We begin rebuild of a 1971 Honda CB 750 K1…

Aluminum-Sheet

Our buddy Rich dropped by the shop with a project in mind, a 1971 Honda CB 750 K1 which was sitting in pieces in his garage.  We decided to take on the challenge of putting it back together, with an eye on some customization he envisioned…

CB 750 K1: a classic enters the shop…

 

These early Honda CB 750 K1 bikes are getting harder and harder to find.  Becoming the go-to bike to turn into “Cafe Racers” has inflated prices  Roughly 5 years ago, poor condition CB’s began fetching exorbitant prices, so finding one that doesn’t break the bank takes some searching.  Since Rich already had most of what was needed for a complete build, we figured it might be fun to throw some MotoPreserve touches onto the classic Honda.

There are several things that Rich wanted done to the bike to make it his own.  He had already painted a classic checkerboard style stripe on the tank – so we could see where this build was going.  We quickly ordered up some parts including: custom oil tank (so it can open up the “triangle” a bit), stainless oil tank lines, modern regulator/rectifier, smaller battery, and a handful of other goodies.  Time to get cracking!

Cardboard test seat and cowl...

Cardboard test seat and cowl…

We decided to start on the seat and rear cowl first.  These custom pieces are going to dictate the look of this bike more than any other component – so it was time for some cardboard engineering.  The biggest challenge was going to be Rich’s request to make the seat capable of 2-up riding.  “Can’t leave the girlfriend at home,” he said.  Well, how the hell do we make a seat look cool, and still provide room for a passenger?

Cardboard is your friend…

 

We often begin with some cardboard cut-outs of various shapes, just to see which direction works best.  The upholstery work scheduled with Corinna over at Via Meccanica, it was time to get the seat pan done!  This pan will be made from 6061 aluminum sheet – easily shaped and welded.  We always have plenty of stock of 6061 around the shop.  After taking some basic measurements we cut out a cardboard ‘test-seat.’  The key was figuring out the angles of the 1971 CB 750 K1 frame tubes that the seat will sit on.  Once we liked the rough shape, we ripped into the aluminum to get the basic outline of the pan.

A template for the seat pan bends...

A template for the seat pan bends…

Once the template is cut from aluminum, it’s time for more measurements and rough sketches.  The sketches will guide the bends that eventually shape the pan.  All shaping is done with hammer and bag, metal dollies, and a 1-gallon paint can for initial rear upsweep radius.  There is probably a more ‘proper’ tool than paint cans, but we have yet to find one…

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The next step was to choose a cowl design.  The obvious choice would be the classic cafe racer hump, but we were looking for something more subtle.  Since the 2-up seat needs to accommodate a passenger, it’s going to be long.  The cowl we designed is closer to ‘tracker’ style, and hopefully provides visual substance to the rear of the bike.

Stay tuned for the final results…

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