. There will be some oil that comes out when the cover comes off, maybe one half a cup. However, since the radiator has to be removed, the coolant does have to be drained as a first step. I will change the oil and filter after the repair, but not until running the tractor for 5 minutes or so to let the old filter catch any pieces of detritus left over from the repair.

Before removing the timing cover, there are two springs in the fuel pump which need to be detached before doing anything. There are three covers which can be removed on the injection pump, but the springs are on the top cover which holds the throttle arm. So, don't waste your time removing the other two covers.

The first peculiar situation I ran into was that the crankshaft pulley nut on this tractor is 29mm, not 46 mm, as is on other variations described in forum DIY's. 29mm is equivalent to 1-1/8". The nut has a lock washer behind it which is bent-up around one edge of the nut, so the washer needs to be straightened-out first.

I did not use an impact gun to remove the nut. What I did instead was use a deep-well, regular-duty socket 1-1/8" with a breaker bar. I propped the bar against the left side of the frame (starter side) and turned the engine over for just a blip of the key. The nut loosened easily.

I lightly rapped the crankshaft pulley with a dead-blow hammer and noticed it moved, so I worked it off alternating sides, with a pry bar, careful not to damage the cover. There are two metric size holes in the pulley designed to be used in conjunction with something like a steering wheel puller.

I wanted to remove the dynamo to replace the bearings, not because the bearings had failed, but because I thought now would be a good time to do them because of the better access.

As widely reported in Kubota dynamo repair threads, there is a hidden nut on the flange of the water neck/dynamo housing, which is extremely difficult to access. I thought it would be easier to get to, after I removed the front timing cover, and for sure, that helped, but it was still not a cake-walk.

There is also a bolt for the timing cover directly under the dynamo housing--don't mistake that for the hard-to-get nut. I found out that I would have had to remove the water housing anyway to get the timing cover off, because there was not enough clearance under the housing to remove that bolt! The problem is that the tab which holds the dynamo output wires covers a half moon cut-out in the dynamo housing which is intended as a way to access the bolt for the timing cover.

From the engine sides, and from the front pivot nut, I had to detach the plate steel frame extension in front of the tractor which holds a couple weights and the front axle. I only needed to pull this out enough so that the bottom of the cover would be free of the crankshaft. However, the front axle should be pulled completely loose so that you can access the bottom area where the cover fits to clean off the old gasket material. The shaft tube will pull loose and leave the shaft from the rear, dangling. Support the tractor with a floor jack coupled with a jackstand.

Since the bolts from the timing cover need to be kept in order, because of their various lengths, I took the new gasket and traced the bolt holes on it onto the bottom of a cardboard box, then I punched out the holes to act as holders for the bolts as I removed them.

When I was inspecting the crankshaft seal land, I was surprised to see that it was a moveable metal collar, and before I could ask myself what kept the oil from leaking between it and the shaft, I noticed an o-ring behind it! The o-ring is something which should be replaced at this time, and the collar shows a significant seal groove, so I'll try to order that too. I might be able to re-use the collar if I can reverse it.

Once the cover was off, sure enough, the camshaft oil galley plug was missing. After cleaning the oil from just inside the oil galley, I could see a land inside to stop the galley plug as you pound it in, if it actually could make it in that far because the depth of the cavity is about 1mm more than the length of the plug. There is some taper to the galley hole, so the plug will go in a little on its own, but it has to be driven in the rest of the way. I drove the plug in without being timid, and got it in to the point the end of the plug was flush with the end of the camshaft. Then, I peened the end of the plug a little to expand it, then put a small spot weld on the edge of the plug as a final measure of security.

I used the steel plug. If you order a 15261-96860, Kubota will send you an aluminum plug. The number does not supersede! What should be used is 15261-96880 , a steel plug. Kubota calls it a blind plug.


Apparently, Kubota issued two TSB's on the low oil pressure and missing cam plug problem. They have been mentioned by others as TSB's #79-07 and # 81-06.


