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Conrods

Steve Jowett www1.kingston.net/~fortierg/mainb.htm

The same con rods were used on all twins from the 1966 650 up to the 850 Commando. They are exceptional rods and give long life. The rod was modified for the 1975 model along with its cap. Although I have found several references to this modification, I can find no reference as to why

Miscellaneous Specifications

Material:- Aluminum alloy B.S. L83 or 2L65 or L77 heat treated Dural tube 'B' or 'S'
Length (entres):- 5.877" - 5.873" (129.276mm - 129.274mm)
Big End Eye i.d.:- 1.8950" - 1.8955" (48.133mm - 48.145 mm) (less shells caps bolted on)
Width at Big End Eye:- 1.010" - 1.008" (25.65mm - 25.60 mm)
Rod Side Clearance:- 0.013" - 0.016" (0.330mm - 0.406 mm)
Rod End Clearance:- Less than .001" (0.0254mm)
Conrod Bolt Torque:- 25 foot pounds

General Notes

I agree with the workshop manual in that when removing and reassembling the connecting rods, new shell bearings should be fitted. This is just good practice and for the number of times you would want to take the motor down to this stage it may save a few years towards that next rebuild. Make sure upon reassembly that you do not scratch or score the shells as they are easily damaged on the bearing face. Special care should be used when dismantalling the cases as the rods could hit the case and cause damage beyond repair. If the rods are nicked or deeply scratched, I would recommend replacement. Polishing the rods can help strengthen them but I would only do this for a racing machine. If you take material off as you would in polishing I would check the weight prior to and after removal. This will have an effect on balancing. Again I cannot stress enough about the cleanliness upon re-assembly. These parts are vital to the operation of your machine and any dirt that becomes lodged now could prove fatal later.

J.B. Nicholson - Modern Motorcycle Mechanics

750 cc Con Rods:- In 1966 when the oil pump speed was increased and other lubrication modifications were introduced on the 750 and 650 motors a 1/16" diameter spray hole through the rod big end was provided to give additional piston and cylinder lubrication. These rods should be installed with the oil spray hole to the outside of the engine, i.e. away from the flywheel on each side. This rod big end spray hole is not recommended on the 1965 and earlier motors with the slower speed oil pump and if a later rod is being fitted to one of the earlier motors the spray hole can be simply peened shut from the outside.

Con Rod Nut Torque:- 1968 on Norton specifications show an increase on this item to 25 foot pounds. The earlier specification was 15 foot pounds. The 25 foot pound torque is considered suitable for all 650 and 750 motors; these use 3/8" diameter bolts. On the earlier and smaller twins models using 5/16" bolts, torque should be limited to 15 foot pounds.

Rod Bearing Caps:- It is essential that these be kept with the rod from which removed and refitted so the cap is the same way around with the register marks on the cap and the rod lined up.

 

Con Rods

1968 Commando
Fastback after Serial Number 126125 - Frame Number 126125
Part No. Description Quantity Models
 25369  Connecting rod with cap 2 All
 23254  Connecting rod cap bolt 4 All
 23253  Cap bolt nut 4 All
 25384  Con rod bearing shell (top half) standard 2 All
 23255  Con rod bearing shell (bottom half) standard  2 All
 25409  Con rod bearing shell (top half) 0.010" 2 All
 25410  Con rod bearing shell (top half) 0.020" 2 All
 25411  Con rod bearing shell (top half) 0.030" 2 All
 25413  Con rod bearing shell (top half) 0.040" 2 All
 25165  Con rod bearing shell (bottom half) 0.010" 2 All
 25166  Con rod bearing shell (bottom half) 0.020" 2 All
 25167  Con rod bearing shell (bottom half) 0.030" 2 All
 25168  Con rod bearing shell (bottom half) 0.040" 2 All

 

1969 Commando
Fastback, S and R after Serial Number 131257 - Frame Number 131257
Part No. Description Quantity Models
 25369  Connecting rod with cap 2 All
 23254  Connecting rod cap bolt 4 All
 23253  Cap bolt nut 4 All
 25384  Con rod bearing shell (top half) standard 2 All
 23255  Con rod bearing shell (bottom half) standard  2 All
 25409  Con rod bearing shell (top half) 0.010" 2 All
 25410  Con rod bearing shell (top half) 0.020" 2 All
 25411  Con rod bearing shell (top half) 0.030" 2 All
 25413  Con rod bearing shell (top half) 0.040" 2 All
 25165  Con rod bearing shell (bottom half) 0.010" 2 All
 25166  Con rod bearing shell (bottom half) 0.020" 2 All
 25167  Con rod bearing shell (bottom half) 0.030" 2 All
 25168  Con rod bearing shell (bottom half) 0.040" 2 All

 

