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Featured Machines of AHRMA Northwest Racers
JP's RN Replica
(words & pics by J.P. Morgen)
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It all started with a poster of Joel Robert's 1972
Suzuki RH72, (his 250cc world championship bike), I received along with a pile of
Suzuki TM400 parts from fellow AHRMA racer, Christian Otero, continued with the strong
passion to build my own works bike replica, and was completed, after four plus years with
the addition of yellow number plates and the number 17 to commemorate Roger DeCoster's
1972 Suzuki RN72, (370cc), Trans-Am machine.
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The 1972 Trans-AMA RN72 Suzukis and thier riders, Joel Robert, Roger DeCoster, &
Gaston Rahier
(picture courtesy www.transworldmotocross.com)
Headaches front to back were:
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Front Fender
It took three tries to find a '74 TM fender that didn't have flaws or cracks in the
translucent plastic under the original yellow paint.
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Front Forks
I turned down the sliders and then cut off the lower ends and replaced them with threaded
in billet pieces to get rid of the four big unsightly studs that normally clamp the axle.
Luckily, just before I did the threading, I realized the left hand pieces would need left
hand threads to prevent them from loosening under braking loads. Also, to hold the
modified forks, I made the billet aluminum triple clamps.
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The Frame
The TM400 motor is longer than its works relative, so I did what I could to emulate the
look and geometry, and I used modern footpegs, because I plan on racing, as well as
showing the bike when done.
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Gas Tank
Originally I was going to learn how to hand hammer an aluminum tank for the project, but
carpal tunnel symptoms from working and riding stopped those thoughts. A friend of a
friend, Rob Diepenbroek, with a shop near mine did the magic, and then Jerry Casciero, of
PJ's Auto Body in Maryland made the stickers and expertly painted the tank, following
detailed and dimensioned drawings I sent along with the tank.
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Engine
I remachined the taper on the full circle TS400 crank to accept a modern KX500 ignition
that would fit under the RM370 mag cover bolted to a flat adapter plate, plus it has a
small external flywheel, so yes more flywheel effect than the original rotar. The TS400
crank although not any heavier than the later TM cranks, does have a bit more effective
flywheel weight because of its shape. The cylinder head is also a TS400 item, with the
very outside fins cut off, and the remaining fins reprofiled on a CNC mill to mimic the
works bike. The autolube pump area was trimmed back and welded up to make the cases look
trimmer.
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Pipe
I wanted to hydroform the whole pipe, but with my techniques not yet fully perfected, I
settled for hydroforming the header and connecting it to 15 separate cone segments, most
of them fused together without any filler rod. I literally built the pipe to 'look' right
on the pipe as compared to an old works bike. Tapered header, big belly curving up just
behind the footpeg, stinger starting, and angled just so, etc. When done, I measured it
and I think it will work just fine, maybe a little punchier than smooth, I will see! I
probably have at least 15 hours in the pipe alone.
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Swingarm
To solve the problems with warpage during heat treating aluminum swingarms, I did all of
the final machining on the axle slots and pivot bearing bores after it was treated. Time
consuming, but both axles slide nicely in and out. The chain guides on the works bikes
resembled closely the later RM production pieces, which are usually missing or in very
poor condition. I CNC machined them out of aluminum plate to look like the stamped steel,
with raised edges and rounded cornerslike on the RM pieces, then bent them to jog in from
the swingarm to line up with the chain, again like the production RM pieces.
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Shocks
I made billet finned shock coolers to slip over the Ohlins shocks to make them look more
period. Suzuki experimented with shocks that looked like this during the '72 Trans-Am, and
then used them in'73.
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Rear Fender
After years of searching, I only found this one example, a NOS aftermarket replica in the
'70 works style, that filled my needs. I had to borrow a tubing bender with a different
radius to get the rear fender loop just right.
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The end result is 208 pounds of steel, aluminum,
plastic, and rubber with a smooth, strong powerband, stable handling, and just the look I
was shooting for.
