THE BEAST NAMED ABRIS

Ever since the times of Tsar Gorokh (or, more precisely, since the early 60s), Kovrov motorcycles began to be equipped with alternating current generators. At first it was G-38, later G-401, G-411, G-421. They were distinguished by the fact that they were extremely simple - no ever-running battery, no capricious brush assembly. In addition, the rotor, which is permanent magnet, reliable as a sledgehammer. But, as you know, every barrel of honey comes with a fly in the ointment. There was one here contact system ignition, in which, in addition to the traditional adjustments of the ignition timing (by turning the generator housing) and the gap in the cams, it was also necessary to “catch” the outline. What kind of beast this was, few people knew, and more than one generation of motorcyclists in the 70s strengthened their muscles by pushing machines that did not want to start at any cost. In addition, such generators had three separate light windings that powered the circuits of everything at once - headlights, brake lights, and flashers. And this increased the likelihood of a short circuit.

A quiet revolution occurred when the G-427 generator, which did not have breaker contacts, was installed on Voskhod-2M (1976). On the rotor, instead of a cam, there is an additional magnet that induces an electric current in the winding of a special sensor. The pulse of this current (output through the terminal marked “D” - “sensor”) was the master in the circuit of the thyristor located in the KET-1A switch. The energy required for sparking was generated by two special coils connected in series, located on the stator (the output was marked with the letter “3” - “ignition”). Adjusting the system was reduced to setting a gap (0.3±0.05 mm) between the magnet rotor and the sensor core plates.

THE SHINE AND POVERTY OF "CONTACTLESS"

The weak point of the first “contactless” generators is the sensors. The vibration caused the fastening screws to loosen and the gap to “go away”. If the sensor came into direct contact with the rotor, interruptions occurred in the motor. By the way, broken crankshaft main bearings can also cause contact with the rotor sensor and, as a result, incomprehensible interruptions in engine operation. In the sensors, the wire in the turns often broke, and the solder terminals fell off. Almost all of these shortcomings were eliminated only in the new generation of generators 2MK-208 (80.3701). They began to be installed on the Voskhod ZM-01, and later on all Kovrov motorcycle products (except for the Pilot and Ptah). In them, the sensor winding is located together with other windings inside the stator, and in the block electronic ignition a voltage stabilizer was introduced (hence the abbreviation BKS - switching-stabilization unit). The Pilot has a flywheel-type generator, that is, the stator windings are located inside a rotating bell-shaped rotor. The bobbin and switch-stabilizer are the same as on motorcycles.

The only adjustment of modern Kovrov generators - ignition timing - is made as on old models - by turning their housing. If the engine runs “hard”, the starter lever pushes against your foot when starting, which means the ignition is too early. Turning the stator clockwise (after loosening the three screws) will eliminate the unwanted effect. “Sluggish” operation of the engine and overheating that occurs in it indicate that the ignition is late. You can set the ignition timing absolutely accurately using car strobe light. The only inconvenience that arises is that it will have to be powered from an external source. DC. When the optimal ignition timing mode is reached, a rotor rib with a circular mark appears in the window of the stator housing. For "Pilot" - the risks on the rotor and stator must match.

"AP-GRADE" IN KOVROVSKY

Why our people love the “Soviet” motorcycle industry is for the scrap interchangeability of parts of its various products. Thus, the new “contactless” devices can be installed on previous models of Kovrov motorcycles with peace of mind - the mounting dimensions and dimensions allow this to be done. Condition - the electrical circuit needs to be modified: connect the CET or BCS. Increased spark energy will require another reel - B300B, interchangeable according to seats with the previously used B300. (By the way, outwardly, the old and new bobbins are no different. However, numerous attempts not to change the old unit sooner or later ended with the windings burning out!) Fans of “upgrades,” that is, increasing the performance of electrical systems, can be advised to install a bobbin manufactured in . Sarapule, from "Izha" (designation: 7.109-37.05.010). Its use increases the spark pulse duration by approximately 15% and its energy by 60%. As a result, starting the engine is noticeably easier. By the way, the reverse procedure - installing a Kovrov reel on an Izh with a contact ignition system does not give anything good. The reel overheats and very soon runs out.

