BICYCLE MOTOCROSSThe trial… This term is familiar to many today. Competition for Moto and bike trial attract thousands of enthusiasts for these new sports. But if the trial fits of the serial technique, for trials on the bike to buy two-wheeled machine in the store is impossible. Athletes tend to create cross bikes themselves, based on one of the models produced by the industry.
In our today’s article we want to acquaint readers with the basic principles of serial alterations of a bike like “Kama” or “Desna” in the car for trial on the basis of the recommendations of the journal “the Practitioner” (GDR).
Increased strength and reliability — that should distinguish the machine from the serial trial folding Bicycle. First and foremost, all this will depend on the quality of welding, which must be undertaken by a fully qualified welder. And such works when modifying the bike will be a lot. In particular, the enhanced frame — single tube becomes spinal with additional horizontal bars in the classic triangular pipe having significantly greater strength and stiffness. The diameter of this additional pipe is about 30 mm, wall thickness — 2.5 mm.
The frame reinforcement helps get rid of the hinge around which the bike was developed. For this purpose the flanges of the first hinge primatyvajutsja to each other by welding the top and bottom, then cut off excess metal with a hacksaw, after which the joint is thoroughly boiled. Weld carefully trimmed so that it does not have sharp edges you can hurt yourself.
The handlebar also needs to be stressed: for example, motocross bikes it needs to have a horizontal jumper. In principle, it is best to use a wheel of a motorcycle or moped, increasing the tube with an external diameter of about 18 mm. makes sense to get rid of the joint at the connection of the wheel steering shaft. For this you need to determine the optimum position of the steering wheel and lock swivel welding.
Fig. 1. Major revision of the serial folding Bicycle with regard to motocross.
Fig. 1. Major revision of the serial folding Bicycle with regard to motocross version:
1 — bracket, 2 — Shoe brake front wheel 3 — steering column, 4 — elastic cushion of safety, 5 — hinge rudder (fixed by welding), 6 — additional crossbar frame, 7 — resilient safety cushion, 8 — hinge (set welding), 9 — shield (steel or dural band).
Fig. 2. The wheel of a motocross bike.
Fig. 2. The wheel of a motocross bike:
1 — steering column 2 — hinge (set welding), 3 — strengthening the steering wheel (pipe Ø 16 mm), 4 — wheel (of a motor scooter or a light motorcycle), 5 — a safety cushion (foam & faux leather).
Bicycle fork must also be modified, as shown in one of our drawings. If your bike wheel has no offset, for improved handling, to the pens of the fork are welded brackets chetyrehkilometrovoy steel sheet. The removal of the wheel axle relative to the fork — about 45 mm.
But still bike fork — not the best option for a motocross bike. And if possible, it is better to be replaced by the corresponding node from a light-moped — for example, “Riga-11” or “Riga-13”.
Wheel motocross bike — standard, from “Kama”. It is advisable to choose a tyre with sufficient tread. You can use the wheels from the moped — they are much stronger and have better maneuverability compared to Cycling, although more severe.
The chain drive is different from the regular. First of all, he has a different gear ratio, usually it is 1. To secure it, replace the leading asterisk on a different, number of teeth same as that of the slave. Clutch for dirt bike don’t need more “direct” transfer. Want to be and the foot brake — the athlete has to slow down sometimes almost simultaneously with the work the pedals and start on the lifts to do it by car with the foot brake difficult. For a motocross bike it is better to use drum brakes with manual transmission — the same that are used on sports cars. Well, if your bike will be set moped wheels with drum brakes, the drive can also be carried out using a standard motorcycle handlebars. It should be noted that the ends must necessarily be equipped with plastic or rubber balls.
A few words about the additional equipment of the bike. First of all, you should secure the upper crossbar of the frame and a jumper handlebar soft elastic rollers — you can make them from foam and faux leather. Another necessary addition to the standard bike — the shield that protects the bottom driving sprocket and a Bicycle chain. Make it from steel or dural strip is first attached to the frame by welding, and the second with clamps and screws with nuts.
It looks like the wheel of a motocross bike.
It looks like the wheel of a motocross bike. Note the hand brake with the drive both on the front and the rear wheel arm with protective washers and a jumper with soft cushion.
Modified caret motocross bike.
Modified carriage cross bike. The photo shows the drive sprocket of smaller diameter, and the safety clip under the caret.
When finished, cover the machine parts, first nitrogenatom, and then, after viskazivaniya, bright nitroenamels. Well, about how to hold the competition on such a bike, you can learn from “M-K” № 8, 1988.

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