IZH Planet 5 goes backwards: causes of failure and solutions

The situation when a powerful motorcycle IZH Planet 5 suddenly loses traction or starts moving in the opposite direction when trying to get going, can shock even an experienced rider. This behavior of the equipment not only creates an emergency situation, but also indicates serious internal damage to the transmission or drive mechanism. Owners of Soviet and post-Soviet classics often encounter this phenomenon, which is popularly called the “reverse effect.”

The main reason that IZH Planet 5 goes backwards, there is a critical destruction of the splined joints of the gear shaft of the gearbox or the driven sprocket. When the splines are completely licked, the shaft begins to rotate freely inside the seat, losing its rigid connection with the wheel. This leads to the fact that when you try to engage a gear and give gas, the torque is not transmitted to the wheel, but simply spins the shaft, or chaotic movement occurs.

Sometimes the problem lies not in the box itself, but in cardan shaft, which connects the engine to the rear wheel. If the splines on the cardan are worn out or the crosspiece is broken (depending on the modification), the motorcycle may behave unpredictably. It is important not to ignore abnormal sounds, such as clanging, crunching or humming, which often precede complete failure of the unit.

Critical wear of shaft spline connections

The most common reason why IZH Planet 5 goes backwards or loses speed - this is the development of splines on the gearbox shaft. The design of the IZH transmission is such that the shaft rotates in a cast iron bushing or directly in the crankcase, and during long-term use the metal wears out. The gap between the shaft and the splines increases, and the shaft begins to “walk”.

If the splines are heavily worn, the shaft may move in the axial or radial direction. When the gear is engaged and the gas is suddenly applied, the shaft may turn in the opposite direction or simply not transmit the impulse to the wheel. This is especially true for motorcycles with high mileage, where the oil was changed rarely and the loads were high.

Diagnostics This defect requires partial disassembly. It is necessary to remove the crankcase cover and inspect the shaft for wear. If the splines are licked to zero or have stepped wear, the part must be replaced immediately.

• 🛠️ Licked splines on the gearbox shaft shank
• 🛠️ Development of the shaft seat in the crankcase
• 🛠️ Lack of lubrication in the shaft friction unit
• 🛠️Using low-quality oil leading to corrosion

⚠️ Attention: Operating a motorcycle with licked shaft splines can cause the shaft to rotate the crankcase, which will require an expensive replacement of the entire power unit.

Breakdowns inside the gearbox (gearbox)

If everything is fine with the shaft, but IZH Planet 5 it still behaves strangely and can go backwards if you look inside the gearbox. The gear shift mechanism on these motorcycles is quite reliable, but if you ride aggressively or shift incorrectly (without pressing the clutch), the gear teeth may chip.

Metal shavings caught in the oil or a broken gear tooth can jam the mechanism. In rare cases where destruction occurs gear shifter or forks, the gearbox shafts can be blocked or rotate in the opposite direction under the influence of the inertia of the wheels when braking the engine

Particular attention should be paid to the condition clutches. If the clutch discs are stuck or the springs are weak, the clutch may not release completely. This creates the effect that the motorcycle jerks or crawls when you engage a gear, creating the illusion of a transmission problem, although the problem lies in the adjustment.

For an accurate diagnosis, it is necessary to drain the oil and, if possible, evaluate the condition of the gears through the inspection window or with the cover removed. The presence of large metal shavings in the oil is a sure sign of destruction of friction pairs.

Cardan and pendulum problems

Model IZH Planet 5 equipped with a cardan transmission, which is its distinctive feature among domestic motorcycles. The driveshaft transmits torque from the gearbox to the rear wheel gearbox. If cardan has looseness or damage, this may cause jerking and strange behavior of the motorcycle.

One of the common reasons that a motorcycle “jerks” or simulates reverse motion is the development of the spline joint on the propeller shaft itself or in the gearbox flange. With severe wear, the cardan begins to beat, creating vibrations that are transmitted to the frame. At the moment of a sharp start, the shaft may slip.

Also worth checking pendulum fork. If the swingarm bearings are broken, the rear wheel may become misaligned. When loaded, the wheel can push against frame or trim members, creating resistance that, when the brake is released, can throw the motorcycle backwards if it is standing on a slope.