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Martin Spriggs' NSU Scrambler "Spriggs Special"
(by Martin Spriggs)
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It all started with a look at the used Victoria web
page motorcycle section. I found the NSU advertised as a incomplete bike, missing many
parts!. What was there was the engine, frame, wheels, and badly dented gas tank. Not
enough stuff to consider doing a restoration! The next best option was a unique trials
bike or a MX bike. Because of my past interest in the NSU engine's power, the choice was
MX, (maybe when I'm too old for MX I'll covert it to a trials bike).
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The first thing to do was to make a stand to mount the
engine on to see if it would run! I made a open top oil tank to sit on the bench, also a
manifold to hold a Delorto carb. With a piece of handlebar held in my vice to hold the
twist grip and a battery to supply the power for the coil ignition. quite a sight to
see...with the engine on the floor in its stand and no exhaust pipe------ the engine came
to life--------the oil pump pumped-----the carburetion was poor!!------ but the thing
ran!!!!!!!!!
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Now, what frame etc to use???? I came across a B25
frame that I swapped a Lotus speedometer for. I also had a MAR OSSA with broken engine
cases. to use for the front forks and wheels.
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After establishing the position of the engine the
frame. I made the engine mounts, foot rests ,wheel spacers. I used Timken taper bearings
in the steering head,and the rubber swing arm bushings were replaced with brass.The kick
start mounting block was machined from 4140 billet and the Ossa pedal heated an bent to a
suitable shape. I decided to use a Amal concentric carb so I machined the manifold from a
billet of 6061 T6 aluminium.
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I used a Motoplat ignition from a Maico. This meant I
had to machine a adaptor to hold the stator, plug the rotor and rebore the taper to suit
the NSU crankshaft. The bottom of gas tank had to be cut out and reshaped to conform to
the cylinder head. I made a Stainless steel gas tap in the Ossa style with a outlet on a
angle to clear the carb. All the unused brackets were cut from the frame and a aluminium
central oil tank fabricated. The steering angle on the BSA frame was good but the Ossa
forks were raked out too far so I modified the center hole in the triple tree to give 5.5
inches of trail.
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The SS is firstly called that, as it is the middle
letters of the bikes it was concocted from i.e.: bSa nSu oSSa or Spriggs Special.
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After 11 months of this bike consuming all my spare
time it was a thrill to have my very first to ride on my SS at THE FARM on Aug12. I am
still not completely happy with the carburetion but will work on that.. We have no where
in Victoria area at this time to really try out our bikes to see if they will run. One
thing I learned early with this project was to think the process through thoroughly so I
did not get ahead of myself and have to redo or change things because I had done them in
the wrong order. It is very satisfying to do this type of a project and watch it grow into
a interesting specimen. Look forward to Sept at THE FARM again. WHAT A GREAT HOBBY.
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Martin and Spriggs Special at the recent Chehalis national
Kevin Blackburn's CZ Typ 968 (250 Twinpipe)
(by Kevin Blackburn)
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After a couple years racing in AHRMA sportsman classes
I realized that I really wanted to build a classic 250 bike to ride. Not only did I want
to get in on the Premier & Classic weekends but the class looked like a bit of fun to
race. I had CZ 380 which I really liked and after considering a few other bikes I decided
to find and build me a CZ 250 Twinpipe. I knew that these are neither easy to find nor an
inexpensive project (I had no idea I found out later) but was really taken with the
mystique and cool factor surrounding these fine bikes.
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Once the "Strangly Remachined Cases" were replaced the rebuild commenced.
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After looking around for awhile I decided to pick up a
running builder bike from NW CZ/Maico. A few phone calls sealed the deal and R. Borg
brought the bike out to the Premier/classic event at Chehalis in September of 2003.
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As it turned out after tearing into it for refurbishing
the engine was a complete mess and well beyond my meager machinist and mechanics skill.
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Kevin debutted the bike at the 2005 Madras NW/Lumberjack round.
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The engine was sent to CZ guru Bertus to see if he
could help. Among the unusable parts were strangely remachined cases, a strange clutch
basket that was welded on the crank end, a "creatively" remachined flywheel
along with the usual worn parts such as shift shaft, gears and countershaft. Luckily
Bertus was able to locate and rebuild the parts needed, (thanks Bertus), and I received
the engine back from him in February of 2005.