Dynamo bearings replacement:

The dynamo is came apart easily once the back nut was off. There was some dirt inside. The bearing retained by the circlip comes out easily, but the one on the shaft is on tightly, so tight that I could not budge it with a puller!

What I did to remove that bearing was to press out the shaft from the permanent magnet housing. Then, the bearing and spacer behind came off as the bolt exited.

When re-assembling the pulley shaft on the permanent magnet housing, first press on the shaft all the way, then press on the bearing spacer sleeve, then press on the bearing which is a 6201. By pressing the spacer sleeve on first, you can see when it has bottomed out; otherwise it is hidden by the bearing as you press them on both at the same time. It is on there tightly, just like the bearing.

The original two bearings were metal side shields. Some grease had escaped. I used rubber shields. My bearings were MRC 201SZZ. "S" means shielded, and the two "ZZ"'s , for this particular brand, mean rubber seal on both sides. I suggest buying a well-known brand name.

Incidentally, the bearing in the fan belt idler is a 6203, another standard size. It is easy to replace. I also used a rubber seal version of this bearing.

The bearing on the shaft was still very smooth in action, but the other one was "roller skatie", which assured me that replacing these at this time was a good decision.

I used a press collar around the permanent magnet housing to cradle the tapered housin while pressing, just to make sure I did not break any of the magnets by stressing the case.


++++

So, tomorrow, I will get some gasket remover and work on the gasket remnants stuck to the aluminum cover. I will also order the crankshaft o-ring and maybe the collar that goes with it. Before buying the collar, I'll clean up the outside of my old one to see if it will work reversed on the shaft so the seal will get a new surface. Looks like new collars are costing around 30$.

I will re-organize this thread, adding more information and pictures. Just trying to get as much down now as I can while it is fresh on my mind.

Daren Todd said:

That bloody gasket on the aluminum cover just plan sucks!!!!!! That was the worst and longest part of the whole job. Nice write up

Click to expand...

Thanks. Yes, it is hard to get off. If you use a metal gasket scraper, it is all too easy to end up with gouges in the aluminum. I got a few. Best to go with a gasket remover spray and then go easy on it.

I managed to get all mine off with careful working with a straight edge razor with my fingers. I brushed the face lightly with a brass brush on any problem areas, and then gently ran a long, fine mill file over it to take out any burrs and even it up.

I'll might use some Aviation 3# on the this gasket when I re-assemble, at least on the aluminum side.

I don't see that any of the timing cover bolts are "wet"; however, maybe I am missing something. Just before I put the cover on at the end of this repair, I noticed hard brown material on the bolt ends. So, cleaned the threads, the bores, and used thread sealant (not locker) on the threads when I put the cover back on.

Re-assembly is on hold while I wait for the crankshaft seal collar and o-ring to come in from the dealer--couple of days. The collar is about 34$, the o-ring, under a dollar. While the old collar can be reversed, the seal lips would be very close to the old tracks, and not worth the risk. I noticed that the collar is hardened on the outside, so it is a quality piece.

I'll post some part numbers now. These are updated numbers:

Gear case gasket: 15263-04130

Crankshaft seal: 09550-00008

(the original seal was a NOK AH1671P; replacement is TTO D448. This crosses to National 223012, SKF 11580, used in Fords and Mazdas. )

3x case o-rings: 04811-06130

Water flange /dynamo housing gasket: 15261-72920

15261-96880 is the steel camshaft oil galley plug you want.

Hardened steel collar on crankshaft acting as inner race for seal: 15532-23250 (36.51$ , 2016)

O-ring for seal collar: 04811-10220

Gasket for injection pump cover over the two springs: 15263-57210 . Mine tore during the removal process.

Kubota dealer blue paint spray can: 70000-00197


Bearings for Dynamo: 6201 (two needed) (generic size and common)

Bearing for tensioner pulley: 6203 (generic size and common)

Here is why the dynamo/water jacket housing must be removed before the timing cover.

