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Crankcase

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

Crankcase

Several significant changes were effected in this time period. Most notable was the change from distributor ignition where the magneto used to be, to points ignition in the timing cover. This initiated changes to the tachometer drive, which was relocated from the timing cover to the crankcase on the timing side now driven from the end of the camshaft via a worm gear. Further changes to the timing side included closing the old distributor opening on the aft-most position of the case. This was later opened again when Norton thought that an electric start might be installed.

From late 1971 through to the end of the 750 production in 1973, the 850 changed to new cases without the opening. This modification was never done until the 1975 model and the action was done in the primary chaincase instead. The breather assembly attachment to the rear for the 1972 model affected the cases which added the opening and threads for this. Another modification was strengthening added around the main bearing bosses. I believe this was done for the introduction of the 850. At the same time the holes and threads were added for the Allen bolts which add additional support for the 850 barrels to the cases.

Some notes on disassembly and reassembly as follows. Make sure you have removed all bolts and studs from the cases before you try to separate them. I myself have forgotten about that nasty one which is only a screw in the near bottom back and after several good raps on the bench have discovered this one still intact. Make sure the conrods are well supported and held away from the case. I highly recommend cutting a template from wood that has holes for a few studs so it can be clamped in place (only clamp the template to one case when separating the cases). This should hold the rods in situ so they don't bang around when working on the cases or timing gear cluster. Another trick is to use an old inner tube and elastic bands. Whatever you do, don't allow the rods to bang against the cases as nicks and dents at this point could case possible breakage of the rods. This support also makes it easier to remove and fit the pistons to the small end eye.

When all is well and clean after disassembly, inspect all the studs, bolts, nuts, and washers and make sure threads are good and all fits together like it should (the NOC cautions against making sure that you clean the thread holes carefully. The use of degreaser will dry out the threads and cause the studs and screws to become locked in place). I would recommend that you put a drop of machine oil in each thread bore upon reassembly. Clean the crankcase jointing faces well and make sure they fit tight together before installing the crank and rods. I have ridden some 30,000 miles on a set of cases without a drop of oil out of them, and no silicon either. Again cleanliness is the key to reassembly.

If you have an unlimited budget and feel it necessary, buy stainless nuts, bolts and washers for the cases. The nice thing is you hardly ever touch them so they should last forever. With a lot of elbow grease and lots of polishing you can make the cases look like they were chromed.

I have heard of several different scenarios for sealing the crankcases so they don't leak oil. Yamabond, available from your local Yamaha dealer, is probably your best bet for the case that doesn't want to seal or for one in which there are deep scratches from some backyard mechanic who thought the best way to separate the cases was with the hammer and chisel method. Also silicon has been used but I would caution against this method as when the cases are pulled together the silicon squeezes out and could become dislodged on the inside and flow to the oil passages where it could block them and create disastrous problems. Again I say clean the case surfaces well with a razor knife or blade so the mating surfaces are clean and without deep scratches. When nipped up tight no oil leaks should be apparent. After running in for several hours check all fastenings on the crankcases to ensure they are still tight and to proper torque specs.

I have left out various parts from the parts list which go into the crankcase, some examples would be cam bushes and main bearings, and only listed parts which are for the case assembly.

Crankcase

1968 Commando
Fastback after Serial Number 126125 - Frame Number 126125
Part No. Description Quantity Models
 060600  Crankcase complete with timing cover                     1 All
 060601  Crankcase halves assembled 1 All
 060602  Crankcase drive side 1 All
 060717  Crankcase timing side 1 All
 24251  Cylinder barrel stud 6 All
 T-2209  Cylinder barrel stud stepped 2 All
 18943  Cylinder barrel stud front 1 All
 24689  Sump screw 2 All
 048023  Oil seal timing side shaft 1 All
 048079  Oil seal circlip 1 All
 16945  Sump filter body 1 All
 16949  Filter/body washer 1 All
 16948  Filter body circlip 1 All
 16946  Filter gauze 1 All
 16947  Filter gauze washer 1 All
 E-4591  Timing cover oilway plug 1 All
 16902  Oilway set pin 1 All
 T-1084  Set pin washer 1 All

