Question about crankshaft journal

[tntatro 174]

Hello, I have a K301 that I rebuilt a while back. I ran it for about five hours, then switched it with another engine to test. Not too long ago I had it sitting under a work bench and I had to move it and grabbed the PTO shaft. I noticed that it had some play in it, mostly in and out and maybe a tiny bit up and down but it was hard to tell if it was just sliding in and out a little. I checked it out today and the crankshaft end play was .014", the specification says .003" to .020". I took out a bearing plate spacer and got it to .007". Of course I didn't think to measure the crank journal but the bearing does slide onto the crankshaft easily. I put it back together and it still feels like it has play in the crankshaft. Is this something I should be concerned about? I'm guessing either the inner bearing race is worn or the crankshaft journal is worn or both. I guess I should have put in new bearings but they are so heavy duty looking. I'd hate to have to take it all apart again to get to the PTO bearing. My main concern is the clearance between the inner bearing race and crankshaft journal and if that might cause bearing failure or crankshaft scoring.

[WHX?? 49,606]

Sounds like you got the end play problem licked but if you can measure the the vertical play do so. More than a couple thou that bearing should be replaced. I have had PTO bearings slide right on the crank with no problems. Might not be a bad idea to plasti gage the big end to crank journal. 

I'll call in a couple of pro builders see what they have to say. @prondzy @richmondred01

[tntatro 174]

I don't know how to measure the vertical play, the flywheel side bearing is easy enough to replace but I hope I don't need to do the PTO side. I don't remember if the PTO side slid on easy but I imagine it did. I had the crank pin machined and new rod when I rebuilt it and it has about five hours since then. The crank pin is .020" under now.

[WHX?? 49,606]

I would have definitely checked the big end to crank journal unless you really got a good crank grinder that you trust. Plasti gage is the only way to do it but any competent shop can do that. Unless you have been following the engine section and how hard it is to find those shops nowadays. Just sayin. 

To accurately  measure end play or vertical play you need a dial indicator with a suitable mounting. 

My set up....

 

[tntatro 174]

Thanks for showing that, so it's clamped onto the bearing plate I see. Do you know if the dial from my bore gauge would be sufficient if I could secure it onto the bearing plate?

 

The machine shop I go to did a few other crankshafts for me. The first one they did .030" under and fit a bearing in the rod. They told me they have done thousands like that so I think they know what they are doing. I guess I should check the big end, I pretty much just trusted that the rod was in spec. I thought you used a micrometer and bore gauge to check the big end to journal and plasti gage was the "good enough" method, although I don't have a bore gauge that small or inside micrometer so plasti gage is all I can do now anyway. I just checked the rod with dial calipers to make sure it was in fact .020" under when I installed it.

[prondzy 3,883]

The crankshaft journal would have nothing to do with the crank moving up and down outside the block only create a knock sound.   Crank bearings however could cause this issue.  The specs are given in a window of safe operation, just remember everyone is worried about too sloppy but too tight can be an issue  because everything expands when it gets hot. If there was to much wobble on the pto side of the crank the seal would not have sealed when you ran it for 5 hours and started leaking. Don't get to worked up sounds like you did everything right.  

 

[tntatro 174]

Okay, thanks. I was wondering if I was overthinking it. Some of the other ones I rebuilt might have been the same but I just didn't notice, I just happened to grab the crankshaft to move it and felt the end play.

[Greentored 3,217]

These guys got ya covered on the clearances. If there is a concern with clearance between the actual bearing itself and where it slides over the crank, no, you dont want any there. If we're talking a couple thousandths, grab a tube of loctite sleeve retainer- thats what this stuff is made for. It will lock it in place and you'll be fine.

Good luck getting it back apart though without some heat and some cussing and swearing ha.

[tntatro 174]

I was thinking about using some loctite 620 that I have but if I did need to take it apart again that would be rough. I used some on some front wheel bearings not too long ago that slid in pretty easy. I put 45 lb wheel weights in front and decided to put on heavy duty needle bearings instead and I really had to beat those little bearings to get them out. That was only a 3/8" wide surface. It would probably be easier to heat the bearing plate and pull it off the bearing if I did that. 

[prondzy 3,883]

4 hours ago, tntatro said:

It would probably be easier to heat the bearing plate and pull it off the bearing if I did that. 

Or melt it or break it. Loctite would be a terrible idea. These engines were designed by engineers,  and it's not like they have a known bearing issue.  If you're that worried about it, replace with new bearings.  But if it ain't broke don't fix it

[tntatro 174]

Yeah, I think I'll leave it. If a seal leaks then I'll look further. As far as the bearing plate, I'm pretty sure it would be easy to heat it with a soldering torch and the bearing would come out fairly easy. I've done that trick many times on magnesium chainsaw crankcases but no point in doing that when new bearings are only $50.