BMW Chopper Build | Born Free USA

This year, I was lucky enough to be invited as a builder to the Born-Free Show. I had attended the show a few years back and it blew my mind, the other builders named on this list are truly world class too so it was a huge honour to be named among them. Born-Free is a motorcycle show set in Southern California and is best explained by the founders themselves “The Born-Free Show is a back to basics motorcycle event built on the shared passion of people building and riding their motorcycles. This is a place where motorcycles of all makes and models take the spotlight. The laid back atmosphere and beautiful landscape of the Oak Canyon Ranch creates a one of a kind family friendly event that is a refreshing change from the controlled chaos of the typical modern motorcycle event. Born-Free features a special invited builder area where thirty of the worlds finest motorcycle craftsmen will debut bikes they’ve been building just for Born-Free. These guys are small shop owners, and garage builders pushing themselves to create new future classics.

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My contribution to next years event will be one air freighted BMW Chopper, it’s a project that I kicked off at the beginning of the year. I took it to a few events to give people an idea of the concept and now things have escalated tenfold and my plans are slightly changing.

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Step one was to pull the motor out of the display frame and prepare it for the frame jig. I have had a 20mm plate kicking lying around since the last build which is drilled with 6.5mm holes every 50mm and allows me to tap M8 threads to make engine mounts on.

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With the bike (or part of it at least) up on the bench, I can start to plan the build. There is a lot to plan but where do I start? I found a rear rim from a 1960’s drum brake BMW for sale so I picked that up and fitted the M&H Racemaster slick from Coker Tyre. I then found a wrecker in Melbourne that had a rear drive unit in good condition and this will allow me to mock everything up. Once back home I could start to get a feel for the overall bike but I just couldn’t get a feel for the lines, it just didn’t look right. I had a length of 50mm tube left over and decided to make a frame to allow me to hang and position components where they need to be. Now I could use magnets and string to get some lines into the build so I can start to see what it will look like. It also allowed me to easily manipulate and reposition items before the final dimensions were locked down.

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I knew something didn’t look right, I dropped the motor 50mm and moved it back 50mm, this gave the frame lines a much more traditional shape. The BMW motor is very short and this gets worse when the alternator is removed which I am replacing with a traditional magneto. I had a good conversation with the guys from Morris Magneto in the USA and they can develop a magneto with a 180 degree cam that drives off the crankshaft. This will allow the bike to have a wireless ignition system that will be rotatable for fine ignition tuning.

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These wheels won't be the ones I am running, the wheels I am running will be the original 1960’s Snowflake design CNC machined out of billet 6061 Aluminium. This rear tyre has a large diameter so I am matching it with a 22″ front tyre that has a 28″ outside diameter. Of course, a motorcycle never came out with a 22″ tyre but I have found one and I will Matt design the rim to suit.

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The frame is a thing of beauty, the way the motor mounts into the frame and the frame's lines produce a really good looking profile. At this point, I needed to up my productivity as BMW had planned a launch night to display the bike. Leading up to this event I worked 16 hour days for a week and a half and then a 38 hour day leading up to the bike being shipped.

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Taking the bike off the jig was a huge moment for the project and made easy because of the three-stage engine mounting system. I have a set of engine mounts that mount to the frame and then those frame rails remove from the frame via a pair of Camburg links to make a strong and uniform joint. Whilst the frame was bolted to the motor in the jig I was able to complete over half the welding which made the frame strong enough to then bench weld to complete the 360 degree welds around all the joins. The straight through Titanium pipes measure 1 7/8″ and have a wall thickness of 1.1mm, I love welding Ti and it really is just like any other metal, lots of argon (purging inside) and cleanliness are key to good results. 

The more I strip off the motor the more I love the shape of it, the black combined with the billet aluminium, titanium, chromoly and the magneto belt drive setup with the dry sump pulleys harks back to my love of vintage drag racing. The negative space under the gearbox is now full of brake and electrical components.

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The reassembly process of the frame onto the motor went extremely well. With the carbs on, brake master cylinders incorporated into the rear engine mount and reservoirs on, it begins to take shape. These Smart Carbs are a thing of beauty, the footpegs are also attached and these have bronze bushes that will form the pivot point for the brake and clutch.

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When I first started to get interested in choppers it was the simplicity and the slim nature of them that I loved, my plan with this bike was to accentuate the size of the engine by building a slim bike around it. I think its working! I had planned to partner up with Volumetric in New Zealand to carbon print a pair of intake velocity stacks but after sitting some titanium on the inlet side of the motor and seeing that flow of titanium to billet alloy carb to billet alloy rocker covers into titanium exhaust I just fell in love with the aesthetic. So 28 hours into my work day, I decided to make some up out of 2.5 inch titanium. This required a mandrel to be made up to expand the inside diameter to suit the carbs. I jumped on the lathe, machined a small taper into some 65mm bar stock and pressed the tube over it in the press.

The rear drive unit comes from the stock R9T I pulled apart to build this bike and is matched perfectly to the engine's output and gearing so I really didn’t want to mess with what is a very well designed unit. Along with making the frame hug the drive unit, I machined up the driveshaft and then welded it together and assembled the universal joints to suit.

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With the pipes and the rear fender attached, the bike was looking amazing! The mix of raw metals looks incredible, stainless steel, titanium, chromoly and aluminium all in their raw state and all welded to the best of my ability over a 32 hour period. The tank came from the good people at Lowbrow Customs in the USA and after I removed all the mounting tabs, it floats and looks great on the frame. From the rear, I am over the moon with the semi finished product and from the front I am even more excited. I can’t wait to ride this!

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With the bike delivered to the BMW launch, I was excited to see its progress, as were many others. I love building things, I love challenges, I love sharing the process and teaching people along the way. I had definitely pushed myself further than I ever had before with the hours I poured into this build so far and I think it shows. With the Born Free Show in the USA looming and the global climate making everything more difficult, I am hopeful this bike will continue the way it has and get the grand treatment that it deserves in the USA.

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