Why is the second gear loss on the motor-block Neva?

Operation and maintenance of the Neva-MB-2

To ensure that the MB-1 and MB-2K minitractors do not malfunction, you should follow all the recommendations for the operation and maintenance of the equipment, prescribed in the manual:

  • It is necessary to make adjustments to the engine. You will need to study the structure of this part, choose the right oil for engine maintenance, spark plugs and fuel.
  • Adjust and tune gearbox and transmission. The serviceability of these parts must be checked each day before starting work.
  • Install additional equipment only in accordance with the manual.
  • Follow the maintenance schedule (points 1 and 2) and the seasonal maintenance schedule (before the summer and winter seasons).

Failure to start the single axle tractor

The real repair of the power tiller with your own hands begins. Clutch lever released, gear disengaged. The diagnostic sequence is as follows.

Check engine cranking with starter rope. Free rotation is a signal of a mechanical problem with the engine. Unusual noises, grinding will confirm that the problem is in the connecting rod, camshaft, valve group. Have the engine repaired at a service center. If you drive the single axle tractor on its side, repeat the start without a spark plug. the reason could be the ingress of crankcase oil into the combustion chamber.

Operation and maintenance of the Neva-MB-2

To prevent malfunctions in the work of the MB-1 and MB-2K minitractors, it is necessary to follow all the recommendations for operation and maintenance of the equipment, prescribed in the manual:

  • Engine tuning must be carried out. To do this you will need to study the structure of this part, choose the correct oil for engine maintenance, spark plugs and fuel.
  • Tune and adjust the gearbox and transmission. The serviceability of these parts should be checked every day before you start work.
  • Install additional equipment only as directed in the owner’s manual.
  • Compliance with maintenance schedule (points 1 and 2) and seasonal maintenance (before summer and winter periods).

Failure to start single axle tractor

The real repair of the motoblock with your own hands begins. Clutch lever released, gear disengaged. The sequence of diagnostics is as follows.

Checking engine cable travel. Free rotation. the reason is a mechanical failure of the engine. Unusual noises, grinding noise confirms that the problem is in the connecting rod, camshaft, valve group. It is desirable to have the engine of a power tiller repaired at a service center. If you drive the single axle tractor on its side, repeat the start without a plug. the reason could be the ingress of the crankcase oil into the combustion chamber.

Types of gearbox malfunctions and how to correct them

If the automatic transmission mechanism ceases to function normally, the following types of problems may occur:

  • Kinematic connection inside the gearbox interrupted.
  • Spontaneous engagement of gears or absence of their locking.
  • Oil leakage at the shift shaft.
  • Malfunction of the axle shaft separation mechanism.
  • No gear shifting.
  • Gearbox jamming.

If there is a kinematic malfunction inside the gearbox or if the sprocket in the assembly breaks off, disassemble the gearbox to replace the problematic sprocket. Oil leakage on the shift shaft may be caused by excess oil in the gearbox, so check the oil level. If the welding pinion joint is broken, disassemble the gearbox and replace the shaft block. After draining the excess oil, check the wear on the sealing lip of the oil seal on the shift shaft, disassemble the gearbox and replace the part.

The reason why the gearshift does not lock or disengages on its own is a defective adjustment of the gear shift mechanism. Making repairs, loosen the screws securing the shift mechanism board.

second, gear, motor-block, neva

Then engage the first gear and tighten the board locking screws. For example, if you make a mini-tractor with your own hands, you must monitor the correctness of adjustment of the drive, changing the tension of the cable to control the half-axle disengagement. To fix a breakage of any element of the half-axle disengagement drive inside the gearbox, you should disassemble the gearbox, replacing the broken parts.

If a broken spring or worn shift knob plate retainers are found, the damaged parts must be replaced and the gear shift adjustments made. If it is missing, the shift knob may be broken or a threaded portion of the shift knob may be sheared off. After disassembling the gearbox it will be necessary to replace the defective parts. If the gearshift fails to change gears, disassemble the gearbox and replace the worn shift fork. If a chain breakage was the cause of the gearbox jamming, it should be disassembled and the chain should be replaced.

