OzVMX Forum

Clubroom => Tech Talk => Topic started by: suzuki447 on March 25, 2010, 10:48:51 pm

Title: 76 rm125 small end bearing query.
Post by: suzuki447 on March 25, 2010, 10:48:51 pm

can anyone help i have 4 76 rm motors one in bike with bottom end done picked up piston kit 2nd oversize but someone who built motor has put larger conrod than standard .my stock smallend bearing is to small for conrod hole,needs approx 20mm size and piston to suit does anyone have an idea ,is rod out of different engine or did suzuki change things ,any help would be good thanks don.

Title: Re: 76 rm125 small end bearing query.
Post by: caps 999 on March 25, 2010, 11:09:42 pm

it was very common for people to run a 77 / 78 rod barrel and head they did this because the 76 rods and pistons are hard to come by i was restoring one but moved it on for this reason i still have a .5os ring set here for one

Title: Re: 76 rm125 small end bearing query.
Post by: Davey Crocket on March 25, 2010, 11:10:49 pm

Do you have an "A" motor?, may have a "B" crank or vice versa?. You can check your engine number on the Vintage Suzuki site to see what it is, check your other engine numbers at the same time. Also you need to check your bore/stroke.... RMA...56 x 50mm, RMB/C 54x54mm. Cheers John.  

Title: Re: 76 rm125 small end bearing query.
Post by: motomaniac on March 25, 2010, 11:17:59 pm

A 's had the old 14mm gudgeon (from memory) B's and on where larger 16mm gudgeon
Like DaveyCrocket said check the strokes maybe you have a B/C motor

Title: Re: 76 rm125 small end bearing query.
Post by: DR on March 26, 2010, 07:51:00 am

Back to front Moto, the A's had the 16mm pin and the all the rest have 14mm ;)  (the A bearing dimensions are 16x21x19.6mm

 

Title: Re: 76 rm125 small end bearing query.
Post by: motomaniac on March 26, 2010, 09:07:23 am

Quote from: Doc on March 26, 2010, 07:51:00 am

Back to front Moto, the A's had the 16mm pin and the all the rest have 14mm ;)  (the A bearing dimensions are 16x21x19.6mm

 

Okay I'm often a bit backward but I knew they were different

Title: Re: 76 rm125 small end bearing query.
Post by: suzuki447 on March 26, 2010, 09:06:48 pm

thanks for all the help everyone the motor im doing up is a 76 but the conrod has 19mm hole for small end bearing ,do u think it could be out of a mid 80,s motor. thanks again

Title: Re: 76 rm125 small end bearing query.
Post by: Lozza on March 26, 2010, 10:24:10 pm

You might have had a rod swap, which is a good thing, as a 19mm pin bore will take a 19 X 15mm bearing and most modern 125 pistons have 15mm pin bores

Title: Re: 76 rm125 small end bearing query.
Post by: suzuki447 on March 28, 2010, 11:10:40 pm

thanks lozza for reply ,does anyone know where i can get a .05 125 piston with a 19mm od small end bearing and pin to match ,i checked at bike shop in wisco catolog but could find one ,can someone help thanks don.