B44 Big Bore Kit

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B44 Big Bore Kit

Post by hhh » Wed Jan 30, 2019 6:31 pm


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Re: B44 Big Bore Kit

Post by hhh » Sat Feb 02, 2019 5:00 am

Maybe a more pertinent question is: is there any technical reason why this is a bad idea? I.e., is there sufficient cylinder wall thickness? Note the bore is Nikasil plated. Is it possible they haven't made any yet and are first gauging demand?

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Re: B44 Big Bore Kit

Post by kommando » Sat Feb 02, 2019 12:35 pm

Mark Cook recommends not going above 82mm on a B44, that's enough for me to never try going above 82mm. Have no direct experience of this kit to know if it can survive Mark's rule but not tempted to try.

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Re: B44 Big Bore Kit

Post by hhh » Sat Feb 02, 2019 4:13 pm

Mark's condition may only apply to the stock liner. Maybe these are thicker? There's not much detail.

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Re: B44 Big Bore Kit

Post by lathejack » Sat Feb 02, 2019 5:59 pm

I think the Nickasil coating will be applied directly to the Alluminium cylinder so they won't have a liner fitted, which is why they can safely go to the 84mm bore size. The crankcase mouth needs boring out to fit these cylinders, so the Alluminium spigot on the bottom of these cylinder barrells is a larger diameter to increase its wall thickness and without interfering with the stud holes.

Looking at the photos of the cylinder it certainly does not appear to have a liner fitted, which is usual with a Nickasil coating. There is no projection, or fire ring, above the top face of the barrell, unlike a standard B44 item with a liner.
Last edited by lathejack on Sat Feb 02, 2019 8:26 pm, edited 2 times in total.
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Re: B44 Big Bore Kit

Post by hhh » Sat Feb 02, 2019 6:03 pm

Thanks lathejack, that all makes sense. The downside being no overbores are possible, but I suppose you could always sleeve it back to stock. Now I just need them to get back in stock and a hard Brexit to crash the pound.

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Re: B44 Big Bore Kit

Post by kommando » Sat Feb 02, 2019 10:26 pm

It's the proximity of the stud holes that is the issue, steel liner or all aluminium barrel does not change that as the material is too thin at these 4 points.

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