There is a metal clip which holds the two wires leading out of the dynamo housing. The clip has a 90 degree bend with a tab fitting into the half-moon cut-out in the dynamo housing obviously intended as a way to access the timing cover bolt in that location.

Unfortunately, it appears that someone at Kubota did not recognize that the tab interfered with the purpose of the cut-out.

I was going to take the clip off and bend it, but I was not able to remove the holding screw.

Pointing to the timing cover bolt under the dynamo. You can see the cut-out in the dynamo housing ostensibly for wrench access to that bolt:



Picture of the problem clip:



Look carefully at the clip and you can see the half moon cutout beneath it that it blocks



I could have cut off the tab, but then I thought I better leave it. I had to wonder if a mud dauber would be able to get in the dynamo using that opening and ruin it.

Here is the camshaft which loses the plug. One look and you have verified the problem:



Below, a close-up of the camshaft showing no plug. Also, you can barely see the land on the inside of the hole which would stop the cam plug from being inserted too far. However, you are only going to be able to drive in the steel plug to about even with the shaft end, which leaves about 1mm before it reaches the step.

The depth to the step is 5.2mm, while the Kubota plug is 4.2mm.



Here is how far the plug goes before it meets resistance due to the taper fit:



Here is what the plug looks like inserted flush with a tack weld. No need to try to stake the plug with a sharp-ended punch like I tried. Otherwise, it will look like a wood pecker has been at it. Just use a flat head punch and just the driving-to-flush will expand the end to stake it. However, doesn't matter much if you tack weld it.

I did the tack with a small diameter 6013 rod, AC welder. It worked, but a MIG welder would be a better tool.

Here is a picture of the two springs which have to be disconnected before removing the timing cover.

One spring is attached to a post on the cover, while the other one is attached to the lever on the governor linkage:

Removing that devilish bottom nut on the dynamo housing stud. Used a 10mm craftsman ratcheting socket--one click only at a time is the best I could do:

Picture of the crankshaft pulley. You can see the two holes in it for use of a puller. That would be a steering wheel type puller. You could make something on the spot with a stiff piece of flat iron with two holes drilled in it.

The holes are M6 x 1.0 thread pitch. I don't know exactly what length you would need.

Fortunately, after a light rap with a rubber hammer, my pulley was loose enough I could work it off. If you try to pry it off from the backside, it is possible to damage the aluminum cover, perhaps even breaking it:



After verifying the rotation of the engine by turning it over with the starter, I arranged my breaker bar and socket to remove the crankshaft pulley nut. I used a zip tie on the bar to hold it squarely, then blipped the starter minimally with the key. Not sure what I am going to do about re-torqueing the nut when it is all going back together. I'll look and see if I can find a spec for it. Maybe with it in gear I can get the torque spec on it without the crankshaft turning. We will see.



The crankshaft pulley is on a shaft key. Don't loose it.

Here is the collar on the crankshaft which serves as the inner race for the seal. It has a slant cut on both ends to butt up against an o-ring which keeps the oil from leaking between it and the collar. Mine was grooved out where the seal lips run, so I replaced it along with the o-ring.




You can see the o-ring still on the shaft, blurry, in the background:



There is also a washer behind the o-ring, butting up against the gear. No need for it to come off. Just thought I would mention it.

The front axle and differential need to be partially detached in order for the cover to clear the crankshaft shaft.

Here you can see I am running into this problem:



I braced the tractor underneath in two places, so I could move the axle about two inches out, without something going squirrelly:



There is one big nut up front, under the crankshaft, which has to be removed. It is the pivot for the axle. You can partially see it on the first picture, above. There is an locking bail wire on the nut, easily removed.

Here is a picture of the dynamo inside. It does accumulate dirt. Just blow it off with compressed air. If you try to soak it in solvent, you risk dissolving the lacquer insulation on the windings.



