Thoughts on engine reassembly problem

[rmaynard 14,861]

Let me start by saying that this is the fourth Kohler engine rebuild/refresh that I have done in four years, and the first time I have had this problem.

 

In the fall I disassembled my K161. The engine came apart easily. The bearing plate easily pulled off of the crankshaft, then the crankshaft easily pulled out of the rear bearing. I removed the rear bearing. The empty crankcase and crankshaft were taken to the machine shop where the cylinder was honed, and the crankshaft journal was polished.

 

Now, fast forward 6 months. I am reassembling the engine. I reinstalled the rear bearing, installed the governor and camshaft, and now, for the life of me, I cannot get the crankshaft to go through the rear bearing. I could tap it through with a block and hammer, but you need to have a little bit of movement to allow for proper end play.

 

So I removed the crankshaft and the rear bearing. Again, the bearing won't slide on the crankshaft. I tried the front bearing and it won't go on the PTO end of the crankshaft either. The front bearing will go on the flywheel end of the crankshaft, but it has to be forced.

 

It almost seems like I am working with the wrong crank or wrong bearings, but I know I'm not since this is the only engine that I am rebuilding, and the crankshaft was marked by me prior to going to the shop.

 

While I sit here and scratch my head   I would like your thoughts.

[Anglo Traction 759]

Bit of a 'Twilight Zone' going on there Bob....... Just wondering if you have Mic'd the Bearing surfaces on the Crank in several positions to see if they're in spec still?.

If you have a bore gauge, maybe check the Inner Bearing bore and see what you get.  Otherwise, I'm lost and have no answer..

 

Regards

[Martin 2,130]

Just wondering if the weather (temperature) has anything to do with fit. Was it really warm when you disassembled the engine? I realize that the crank as well as the bearings will both change size from being hot to cold, but if all else is the same, maybe something like temp is to blame? just throwing the thought out there....

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[rmaynard 14,861]

Only tool I have is a vernier caliper. That of course is not accurate for these kinds of measurements. 

[rmaynard 14,861]

Martin,

Funny you should ask. It was warm when disassembly took place. However, I am now working on the theory that since my crankshaft was at room temperature, and the bearing had been out in the unheated garage, there may be an expansion/contraction issue. I have the bearing sitting on the stove as I type. I am going to allow it to get hot, then return to room temp. Once both items are at the same temperature, I will try again. 

[squonk 38,842]

I has almost the same problem working on a gear drive deck I removed  the spindles no problem but when I went to put it together, the blade cups wouldn't go back on.

[squonk 38,842]

Martin,

Funny you should ask. It was warm when disassembly took place. However, I am now working on the theory that since my crankshaft was at room temperature, and the bearing had been out in the unheated garage, there may be an expansion/contraction issue. I have the bearing sitting on the stove as I type. I am going to allow it to get hot, then return to room temp. Once both items are at the same temperature, I will try again. 

I rebuilt a newer style mower spindle the same way. I put the spindle housing on a heater and stuck the bearing that had to go in it in the freezer. Parts fell together!

[rmaynard 14,861]

Martin,

Funny you should ask. It was warm when disassembly took place. However, I am now working on the theory that since my crankshaft was at room temperature, and the bearing had been out in the unheated garage, there may be an expansion/contraction issue. I have the bearing sitting on the stove as I type. I am going to allow it to get hot, then return to room temp. Once both items are at the same temperature, I will try again. 

I rebuilt a newer style mower spindle the same way. I put the spindle housing on a heater and stuck the bearing that had to go in it in the freezer. Parts fell together!

But will you ever get them apart again? I guess that will be someone else's problem 50 years from now.

[buckrancher 2,668]

 sounds right to me Bob the bearings should not slide on the crankshaft easy you should have to tap the bearing on lightly as they are not designed for a slip fit

 

Brian

[rmaynard 14,861]

If it's a tight fit, how do you adjust for end play if you can't move the crankshaft?

[Anglo Traction 759]

If it's a tight fit, how do you adjust for end play if you can't move the crankshaft?

If I understood your question correctly Bob,   It's a pain when they're too tight, but if you have pressed the Crank WELL home onto the fitted Rear Bearing (you don't want the Crank to move easily in and out at this point) and you have just the Bearing Plate to fit. It's a matter of bolting it on with just the Gasket first. 

Measuring the End Float gap , then removing the Bearing Plate again with a Puller to fit the Shim Gaskets (if req'd) to achieve your prefered End Float Gap.  The crank will settle out when it's running and had a few PTO pressure cycles on it. 

 

....................I feel like I'm teaching my Grandfather how to suck Eggs here.

[rmaynard 14,861]

UPDATE:

 

I heated both the crankshaft and bearings to +/- 150 degrees for several hours. Then I returned them to room temperature and let everything sit over night. I applied a light coating of Teflon lubricant to the journals, and everything went together like butter. 

 

So my conclusion is that the problem was mainly due to differences in temperature between the bearings and the crankshaft causing the bearing to contract slightly. Returning everything to normal solved the problem. I have enough movement that I can accurately adjust the end play.

 

Also, if I had just waiting until this morning to start assembly the engine, the problem would not have existed. Sometimes a good nights sleep can solve even the most perplexing problems.

[dclarke 4,011]

Bob, I knew you'd get if figured out. Good information to know. 

[Don1977 604]

The engine was oily when you took it apart, with the parts cleaned they don't slide together as well. Might work better with a little oil on the bearing and crank shaft. Once you have the gears in time and started together a rubber hammer may help. If you didn't remove the old crank shaft seal that can cause it to be hard to the the crank in.