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If there is excessive gearbox noise, it may be caused by insufficient oil in the gearbox or by the lubricant quality mismatch. Select oils of appropriate brand and purity. If there are any problems, the oil needs to be changed or refilled.

Noise in the transmission units of your MotoBlock can be caused by loose fasteners, so you need to inspect the fasteners, tighten them properly.

Frequent noise is caused by worn gears and bearings. This can be the cause of more serious damage to your powerpack gearbox. To avoid their appearance is not difficult, if you do timely inspection and repair. The routine replacement of worn out parts and assemblies.

If there is heating of the transmission components of the motor-block, the following main causes of this malfunction are distinguished:

There can be two reasons for the faults to be corrected:

In order for the gearbox or homemade gearbox to last longer, you should periodically check the oil level in it for fear of sudden changes in load.

Signs of irregularities associated with difficulties in shifting speeds, spontaneous shutdown, disruption of the process of turning on the unit, occur for the following reasons:

Shafting (wear) of the faces of the engaging gears causes two problems, leading to selfshutoff or incomplete engaging of the gears.

Main faults

The cause of repair of the Neva MB-2 motoblock may be:

  • Improperly adjusted valve belt;
  • Gearbox oil seals;
  • Improper carburetor system settings;
  • Faulty ignition;
  • spark plug malfunctions.

Belt adjustment and dimensions

The V-belt on a power tiller helps the machine move forward and backward. When the drive belt comes off, the machine no longer functions properly.

To determine the size of this part, measure the gap from the pulley to the rollers. Recommended belt width 0,85 cm, height 0,6 cm.

To tension the belt, proceed as follows

  • Remove the guard.
  • Loosen the screw of the tension of the standard belt part.
  • Remove all the screws that hold the bracket to the body of the motoblock.
  • Pull out the old part and adjust the pulleys.
  • Wipe the area between the parts and blow out the rods.
  • Install a new belt, one end of which must be connected to the shaft and the other end to the pulley.

Replace the gearbox oil seals

Improperly functioning oil seals could be the cause of gearbox failure. Therefore, the repair of the gearbox of the Neva motoblock can include the following actions:

  • Dismantle the cutters from the shaft.
  • Clean the shaft and cover of dirt and oil residue. All screws should be removed from the cover and washed.
  • Replace the old part with a new one and wipe the whole mechanism dry.
  • Replace the cover and fasten it with the screws.

In some cases the gearbox may need to be disassembled:

  • Remove the gear head from the shift knob.
  • Remove the bush and spring from the shaft end.
  • Remove all screws and bolts.
  • Remove the right side of this part using a thin screwdriver or knife.
  • Flush out all removed parts and replace defective parts.
  • Reassemble the gearbox in the reverse order.

Before adjusting carburetor, adjust centrifugal regulator according to operator’s manual.

  • Tighten the bolts for low and full throttle to the maximum and then turn them back 1.5 turns.
  • Fit the choke shutter so that a gap of suitable parameters appears between the base and the air duct.
  • Try to start the engine. If it starts, you need to wait for it to warm up.
  • Adjust throttle control knob to minimum RPM.
  • Set the idle speed at a minimum by means of the choke shutter screw.
  • Set revolutions to maximum, using the low throttle screw.
  • Repeat the last 2 steps until the engine runs smoothly.
  • Set the control lever on the throttle.

Valve adjustment

The adjustment of the valves on the Neva power tiller is done as follows:

  • Set the machine on a flat surface.
  • Start the engine and let it cool.
  • Remove the cover.
  • Remove the valve cap to access the parts underneath.
  • Unscrew the lock nut.
  • Adjust the valves. Loosen the nuts, insert the dipstick and adjust the valves.
  • Re-tighten throttle valve nut.
  • Insert the razor blade (max 0,2 mm thick) into the gap formed. It should pass freely between the piston part and the valves of the motoblock.
  • Screw all the parts back on.