The grease you see is what has come out of the bearings over 35 years.

Here is what the new bearing looks like installed. Make sure it is all the way down so the circlip seats fully. You need circlip pliers on the small side to get in the cavity with enough clearance:



I tried a puller on the bearing on the shaft part, but even after grinding some clearance on the puller arms so that the permanent magnets would not break, the bearing would not budge, so I drove the shaft out with a press:



The bearing puller collar you see underneath the housing is just for even support of the housing during the pressing operation.

This is a good time to evaluate the insulation on the two dynamo wires leaving the case. Where protected by the wiring sheath, these looked ok, but previously, I replaced the dynamo wires elsewhere, all the way up to the regulator because of breaks in the insulation. The problem is a close proximity to the exhaust system. I previously verified that this dynamo charged, and that should be done before prior to this sort of repair, because now would be the best time to replace it.

That is getting near the end of my pictures. Here is how I kept the bolt straight, since they have various lengths. Traced out the holes with the new gasket and then punched holes in the box to stick the bolts as I removed them:



I put the seal in the timing cover tonight. The bore in the cover does not have a step to back the seal. I used a socket and a press to get an even install depth. I went slightly below the surface of the cover by 1 mm. With a film of engine oil on the outside of the seal, it goes in very easily.

I also noticed that the crankshaft bolt goes on one way. There is a circular land on the bolt which should be up against the pulley. The washer goes on only one way since it has a anchoring tab, and I'll try to bend the locking tab from the unbent side. The diameter of the crankshaft at the bolt threads is 20mm.

Today, I noticed that the front axle pulls right out from the front of the tractor. The shaft tube pulls out of a boot and leaves the shaft itself hanging, attached midway under the tractor.

So, I pulled it out to help the cleaning process. Good thing, because I found a blob of gasket I missed, located underneath the oil pump.

I thought to pull out the center pivot pin to grease it and found it fairly worn.

I don't know what a new pin costs, but from the parts diagram I also see 4 O-rings and two bushings which go along with it.

I didn't see any O-rings fall out. My guess is that they are on the inside and outside of the bushings (correct).

Update: numbers have changed for the pin and sleeves.

Pin is 37$ and each sleeve is 21$

Here are the updated (2016) part numbers:

66802-56110 center pivot pin

66591-56120 pin bushings (x2)

04816-00200 O-rings (x2) (go inside in bushings)

04811-50250 O-rings (x2) (go outside on bushings.)

I can do this pin job for under 100$, so I am going to go for it. Hopefully, I won't have any trouble getting the bushings out. I am still trying to get the frame plate off the top. It is hung up on one of the bushings. I'll try knocking it back a little.

I read that the slotted pivot pin nut gets 7 lb-ft of tightening torque.


Update: added pictures of the pivot pin. Most of the wear appears to be where it rides the bushings:

North Idaho Wolfman said:

Very good write up, but you do realize that all of what you are doing is spelled out in the WSM along with pictures.

Click to expand...

Sorry, but I did not have a WSM, but that would have been worth buying beforehand. The only manual online I could find was the 3 part IT manual, and it is not as comprehensive as the WSM. Someone has put up a WSM , however, for the later hydrostatic version of the B7100, and some of that information is helpful. Thank you for the compliment.

Bill, thank you for the comment and for giving me the link to your front axle rebuild thread. I had not seen it.

I am thinking much of the wear I am seeing on the pin might have something to do with the three 25 KG suitcase weights on the front. I assume they were attached there to counter-balance a Woods "Billy Goat" bush hog on the back, but since the top link is not used to completely lift the mower off the ground, my guess is that the hog was too heavy for the hydraulics to lift.

I have to have the weights for the mower. I tried without and the front end loses all traction.