The transition from KETs to BKS (with the advent of the new generator 43.3701 on Voskhod-ZM) marked the advent of the era of 12-volt electrical equipment. The headlights have become not only brighter, but also more stable. Supports constant voltage stabilizer built into the BCS. However, owners of new 12-volt generators can, if necessary, connect the KET-1A unit for operation. It is connected to the wiring terminals according to the letter designations (see diagram). But the lighting devices in this case will not “want” to work. To “want”, you should install a regular BCS. Owners of old motorcycles are luckier: instead of KET, they can safely install BKS. Their ignition circuit, as before, will be 6-volt (since the generator has not been changed), in which voltage stability is maintained (by the way, rather mediocrely) by a special DR100 choke located in the tool box.

SEEK AND YOU WILL FIND

Although modern system The ignition of Kovrov motorcycles is quite reliable, and it can fail. Before delving into the elements of the system, check for breakdown of the spark without a spark plug cap - set a gap of 6-7 mm between the high-voltage wire and the ground of the cylinder head. If there is no spark, begin to search for it more methodically. You probably did not connect the plug connectors tightly. Poor contact of the base of the BCS housing with ground does not have any effect on the operation of the system - ground is output by a separate wire. But in old KETs, the “mass” was brought out to the body, and its contact with the frame is necessary.

The generator itself, both “owl” and “pilot”, fails extremely rarely. To check its performance, you need a tester with an ohmmeter function. So, the resistance of the charging windings (red wire and body, or terminals “3” and “M”) should be within 400 Ohms; the resistance of the sensor windings (black and pink wire, or terminals “D” and “M”) is 40 Ohms. The winding resistance of the lighting circuit (purple wire and housing) should be 0.4 Ohm.

All resistance measurements are made on the sockets of the generator harness plug block disconnected from the BCS. Old generators with KETs are checked in the same way. Instead of resistance, you can measure the magnitude of AC voltage. On the charging windings, when cranking the crankshaft with a kick, it is approximately 50 V, on the sensor windings - about 2 V. The specific voltage value depends on how sharply the kickstarter lever is pressed.

The rotors of Kovrov motorcycles are an eternal part. But with the "pilot's" early years release problems may occur. The fact is that their magnets were glued to the rotor with an epoxy composition, and over time, the magnets often broke out of the housing under the influence of centrifugal forces. The rotors of modern Pilots do not have these shortcomings.

The bobbin (high-voltage transformer 2102.3705, 1480026900001) is also checked using an ohmmeter with the wires disconnected. The resistance of the primary circuit should be within 0.4 Ohms, the secondary circuit - 6.7 KOhms.

But even if the winding resistance is normal, and a spark jumps when you press the kick, the unit may still be faulty. It happens that the motorcycle starts, but when the speed increases, interruptions begin and the engine stalls. This is a consequence of broken contact inside the housing. Therefore, the only reliable diagnostic method should be to replace it with a known good part. Ideally, you should carry a “gentleman’s kit” with you - high voltage wire with cap, reel and BCS. Serial connection These components can quickly identify faults.

Unfortunately, neither the reel nor the commutator can be repaired, since they have non-separable housings. Take this advice: once you are sure that a part is faulty, throw it away immediately.

UNIQUE DIVERSITY

The ignition systems described above were equipped not only with motorcycles from the V.A. Kovrov plant. Degtyareva. Generators G427 and KET1 were used by Minsk motor builders. On modern model"Minsk" ("MMVZ 3.11311") installed an original flywheel-type generator, but the BKS is completely identical to the Kovrov one. The place of its manufacture is the Republic of Belarus, the BATE plant. In Russia electronic components they do it in two places at once: in Kherson and Kovrov itself. These BCS are distinguished only by the brand mark; in terms of connecting connectors they are completely identical. However, there are still differences. But we'll talk about them another time.

