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Featured Machines of AHRMA Northwest Racers

Jay Aitcheson's
Yamaha 100 Motocross
(By Jay Aitcheson)

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Stock bike at Rattler's Run in 2013 (with the only true "vintage" piggy back shocks, Yamaha Thremal Flows)

My project started with the idea of racing vintage motocross and a bone stock 1975 Yamaha MX100, (like design to the 74 MX100). I put a Jemco expansion chamber on the bike, a set of Pro Taper Evo Bars, widened the footpegs, and headed to my first vintage race, the AHRMA NW/Lumberjack event at Hannegan Speedway (Bellingham WA). I was amazed and inspired at what people had done with their bikes. That was three seasons ago.

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After that first race I replaced the stock carb with a larger 28mm Mikuni and added a set of Boysen Power Reeds. I found a NOS Preston Petty front fender and put that on as well.

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The following winter the swingarm was lengthened and 14” Works Shocks replaced the 12” stockers (the mounts on the frame were modified to prevent the chain from rubbing on the larger shock spring). The original front end was replaced with a complete 1974 MX250 front end. Race Tech fork springs were substituted for the Yamaha springs and the old ball bearing set up in the steering stem was replaced with an All Balls tapered bearing kit. I also went for some comfort and put aluminum risers into the Pro Taper bar adaptors and added a set of ASV C6 Pro Levers.

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During a gap in the race schedule last summer I decided to make the bike look better and weigh a less. I broke the 100 down, had all the unnecessary brackets (skidplate, kickstand, etc.) cut off, the gussets drilled, and then I painted it red. The engine was also bead blasted. An aluminum rear sprocket replaced the steel unit, and I replaced the steel tank with a Clark plastic YZ replica. The steel brake stay made room for an aluminum version.

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Prior to this season a Wiseco Piston was put in, the casting marks were smoothed out of the intake port, the exhaust port was polished, and a PVL Digital CDI was added. I came across a really nice aluminum chain guide/tensioner with a sealed bearing roller and that took the place of the stock guide. The finishing touches were combining an IMS folding shifter with the stock shifter and adding a set of Jake’s Garage number plate graphics with custom tank badges.

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Jay at the 2014 Steel Stampede at Crooked River Ranch Oregon

To sum it up, the different modifications made a very dramatic improvement in my bike's performance. The longer swingarm in combination with the improved suspension components made the little Yamaha handle much better. The ignition change made for a big change in the engine's character, and the altered power delivery improved my starts immediately. The reduced weight of the bike has given me more confidence on the race track and has helped me get out of trouble on more than one occasion.

This project has been a lot of fun and has made my time on the track much more gratifying. Riding the 100cc Motocross Class has been a great experience. My thanks to all the racers I have had an opportunity to share the track with over these past three seasons.

Kevin Blackburn's
Jawa typ 575/01 (1963 350 Moto-cross)
(by Kevin Blackburn)

In 2004 I bought John Astleford’s, (RIP), Jawa 1964 Type 579/01 250cc scrambler/motocrosser.  John had rebuilt this bike, raced it and collected many parts along the way.  The 579 was and is a blast to ride.  When I purchased the 579 he also had many parts for a type 575/01 350cc engine which, I was told, was legal for the Premier 500 class.  The 350cc Type 575/01 is the big brother to the Premier lightweight legal Type 579/01.  The idea at the time was to someday build a 575 engine and change between the 250 and 350cc engines depending on which class I wanted to compete in.

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Well this was no new idea, as Reese Dengler had already been at work on this back in 1995 and had gotten the 575/01 approved by AHRMA to compete in the Premier 500 class and he had the same idea about changing engines back and forth.

The Jawa type 575/01 350 Moto-cross was first introduced in 1963.  This model replaced the earlier 350 twin moto-cross bike, the type 558 which went back to 1957.   Jawa was one of the few, perhaps the only motorcycle company that produced open class 2-stroke moto-cross motorcycles in the pre 65 era.

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In winter 2010 Reese let go of an unrestored Jawa  575/01 and extra parts that were needed to bring this bike back out to the track.  Key engine parts and a rough frame were the main ingredients that Reese had. Now that I had an original frame to work with I started out to build a complete new racer.

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I started by tearing the frame down , sandblasting, adding and removing tabs as needed for the secondary coil, air box and number plates.  Repairs to the frame were made at this time also. An aluminum spacer was made to accommodate a CZ rear hub and chain adjusters.  The front end is CZ with a Sidepipe steering stem.

The fiberglass seat base was made on the bike with cardboard forms.  The foam is a cut and modified CZ firm seat with a custom seat cover.  Both front and rear fenders are old style fiberglass.

