Step 1
We will be building a 1974 Husqvarna CR 250 MAG from the ground up using only the finest, trickest, lightest, fastest and best parts and components available today. Each step will show a picture and give a description of any significant changes or modifications. We intend on building the "Worlds Trickest 250 MAG" for the purpose of racing it in AHRMA vintage motocross competiton. This bike is not intended to be a "Show Winner" but rather a racing restoration that is going to be used, abused and thrashed on every possible occasion. We will spend most our time, effort and money on performance enhancement rather that cosmetics, however, it will look good too. Hopefully, this project will inspire and educate those in need and we hope everyone will want to buy our trick parts and performance accessories for their Husky.
We will start with a bare 1974 MAG frame and swingarm. This frame is completely stock and has been bead blasted and immediately sprayed with a light primer coat. A bead or sand blasted frame will start to rust within hours without some type of protection. The ID number on this frame is MK 15702. All mag frames were stamped with MK and started at 10500 and went up from there.
We will start with a bare 1974 MAG frame and swingarm. This frame is completely stock and has been bead blasted and immediately sprayed with a light primer coat. A bead or sand blasted frame will start to rust within hours without some type of protection. The ID number on this frame is MK 15702. All mag frames were stamped with MK and started at 10500 and went up from there.
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Step 2
Plan ahead. Even though this step is an early one, it is very important. It is now necessary to decide what type of equipment you are going to bolt up to your new mag. You will have many choices to make, like which Triple Clamps to use, stock or aluminum with reduced offset and tapered roller bearings, Aluminum swingarms with needle bearings, GP swingarm upgrades or stock. If you are building a serious racer you will be going with the trick Aluminum upgrades. If you are just fixing up your old bike you may choose to keep it stock. With this project we are going to take it to the limit.
We have removed the stock Mag swingarm and have sent the bike out for some chassis mods and high quality paint. The chassis mods consist of 3 parts.
1. The tail section has been modified to lower the seat height in the rear, raising the seat height in the front and moving it forward. This makes for a level seat, improving the comfort and posture of the rider. It also closes the gap between the tank and seat. The adjustment also brings the upper shock mounts up and forward allowing the use of a 1" longer shock. If you ever ride a Husky with this modification you will be surprised how much easier it is to ride fast.
2. We have added the rubber, ML GP style steering stops to the front since we will be using aluminum triples and don't want steel to aluminum contact. Very nice.
3. Our racer is going to have the engine lowered just a bit to lower the center of gravity and give more clearance between the top of the engine and the bottom of the gas tank. This will help cornering and allow us to use the trick pipe. The rear motor mount holes have been welded up and new holes have been added to allow the change in engine angle.
After all the improvements are finished, the frame is cleaned and professionally painted using the correct color formula, high quality automotive paint and clear coat. It looks great and is now ready to have the engine installed. All of the above listed mods were performed by John at Vintage Husky in San Marcos, California. The quality of his work and his knowledge of Husqvarna motorcycles is second to none.
We have removed the stock Mag swingarm and have sent the bike out for some chassis mods and high quality paint. The chassis mods consist of 3 parts.
1. The tail section has been modified to lower the seat height in the rear, raising the seat height in the front and moving it forward. This makes for a level seat, improving the comfort and posture of the rider. It also closes the gap between the tank and seat. The adjustment also brings the upper shock mounts up and forward allowing the use of a 1" longer shock. If you ever ride a Husky with this modification you will be surprised how much easier it is to ride fast.
2. We have added the rubber, ML GP style steering stops to the front since we will be using aluminum triples and don't want steel to aluminum contact. Very nice.
3. Our racer is going to have the engine lowered just a bit to lower the center of gravity and give more clearance between the top of the engine and the bottom of the gas tank. This will help cornering and allow us to use the trick pipe. The rear motor mount holes have been welded up and new holes have been added to allow the change in engine angle.
After all the improvements are finished, the frame is cleaned and professionally painted using the correct color formula, high quality automotive paint and clear coat. It looks great and is now ready to have the engine installed. All of the above listed mods were performed by John at Vintage Husky in San Marcos, California. The quality of his work and his knowledge of Husqvarna motorcycles is second to none.
Step 3
In this step we have installed the engine. A true 1974 250 mag engine will have 2033-xxxx as the ID number. Our engine number is 2033-1245. It is easier to install the engine without the head and cylinder, it is smaller, lighter and easier to move into place without scratching the newly painted frame. We have taken this opportunity to do some performance mods while rebuilding the engine. This engine rebuild was fairly simple since the engine we used was not completely trashed but in pretty good shape.
