Engine repair during normal operation of a motorcycle, as a rule, becomes necessary after several tens of thousands of kilometers, when power drops noticeably due to a decrease in compression in the cylinders, oil consumption increases and mufflers smoke more strongly, knocks and noises appear. With sufficient experience, you can judge the condition of the engine by the noise of its operation or by external signs. If any violations appeared suddenly, it is advisable to establish the cause of the malfunction before disassembling the engine so as not to touch unnecessary components. because in this case, the connections of the run-in pairs and seals are broken. (Behind the wheel, No. 2, 1984)

When disassembling the engine, as well as other mechanisms (partial or complete), it is recommended to mark the parts so that, after checking, fit and slightly worn ones can be installed in their places.

In a motorcycle engine, piston rings are among the wear parts. They are made from special cast iron.

The oil scraper rings of the engines of all motorcycles "Dnepr" and "Ural" are interchangeable, the height of the ring is 5-0.015 mm. Compression rings are not interchangeable: ring 7201217-01 (K750M) has a height of 3, and 6101217 (MT) - 2.5 mm. Designations and dimensions piston rings are given in Table 1.

Signs of failure of the rings - smoke from mufflers, increased consumption oil (more than 300 cm3 per 100 kilometers), a decrease in compression, a malfunction of the ventilation system (an increased release of oil through the breather tube is possible). In this case, it is necessary to remove the cylinder heads, and then check the condition of the parts of the piston group.

When the rings are worn, the gap in their locks increases. The maximum allowable is 3 mm. To measure it, the rings are removed from the piston, marking their location. Then the ring is inserted into the cylinder, its position is aligned with the piston and the gap in the lock is measured with a feeler gauge.
The worn ones are replaced for the first time with rings of normal size, and then, when the cylinder is worn out and bored out, rings and a piston of a repair size are installed. Before installation, a new ring is inserted into the cylinder and the gap in the lock is checked, which should be in the range from 0.20 to 0.6 mm.

Before installing the cylinder in place, lubricate its mirror and piston skirt engine oil, separate the rings so that their joints are located at an angle of 120 ° to one another. When putting the cylinder on the piston, the rings are compressed with a clamp, which can be easily made from tin.

A sign of piston wear is a dull metallic knock in the cylinder area, especially noticeable after starting a cold engine.

The right and left pistons in both engines are the same, cast from heat-resistant aluminum alloy KS-245. The cross section of the skirt is oval. and along the longitudinal - conical shape. In the MT engine, the axis of the hole for the piston pin is shifted from the plane of symmetry by 1.5 mm.

For correct installation piston into the cylinder on its bottom is filled with an arrow, which during installation should be facing forward, that is, towards the centrifuge. In this case, when looking at the MT engine from behind, the finger in the piston of the right cylinder is shifted down, and in the piston of the left - up.
The holes for the piston pin are divided into four groups by diameter (through 0.0025 mm) and are marked with paint on the boss (Table 2).

Outside diameter (measured under oil scraper ring) pistons are sorted through 0.01 mm into four groups. The size of the piston group is stuffed on the outer side of the bottom with numbers: "77.95". "77.96". "77.97", "77.98" for the MT engine and "77.93". "77.94", "77.95". "77.96" for K750M. In addition, the pistons are divided into groups by weight, which matches the color index of the piston pin hole.

The piston must be replaced if the gap between the cylinder bore and the largest diameter of the skirt (in a plane perpendicular to the axis of the pin, below the groove for the oil scraper ring) exceeds 0.25 mm. The clearance can be measured with a feeler gauge when the piston is at the bottom of the cylinder.

If the piston is normal, and only the grooves of the upper, compression rings are worn out (end clearance is more than 0.15 mm), you can install a ring from the K750M engine on the MT engine. after grinding it in height, taking into account the end clearance within 0.04-0.07 mm for the upper ring and 0.025-0.055 mm for the lower one.

Usually, when the pistons are first replaced, when the cylinders are still a little worn, to reduce the gap between the mirror and the skirt, you can install a “normal” piston, but with a larger skirt diameter. For example, if the cylinder diameter of the MT engine of group “1” (78.01-78.00 mm) during operation increased to 78.04-78.03 (which corresponds to group “4”), then the piston “77.95” standing in it should be replaced with a piston with designation "77.98". In this case, the required clearance of 0.05-0.07 mm will be restored. In the K750 engine, pistons are selected taking into account the provision of a gap of 0.07-0.09 mm.

Pistons are selected not only by the diameter of the skirt, but also by weight in order to maintain the balance of the engine. The difference in weight of the pistons must not exceed 4 g.
The piston pin is made of 12KhNZA steel, cemented and heat-treated to a hardness of HRC 5v-63. It rotates freely in the upper head of the connecting rod with a clearance of 0.0045-0.0095, but is pressed into the piston bosses with an interference of 0.0045-0.0095 mm. According to the outer diameter, the fingers are divided into four groups at intervals of 0.0025 mm and are marked with paint on the inner surface (see Table 2).

Clearances of more than 0.01 mm in the connection of the pin with the piston and more than 0.03 mm in the connection of the pin with the connecting rod can cause distinct sharp knocks and intensive wear of parts when changing the engine operating mode. To eliminate these phenomena, it is necessary to replace the piston pin, observing the required marking and its fit in the piston and connecting rod according to Table. 2. When installing the finger, the piston is heated to 80-100 ° C in the oven or in boiling water; Before assembly, the finger is lightly lubricated with engine oil, then the holes in the piston and the upper head of the connecting rod are aligned and the finger is hammered into them with light hammer blows through the mandrel. A lubricated piston pin fits into the top end of the connecting rod when it slides easily into the hole, but does not fall out when its axis is vertical.