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The engine is a stock 350cc 2 stroke single port with 2 exhaust pipes.   From a few core engines a good crank was found.  A new piston was fitted in a new bored cylinder; new seals and bearings were installed throughout.  A close ratio gearbox and Vape electronic ignition are used. A 34mm Mikuni carburetor fits between the custom intake flange and CZ air box.  The chrome head pipes are from a Jawa Type 559 street bike and the chamber cones are made from 2 cones each out of 18 gauge steel.   The stingers are SS with restrictor washers installed.  The pipes were probably the most challenging to build for the bike.  Not only the design but the fabrication and mounting had their own problems and expense.

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The bike took about a year to build from start to finish and after the initial testing was out for the first time at the “Steel Stampede” event at Crooked River Ranch, Oregon.  I have to say these Jawas handle great.  The engine is really torquey, owing that probably to the 17+lb. crank.  The bike ran great and seems to be a real weapon in the Premier 500 class.

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They didn't think this bike existed???

I want to thank the following for their help and input. John Astleford, (posthumously), Reese Dengler, Doug Whitney of “Precise Machining” of Stanwood, “Superior Systems” of Burlington, AMS racing, CR Hi performance, Tucker’s upholstery, Lee Holth, Mr. Deez graphics, and Western Specialties of Mt. Vernon.

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Kevin and the Jawa typ 575/01 at the 2011 "Steel Stampede", Crooked River Ranch, Oregon

Ed Parson's 350 Velocette Scrambler "Mestizo"
(words by Ed Parson)

The bike is a 350cc Velocette with scrambler transmission stuffed in a BSA frame. With Can-AM forks and front wheel. BSA rear wheel, B50 seat and after market alloy tank.

The intake port was moved to the center to allow the carburetor and air-cleaner to fit between the frame rails. The exhaust port was sleeved to inch and a half and coil valve springs replaced the hairpins. The guides were made of alum/bronze and B50 BSA valves were used.

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The bottom end was put together using a Velocette big end bearing with the outer race ground to fit a Carillo rod for a Gold Star. A 750 Triumph piston was used. As a result of this the cylinder had to be shortened. The cylinder had to be shortened from the top which removed to many cooling fins so an alloy cylinder was machined from a billet and an iron sleeve installed.

The shocks are NJB's from Speed & Sport. I made the side panels, oil tank, pipe and foot pegs. I located the footpegs back a little so my feet are directly under me. It makes it easier to stand without pulling on the bars. The brake pedal is also homemade.

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The maiden voyage was the Works Performance Premier/Classic Weekend at Chehalis. It was raced in the Premier 350 & Premier 500 classes there. I did build the bike for the Premier 350 class but will also ride it in Premier 500 at regional races.

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A pair of Ceriani forks and a Rickman front wheel are being fitted to make the bike more period correct.
The bike runs good and is a blast to ride.

I call the bike "Mestizo" because that's Spanish for "Mixed Blood"

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Terry Hyde's Rigid Cheater Cub*
(words & pics by Terry Hyde)

This Tiger Cub project all started about 4 years ago when I acquired a 1954 Triumph Terrier frame from a collector Bevin Gore-Langton. having many years of tiger cub experience in my boyhood years, my father Joseph purchased a 1957 T20C for me when I was 11 years old. So I have a soft spot in my heart for any Tiger Cub. With the acquisition of this cub frame I knew in time I would find the missing parts and get it to run.

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A year ago at the AHRMA Bellingham trial and m/x Steve and Jon Vasilauskas approached me after the trial asked me if I wanted any more Cub parts, we struck a deal and I was on my way to a young boys dream of giving birth to more Tiger Cubs. So the end result was two new Tiger Cubs a rigid trials and a 200cc moto cross for Premier Lightweight.

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These contents are for the trials bike. The entire frame is stock 1954 T15 terrier 150cc the wheels are original with the exception of a 21in front wheel and Michelin trials tires, the controls are Amal with modern alloy trials bars. The footpegs were relocated to the rear 4in. and are from a Bultaco Sherpa T, the motor is a 1960 T20SL 200cc that is stock it uses the Triumph Sports R cam with 7-1 piston and large port cylinder head.

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There is not much to these little bikes from England there very simple and when set up right they are a very good trials bike with a strong torquey motor. The frame geometry is excellent the way they were built a the factory,   my first event for the cheater cub should be at Bellingham 1 year after I acquired all the parts to complete this fun project.

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JP's RN Replica
(words & pics by J.P. Morgen)

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

Headaches front to back were:

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.

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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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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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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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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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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J.P. race debuting the RN Replica at the 2008 Chehalis Classic

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Saturday January 31th 2009, San Francisco supercross, Roger checks out the RN Replica


Martin Spriggs' NSU Scrambler "Spriggs Special"
(by Martin Spriggs)

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!!!!!!!!!

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.

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

* Editors Note: The web builder does not think Triumph Cubs are really "Cheater Bikes". The term "Cheater Cub" is being used in a sarcastic manner. The web builder does NOT think Triumph Cubs should be moved to the Classic class.