Crank Shaft Bearing Replacement Process

[Ironlegs]

I'm wondering if a full disassembly of the tractor/engine is necessary to replace the three crank shaft journal bearings. In reading about this topic, I ran across wording to the effect that the Cub crank shaft bearings could be removed through the oil pan opening in the block and on the tractor. If this is possible, I will proceed with crank and rod bearing replacement after the mowing season concludes with the goal of improving engine oil pressure. I am aware of the need to properly measure and assess the crank, rods and bearing surfaces...especially on a 1958 year machine.

[Bill V in Md]

In an emergency this could be done. But the time you will have invested to remove the crankshaft including removing the oil pan, front cover, flywheel and rear crankshaft seal retainer you may as well invest a little more time and finish the job. If the main and rod bearing are worn enough to require replacement, it would be prudent to thoroughly clean the entire crankcase, especially if the bearings are being replaced due to lack of lubrication. You will probably also want to replace the crankshaft front and rear main oil seals. You didn't mention whether the engine is burning oil, but with this much time invested, I would also seriously consider measuring the pistons and bores to see what condition they are in.

[Eugene]

In tractor overhaul can be done. Much easier to work on the engine with it on the bench or engine stand.

Agree will Bill. Complete engine overhaul.

[ricky racer]

In tractor overhaul can be done. Much easier to work on the engine with it on the bench or engine stand.

Agree will Bill. Complete engine overhaul.

You'll never regret it....
Rick

[John *.?-!.* cub owner]

I will agree that a rebuild is the way to go, but can be done in frame. You will need to remove the pan, and the oil pickup screen, then remove all 3 main bearings. A thin screwdriver can be used to start the caps moving around the journal, and keep working them by using screwdriver on out side of the bearing while turning the crank. Note they have a tab on one end, so that is the end that must be turned out. Auto parts stores used to sell a bearing roll out tool that went in the oil hole of the crank and pushed the bearing out as you turned the crank. You can make one using a small nail (about a 6 p if I remember right), cutting it off short and bending it right at the head. May take a couple tires to get it right. Just found a couple notes that a cotter key is easier to make one from. Google crankshaft bearing roll out pin.

[Ironlegs]

I replaced the piston rings and rear crankshaft seal when I replaced the clutch about two years ago. My Cub does not need rings or seals so I am considering a limited service project of crank and rod bearings given they all can be replaced through the oil pan block opening with the tractor assembled.

One of the responders posed the question about oil burn. I'm getting limited and intermittent oil smoke in the exhaust which I understand results when the rod bearings are worn and allow too much oil splash in the lower portions of the cylinders. This mostly occurs when the Cub is working hard on a slope. In any event, I just have to address the loss of oil pressure to avoid wear and/or damage that's sure to arise. The unit has new good rings that were properly sized for the cyclinders so I was pointed to look elsewhere for the occasional oil smoke which led me to learning about smoke when rod bearings are too loose. I can hear no knocking from the engine under any conditions.

I measured the rod bearings two years ago when I did the other work and found some wear but deemed it not requiring attention. I have a feeling the crank bearings contain most of the wear that's leading to low oil pressure. Two years ago, I didn't have the benefit of the advice of the forum members and didn't attempt to fully inspect the crank bearings (tractor assembled and working through the oil pan opening). Once I get the mowing season behind me, I intend to remove all the lower bearings, perform an inspection through the oil pan and get some answers about what is needed. Replacing all the lower end bearings would probably be the right action...and knowing I can do this without a complete disassembly is great.

[tst]

Just remove the crank bearing cap, put a small screw in the oiling hole in the crank, rotate the crankshaft slowly and it will spin the bearing out, can be replaced the same way

[pickerandsinger]

Just remove the crank bearing cap, put a small screw in the oiling hole in the crank, rotate the crankshaft slowly and it will spin the bearing out, can be replaced the same way

Nice Tim Dave

[Matt Kirsch]

Yup, the process is called "rolling in" new bearings and is/was done as a "farmer fix" for many years to improve oil pressure.

In fact Dad rolled in a set of .002" undersize main bearings on the Super M shortly after he bought it in 1975, and it's been running that way ever since. Worked hard, overloaded, abused for many of those ensuing years. The undersize bearings were probably not the best idea, but the crank ended up being worn just enough that it worked out.