 

1969 Commando
Fastback, S and R after Serial Number 131257 - Frame Number 131257
Part No. Description Quantity Models
 061099  Crankcase complete with timing cover    1 All (hole closed) 
 061112  Crankcase halves assembled 1 All (hole closed)
 060602  Crankcase drive side 1 All
 061100  Crankcase timing side 1 All (hole closed)
 24251  Cylinder barrel stud 6 All
 T-2209  Cylinder barrel stud stepped 2 All
 18943  Cylinder barrel stud front 1 All
 24689  Sump screw 2 All
 048023  Oil seal timing side shaft 1 All
 048079  Oil seal circlip 1 All
 16945  Sump filter body 1 All
 16949  Filter/body washer 1 All
 16948  Filter body circlip 1 All
 16946  Filter gauze 1 All
 16947  Filter gauze washer 1 All
 E-4591  Timing cover oilway plug 1 All
 16902  Oilway set pin 1 All
 T-1084  Set pin washer 1 All

 

1970 Commando
Fastback, S, R and Roadster after Serial Number 135140 - Frame Number 135140
Part No. Description Quantity Models
 061537  Crankcase complete with timing cover  1 All (hole opened) 
 061417  Crankcase halves assembled 1 All (hole opened)
 061538  Crankcase drive side 1 All (hole opened)
 061415  Crankcase timing side 1 All (hole opened)
 24251  Cylinder barrel stud 6 All
 T-2209  Cylinder barrel stud stepped 2 All
 18943  Cylinder barrel stud front 1 All
 24689  Sump screw 2 All
 048023  Oil seal timing side shaft 1 All
 048079  Oil seal circlip 1 All
 16945  Sump filter body 1 All
 16949  Filter/body washer 1 All
 16948  Filter body circlip 1 All
 16946  Filter gauze 1 All
 16947  Filter gauze washer 1 All
 E-4591  Timing cover oilway plug 1 All
 16902  Oilway set pin 1 All
 T-1084  Set pin washer 1 All

 

1971 Commando
 Fastback, Roadster, Hi Rider and SS after Serial Number 141717 - Frame Number 141717 
Part No. Description Quantity Models
 061537  Crankcase complete with timing cover  1 All
 061417  Crankcase halves assembled 1 All
 061538  Crankcase drive side 1 All
 061415  Crankcase timing side 1 All
 24251  Cylinder barrel stud 6 All
 T-2209  Cylinder barrel stud stepped 2 All
 18943  Cylinder barrel stud front 1 All
 24689  Sump screw 2 All
 048023  Oil seal timing side shaft 1 All
 048079  Oil seal circlip 1 All
 16945  Sump filter body 1 All
 16949  Filter/body washer 1 All
 16948  Filter body circlip 1 All
 16946  Filter gauze 1 All
 16947  Filter gauze washer 1 All
 E-4591  Timing cover oilway plug 1 All
 16902  Oilway set pin 1 All
 T-1084  Set pin washer 1 All

 

1972 Commando
Fastback, Roadster Roadster Combat, Interstate and Hi Rider
after Serial Number 200001 - Frame Number 200001
Part No. Description  Quantity  Models
 063334  Crankcase halves assembled 1 All (altered
 for breather) 
 NM11790   Crankcase dowel (timing cover) 1 All
 062621  Crankcase dowel (front and rear case)  1 All
 062639  Cylinder barrel stud 6 All
 062640  Cylinder barrel stud stepped 2 All
 062641  Cylinder barrel stud front 1 All
 062664  Oil pump stud 2 All
 27815  Nut, oil pump stud 2 All
 062638  Grub screw, oil stop 1 All
 NM21287  Junction block dowel 1 All
 22850  Sump plug 1 All
 062624  Washer, sump plug 1 All
 000012  Washer, blanking plate bolt 2 All
 060633  Bolt, blanking plate 2 All
 062548  Gasket, blanking plate 1 All
 061542  Blanking plate 1 All
 061921  Bolt 1 All
 16228  Split pin 1 All
 0700223  Nut 1 All