• 🔧 Play in the cardan shaft crosspieces
• 🔧 Making splines on the cardan flanges
🔧 Rupture of the rubber cardan coupling (if applicable to the modification)

Some modifications use elastic couplings. Their rupture leads to a complete loss of connection between the engine and the wheel, which can be perceived as a gearbox failure.

• 🔧 Lack of lubrication in the rear wheel gear housing

⚠️ Attention: When replacing the driveshaft, be sure to use only special transmission oils for gearboxes. Conventional motor oil may not provide adequate protection to hypoid gears.

Influence of rear wheel and brake condition

Sometimes the reason why IZH Planet 5 behaves unpredictably, lies not in the engine at all, but in the chassis. A stuck rear wheel brake can create the illusion of a transmission failure. If the pads do not release, the motorcycle will be difficult to move and may roll back jerkily when released.

Check status brake drum and pads. Oxidation of the pad axle or breakage of the return springs leads to the fact that the brake constantly slows down the wheel. When you try to start, the engine stalls or the motorcycle jerks, and on a descent it rolls back uncontrollably.

It is also worth paying attention to the spokes and rim of the wheel. If the wheel has a strong “figure-of-eight” wheel, it can touch the brake shield or chain (if we are talking about alterations), which causes jerking. However, for classical Planets 5 with a cardan this is less likely, but possible with impacts.

Brake check procedure:
1. Raise the rear wheel onto a stand.
2. Spin the wheel by hand - it should rotate freely.
3. Press the brake pedal - the wheel should lock.
4. Release the pedal - the wheel should rotate freely again, without friction.

If, after releasing the pedal, the wheel continues to brake, it is necessary to remove the brake shield and clean the mechanism of dirt and rust, and also lubricate the pad axle with graphite lubricant.

Diagnostics and troubleshooting

To determine exactly why IZH Planet 5 goes backwards or loses traction, it is necessary to carry out a comprehensive diagnosis. You should start with the least labor-intensive operations. First of all, check the level and condition of the oil in the gearbox and gearbox.

Then you should inspect the external elements: the driveshaft for play, the condition of the brakes. If there are no external defects, you will have to open the engine crankcase. This is a labor-intensive process that requires removing the engine from the frame or disconnecting the rear section.

When disassembling, pay attention to the color of the oil. If it is silver, the gears are wearing out, if it has a copper tint, the bushings or sliding bearings are wearing out. The presence of large metal fragments will indicate the location of the breakdown.

Don't forget about electrics. Although it rarely affects driving mechanics, a malfunction in the ignition system can cause traction "slips" that the driver perceives as a mechanical problem. Check the spark plugs and breaker.

Repair and replacement of worn parts

Repair IZH Planet 5, especially regarding gearboxes, requires precision and cleanliness. If wear on the shaft splines is detected, the gear shaft must be replaced. On sale you can find both original spare parts (if you’re lucky) and modern analogues, which are often stronger than Soviet ones.

When assembling the gearbox, it is important to set the bearing clearances correctly. The use of shims of different thicknesses allows you to adjust the preload of the bearings. Incorrect assembly will lead to rapid heating and repeated failure.

If the gears are damaged, they need to be replaced in pairs. Installing a new gear in a pair with an old, worn one will lead to rapid failure of both elements due to mismatched tooth profiles.

• 🔨 Use a puller to press the bearings
• 🔨 Use a torque wrench to tighten the nuts
• 🔨 Use crankcase sealant (or gasket)
• 🔨 Wash all parts with kerosene before assembly

⚠️ Caution: When assembling the engine crankcase, do not use silicone sealant where gaskets are provided. The silicone can come off and clog the oil passages, leading to oil starvation and engine seizure.

To avoid a situation where IZH Planet 5 starts to go backwards or stalls, it is important to follow the maintenance regulations. Regularly changing the gearbox oil (every 10-15 thousand km) significantly extends the life of splines and bearings.

Use high-quality fuels and lubricants. For IZH Planets 5 It is recommended to use oils of SAE viscosity appropriate to the climatic conditions. In winter the oil should be thinner, in summer it should be thicker.