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Nice and clean on Saturday but it did not stay that way.
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Meanwhile I started on the rest of the bike. My idea
was to make a racer out of it and not a show bike. New suspension was needed via
Progressive (since have gone to Ohlins) and new fork springs and valving. An aftermarket
fiberglass tank is used. Excels with SS spokes were installed on redone hubs. Electronic
ignition and a 32MM Mikuni was added along with plastic fenders and airbox. I use a tall
firm GP style seat to keep from that vintage “knees in my chest" feeling.
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In action at the 2005 Chehalis Premier/Classic.
(Kevin won the 2006 Lumberjack Classic 250 Intermediate title on the CZ)
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Finally I was able to put my classic 250 racer
together. The Madras Oregon event in the spring of 2005 was its first event and except for
a few minor hitches the bike has turned out to be exactly what others have raved about. It
is light and nimble, fast, fun and handles like a dream.
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Kelly Shane’s Premier Open Twin Norton
(By Kelly Shane)
The Beginnings
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Ever since I discovered British motorcycles while in
college, I’ve always had a hankering for a big twin. But not just any twin would do.
I knew that I wouldn’t be happy on anything common like a Triumph or BSA. No, I
needed a… (cue drum roll here)… Norton. In the fall of 2004, I finally gave in
and started gathering all the necessary bits. John McCoy provided a new Cheney/Matchless
frame, which by coincidence just happened to be hanging on the wall in my shop. I rooted
thru my shop and attic and found a pair of CZ hubs, some Ceriani forks, an A-10 primary
case, a Norton Atlas clutch, and a bucket full of parts from several Norton and Matchless
trannys. A 750 engine was donated from a rather bent Commando. By early December, I had
stripped the engine, made the engine and tranny plates, laced Excell rims to the CZ hubs,
and had pretty much stacked all the loose bits into a pile which looked remarkably like a
motorcycle. Of course, the engine didn’t contain a single moving part, the tranny
case was empty, and there wasn’t a bolt with a nut anywhere close to it, but sitting
on a milk crate in the middle of the shop floor, it sure looked like a motorcycle.
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Coming Together
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Every spare moment for the rest of December and all of
January was spent rebuilding the engine, fitting the engine in the frame, assembling the
tranny (several times before it finally had 4 gears and 1 neutral), making up exhaust
pipes, taking the engine out of the frame, fitting up the air-cleaner and single 34mm
Mikuni, building a head-steady, putting the engine back into the frame, lining up chains,
sending the crank to Ed Crowell for rebalancing, boring the cylinders and fitting Combat
pistons, slipping in a new cam, putting the engine back in the frame, welding footpeg
mounts to the cases, taking the engine out of the frame, etc…...
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The Norton at the muddy 2005 Madras NW/Lumberjack round.
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A box of steel bits was sent out for nickel plating,
the pipes were sent to for ceramic coating, and the tank was painted. Finally, on the
Wednesday afternoon before the Nat’l in Arizona, the engine was installed in the
frame for the last time and on Thursday, UPS delivered the ARD ignition. The various
compartments were filled with oil- none of which ran out onto the ground in alarming
quantities- and after a couple of preliminary stabs to the kick-starter (I wasn’t
exactly sure about the timing, not to mention a hard-earned respect for unfamiliar
kick-starters), a healthy kick prodded it into life. Damn this thing is loud- cool!
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Kelly and Norton ready for the Madras mud. Kelly and the Norton won Premier Open Twins
Expert
titles in the AHRMA nationals in 2005 and the AHRMA NW series in 2006
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Riding the Norton is probably the most fun to be had
with your clothes on. The Cheney frame goes where ever you point it- just roll on the
throttle and steer with the rear wheel. It is just like riding a big single. There is gobs
of mid-range power, and the engine doesn’t need to be revved. In fact, to make it a
bit more tractable and slow down the hit, I replaced the ¼ turn Motion Pro throttle with
an older Magura 3/8 turn. The weight is a bit heavier than I hoped for- with the aluminum
Dunstall barrels; it came in at 295#. Unfortunately though, the head bolts kept pulling,
so I had to fit up a set of standard cast iron barrels which has pushed the weight to
305#.
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