On the inside, we split the cases and installed the following brand new parts; crank seals, crank bearings, Rod, Wiseco piston (137 P6 1.50mm), clutch plates and gaskets. After we bored the cylinder for the new piston we cleaned and matched the ports with some extensive porting on the intake and exhaust areas. We also shaved 20 thousandths off of the head for increased compression and horsepower. All of these mods done together will make a noticeable increase in performance. The original mag head was traded for a 75-76 GP radial head for better cooling and lower profile. They just look cool too.
On the outside, we cleaned it up and applied 3 coats of high temp semi gloss black engine paint. We replaced all of the old case and side cover screws with new stainless steel socket head cap screws and washers. Next we bolted it into the frame with new stainless mounting bolts and nyloc nuts. To round it out we installed the aluminum case saver, new kick lever rubber, new ML series rubber steering stop bumpers, new 10 tooth countershaft sprocket, Splitfire SF406C spark plug and new tranny case breather hose.
On the inside, we split the cases and installed the following brand new parts; crank seals, crank bearings, Rod, Wiseco piston (137 P6 1.50mm), clutch plates and gaskets. After we bored the cylinder for the new piston we cleaned and matched the ports with some extensive porting on the intake and exhaust areas. We also shaved 20 thousandths off of the head for increased compression and horsepower. All of these mods done together will make a noticeable increase in performance. The original mag head was traded for a 75-76 GP radial head for better cooling and lower profile. They just look cool too.
On the outside, we cleaned it up and applied 3 coats of high temp semi gloss black engine paint. We replaced all of the old case and side cover screws with new stainless steel socket head cap screws and washers. Next we bolted it into the frame with new stainless mounting bolts and nyloc nuts. To round it out we installed the aluminum case saver, new kick lever rubber, new ML series rubber steering stop bumpers, new 10 tooth countershaft sprocket, Splitfire SF406C spark plug and new tranny case breather hose.
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Step 4
In this step we have installed the following items and the reasons why. It was also a good time to move the project down to the bike stand from the work bench. Even though the target weight of the bike will be under 200 pounds when finished, it is going to become a little cumbersome to pick up and move.
We installed the motoplat ignition and coil. It bolts right up and stock timing specs can be used. If a good used motoplat is not available, a new PVL ignition can be substituted quite easily and they are readily available. They come with the coil, flywheel puller, directions and throw a spark you could weld with. Also a good choice.
We mounted the converted countershaft cover to work with the case saver. It has been trimmed to shed the dirt and mud but will still protect the c/s sprocket and your ankle.
The trick aluminum foot pegs have been bolted on with the return springs in place. These are a wider version of the stock pegs but are much lighter and have an aggressive cleat design. Very nice.
The reed valve assembly we chose to use is a high performance, high volume unit manufactured by Mossbarger. These are the same units used by Factory Husqvarna during the 70's and 80's. More flow means more go. These bolt right on but the air box will need to be modified to fit properly. These reed assemblies are available with a bing adapter or Mikuni adapter at no extra charge. Specify when ordering.
The Triple clamp assembly on this bike is nothing less than a work of CNC art. Offset is reduced 10mm to improve the steering. 16 pinch bolts altogether increase clamping pressure and rigidity. These units come with Timken tapered roller bearings, cups and races. They also come with standard sized aluminum bar mounts, however, we used our own aluminum fat bar mounts in order to use Protaper fat bars. Fat bars are a new type of aluminum handlebar using dual wall technology. They allow a small amount of flex, reducing vibration. rider fatigue and wont bend as easily as steel bars. They still use standard grips and levers.
The aluminum rear brake lever assembly was added to replace the huge, heavy steel lever. This lever assembly allows removal of the steel pipe from the lower frame area that was part of the rear brake lever. A sealed bearing is used in the lever in place of a bushing. Comes with all mounting hardware and lever leash.
Finally, we added a new aluminum swing arm by Novation Racing. These arms are 1" longer than the stock mag arm to aid stability at high speed. They are lighter than stock and flex less. These work excellent in combination with the reduced offset triples up front. They come with all mounting hardware and bolt on with no modifications needed. They also come with needle bearings in place rather than bushings.
We installed the motoplat ignition and coil. It bolts right up and stock timing specs can be used. If a good used motoplat is not available, a new PVL ignition can be substituted quite easily and they are readily available. They come with the coil, flywheel puller, directions and throw a spark you could weld with. Also a good choice.
