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|MZ:||The Stock Bike||The 2001 & 2002 machine||Big Changes for 2003|
|In 2006 I'll be riding a Tigcraft chassis bulit for the Yamaha YZ450F engine.|
|2006 Machine Specifications:|
Engine: Yamaha YZ450F - Tuned By Clayton Williams
Power: approx. 55Hp
Transmission: Close ratio 4 speed with STM slipper clutch
Weight: 210 lbs. wet w/ half tank of fuel
Forks: Honda RS125
Shock: Penske (no suspension linkage)
Front Brake: Brembo radial master cylinder and radial mount caliper. Brembo Rotor.
Wheels: PVM for RS125 (TZ250 cush drive)
|The Single Cell Racing Tigcraft MiniMono|
Tigcraft's Dave Pierce designed the MiniMono to combine the light weight and sharp handling of a 125GP bike with the power and torque of the new generation of four stroke motorcross engines. The concept worked, bringing home series championships in the liquid-cooled European Supermono Series in 2003, and the British Supermono series in 2004 (an engine failure preventing a 2004 European championship for the Tigcraft factory bike and rider Mike Edwards).
The tubular steel chassis uses Honda RS125 components in many places including forks, wheels, tail section and footrests, this keeps costs down and means that crash spares are readily available. Many MiniMonos also use RS125 bodywork swingarm, shock and rear linkage, but this particular version uses a slightly longer swingarm with a linkageless shock mount, as well as Honda RS250 bodywork - 'cause honestly there's no way I'm getting all the way behind a 125 fairing.
|A left side view of the MiniMono. Note the RS125 forks, and the long swingarm. The RS250 fairing is fairly large. Clearance problems with the lower led to some serious trimming later in the season!||An aluminum plate keeps road spray out of the Keihn FCR carb. Also visible on the front of the footrests are Steve Patrickson crash protectors. For this year I'll be using 25mm longer rearsets in order to get a bit more leg room.|
Despite some early season mechanical issues which were readily sorted out, I got on with the little Tig right away. Racing this bike is by far the most fun I've had on a motorcycle! A word of warning: once you try riding a purpose made race bike you will never want to go back to anything else. The light weight, minimal rotating and unsprung mass, and the precise feedback offered by the chassis make the bike both scary quick and confidence inspiring all at once. Which is a good thing because you definitely have to ride this bike hard for the package to work. This is not a bike that will placidly motor around at a track day pace - it's touchy, skiddish and nervous if you're just poking about, but get on it, and you rapidly find that the harder you push, the more planted the bike becomes. Great stuff!
The bike needs to be ridden very hard due to its relative lack of power (I'm sure I'm not saying anything new to 125 riders). Getting bogged down in a corner will cost you dearly, and it's easy to get stuck playing follow the leader with slightly slower but more powerful bikes, so you need to exloit the handling to full advantage to pull off passes. You can't afford to be overly polite or cautious if you want to get around folks on this bike. In other words this bike (like a 125) is a great way to learn to actually RACE. I obviously still have a lot to learn, but just one season on this bike has really improved both my skill and judgement.
2005 UpdatesFor the 2005 season we have swapped out our WR450 engine for a YZ450 unit, eliminating the charging system which should free up some power, and allow the engine to rev more rapidly. The four speed transmission from the YZ450 was replaced by a close ratio 5 speed box from the YZ426 (the wide ratio 5 speed from the WR was really too wide from roadrace use, with 1st and 2nd gear being used only on launches).
Also new for 2005 are a set of 2004 RS125 forks with a radially mounted brake caliper. These forks were worked over by Ktech and seem to be a nice improvement over the stiction-laden units we used last season. Fitting my 6'3" body on a small bike was a bit of a struggle last season, so for 2005 ergonomics will be improved by a Sharkskinz large kit tail which will add about 1 inch of leg room, as well as 20mm extended footrests and 10mm forward extended clip-on mounts from Steve Patrickson. I'm looking forward to testing out the new set-up at Jennings FL this March prior to the start of the LRRS season in April. I'll keep you posted!
The MiniMono cockpit. A Mychron electronic dash gives RPM, water temp, and lap time information as well as providing sequential shift lights. Engine vibrations made reliable wiring on the tach difficult to achieve.
A detailed view of the very nice aluminum gas tank that comes with the MiniMono chassis kit.
The high mount exhaust system actually extends through the swingarm, keeping it tucked out of the way in crashes, and providing plenty of cornering clearance. For 2005 melted boots will be prevented by exhaust wrap on the mid-pipe.
The Skorpion series of road singles was produced in Germany by MZ (briefly renamed MuZ thanks to copyright issues concerning the MZ name). These bikes were imported to the US from 1995-2002 in five variations, ranging from a sport touring bike to a replica of the factory Supermono racer. The bikes all shared a tubular steel perimeter frame as well as a 660cc liquid cooled Yamaha single cylinder engine (the same engine currently found on the Yamaha Raptor ATV).