ELECTRICAL EQUIPMENT FOR KOVROV MOTORCYCLES

Motorcycle brand, year of production	Generator	Generator power, W	Switch	Spool	Voltage in the lighting circuit, V	Peculiarities
"Voskhod-2", 1972	G-421	45	-	B-300	7	Mechanical contact ignition system
"Voskhod-2M", 1976	G-427	60	KET-1A	B-300B	7	Electronic contactless ignition system
"Voskhod-ZM", 1983	43.3701	65	261.3734	21.3705	14	Transition to 1 2-volt electrical equipment, stabilizer and switch combined into one unit
"Voskhod-ZM-01", 1989, as well as "Owl", "Farmer", "ZiD-200"	2MK-208 (80.3701)	90	BKS-1MK211 (70.3734)	2102.3705	14	The sensor winding is inserted inside the stator
"Pilot", 1995	190003090001	60	BKS-1MK211	1480026900001	14	Flywheel type generator
"Bird", 1998	164003090001	20	BKT1 164	-	14	Flywheel type generator, bobbin combined with commutator

For several years now domestic mopeds(mokiki) and light motorcycles from the Kovrov and Minsk plants are equipped with a contactless electronic ignition system (BESZ), which was described in detail in the October 1978 issue of “Behind the Wheel.” It provides more reliable engine starting compared to a conventional system, is less sensitive to carbon deposits on the spark plug, and requires virtually no maintenance.

These qualities are appreciated by motorcyclists. However, the specificity of BESZ for many of them becomes a stumbling block as soon as the need arises to eliminate any malfunction that affects the operation of the engine. As a rule, in these cases, the motorist buys and successively replaces the system devices until he discovers a faulty one. Of course, this path leads to unnecessary costs and unjustified consumption of spare parts.

Meanwhile, having basic electrical skills and knowing the procedure for checking system components, in most cases you can independently identify and repair a faulty device. VNIImotoprom specialist A. SINYAEV talks about how to do this.
Before working on the ignition system, you must make sure that engine problems are caused by it. Therefore, first check the carburetor adjustment, condition air filter, exhaust system, correct ignition timing.

A malfunction of the ignition system ultimately manifests itself in the fact that there is no spark at the spark plug, or it is very weak, or it occurs at an arbitrary moment.

The search begins with a candle. They unscrew it from the cylinder, put on the tip and apply it to the engine (“ground”). Turn on the ignition and turn crankshaft kick starter, as when starting an engine. If a spark occurs between the electrodes, it can be assumed that the spark plug is working; When electrical discharge goes through the spark plug body to ground, the spark plug must be replaced.

When assessing the quality of a spark on a spark plug, one must keep in mind that its power will be sufficient to ignite the mixture if a discharge is formed between the “ground” and a high-voltage wire (without a tip) separated from it by 5-7 mm.

But when there is no spark at all or it appears only when there is a gap of 1-2 mm between the spark plug body and the ground, the high-voltage wire along with the tip should be replaced. If this replacement does not restore normal sparking, proceed to checking the electrical parameters of the ignition devices shown in photos 1 and 2. The monitored values ​​are indicated in the table. For measurements, a universal or automotive tester is most convenient. We connect one wire to the terminal indicated in the table, the other to terminal M (“ground”).

