Farm Equipment - Allis B 125 rod bearing clearances

Print Page | Close Window

Allis B 125 rod bearing clearances

Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=55183
Printed Date: 09 Sep 2025 at 7:49am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com

Topic: Allis B 125 rod bearing clearances

Posted By: rellis73
Subject: Allis B 125 rod bearing clearances
Date Posted: 13 Aug 2012 at 12:07pm

Hey all! Ya'll have been a huge help in the past so I hope you can help again. We are trying to put the motor back together for the B and are having binding problems with the rod bearings. It would appear that on 2 out of the 4 sets of bearing shells there is a lip of about 1/32" where the shell sticks above the rod cap. The other side of the same bearing however does not come up short that 1/32" so when you put the rod together we are having a crushing problem where the shells come together which in turn is causing a binding problem on the crank. I guess my question is: Is this normal or something that someone else has run into and can be taken care of with the shims under the rod caps. We did plastigauge the rods when we put them together and got the correct clearance under the bearing but obviously have too much crush as evidenced by the binding. Anyone have any suggestions?

Replies:

Posted By: Hartland Farm
Date Posted: 13 Aug 2012 at 1:24pm

Yes get a manual. The clearance is .002 and is gotten by shimming. Those are crush type bearing to dispence heat. Get a manual. Joe

Posted By: rellis73
Date Posted: 22 Aug 2012 at 10:02am

Thanks for the response. I have a manual and knew that the tolerances were between .001-.003 for the rod bearings but the problem was that #4 piston rod and cap was the only one were the protrusion of the bearing shell was about .015 - .020 above the cap. I also knew that shaving the end of the bearing shell was going to cause other problems; short and long range. After making new shims out of brass stock and adjusting, testing, adjusting, testing, adjusting, testing I got the clearance where it should be and maintained the correct crush on the bearing shell and she purrs like a kitten without the dreaded rod ping. Thanks again!