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Norton Twins Heavy Duty Crankcases

Norton Twins Heavy Duty Crankcases



Starting with a set of MK2 850 Commando Crankcases, we have created our own patterns to sand cast these cases but strengthened in the areas where we know they are prone to breaking! Particularly at the top side of the timing case cavity and the upper areas of the drive side.

Cast in fully heat treated LM25TF, they are machined on one of our state of the art 5 axis machines to give a product of a quality that has not previously been available. 

As standard, we make to 750/850 spec, but we also produce our 1,000cc cases where the bores and main bearings have been moved further apart to accommodate the bigger bores. 

All variants can be supplied to " Road" spec which allows the fitting of the standard alloy chaincase, or "Race" spec where the drive side outer is left with 12mm more material on it, for maximum strength - to be used only with belt drive primary & an outer cover only. 

Cases are supplied bare with:

  • Camshaft bushes fitted & reamed
  • Helicoils for the 4 through bolts fitted
  • The pesky little circlip for the intermediate gear spindle fitted
  • 850 style angled steel breather pipe at the back of timing cover fitted (unless this breather specifically deleted)
  • Blanking plugs for oilways fitted

We produce our cases with the drive side oil seal retained by circlip 06.5245 (not included) as on Mk3, not with the thin lip as used on earlier variants which always broke off. As standard, we produce with the 850 style breather at the back of the timing chest, but can produce with no breather or with `Combat` style breather at back of crankcase to special order. Can also produce to take magneto, again to special order. All `specials` have price premiums attached and can ONLY be incorporated when we are making a new batch which is typically only once every 12 to 24 months.

New batch in stock now!




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