The next step is to check the gap between the rotor and stator of the sensor, which should be within 0.3-0.5 mm, and the presence of an electrical signal on it. To do this, connect the tester, set to a measurement limit of 2.5 V, to terminal D of the generator and ground. We turn the crankshaft with the kick starter, observing the instrument reading. Its needle should briefly deviate to a value of 0.5-0.6 V. If there is no signal, check the reliability of the contact between the terminal and the sensor coil (breaking it is quite common at min.
ski motorcycles). Having set the tester to a measurement limit of 10 V, in the same way we determine the presence of voltage at terminal 3 of the generator, which should be 1-2 V. If it is absent, we check the contact between the terminals and the ignition windings of the generator and at the same time see if they are shorted to ground. . In such places, black burn marks are usually visible. If everything is in order here, we check the following sections of the circuit, determining the signal directly at terminals D and G of the KET-1A switch or terminals D and 3 of the BKS unit. If the electrical wiring is in good working order, the voltage values ​​should be the same as on the generator. Here you also need to make sure that the switch is in reliable contact with ground, the absence of which causes interruptions in engine operation.

Finally, we check the B300B ignition coil by measuring the resistance of its primary and secondary windings with a tester. They should be equal to 0.9-1.2 Ohms and 5.8-6.2 kOhms, respectively.

The parameters of the output signal at terminals K of the KET-1A and BKS 251.3734 switches can only be measured using a special stand, therefore, in the case where all previous checks have shown the generator, sensor and coil to be serviceable, all that remains is to replace the switch. However, it is worth keeping in mind that defects in this device are extremely rare, unless, of course, it was mechanically damaged. By the way, other devices, especially the sensor, should be protected from impacts.

Resistance values ​​on different generator windings

Winding being tested	Generator 26.3701 (Fig. 1)		Generator G427 (Fig. 2)
	terminal designation *	resistance, Ohm	terminal designation	resistance, Ohm
sensor	D	39	D	39
ignition	Z	390	Z	540
lighting	ABOUT	0,34	ABOUT	0,7
pointers turning	-	-	U	1,6

* There are no terminal markings on the generator

: 1 - generator 26.3701; 2 — block switch stabilizer BKS 251.3734; 3 — ignition coil B300B; 4— plug block for generator wires (bottom view); 3. O, D - terminals are extinguished, respectively, ignition, lighting, sensor; M - "mass".

: 1 — generator G427; 2 — switch KET-1A; 3 — ignition coil B300B; Z, U, T, D, O - terminals of the coils, respectively, of the ignition, turn signals, brakes, sensor, lighting; M - "mass".

More than two years have passed since I installed Izh-Jupiter 4 on my motorcycle contactless ignition based on a Voskhod generator, a 262 3734 switch and a homemade diode mixer (Fig. 1). After making sure reliable operation my creation, my colleagues decided to make a similar improvement to their motorcycles. However, questions like “I assembled it according to your scheme - explain why it doesn’t work for me” arose.

Here are some typical faults:

No spark at all;

The engine works well at idle, but fails at speeds above average;

The engine starts well, but mainly one cylinder works, the second one picks up occasionally, the flashes follow unevenly,

There is no spark only when installed in the Izha circuit - on Voskhod there is a spark, when replacing the switch-stabilizer unit (BKS) with a similar one of a different type (251 3734 on KET 1-A), the fault disappears.

All of the above troubles indicate a defect in the BCS. Let's look at the factory diagram of the block (Fig. 2.). It is copied from the KET 1-A block produced in the 1980s. In terms of switches, the VD2 zener diode is represented by KS650 (or two D817B connected in series). The latest versions of BKS - 251 3734, 261 3734, 262 3734 are not schematically different. Only the appearance and type of some parts have changed.

The operating principle of the devices is the same: capacitor C2 is charged from the high-voltage winding of the generator along the circuit VD1, C1, VD2, VD4, R2. With a positive voltage pulse from the transmitter, the thyristor VS1 opens through VD3, which discharges C2 onto the winding of the ignition coil TV1, forming a spark on the spark plug F1. Zener diode VD2 limits the voltage on C2VS1 at 130 - 160 V. However, on a working switch, the voltmeter showed 194 V - an obvious overvoltage, the influence of the spread in the parameters of the zener diode. I would like to note an interesting detail - two MBM type capacitors were used as C2. Such capacitors can operate in pulse mode for a long time. Being “self-healing”, they easily tolerate short-term overvoltages. The breakdown areas of the plates are filled with paraffin impregnation of the dielectric. Unfortunately, this does not go unnoticed - over time, the foil of the coverings begins to resemble a sieve, and the capacity of the device decreases. Dielectric breakdowns lead to an increase in conductivity and the appearance of leaks. When working in a switch, such a capacitor simply does not have time to accumulate charge during the time between two sensor pulses. This is why the unit that normally works on Voskhod (Minsk) malfunctions in the Izha circuit, where the frequency of the trigger pulses is twice as high.

