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Old 11-01-2012, 12:23 PM   #7
bmweuro
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Joined: Nov 2003
Location: Chico, California
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Quote:
Originally Posted by supershaft View Post
I have no expereince with nikisil big bore kits. I do have experience with iron lined big bore kits. They run great for a while. Then they start leaking oil for not enough gasket area at both the head and the case. It's miracle they don't blow a head gasket at their super then area between the cylinder stud hole and the bore. Then by around 20k miles the cylinder walls become very distorted for not being thick enough. Oil usage goes up and performance goes down. You can run a Sunnen hone done the cylinder and see that the bore is corrugated right in sync with the cylinder fins. It gets pretty ugly pretty fast. Our engines aren't the only ones that have had the bores taken out too far for their own good. Some people go there with about everything. BMW stopped at 94mm for a lot of good reasons IMO. They actually thought 94mm was too far and that is one of the reasons why they quit making 1000's for a while. I don't know from experience but I would think that super thin nikisil plated aluminum would distort a lot more that super thin iron or steel but . . . .

Better performance? I am all for more displacement. Consider your 980cc bike a hogged out 750 and look elsewhere for more performance. At 980cc's your engine is already a super short stroke engine for a two vavle hemi head at 1.33:1 bore to stroke ratio. 1.33:1 was THE limit for over squared engines for years mostly because you get to point of diminishing returns with a wide included valve angle and a super short stroke. They stopped there with their 450cc engine too. R65's have the exact same bore to stroke ratio as a R100.
You are comparing apples to oranges here. This is not a modified BMW cylinder etc.
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