These motorcycles are light in weight (370+- lbs. dry) and posess an excellent chassis. Thus they handle extremely well even in completely stock form. They are also dead reliable, simple to maintain, and actually quite comfortable. In the Summer of 2002, my wife and I rode two MZ's fully loaded with gear over 5000 miles round trip to the northwestern tip of Newoundland for our honeymoon. The bikes performed fantastically, and even in rough conditions there were never any serious mechanical issues. Shown below are the specifications for the stock Skorpion Sport:
|Engine: 660cc liquid cooled 4 stroke, 5 valve
Bore /stroke: 100mm X 84mm
Compression Ratio: 9.2:1
Hp / torque: 48Hp (closer to 42 at the rear wheel) / 56Nm
Length / width / height: 2145mm / 750mm / 1140mm
Seat Heigt: 770mm
Dry Weight: 173kg
The stock Skorpion Sport Cup
I picked up the MZ destined to be my racebike used at Bikeworx in Maynard MA in the summer of 2001. The bike had 25,000 street miles, and remained bone stock for the rest of that season, with the exception of Race Tech cartridge emulators in the front forks, and modified ride height front and rear. For 2002 I modified the bike's controls and instrumentation, replacing the stock bars with Woodcraft clipons and eliminating the switchgear. I also added Axljak rearsets (image) to gain a little more cornering clearance, and began to run fairing lowers (mainly to protect the engine cases in case of a crash).
The most major change came with the addition of a Penske racing shock to replace the somewhat tired and mushy stock unit. This setup served me well in 2002, and I went the entire season without a mechanical DNF.
|The Cockpit. MyCron lap timer, and SPA tach / temp guage are attached to a modified stock instrument bracket. Note Woodcraft clipons and Gustafsson Plastics double bubble windscreen (added for 2003).||Penske 8100 series racing shock. Adjustable for ride height, preload, compression damping and rebound damping, this unit was a big improvement over the mushy stock unit on the bumpy Loudon track.|
The only difficulties I encountered were late in the season as my lap times became somewhat faster. Ground clearance with the exhaust system became a bit of an issue, especially over the transition bumps in turn 3 at Loudon. Though I couldn't manage to eliminate the problem with different suspension settings, there was never a serious scare. At the same time, the grinding of the fairing and pipe bracket throughout the turn made me a bit nervous on a couple of occasions.
For 2003 Some major modifications are being made to the bike. First and foremost, the motor is being heavily overhauled. Galen Miller at Bikeworx is punching out the motor to 720cc. In addition to boring and re-sleving, the mill will get a higher compression piston (bringing compression to around 12:1), a ported head, a more agressive cam, and a revised CDI box that will allow higher revs. To handle the increased power, the tranny is undercut, and an oil cooler added. To aid in breathing, new carbs, a K&N filter, and a new dual exhaust are also on tap. All told, the motor should move from around 46hp to over 70hp at the rear wheel and will run Power Mist TO-72 oxygenated race fuel. Still more power could be had from the engine with more extensive head work, and an even more agressive cam. As evidence Galen's motor put up over 80hp at the rear wheel when tested by Yamaha. Realistically though, this year I'm going to have my hands full, and I'm sure that I wouldn't be able to exploit that extra power, in fact, the milder X-3 cam will probably help at a tight track like Loudon.
|The new Axljak / Bikeworx aluminum subframe wighs only 4 lbs, eliminating a lot of weight that was carried far from the center of gravity||Another view of the new aluminum subframe, supporting the smaller battery tray, ignition box, programmable rev limiter, shock revervoir, and dual exhausts.|
The bike also goes on a diet for 2003, shedding about 30 pounds in the form of an aluminium subframe (good for about 15 lbs) and Dymag magnesium three spoke wheels. The Dymags not only save about 12 lbs of rotating unsprung mass, but are also substantialy wider than the stock units - (a 3.5inch front instead of 3, and a 5.25in rear replacing the stock 4incher) and will thus allow me to run a better selection of tires. The improvement in accelleration and handling should be substantial. (A tip to anyone ordering Dymags in the US. It may well be cheaper to get the wheels in England and have them shipped here. I did this through a group called Bike HPS they were very easy to deal with and the savings over any price I could find in the US more than outweighed the $100 shipping cost)
Cosmetics are improved for 2003 with some new fiberglass (from Beasley), a new paint scheme (from a can), and a new double bubble windscreen from Gustafsson Plastics. The screen has very good clarity and does produce a substantially larger pocket of quiet air.
|The 2003 bike, sporting fresh paint, and exhausts borrowed from Galen Miller||A front view of the Gustafsson double bubble screen.|
I tried out the new set up at a track day at Jennings GP in Northern Florida. Though I was taking it pretty easy, and just trying to break in the new motor, I was amazed by the power and torque of the new engine. Suddenly, I was passing SVs and Aprilia RS250s on the gas! On short straights I had no problem staying with, or actually outdriving 600s. Corner speed, combined with torque coming out of the corner, meant that only on the longest straights did the big multis pull a substantial gap. Throttle response from the dual flatslide carb setup was also much improved, giving a much more direct link between the twistgrip and the rear tire.
The only difficulty I had with the new setup was a lack of ground clearance. I managed to grind through the fairing on both sides in just a few sessions, and took a moderately large scuff from the exhaust pipes Galen Miller was kind enough to loan to me. As much as I might like to fool myself, I know I'm not running the bike to the limits right now, so I feel pretty confident that I can cure the clearance problems through a combination of a stiffer sping rate / more preload / more ride height in the rear, and a steeper and lower front end geometry.
That doesn't belong on the ground...