A leaky capacitor is identified using a simple diagram (Fig. 3). In compliance with safety measures (the circuit is galvanically connected to the household network), we connect the capacitor being tested into the circuit. The indicator lamp should not light up - the glow indicates the presence of a leak. Check time is 15 - 30 minutes (in doubtful cases - up to 1 hour). Despite the somewhat barbaric method of testing, it is practically safe for the capacitor. During operation, it is subjected to heavy loads. Thus, I identified thirteen capacitors with obvious leaks, four of them in blocks that worked normally on single-cylinder engines, but failed in the Izha circuit. Replacing capacitors in KET-1A is not difficult - the unit can be easily disassembled. The same replacement performed by 252.3734 is more difficult. First, remove the porous mass filling the housing by boiling the switch in boiling water for 15 - 20 minutes. Then we carefully pluck out the filler with tweezers. By pulling the connectors, we remove the board and gain access to the printed circuit board. You can, of course, replace a faulty device with a similar one, but there is no guarantee that the new one will not fail soon either (see the reason above), so I recommend replacing it with capacitors like K73-17 1.0 μF/ 400 V (or even better, 4x0.47 μF/ 630V). Two capacitors are normally located on the board. We seal the block by filling it with construction foam or a rubber plate cut to size. I would warn you against using various auto sealants - their active components will eventually destroy the copper traces of the board. In order to ensure maximum reliability of the device, I consider metal-paper capacitors of the MBG, MBGP, MBGCh types (the letter G indicates the design of the device), designed for a voltage of 400 - 630 V, as a “no alternative” option. The only problem in this case is the dimensions. A compromise option in the circuit for “Izh-Yu” is possible: we reduce the value of C2 to 1 μF. This will ensure its guaranteed charge in half a revolution of the crankshaft.

The remaining elements of the device usually do not cause any particular complaints. S1 (K73-15) is quite reliable. I advise you to replace diodes VD1, VD4 with KD226G (with a yellow ring) VD3 is practically “indestructible”. It happens that the VS1 thyristor changes its characteristics (the engine starts to start in the opposite direction) - this can be eliminated by replacing it with a KU202N or (even better) with a T122-20-10. It is extremely rare for KU221G (KU240A1) to fail. Replacing the SCR involves selecting the minimum control current. This ignition circuit is very demanding on this parameter. I carry out the selection using the circuit shown in Figure 4. Moving the R1 slider from bottom to top, we use the PA1 milliammeter to note the opening current of the test SCR VS1 at the beginning of the EL1 lamp glow. For use, we select specimens with a control current I = 1 - 8mA. Unfortunately, there are SCRs with increased leakage current. This parameter is checked according to the diagram shown in Figure 3. The glow of the lamp will indicate a malfunction of the device.

The BKS restored in this way is suitable for further use in the ignition system of both single- and two-cylinder motorcycles.

D. RASKAZOV, Kashira

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Old Minsk and Voskhod motorcycles used . They related only to ignition and had nothing to do with lighting. Modern motorcycle switches Minsk and Voskhod They additionally have voltage stabilizers, so they play a playing role in the entire electrical chain. In this article I will talk about the KET-1A switch for 6-volt motorcycles. But the very principle of operation ignition switch it’s the same everywhere, which means the article is worth reading for owners too modern motorcycles, if you want to understand contactless system ignition

As already noted, the article contains several photographs. I found it on purpose switch circuits KET 1A and even took a photo of him inside. This will make the situation much clearer if someone doesn’t even know what they look like.

