Engine "Blueprinting"? What exactly does this mean?

LuckyStar64

LuckyStar64

PR Addict
So I've been doing some online surfing, and looking at vintage bike builds. If earning a living wasn't mandatory, I'd spend my time building cool $h!t, like vintage motorcycles, cars (I'm a Corvette freak, partial to all pre- 1974's. I actually have a super sweet '04 project I put together, but I love the old ones), and I LOVE, LOVE, LOVE 1940's-'60's mahogany Chris Craft and Hacker Craft speed boats. Especially the barrel backs.

Anyway-- I keep coming across write ups on vintage bike builds people have done, and the term "blueprinted" keeps coming up when they're talking about the engine. As in "The motor is stock, but it's been blueprinted". What the hell does that mean? Wasn't it blueprinted at the factory by the manufacturer? Like the parts breakdown? How is this any benefit? You can't get most of the parts anyhow? I was figuring that somebody here would put me up on the term. --L*64
 
When engines are built at a factory assy line, alot of little things don't exactly match up, as it's just inherent with the assy line process. Blue printing is basically matching the engine cases together where they meet the cylinder and machining that to a even surface, matching the gaskets so there isn't any overlay in the ports or anywhere that would restrict flow, either oil, fuel or water, so that it increases flow of everything as it was intended when drawn on the blueprints. Everything gets matched as intended. It's more of a difference in jap bikes than KTMs and Maicos as they were more hand built. I hardly saw anything with the Maicos I had.
 
Oh. I see. I was thinking that it meant that they made a diagram or something. So it basically means that it's been cleaned up, and the cases matched. --L*64
 
That's part of it... the biggest part is in the bearings and friction surfaces. When blueprinting you are also matching bearings to crank/rod to the best clearances for that application. usually upgrading the bearings as well. in a single it's not as big as when dealing with multi-cylinder machines. it "frees" up the motor, allows quicker revs and maintains a better balance.
 
Got it. It seemed like a "blueprint" meant that they were measuring, planning, designing, etc. So I was wondering why they'd do a "blueprint", and nothing else. --L*64
 
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