The size of the gap can be checked by inserting a feeler gauge under the valve if the cut is correct.

Checking and adjusting the clutch

  • When the clutch lever is in the “off position.When the clutch is in the “check and adjust” position, the cable should be loose. The tension pulley moves to the bottom position and contacts the drive belt.
  • When the crank is in the “On” position, the clutch cable should be loose.”The cable tightens the pulley and the underside of the belt is pressed firmly against the pulley. Small pulley transmits power to large pulley and causes power transfer.
  • If the 2nd gear kicks out when the clutch lever is engaged. It must be in the right position. To do this, place the V-belts in parallel on both sides of the motor pulley.
  • If 2nd Gear Leaks with Clutch Knob Off. Always check the position of the V-belts, they must be parallel to each other.
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How to turn the ignition

Procedure for adjusting the ignition of a power tiller:

  • Turn the crankshaft so that the marks made on the pulley and the gas equipment of the machine are aligned.
  • The spark plug, which is responsible for distributing the gas flows, must be pointed at the high voltage wire of the cylinder.
  • Loosen the nut and remove the high-voltage wire from the cover of this system.
  • Position the contacts at 0.5 cm from the technique.
  • Turn the ignition.
  • Turn the mechanical construction in the opposite direction.
  • After the spark appears, you must quickly tighten the screw.

Trouble with spark plugs

  • Unscrew the spark plug element.
  • Clean the electrodes.
  • Remove any carbon deposits.
  • Rotate the crankshaft to the position where the pulley and gas gauge marks are aligned.
  • Point the slider at the high voltage surface of the cylinder.
  • Loosen the screw and take out the wire.
  • Turn ignition key. If there is no spark, the spark plugs are faulty and must be replaced. Before installing a new element, make sure that there is no sealing washer from the previous part in the cylinder head.

It is also necessary to check the parameters of the gap between the electrodes of the plugs:

Why does not start, shoots, smokes, and what to do about it

If the engine does not start, the cause may be the following:

  • No spark. In this case, it is recommended to take out the spark plug element and insert it in a special candlestick, and put the housing on the cylinder. After that you need to restart the engine. If the spark did not appear, it is recommended to replace the spark plug.
  • Fuel does not reach the engine. You need to inspect and purge the hose that connects the carburetor and the valve. If necessary, you can disassemble the carburetor and wash it from the inside with gasoline A-95.

If the power tiller smokes at idle speed, you need:

If the engine is firing, it may be caused by the tension of the working spring. It should be adjusted in case of malfunctions.

How to install an alternator

In order to install the electric generator, you need to do the following:

  • The generator has 4 wires, 2 of which are blue. To these 2 wires you need to connect the power converter.
  • The black wire should be connected to the motor.
  • Connect the remaining red wire to the parts responsible for the exterior lighting and the horn.

The alternator generates electrical power, which is fed to the rectifier. When the engine starts, the adjusted belt transmits the torque to the rotor part of the machine. The electric unit generates the voltage from which the battery of the motoblock works.

The power of the selected generator must not exceed 220 V. It is advisable to choose a part with a capacity suitable for the intended load.

The gearbox has 5 positions. When the user presses the gearbox lever, the fork moves the clutch out of engagement position. When you drop the handle, it goes back to the original position.

In order for this mechanism to function properly, it is necessary not to make any sudden movements and clean all parts from dirt in time.

Gearbox is responsible for the transmission of torque from the engine to the wheels and additional equipment. To avoid service interruptions during operation, the motor must be serviced in good time.

No doubt, going to the service center is the right decision. But when the time is running out, it is worth to cope with what malfunctions occur more often. You can compare manifestations by description, roll up your sleeves and repair the motorblock “Neva MB-2″ with your own hands.

First run-in and startup

A running-in period is required so that all parts can be lapped up. After a short period of operation at a minimum load level, the single-axle tractor will break down less often in the future.