In one of the photos we see electronic circuit the ignition system and the circuit diagram and the switch itself. It is on the basis of this diagram that we will explain operating principle of KET-1A. And now to the point, we read very carefully and immediately compare everything said with the ignition circuit from the figure.

When the crankshaft begins to rotate, let’s say we press the kickstarter or simply take some moment while the engine is running, a current arises in coil 1. This current flows ( AC) from terminal 3 to the input of the switch, enters diode D1 (the diode rectifies it to constant), then passes through resistor R1 (this is a load resistor), enters diode D2 (here it is rectified again) and enters capacitor C2. The other end of the capacitor is connected to a high-voltage transformer, which means that the current in this case charges capacitor C2. The high-voltage transformer in this chain acts as a load, an ordinary resistor, or even more simply, an ordinary connecting wire. Having understood what has been said, we see that only the upper part of the diagram has been discussed by us. Now let's move on to other parts switch KET-1A. They can be divided into lower left and right, the left part has two diodes D4 and D5. These are zener diodes that perform the role of stabilization. They are designed for a voltage of 150 V. Thanks to them, voltage exceeding 150 V goes to ground through these zener diodes. They were introduced to stabilize the current so that too much current does not flow to the bobbin (high-voltage transformer), which can cause it to fail. Now the bottom right corner remains. Here we see a thyristor connected to ground and a capacitor, and diode D3 with resistor R2. Let me explain this part. What is a thyristor? This is an element similar to a diode, but it does not allow current to pass through until a certain point. In order for the thyristor to pass current, a certain signal must be applied to its third contact, the so-called “key”, its “gate”. When this signal arrives there, that is, a current of a certain structure, the thyristor will open and release voltage through itself. It was precisely thanks to the thyristor that it was possible to create a spark only at a certain moment. When the cylinder piston approaches TDC (top dead center), the thyristor switch KET-1A opens and we have a chain that already consists of a capacitor and a high-voltage transformer connected in parallel. What does this mean? The capacitor is discharged and instantly supplies all its energy, that is, current, to the bobbin, and it, having converted it into high voltage, supplies current to the spark plug. At this moment we have a spark. When the piston passes TDC, the signal to the “gate” of the thyristor disappears and it closes, immediately activating the circuit described above. That is, voltage comes from the generator again and capacitor C2 is charged again. The last details that almost nothing has been said about are the diode D3 and the resistor near it. They are designed so that only the required signal is sent to the thyristor “switch”, and not just any signal, otherwise it may accidentally open on similar signals, because the sensor constantly supplies a certain current.

And now the second part, without any introductions.

I have already said in popular scientific style how KET-1A works. I don’t know if it will be easier to describe everything, but I’ll try if someone didn’t understand everything mentioned in the first part.

The switch has a capacitor, it is charged from the generator. The entire circuit is designed in such a way that the current does not flow to the bobbin itself directly from the generator. In order for the current to flow, it is necessary to make the capacitor C2 a kind of battery. This is done using a special electronic switch. This switch connects capacitor C2 to ground at the moment when a spark needs to be made. All this happens electronically, not mechanically. And when a spark should jump through the spark plug, this electronic toggle switch - a thyristor - supplies the other end of the capacitor to ground, it turns out that all the charge in it flows to the bobbin and, converted into high voltage, to the spark plug. A spark passes. Here's another way to explain the electronic ignition switch.

I really hope that I explained the essence clearly electronic system ignition and circuit, switch device KET 1A. I repeat, there is nothing complicated here if you understand at least at the school level in electrical engineering. If you wish, you can learn even more about ignition by looking for my old articles from last year. In some notes I talked a lot about ignition with contacts and with a switch. Read it, it's very valuable information.