1970 Commando
Fastback, S, R and Roadster after Serial Number 135140 - Frame Number 135140
Part No. Description Quantity Models
 25369  Connecting rod with cap 2 All
 23254  Connecting rod cap bolt 4 All
 23253  Cap bolt nut 4 All
 25384  Con rod bearing shell (top half) standard 2 All
 23255  Con rod bearing shell (bottom half) standard  2 All
 25409  Con rod bearing shell (top half) 0.010" 2 All
 25410  Con rod bearing shell (top half) 0.020" 2 All
 25411  Con rod bearing shell (top half) 0.030" 2 All
 25413  Con rod bearing shell (top half) 0.040" 2 All
 25165  Con rod bearing shell (bottom half) 0.010" 2 All
 25166  Con rod bearing shell (bottom half) 0.020" 2 All
 25167  Con rod bearing shell (bottom half) 0.030" 2 All
 25168  Con rod bearing shell (bottom half) 0.040" 2 All

 

1971 Commando
Fastback, Roadster, Hi Rider and SS after Serial Number 141717 - Frame Number 141717
Part No. Description Quantity Models
 25369  Connecting rod with cap 2 All
 23254  Connecting rod cap bolt 4 All
 23253  Cap bolt nut 4 All
 25384  Con rod bearing shell (top half) standard 2 All
 23255  Con rod bearing shell (bottom half) standard  2 All
 25409  Con rod bearing shell (top half) 0.010" 2 All
 25410  Con rod bearing shell (top half) 0.020" 2 All
 25411  Con rod bearing shell (top half) 0.030" 2 All
 25413  Con rod bearing shell (top half) 0.040" 2 All
 25165  Con rod bearing shell (bottom half) 0.010" 2 All
 25166  Con rod bearing shell (bottom half) 0.020" 2 All
 25167  Con rod bearing shell (bottom half) 0.030" 2 All
 25168  Con rod bearing shell (bottom half) 0.040" 2 All

 

1972 Commando
Fastback, Roadster Roadster Combat, Interstate and Hi Rider
after Serial Number 200001 - Frame Number 200001
Part No. Description Quantity Models
 25369  Connecting rod with cap 2 All
 23254  Connecting rod cap bolt 4 All
 23253  Cap bolt nut 4 All
 25384  Con rod bearing shell (top half) standard 2 All
 23255  Con rod bearing shell (bottom half) standard  2 All
 25409  Con rod bearing shell (top half) 0.010" 2 All
 25410  Con rod bearing shell (top half) 0.020" 2 All
 25411  Con rod bearing shell (top half) 0.030" 2 All
 25413  Con rod bearing shell (top half) 0.040" 2 All
 25165  Con rod bearing shell (bottom half) 0.010" 2 All
 25166  Con rod bearing shell (bottom half) 0.020" 2 All
 25167  Con rod bearing shell (bottom half) 0.030" 2 All
 25168  Con rod bearing shell (bottom half) 0.040" 2 All

 

1973 Commando
Roadster, Hi Rider and Interstate
Part No. Description Quantity Models
 25369  Connecting rod with cap 2 All
 23254  Connecting rod cap bolt 4 All
 23253  Cap bolt nut 4 All
 25384  Con rod bearing shell (top half) standard 2 All
 23255  Con rod bearing shell (bottom half) standard  2 All
 25409  Con rod bearing shell (top half) 0.010" 2 All
 25410  Con rod bearing shell (top half) 0.020" 2 All
 25411  Con rod bearing shell (top half) 0.030" 2 All
 25413  Con rod bearing shell (top half) 0.040" 2 All
 25165  Con rod bearing shell (bottom half) 0.010" 2 All
 25166  Con rod bearing shell (bottom half) 0.020" 2 All
 25167  Con rod bearing shell (bottom half) 0.030" 2 All
 25168  Con rod bearing shell (bottom half) 0.040" 2 All

 

1974 Commando
Roadster, Hi Rider and Interstate
Part No. Description Quantity Models
 25369  Connecting rod with cap 2 All
 23254  Connecting rod cap bolt 4 All
 23253  Cap bolt nut 4 All
 25384  Con rod bearing shell (top half) standard 2 All
 23255  Con rod bearing shell (bottom half) standard  2 All
 25409  Con rod bearing shell (top half) 0.010" 2 All
 25410  Con rod bearing shell (top half) 0.020" 2 All
 25411  Con rod bearing shell (top half) 0.030" 2 All
 25413  Con rod bearing shell (top half) 0.040" 2 All
 25165  Con rod bearing shell (bottom half) 0.010" 2 All
 25166  Con rod bearing shell (bottom half) 0.020" 2 All
 25167  Con rod bearing shell (bottom half) 0.030" 2 All
 25168  Con rod bearing shell (bottom half) 0.040" 2 All

 

1975 Commando
Roadster, Hi Rider and Interstate
Part No. Description Quantity Models
 064896  Connecting rod with cap 2 All
 066486  Connecting rod cap bolt 4 All
 067827  Cap bolt nut 4 All
 064285  Con rod bearing shells (pair) standard           2 All
 064286  Con rod bearing shell (pair) 0.010" 2 All
 064287  Con rod bearing shell (pair) 0.020" 2 All
 064288  Con rod bearing shell (pair) 0.030" 2 All
 064289  Con rod bearing shell (pair) 0.040" 2 All

 

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