I'm going to have to amicably disagree with those who say that any time you crack an engine open, you have to take it to the machine shop for a complete overhaul. Yes it's the "right" thing to do and probably the "best" thing to do also, but it's not always part of the plan. You may not have $1200+ to pay a machine shop. You may not WANT to pay $1200 to a machine shop for a tractor that runs 5-10 hours per year. You may need the tractor tomorrow.

As long as you you replace like-for-like with the bearings, (i.e. if the ones that come out are .010" undersize, replace them with .010" undersize), and the journals look okay, you really can't go wrong. Yes you've put forth the effort and "wasted" a set of bearings if you end up going for an overhaul anyway, but odds are you won't need that overhaul for a long-long time now, if ever.

[bythepond88]

I suggest that you plastiguage the bearings before buying parts or starting any replacement. That will give you a better idea of whether that's the problem.

[Ironlegs]

Oil pressures between 5 and 10 psi with the engine hot and idling is the cause for my anticipated repair. Just after a cold start, oil pressure is something like 20 psi. I use thirty weight oil. I've been watching the slight bit of smoke in the exhaust this summer...the crank case oil level has not gone down enough to bother re-filling...the smoke is hardly noticeable.

I'm wondering if the oil pump is part of the problem. Do these wear internally to the point where they are a problem? Is there a repair/adjustment to the oil pumps? I kick myself because I could have serviced this when I replaced the clutch a while back and didn't. When I get the pan off, I intend to do a thorough cleaning of the oil intake screen.

These little tractors are handy to have and use. It's a blessing to have sources for repair parts. I gather with my 8 year old son when using and working on this machine. I have him mowing open, level areas with it which gives me quite a bit of his attention. The father-son times with the Cub are priceless.

[John *.?-!.* cub owner]

20 psi idling cold and 5 to 10 idling hot is normal for 60 year old low rpm IH engines, and anyone else's for that matter. Are you getting higher pressure at working rpms? Remember, these are low volume, low pressure pumps to start with. The relief valve kicks in at 35 psi. You can have the crank turned and put new bearings in and after about 20 or 30 hours of working the idling pressure will be down to 10 or 15. Also, do not make the same mistake I did a couple years ago. I thought there was a problem with my rebuild because the idling pressure was low, and finally got smart enough ti figure out my gauge was bad. it was correct at the 35 psi, but at 15 psi it read 5.

[Ironlegs]

The first step I took in evaluating my Cub's lack of oil pressure was to remove the gauge and check it with compressed air...it functions and meters correctly. Working the Cub this summer and watching the lack of oil pressure has kindled my concerns and motivated me to search for advice, written/published and in this forum. When I found the article that mentioned exhaust smoke from excessive oil splash on the lower portions of the cylinders from worn bearings, the situation matched.

The engine work performed two plus years ago included Plastigaging the rod journal bearings...I recorded and saved the measurements...only slight wear on all four with no signs of smearing or worn areas. This check did not include the crank shaft journals although I did check for thrust and radial looseness and found very little. It's very possible that all seven journals have 0.001 to 0.003 wear (radial) and, combined, substantially lower the oil pressure and cause oil burn under load, especially on slopes.

The "rolling out" process the one fellow suggested sounds do-able (by me)...clever and practical! I will have my Cub for many more years and need it to perform well, mowing and doing chores in the winter time so investing in new journal bearings will not be wasted effort and cost. I would not sell it with known deficiencies unless I couldn't do the upgrade or openly declared the worn condition.

I'm more than a little appalled at how many sellers nowadays feel justified in selling used equipment that is in seriously degraded condition in a deceptive manner...it's not okay to be dishonest and deceptive, ever. Shame on them.

[Hengy]

Did the "rolling out" and "rolling in" process on my 1949 Cub, Merlin, several years ago, and it worked brilliantly. Good oil pressure at all RPM's. I plastigaged my new bearings when I put them in and the clearance was acceptable. I replaced the rod bearings at the same time that I did the mains as well. I also replaced the rings "in frame" on this tractor. Probably needed machining, but didn't have the cash at the time to do it right at the time.

Mike