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Bb shears on 421


Timshee

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Hey.....that's my job chief!

LOL

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They should be small bores. Unless maybe you hot lap motors 8-10 times it mike make that kind of heat, but a set of small bores would do it justice.

 

Not sure on the difference but I know the cut off for big bore pipes is a bit different between CPI and Shearer

Edited by trickedcarbine
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I'm just going to get some sb if anybody has some I'm ready to buy

Good luck on that. I let a buddy bolt my shearers on this weekend and that poor bastard had to cave and order a new show chrome set from fast. The used ones literally list for minutes to hours, then they're gone
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I would try to run the big bores and see how they do.  I have seen some really good running 421 motors with Shearer Big Bore inframe pipes.  The small bore Shearers will be better for a drag motor but at least you could run the bike until you get a set of small bores.

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I'd run what you own. (Like everyone else does)

Then if the bike runs at all you can tell everyone how you ran BB pipes on a motor that SB pipes were specifically designed for and they worked. You won't have anything to compare them to…….So you can tell everyone they worked great. (Kinda like everyone else) LOL

 

Or….you can call the guy that designed and built the pipes and he'll tell you what a bad idea it is and how much more you can make with the right sized pipe.

 

Or…..decide to "Try them and see" Like everybody else does………..

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