I also thought about what might help the lubrication of the pin, and the only thing I could think of was to drill a long bore in the pin with exits for the grease where the bushings ride. A grease fitting could be installed on the pin end.

Also, thanks to 85Hokie for sending me a link to his dynamo rebuild : http://www.orangetractortalks.com/forums/showthread.php?t=24290&highlight=dyno

Back to finishing up the cam plug repair project:

Reassembling, I decided to put the dynamo housing on first, after doing a dry fit to make sure I could get a socket over the top middle timing cover bolt when the dynamo was in place.

For that particular bolt I used a 1/4" ratchet drive, extension bar, and a 10mm swivel socket.

I would not be able to do this if I had not bent the holding tab for the dynamo wire harness to roughly follow the half moon cut-out access in the dynamo housing flange. I discussed this previously.

The reason to do the dynamo first is for better access to the problematic bottom middle nut on the dynamo housing. If the cover were on first, I wouldn't even want to think about it!

So, since the aluminum gasket flange on the housing was not perfect, I coated it and the gasket matching side with Aviation #3, then I also decided to do the block side the same way.

Before the sealant dried, I needed to get that problem nut on and I realized I should have gone through a dry run for that, too!

Using a small flashlight and peering under the muffler, I put the lockwasher on with some small needle nose pliers.

The nut did not respond to the same treatment. After fiddling this-way-and-that with it, I finally was able to get it on.

How I did that was to stand over the dynamo and used both hands to reach under the housing: one hand from one side, and the other, for the other side. In about 6 minutes, I was able to get it threaded.

With trepidation, I take on the final step, which is to put the cover back on. I was a little worried when I put the 3 O-rings in the cover since they kept wanting to worm-out. After a while, I got them in so they stayed if I left them alone.

I will put on the cover gasket mostly dry, only dabbing one or two little areas where there was some scraper damage, with some Aviation #3.

As an afterthought, since the nut on the dynamo housing is so difficult to access, unless one is very confident in their finger dexterity, a fast-drying gasket sealer would not be a good idea. I could foresee someone fumbling with that nut, for hours. If your gasket mating surfaces are level (not gouged), a gasket dressing would not be need at all.

It would have been nice if pry tabs had been cast into the edges of the aluminum dynamo housing. If the housing is really messed-up from a tough removal, might be a good idea to replace it.

Finally, I noticed some hard brown material on the ends of many of the cover bolts. It chips off. I suppose this was thread sealer. Accordingly, I cleaned out all the bolt bores, cleaned the bolt threads, and applied thread sealant to all of the bolts for the cover.

Thank you.

Here is a picture of the dynamo harness holding tab which I bent by hammering it with a punch:



Don't forget a new o-ring here:



Verifying that the 3 O-rings in the cover are still in place. They seemed a little too big on the od, making them want to squirrel out, but they did stay in place. It would have been better to put two small dabs of sealant on their backsides to hold them:



Here is the cover back in place. I bought a can of Kubota blue spray to make things look happier:



Does not seem to be much of the splines left on the front crankshaft. They have been stripped. I vaguely recall that the mower was first set-up with a belly mower and I expect these were the result of a problem with that:







Not having torque values, I went with 10 lb-ft for the cover bolts (I think I read somewhere it was 7 lb-ft, 10 is the lower limit for my torque wrench), and put the crankshaft nut on at 100 lb-ft. When torqueing the nut, I held the crank fast by inserting a pry bar into the starter hole and wedging it between two teeth of the flywheel.

The starter comes out easily and can be suspended with a rope off the exhaust manifold.

One last thing I need to order is a new gasket for the top cover over the injection pump springs. Much of the repair time for this project was having to order more parts and running to town to pick them up. Hopefully, the lists of parts, earlier, will save someone else some time.

And Oops, I put all the cover bolts in without attaching the idler pulley bracket. I'll have to remove three of the case bolts to install the bracket and renew the thread sealant. I also attached the bolt a holding spring for the crankcase vent hose: