Author Topic: Connecting Rod Bearings  (Read 513 times)

0 Members and 1 Guest are viewing this topic.

Offline Onlyboards

  • Jr. Member
  • **
  • Posts: 40
  • Karma: 0
    • Carbondale, CO USA
Connecting Rod Bearings
« on: August 07, 2018, 02:38:48 AM »
First of all I just want to thank everyone for all your help.  All my machine work is back from the shop and my .50 2f1 high compression pistons are nice and snug.......literally it gives me a warm fuzzy feeling because tracking those down was a pain. 

anyhow, there Is a post where Guy chimed in regarding con bearing sizing.  I followed the instructions in relation to the crank numbers then used the appropriate formula to get new bearings.  After installing the #1 size con bearings I noticed a small amount of vertical play even after I torqued the bolts to spec.  One rod feels like a dream and the other is a hair sloppy.

Obviously there is plasti gauge for measuring oil clearance, but as Guy pointed out you have to have some practice with that stuff, and even then its a bitch because there is limited amount of space to work.


I have Micrometered the crank on both connecting surfaces and they come up with the same number.  I'm already using the 371-11656-03-00 bearing (which according to Guy's great explanation on bearing size) is already the thickest bearing available and should give me the smallest inside diameter. 

are there charts of measurements that correlate what the #1 connecting rod bearing inside diameter is when installed?

Also I may just have some kind of a manufacturing anomaly and the bearings just arent equal for some reason.

Is there some bearing I can use that is slight thicker than the #1 to take care of the play I'm feeling?


sorry for all the questions, but I finally see the light at the end of the tunnel after about two years.  cant to wait to ride her. thnx

Offline guylr

  • Administrator
  • Hero Member
  • *****
  • Posts: 1126
  • Karma: 17
    • ATL in the USA
Re: Connecting Rod Bearings
« Reply #1 on: August 07, 2018, 04:29:12 PM »
No charts that I've ever seen. The differences in the thicknesses of the bearing shells from one to another is only something like three thou of a millimeter so something must be off.  Will the rod with good fit work on the side that is loose? If the crank journals measure the same then it has to be the rod and not the crank. Post your rod and crank numbers.

Guy
Now Retired Yamaha guy. Cut me and I bleed "Cinquasia Red"

Offline Onlyboards

  • Jr. Member
  • **
  • Posts: 40
  • Karma: 0
    • Carbondale, CO USA
Re: Connecting Rod Bearings
« Reply #2 on: August 07, 2018, 09:10:16 PM »
Guy,  thnx for the response.

I'm laughing right now because of course I didnt try to switch the good fitting one to the other journal.  Honestly It never crossed my mind because it fit so damn perfect. lol

I'll give it a go and post the
 numbers of my con rods and crank.


Paul

Offline Onlyboards

  • Jr. Member
  • **
  • Posts: 40
  • Karma: 0
    • Carbondale, CO USA
Re: Connecting Rod Bearings
« Reply #3 on: August 07, 2018, 11:56:58 PM »
Still sloppy even with the other rod.  crank case numbers (looking at front of engine)"exhaust side", left to right, 13.5,7,9,11

number on the crank itself stamped numbers 12 3,  raised numbers 14

connecting rod 1, y1 raised on connecting portion, 6f stamped on big end

connecting rod 2, @2 raised on connecting portion, 6h stamped on big end

Offline Onlyboards

  • Jr. Member
  • **
  • Posts: 40
  • Karma: 0
    • Carbondale, CO USA
Re: Connecting Rod Bearings
« Reply #4 on: August 07, 2018, 11:57:52 PM »
I'm thinking someone may have replaced a rod at somepoint in this bikes existence.


Offline Onlyboards

  • Jr. Member
  • **
  • Posts: 40
  • Karma: 0
    • Carbondale, CO USA
Re: Connecting Rod Bearings
« Reply #5 on: August 07, 2018, 11:59:01 PM »
13,5,7,9,11

Offline Onlyboards

  • Jr. Member
  • **
  • Posts: 40
  • Karma: 0
    • Carbondale, CO USA
Re: Connecting Rod Bearings
« Reply #6 on: August 08, 2018, 12:12:13 AM »
I would like to stress that I have the shop manual,  but even with that my numbers just dont seem to be making any sense.   Thanks for any help Guy


Offline guylr

  • Administrator
  • Hero Member
  • *****
  • Posts: 1126
  • Karma: 17
    • ATL in the USA
Re: Connecting Rod Bearings
« Reply #7 on: August 08, 2018, 04:16:45 AM »
I believe you are looking at the wrong crankcase numbers. If they are raised as cast they are the nut tightening sequence not the three journal size numbers which are stamped into the bottom side of the top front mounting lugs.

The crank numbers for the mains are the 1,2 and 3 but the rod journal numbers are not raised, they are stamped into the machined flat area on the left most crank wheel, side by side. The left number for the left rod and the right for the right. Both of your rods are #6.

Guy
Now Retired Yamaha guy. Cut me and I bleed "Cinquasia Red"

Offline Onlyboards

  • Jr. Member
  • **
  • Posts: 40
  • Karma: 0
    • Carbondale, CO USA
Re: Connecting Rod Bearings
« Reply #8 on: August 13, 2018, 06:34:53 PM »
Guy,  is there such a thing as an oversize con rod bearing for these bikes?  I cant seem to find anything about oversized bearings?   what the hell do people do when they machine the crank down for a rebuild?

Offline guylr

  • Administrator
  • Hero Member
  • *****
  • Posts: 1126
  • Karma: 17
    • ATL in the USA
Re: Connecting Rod Bearings
« Reply #9 on: August 13, 2018, 11:18:23 PM »
You either have to weld up the journal and remachine it to original size or trash bin the crank.

Guy
Now Retired Yamaha guy. Cut me and I bleed "Cinquasia Red"

Offline Onlyboards

  • Jr. Member
  • **
  • Posts: 40
  • Karma: 0
    • Carbondale, CO USA
Re: Connecting Rod Bearings
« Reply #10 on: August 14, 2018, 12:44:25 AM »
awesome.  know any people with any decent crankshafts for sale? haha!!! my measurements were off on the journals.  my crank is toast.   looking for one of the heavier ones from the later models probably.

Offline guylr

  • Administrator
  • Hero Member
  • *****
  • Posts: 1126
  • Karma: 17
    • ATL in the USA
Re: Connecting Rod Bearings
« Reply #11 on: August 14, 2018, 01:44:44 AM »
Good plan. Cranks were heavier from the 75 model on.

Guy
Now Retired Yamaha guy. Cut me and I bleed "Cinquasia Red"