Among the breakdowns in the switch there are different ones, now I’ll list them a little. Diodes, zener diodes, thyristors, and capacitor C2 may burn. These are the very first places to search. Resistors rarely burn out. Often there may be desoldering of contacts. Personally, I had three times when parts inside fell off over time. To doubt whether this is really the case with the switch or not, you can simply check by taking another switch and trying it. It is not difficult to remove this spare part, so a neighbor, and even more so a friend, can easily agree to help out. You can also try to check before doing this whether current is flowing into the switch itself. By placing our hands on the output of the generator at the KET, we feel the current by turning it slightly with the kickstarter. Don't be afraid, it won't hit you too hard unless you hit the kickstarter too hard.

From the photos provided, as I mentioned, you can see for yourself KET 1A and its structure, dimensions, internals. In conclusion, I would like to say that many motorists call the KET-1A a six-volt switch. This is not right! In the KET 1A switch only the ignition voltage passes, and about 150 volts. It is the new switches that have a network stabilizer and they can theoretically be called twelve-volt, although this is not entirely true. And yet, it is quite possible to use it for new motorcycles, the structure is the same, but the connections will not fit. In this case, lighting can be supplied through another switch (if only the ignition part has burned out, but the lighting part is working properly) or directly. In this case, the light will depend on the “gas” and the bulbs will light up at high levels. But you can connect without fear, the bobbins are the same, the voltages are also the same. Personally, I installed it myself Minsk 12 V and Voskhod 12 V such a switch (by the way, the one in the photo, I used it once) and everything worked quite well. Which is understandable, the principle of operation itself is completely identical.

Switches KET-1A, BKS 251.3734, BKS 261.3734, BKS 1MK211, BKS 70.3734, BKS 94.3434 designed to work with generators 26.3701 (6V 45W), G-427 (6V 65W), 43.3701 (12V 65W), 80.3701 (12V 90W), GM-02.02, GM-03.02, R71, 92.3702M-02.02, GM-03.02, R71, 92.3702.

The scheme works as follows. AC voltage generator with ignition windings L1 arrives at rectifier diode V1. Rectified voltage through the R6 V5 chain and ignition coil charges capacitor bank C2 C3. Some time after charging capacitor enters signal from the sensor generator L2 to the control electrode of thyristor V6. Thyristor V6 will close the battery of capacitors C2 C3, which will cause a sharp change in induction in the ignition coil and sparking on spark plug electrodes(voltage at secondary winding ignition reaches several dozens kilovolt). Current limiting resistor R6 and smoothing capacitor C1 are used to ignition winding current limitation L1 and smoother charging of the battery of capacitors C2 C3. Zener diodes V3 V4 provide voltage stabilization at the level of 150 V. Voltage stabilization is necessary so that the battery of capacitors C2 C3 and thyristor V6 do not fail due to overvoltage. Chain V2 R2 is necessary to rectify and match the signal from sensor L2 with the control electrode of thyristor V6. This switch has a number shortcomings and weaknesses:

• The maximum operating voltage of capacitors C2 C3 is 160 V, and since the voltage is stabilized by zener diodes V2 V4 at 150 V, the capacitors operate at the limit of their capabilities. Zener diodes of the D817 series have an error of 10%, so the risk of failure of capacitors C2 C3 is quite high.
• When the switch operates for a long time, resistance R6 becomes very hot. As a result, the soldering may melt or the resistor itself may burn out.
• The circuit between the generator sensor and the control electrode of thyristor V6 does not contain a filter against interference and interference, as well as overvoltage protection (stabilizer). The result is unstable operation and the possibility of failure of the V6 thyristor at high speeds.
• At high speeds engine capacity C2 C3 will not have time to charge - resistor R6 will limit capacitor charge current.

Switch diagram BKS 251.3734, BKS 261.3734 presented in the figure.