  • The running-in process should be no shorter than the time specified in the instruction manual.
  • Allow only little strain on the machine. For example, if the maximum working depth is set at 50 cm according to the technical data, it is recommended to limit the maximum working depth to 30 cm during initial start up and running-in.
  • Fill the engine with oil before the initial run-in period.
  • Fill up the fuel tank.
  • Run the machine at a medium speed.
  • Check that all gears work properly within 60 minutes.
  • Perform a small amount of cultivation, plowing and transporting small loads.
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Gearbox on the Neva power tiller

The gearbox of a Neva power block is responsible for the transmission of engine torque to the wheels and other attached implements. It controls the rotational speed, speed, and direction. forward or reverse. In principle, the reducer for the MB 2 and MB 1 models do not differ much, so here we will consider the second option. The design of the gearbox is made so that the components necessary to change the gears are located on the outside of the housing.

second, gear, motor-block, neva

The gearbox lever has 5 positions. When you push it, the fork disengages the clutch. When you drop the lever, the fork goes back to its original position. A single-axle tractor will pause when the drive is connected to the right half-axle. There is torque coming from the sprocket. When the knob is recessed, engaging the left sprocket, the gear is downshifted. If you want a higher gear, you have to push the lever all the way out.

How to adjust the carburetor on different power tillers?

It is recommended to adjust and tune the metering unit when the first engine malfunctions. The process of adjusting the carburetor depends on the brand of motoblock.

In general, the process of adjusting the engine speed of power tillers “Neva” involves a sequence of actions:

second, gear, motor-block, neva
  • screwing the small and full throttle screws to the stop;
  • setting the throttle valve until a gap is formed between the base and the air duct;
  • engine start;
  • setting the control lever to minimum revolutions;
  • adjustment of throttle valve screw until minimum idle speed is reached;
  • adjusting the low throttle screw until maximum idle speed is reached;
  • alternation of minimum and maximum to get continuous engine operation;
  • transfer of the power unit control lever to gas;
  • adjustment of the screw responsible for the mixture quality.

This scheme is suitable for the carburetors K-45, which are put on the “Neva” MB-1 and MB-2 models.

Small agricultural machinery units from Ufa are also popular with domestic farmers. They are valued for high quality components, low price and smooth operation. Powerful UMZ-341 engine, working with single-chamber float carburetor K-45R, is installed on the “Agro” machines.

The principle of operation of the dosing unit is very simple: when idling, the gasoline supply is minimal; when in working mode, it is fed according to the manual to keep the power tiller in working order. If the engine is unstable, it is necessary to adjust the carburetor:

  • Start the engine and warm it up for a few minutes.
  • Unscrew the screw, regulating idling speed, until the engine almost stalls.
  • Tighten the screw, having achieved a stable work of the engine.
  • Adjust throttle valve position to achieve minimum clearance between the throttle valve and the body of the metering unit.
  • Changing the “quality screw” position to achieve the maximum engine rpm.
  • Re-adjust the throttle position.

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Indicator of serviceability of an internal combustion engine will be stable engine work at idle and rpm.


Technique of Minsk tractor plant is valued by domestic agrarians for stability in operation. But it also can fail in the course of time. If the engine malfunctions, especially if the unit has been idle for a long time, you have to adjust the carburetor.

  • Start the engine and wait until it is completely warmed up.
  • Screw in maximum and minimum throttle bolts at maximum, and then unscrew them by one and a half or two revolutions.
  • Set the control lever to XX mode (minimum rpm) and make sure the engine does not stall.
  • Adjust idle rpm with the throttle trigger. There must not be any extraneous noise in the engine.
  • Use the maximum power controller to bring the crankshaft speed to its maximum permissible value.
  • Adjust fuel supply by means of fuel screws.
  • After obtaining optimum engine performance, tighten all screws.

The period of carburetor operation coincides with the service life of the engine. Dosing unit adjustment and service prolongs life of the engine. After adjusting the dosing assembly you can achieve stable operation of the machine and reduce fuel consumption.

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