We mounted the converted countershaft cover to work with the case saver. It has been trimmed to shed the dirt and mud but will still protect the c/s sprocket and your ankle.
The trick aluminum foot pegs have been bolted on with the return springs in place. These are a wider version of the stock pegs but are much lighter and have an aggressive cleat design. Very nice.
The reed valve assembly we chose to use is a high performance, high volume unit manufactured by Mossbarger. These are the same units used by Factory Husqvarna during the 70's and 80's. More flow means more go. These bolt right on but the air box will need to be modified to fit properly. These reed assemblies are available with a bing adapter or Mikuni adapter at no extra charge. Specify when ordering.
The Triple clamp assembly on this bike is nothing less than a work of CNC art. Offset is reduced 10mm to improve the steering. 16 pinch bolts altogether increase clamping pressure and rigidity. These units come with Timken tapered roller bearings, cups and races. They also come with standard sized aluminum bar mounts, however, we used our own aluminum fat bar mounts in order to use Protaper fat bars. Fat bars are a new type of aluminum handlebar using dual wall technology. They allow a small amount of flex, reducing vibration. rider fatigue and wont bend as easily as steel bars. They still use standard grips and levers.
The aluminum rear brake lever assembly was added to replace the huge, heavy steel lever. This lever assembly allows removal of the steel pipe from the lower frame area that was part of the rear brake lever. A sealed bearing is used in the lever in place of a bushing. Comes with all mounting hardware and lever leash.
Finally, we added a new aluminum swing arm by Novation Racing. These arms are 1" longer than the stock mag arm to aid stability at high speed. They are lighter than stock and flex less. These work excellent in combination with the reduced offset triples up front. They come with all mounting hardware and bolt on with no modifications needed. They also come with needle bearings in place rather than bushings.
Step 5
Now that we have the aluminum triple clamp assembly installed, we can put the front end together.
First we will mount the forks, which have been completely rebuilt with many new parts. We are using the twin rib black leg forks from a 1976 GP model. These forks allow the maximum 7" of travel to remain AHRMA legal and also incorporate newer and revalved dampening rods for improved performance. The tubes were then reassembled with new Progressive springs, plastic dampening washers, fork seals, dust covers and filled with a custom blend of fork oil. (7 oz.) Its important to remember that these forks were designed and built before the introduction of the highly refined, lightweight fork oils used in today's modern bike forks. It is therefore necessary to keep the viscosity and weight similar to the originally intended oil. We use a blend of the recommended 30 W non detergent motor oil in combination with modern fork oil as an anti foaming agent. This combination works great and is readily available. Finally, we added a pair of Goki air fork caps. Not to be used a full air forks, but as an adjustable air assist system. With only 2-4 pounds of air in each fork leg, these caps allow the rider to easily dial in the correct amount of compression resistance based on rider weight, ability and or track conditions. When you only have 7 inches of travel to begin with, don't waste 3" on sag.
There are 3 major components involved in making a bike turn.
1. Correct triple clamp offset.
2. proper fork action, not too stiff- not too soft.
3. the right tire pressure.
Get all 3 of these components working together and the bike will go where you point it. Every time!
The new forks are now mounted in the alloy triples with the top of the fork tubes flush with the top of the upper clamp. The forks can be raised or lowered in the triple assembly for added rigidity, depending on which triple assembly you use (alloy with Timken bearings, Profab or stock).
The front wheel was completely rebuilt. We opted for a 74 CR 400 hub rather than the smaller 250 unit for two reasons.
1. Larger hub diameter means more braking surface.
2. New brake shoes for the larger hub are readily available and were installed. Good quality shoes for the smaller 250 hub are very hard to find. The weight difference between the hubs is negligible.
New wheel bearings were installed, hubs painted and then turned on the lathe for accent. New stainless steel spokes were used to lace up the new Excel alloy rims. Michelin S12 tires and tubes round out the wheel work.
While up front, we installed a set of Moose multi wall aluminum fat bars. You can also use Renthal fat bars, they are just a little more $$. High quality Magura dog leg lever assemblies were then added. On to step 6.