All BKS switches contain two circuits: ignition and lighting. Scheme ignition is similar to the KET-1A switch, therefore it has the same flaws. The truth is in switches of later releases (since the late 80s) capacity C1 is 2.2 µF 250 V (as in 2MK211). Let's consider the principle of operation of the circuit lighting stabilizer. From the lighting winding of the generator L3, alternating voltage is directly supplied to contact 02 of the switch output (according to the diagram on the right). Thyristor V5 is closed. At the moment when the voltage of winding L3 exceeds the specified value ( 14 V or 7 V), thyristor V5 will open and short circuit winding L3 to ground. This will only happen with a positive half-cycle (relative to ground) at terminal 02. Thyristor control circuit works as follows: the alternating voltage is rectified by the diode bridge V9 and supplied to the voltage divider R2 R3 R4. The ratio of R2 and R3+R4 determines the division coefficient. Smoothing capacitor C3 ensures stable operation of the circuit. When the voltage in section R2 R3 exceeds a certain value, zener diode will open by applying voltage thyristor control electrode. For 12 V lighting circuits Zener diode V7 D814A(opening threshold 7.7 V), and for 6 V respectively KS147A(opening threshold 4.7 V). The zener diodes are selected in such a way that the voltage at the control electrode does not exceed 3 volt, otherwise the thyristor will quickly fail. Therefore, when switch rework For a different voltage it is necessary to replace the zener diode. By selecting resistor R3, adjustment voltage at the switch output. The advantage of the circuit is that the voltage from winding L3 does not decrease when thyristor V5 is closed, since it is connected in parallel with the lighting winding. This is important when the engine is running idle speed .

Switch BKS94.3734 designed for use with generators GM-02.02, GM-03.02, R71, 92.3702. The main feature of the switch is the absence of sparking when generator reverse. Chain V2 R5 VT1 shunts the signal from sensor L2 when the rotor rotates in the opposite direction and in the presence of a false signal ( sensors located inside generator).

Block BKS 70.3734 predecessor of the Kovrov 2MK211. The blocks are designed for generators with internal sensor and are practically no different. Below are BKS 1MK211 switch diagrams And BKS 70.3734.

Device block BKS 70.3734 as well as PCB topology.

Ignition circuit slightly different from KET-1A. The above deficiencies have been eliminated. The sensor circuit contains rectifier V6, filter R1 C4 C5, as well as voltage stabilizer R1 V3. Such a switch is more resistant to interference and interference in the sensor circuit. However for forced engines it won't fit. The lighting circuit of the switch is similar to BKS 261.3734.

How to increase (the lamps shine dimly) or lower (the lamps burn out) the voltage from the switch. If we are not talking about converting 6V to 12V or vice versa, then it is necessary to select resistance R3. First you need to open the switch case, namely remove polyurethane foam. The process is quite tedious and can take 30-40 minutes. This is easier to do if you preheat the case - pour boiling water over it from a kettle or place it in a warm place (for example, on a radiator). Next you need to find resistor R3 (it is highlighted in red in the photo).

Please note that this resistor soldered on top to the board. Unsolder this resistor and solder a variable resistor (rheostat) with a nominal value of 200...1000 Ohm with wires 20...30 cm. Then install motorcycle switch and start it. When adjusting the variable resistor, find its optimal position - the light in the headlight should not flicker at idle engine speeds and should not burn too brightly at high speeds ( lamps burn out) . After adjustment, measure the resistance multimeter and select the resistor value. If the value is not a multiple of the nominal values, you can take several resistors and turn them on daisy chain(resistances are summed up). Solder the resistances and fill the case with foam.

How to convert a 6V switch to 12V and vice versa. For this modification, you will need to completely clean the case of foam and remove the board.

Remove the foam from the back of the board.

Replace Zener diode V7: for 12 V circuit D814A(any 7...9 V zener diode will do), but for 6 V KS147A(any 4…5 V zener diode will do). In the photo, the D814A-1 zener diode is highlighted in red.

Next, you need to carry out all the operations to select resistance R3 (see above). If desired, you can solder in a variable resistor instead of R3 and bring out the movable part of the resistance handle in order to immediately fill the switch with foam and make adjustments “on site”.