920 cc Conversion of Iron 850 Cylinders

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I think the biggest problem of going that route is the area between the bores and heat, and the fact the transmission is not up to it. It could create many more problems than it would be worth.
 
I'm hoping that taking lots of weight of the bike will help. Ideally this will reduce stress on the transmission enough to let it live with a moderately tuned 920.
Also, using an Alloy barrel should be a positive for heat dissipation.
I wonder if the problematic Alloy barrel 920s and possibly the cast iron 920s suffer from inadequate interference between liner and barrel.
Vincents require 6 thou interference between the liner and the alloy muff. Any less and hot spots show up in a hurry.
At 6 thou interfence the heat transfer is good, the bores last and last.
That's an 84 mm bore so I'm thinking of going 5 thou interference at 81 mm ( 920)
The individual Vincent cylinders completely out in the breeze do have a big cooling advantage over even an alloy Norton twin barrel.

With the ventilated cast iron the interfence fit can't be very much, even where there is metal.

Glen
 
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I have two Enfield Interceptors. One standard issue the other a Rickman. Exact same power unit. The Rickman is significantly lighter. Just in straight ahead acceleration the difference is quite noticeable. Weight matters.
 
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