First we will mount the forks, which have been completely rebuilt with many new parts. We are using the twin rib black leg forks from a 1976 GP model. These forks allow the maximum 7" of travel to remain AHRMA legal and also incorporate newer and revalved dampening rods for improved performance. The tubes were then reassembled with new Progressive springs, plastic dampening washers, fork seals, dust covers and filled with a custom blend of fork oil. (7 oz.) Its important to remember that these forks were designed and built before the introduction of the highly refined, lightweight fork oils used in today's modern bike forks. It is therefore necessary to keep the viscosity and weight similar to the originally intended oil. We use a blend of the recommended 30 W non detergent motor oil in combination with modern fork oil as an anti foaming agent. This combination works great and is readily available. Finally, we added a pair of Goki air fork caps. Not to be used a full air forks, but as an adjustable air assist system. With only 2-4 pounds of air in each fork leg, these caps allow the rider to easily dial in the correct amount of compression resistance based on rider weight, ability and or track conditions. When you only have 7 inches of travel to begin with, don't waste 3" on sag.
There are 3 major components involved in making a bike turn.
1. Correct triple clamp offset.
2. proper fork action, not too stiff- not too soft.
3. the right tire pressure.
Get all 3 of these components working together and the bike will go where you point it. Every time!
The new forks are now mounted in the alloy triples with the top of the fork tubes flush with the top of the upper clamp. The forks can be raised or lowered in the triple assembly for added rigidity, depending on which triple assembly you use (alloy with Timken bearings, Profab or stock).
The front wheel was completely rebuilt. We opted for a 74 CR 400 hub rather than the smaller 250 unit for two reasons.
1. Larger hub diameter means more braking surface.
2. New brake shoes for the larger hub are readily available and were installed. Good quality shoes for the smaller 250 hub are very hard to find. The weight difference between the hubs is negligible.
New wheel bearings were installed, hubs painted and then turned on the lathe for accent. New stainless steel spokes were used to lace up the new Excel alloy rims. Michelin S12 tires and tubes round out the wheel work.
While up front, we installed a set of Moose multi wall aluminum fat bars. You can also use Renthal fat bars, they are just a little more $$. High quality Magura dog leg lever assemblies were then added. On to step 6.
Step 6
Moving to the rear.
A new pair of Ohlins Classic MX shocks were bolted on. Probably the most expensive choice in vintage shocks but by far THE BEST. These shocks will perform at optimum levels being bolted to the Novation swingarm with needle bearings. When these shocks are not financially possible there are a few other good quality, lower priced options in Progressive and Works Performance.
The rear wheel was rebuilt with the same high quality parts and upgrades as the front wheel, mentioned in step 5. Both front and rear wheel use the same size brake shoes. An alloy 56 tooth rear sprocket was added and a new RK 520 chain. We didn't go the O'ring route since it robs some of the H.P. and is fairly expensive. The alloy rear brake torque arm went right on and uses sealed bearing roller wheels in the built-in chain guide.
We couldn't wait to install the high performance expansion chamber. We had ours chrome plated and it turned out awesome. Fits perfectly, mounts easily with no modifications, is much lighter than stock, won't burn the inside of your left knee and has a very trick rebuildable aluminum silencer. Makes more power too.
Plastic rear and inner rear fenders are on and we chose the glossy finish version. Very nice!
A new pair of Ohlins Classic MX shocks were bolted on. Probably the most expensive choice in vintage shocks but by far THE BEST. These shocks will perform at optimum levels being bolted to the Novation swingarm with needle bearings. When these shocks are not financially possible there are a few other good quality, lower priced options in Progressive and Works Performance.
The rear wheel was rebuilt with the same high quality parts and upgrades as the front wheel, mentioned in step 5. Both front and rear wheel use the same size brake shoes. An alloy 56 tooth rear sprocket was added and a new RK 520 chain. We didn't go the O'ring route since it robs some of the H.P. and is fairly expensive. The alloy rear brake torque arm went right on and uses sealed bearing roller wheels in the built-in chain guide.
We couldn't wait to install the high performance expansion chamber. We had ours chrome plated and it turned out awesome. Fits perfectly, mounts easily with no modifications, is much lighter than stock, won't burn the inside of your left knee and has a very trick rebuildable aluminum silencer. Makes more power too.
Plastic rear and inner rear fenders are on and we chose the glossy finish version. Very nice!
Step 7
As you can see, the mag project is complete. The following final touches were added. Billet air bell assembly with Uni filter, Gunnar Gasser throttle, Terry cables, restored aluminum fuel tank, billet gas cap, alloy plate mounts, IMS cable guide, oem petcock, brand new Bing 54 carburetor, plastic number plates and seat assembly consisting of fiberglass base, aluminum brackets, new foam and new cover. High quality stainless steel hardware and fasteners were used throughout.
The bike is beautiful and is almost too nice to get dirty not to mention it looks great in the trophy room.
The bike is beautiful and is almost too nice to get dirty not to mention it looks great in the trophy room.
