« Reply #16 on: January 09, 2013, 02:24:34 pm »
I really hope that you keep this bike and actually race it in the pre 60 and pre 65 class. For months you've been harping on about how nobody brings their old pre 65 250 race bikes out to race any more so now you've got one of the most unique bikes in Australia there's nothing stopping you. I've known this bike its whole life since being rebuilt and know the dedication and engineering genius that went into it. What scares me Dave is that you'll tire of it after a month and sell it off again, this unique bike deserves a better fate than that. The world is watching.
This Adler MB250 was also featured in VMX # 37. 
The first thing that must be noted in coming across an Adler is that we don’t come across many Adlers! Examples of these German-made machines are here in Australia, but in very small numbers. Of that quantity, road bikes make up the majority, with the off-road and competition models, like this ‘Motocross’ 250cc twin, exceedingly rare indeed. In fact, we wouldn’t be surprised if Gus Priem’s replica of a 1957 250 Motocross is the only example of an off-road Adler in this country.
Gus explains the story of how he turned a pile of rough and rusty Adler parts (‘Adler’ means ‘Eagle’ in English, if you were wondering) into an impressive classic scrambler.
1957. A very good year. I was a lad of 17, living in Amsterdam in the Netherlands when these two Fire Engine Red Motocross Adlers came on the scene. What a sight! Back then, Dutch scramblers Rudy Boom and Jan van der Hoek cleaned up the opposition on these German-made machines. Against pilots on the likes of Jawa, CZ and Maico, Boom and Hoek cleaned up most of the trophies between them, until the Greeves, DOT and Cotton machines came along.
These twin cylinder Adlers made a lasting impression on me. Not just for their looks, but their awesome sound as well. From the factory, these bikes had no air filter, just a funnel with some gauze over it. So, combined with the sound of the exhaust, the induction noise when accelerating was sweet music to my 17-year-old ears!
Fast forward a few decades, and I’m retired, with the time to relive those youthful days, so I decided to build myself a copy of those Fire Engine Red Adler machines from my youth. Given the passage of time and the increasing rarity of parts, I knew it wouldn’t be easy, but I was determined to build myself an Adler 250 Motocross as accurate to the 1957 original as was practical.
I started by advertising in the ‘Wanted to Buy’ section of all the motorcycle magazines for a complete Adler motorcycle or parts. Adlers weren’t a common bike here in Australia, so I knew I’d have to be lucky. Fortunately, I was! One Friday night, a bloke rings me. ‘I’ve got three of the buggers,’ he said. ‘If you want them, you’ll have to buy the lot.’ He lived in Melbourne; me in Sydney, so we arranged a mutually-agreeable meeting point, and one Sunday morning, I got my first look at the bikes.
The fact they all fitted in the back of a canopied ute wasn’t encouraging, and opening the tailgate revealed more disappointment. The three ‘bikes’ were actually three frames, with some wheels, guards, fuel tanks and engine parts. However, sorting through the haul was more encouraging. There would certainly be enough there to make one good bike, maybe even two. I was pretty happy with it, actually. So, after a bit of a price adjustment, the Adler haul was packed into my ute, and I was on my way back to Sydney with the basis of my cherished project.
While my memory of the Adlers was vivid, I couldn’t rely on that alone when it came to restoring my motocross machine, so I sourced some period factory images from a Dutch motorcycle magazine to use as the basis for the restoration.
I started by rebuilding the wheels. Standard rims on the Adler Motocross were 16-inch. I managed to source some 21 and 18-inch rims from swap meets, then painstakingly relaced the spokes.
All the Adlers I had bought were road bikes, which have a different frame geometry and suspension setup to the Motocross, but as I had three frames to work with, I could afford to sacrifice one to bring it closer to the shape and spec of the Motocross model. That meant a lot of cutting, bending and shaping. In one of the photos, you can see the difference between the stock Adler road bike frame with plunger rear suspension, and the motocrosser I created.
I started by separating the top tube from the rest of the loop, and adding a deliberate bend, courtesy of some chains and a bottle jack! It took some time, but I got there. I decided the Adler’s original plunger rear suspension was one piece of the puzzle I couldn’t get hold of. I ended up cutting the frame I had selected for this project in order to accommodate a Suzuki TS swingarm and rear shocks instead of the slim, angled Adler factory swingarm.
The front ends on Adler road bikes from this period were short leading-link type, which meant I had some work to do to make the Motocross models Earles-style front forks. Most of the tubes were bent and shaped from scratch, with the uprights salvaged from a surplus Adler frame’s front down tubes. The final shapes of the front suspension sections were achieved through a combination of heated and mandrel-bent sand-filled tubing for the big bends, and an hydraulic pipe bender for the tighter bends, the use of which was paid for with a slab of Heineken! The bracing sections were welded on and the result looked good and pretty close to the factory front suspension, given I only had old photos and illustrations to work from.
The seat had to be made from scratch. A curious feature of the Adler Motocross seat is that it was big enough for two, while the Adler ‘Sixdays’ model (produced at the same time as the Motocross), only had a solo saddle. Odd! Anyway, using some timber and paper patterns, I made the seat from sheetmetal and pop rivets, and had it professionally upholstered.
The ‘peanut’ style of tank came from an Adler M100 – the tank was common to both road and Motocross models - and was sourced from the USA. The rear guard is a repositioned and modified front guard from a road model, something the factory did on the Motocross models. The front guard on my bike came from a CB 750 Honda. A 1960s-era Honda Hawk provided the brake pedal, while the handlebars are from a CT110 Postie bike, with Yamaha XS650 triple clamps.
For the exhaust system, I spun up the muffler end parts over a die on a mate’s spinning lathe. The front muffler pieces were Adler factory items, while the middle was made up from galvanised sheet steel. The pipes themselves were bent by a local exhaust mob.
I was lucky to have enough bits to build a complete engine, and left it in the factory spec, including the 54mm factory standard bore. The cone-shaped works air filter I mentioned earlier is a distinctive feature on the Adler Motocross model, and the polished-up example on my bike looks good. For the Suzuki coil electrics, I got creative, using the 14.4 power pack from a portable drill. This works and supplies power through the standard points without any problems.
With the frame and all the suspension bits done, it was time for the part of the project I was really looking forward to – painting! As you can imagine, there was only one colour choice for this bike – red! What I selected was very close to the Fire Engine Red of my memory, and with the white coachlines on the guards and tank, looked sensational when completed.
With everything painted and reassembled, the bike looked fantastic, and given some of the parts came from some unusual sources, I was very happy with how close I’d managed to get it to the factory Adler Motocross 250 twin. The finishing touches were ‘50s-style sand covers for the levers, and ‘H19’ and ‘H20’ race plates, which were the international licence numbers for Rudy Boom and Jan Hoek. As a tribute to the heroes of my youth, I really enjoyed building this bike and was very happy with the finished result. I reckon Boom and Hoek would be, too.
http://www.justauto.com.au/justbikes/know/news/5f087746-3610-4cf8-8d2a-4279afc8b31d
« Last Edit: January 09, 2013, 02:42:04 pm by firko »
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'68 Yamaha DT1 enduro, '69 Yamaha 'DT1 from Hell' '69 DT1'Dunger from Hell, '69 Cheney Yamaha 360, 70 Maico 350 (2 off), '68 Hindall Ducati 250, Hindall RT2MX, Hindall YZ250a , Cycle Factory RT2MX flat tracker, Yamaha 1T250J, Maico 250 trials, '71, Boyd and Stellings TM400, Shell OW72,750 Yamaha