 

1973 Commando
Roadster, Hi Rider and Interstate
Part No. Description Quantity Models
 060600  Crankcase complete with timing cover                       1  All (750) 
 060601  Crankcase halves assembled 1 All (750)
 060716  Timing cover 1 All
 060602  Crankcase drive side 1 All
 060717  Crankcase timing side 1 All
 060719  Timing cover gasket 1 All
 24251  Cylinder barrel stud 6 All
 T-2209  Cylinder barrel stud stepped 2 All
 18943  Cylinder barrel stud front 1 All
   Timing cover screw (long) 6 All
 E-6980  Timing cover screw (short) 6 All
 24689  Sump screw 2 All
 T-2036  Camshaft bush timing side 1 All
 T-2037  Camshaft bush drive side 1 All
 048023  Oil seal timing side shaft 1 All
 048079  Oil seal circlip 1 All
 16945  Sump filter body 1 All
 16949  Filter/body washer 1 All
 16948  Filter body circlip 1 All
 16946  Filter gauze 1 All
 16947  Filter gauze washer 1 All
 E-4591  Timing cover oilway plug 1 All
 16902  Oilway set pin 1 All
 T-1084  Set pin washer 1 All

 

1974 Commando
Roadster, Hi Rider and Interstate
Part No. Description Quantity Models
 064045  Crankcase complete with timing cover                       1 All
 060601  Crankcase halves assembled 1 All
 060716  Timing cover 1 All
 060602  Crankcase drive side 1 All
 060717  Crankcase timing side 1 All
 060719  Timing cover gasket 1 All
 24251  Cylinder barrel stud 6 All
 T-2209  Cylinder barrel stud stepped 2 All
 18943  Cylinder barrel stud front 1 All
   Timing cover screw (long) 6 All
 E-6980  Timing cover screw (short) 6 All
 24689  Sump screw 2 All
 T-2036  Camshaft bush timing side 1 All
 T-2037  Camshaft bush drive side 1 All
 048023  Oil seal timing side shaft 1 All
 048079  Oil seal circlip 1 All
 16945  Sump filter body 1 All
 16949  Filter/body washer 1 All
 16948  Filter body circlip 1 All
 16946  Filter gauze 1 All
 16947  Filter gauze washer 1 All
 E-4591  Timing cover oilway plug 1 All
 16902  Oilway set pin 1 All
 T-1084  Set pin washer 1 All

 

1975 Commando
Roadster, Hi Rider and Interstate
Part No. Description Quantity Models
 065666  Crankcase halves assembled                                        1 All
 066161  Timing cover 1 All
 061092  Timing cover gasket 1 All
 24251  Cylinder barrel stud 6 All
 T-2209  Cylinder barrel stud stepped 2 All
 18943  Cylinder barrel stud front 1 All
   Timing cover screw (long) 6 All
 E-6980  Timing cover screw (short) 6 All
 24689  Sump screw 2 All
 T-2036  Camshaft bush timing side 1 All
 T-2037  Camshaft bush drive side 1 All
 048023  Oil seal timing side shaft 1 All
 048079  Oil seal circlip 1 All
 067676  Sump filter body 1 All
 067680  Filter/body washer 1 All
 067679  Filter body circlip 1 All
 067677  Filter gauze 1 All
 067678  Filter gauze washer 1 All
 067600  Timing cover oilway plug 1 All
 16902  Oilway set pin 1 All
 T-1084  Set pin washer 1 All

 

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