You can remove the finger without heating the piston, but you must use a special tool. If not, you can heat the piston crown blowtorch through a metal sheet and using a mandrel made of soft metal (copper or aluminum), knock out a finger, as shown in fig. one.

The cylinders of the MT engine are the same, interchangeable. The sleeve is cast from special cast iron and connected in one piece with an aluminum alloy jacket. Sleeve hardness HB 207-255. K750M cylinders are cast from special cast iron, their hardness is HB 207-255. The left and right are not interchangeable, since they differ in the position of the inlet and outlet valves.

Cylinders are divided into four groups according to the inner diameter at intervals of 0.01 mm. The size of the group at MT is stuffed in the lower part of the cylinder shirt (near the flange) from the side of the casings of the rods with the numbers "1", "2", "Z" and "4", which correspond to diameters 78.01-78.00; 78.02 - 78.01; 78.03 - 78.02 and 78.04 - 78.03 mm. For K750M, the group index is stuffed on the plane of the valve box.

The cylinder must be replaced or bored to the nearest repair size of the piston if the wear of the upper part of the mirror is 0.15-0.20 mm. When the cylinder becomes tapered (wider at the top) and oval, it is no longer possible to restore normal compression by installing new pistons and rings.

Cylinder wear is determined by measuring its diameter with an indicator-caliper in three belts located at distances of 15, 50 and 90 mm from the upper end of the cylinder in the connecting rod swing plane and in a plane perpendicular to it.

The worn cylinder is bored and honed to fit the repair diameter of the pistons (increased by 0.2 or 0.5 mm). After processing, the ovality and taper of the mirror must be no more than 0.015 mm, the finish of processing is not lower than class 9, the beating of the landing end relative to the mirror is not more than 0.05 mm, the misalignment of the mirror and the outer surface of the cylinder mating with the engine crankcase is not more than 0.08 mm . The piston is selected so that the mounting gap between the largest diameter of its skirt and the cylinder for the MT is 0.05-0.07 mm, for the K750M it is 0.07-0.09 mm. When installing a new piston in the cylinder, it is necessary to be guided by the information given in Table. 3.

The connecting rod and its cover for the MT engine are stamped from 40X steel, hardness is HB 217-266. The bottom covers of the connecting rods are not interchangeable, so each must be put in its place during assembly. When installing connecting rods on crankshaft the protrusions in their middle part should be directed outward relative to the middle cheek of the shaft. In the lower head there are liners that are interchangeable with the connecting rod liners of the Moskvich-408 engine. A bronze bushing made of BrOTsS-4-4-2.5-PT-1.5 tape is pressed into the upper head. the hole is made with great precision. According to its diameter, the connecting rods are divided into four groups (through 0.0025 mm) and marked at the head with a color index (see Table 2).

The assembled connecting rods are divided by weight into seven groups (after 5 g) and marked with paint. Connecting rods with one-color markings are installed on the crankshaft. nuts connecting rod bolts tighten with a moment of 3.2-3.6 kgf / m. The pin must fit tightly into the bolt hole. Used pins must not be used.
Possible defects of the connecting rod - wear of the bushing under the piston pin, bending and twisting of the connecting rod body.

The bushing diameter can be measured with an indicator caliper. If the clearance between bushing and piston pin is more than 0.03 mm, the bushing must be replaced. To do this, it is necessary to make a new bushing from BrOFYu-1 or BrOTsS-4-4-2.5 tin bronze and press it in with an interference fit of 0.027-0.095 mm. Drill a hole with a diameter of 2.5 mm in the bushing to lubricate the piston pin and turn it with a reamer to a diameter of 21 mm. Remove the chamfer 1x45 ° from the highlanders of the bushing. It remains to measure the actual size of the hole. mark it in accordance with the table. 2 and select a piston pin with the corresponding color marking.
The bending of the connecting rod is characterized by the relative displacement of the axes of the holes of the upper and lower heads in the vertical (bending) or horizontal (twisting) planes. Axis displacement is allowed no more than 0.04 mm over a length of 100 mm. The center distance between the axes of the new connecting rods is 140 ± 0.1 mm.

Connecting rod bolts must not have dents, traces of drawing and thread stripping, cracks and other defects. The diameter of the lower head of the connecting rod is measured with the inserts inserted and the cover bolts tightened with a force of 3.2-3.5 kgf.

If the clearances in the connecting rod bearings are not more than 0.10 mm, and the ovality and taper of the crankshaft journals do not exceed 0.05 mm, you can not grind the necks. and install liners of normal or reduced size by 0.05 mm (first repair).
The crankshaft of the MT engine is cast from high-strength cast iron VCh50-2 and heat-treated to a hardness of HB 212-255. The nominal diameter of its main journals is 45 ± 0.08 mm, the connecting rod journals are 48-0.025 mm.

The suitability of the crankshaft for further operation is determined by the degree of wear of the connecting rod journals. Their diameter is measured with a micrometer in two mutually perpendicular planes in two places at a distance of 2.5 mm from the fillets. The distance between the cheeks of the connecting rod journals is 28.5 + 0.14 mm, the radius of the fillets is 1.5-2.0 mm, the finish is not lower than the 9th grade.

In a new engine, the gap between the neck and the liners is 0.025-0.085 mm. A sign of wear on the connecting rod journals is the appearance of thuds in the lower part of the crankcase and a decrease in pressure in the lubrication system.
With significant wear, the necks are ground to the nearest repair size (Table 4) and the corresponding liners are placed. After processing the necks, all channels, including traps, must be cleaned of chips and washed several times under pressure. As a result of grinding, the connecting rod journals must meet the following conditions: ovality and taper not more than 0.015 mm; non-parallelism of the axes of the connecting rod journals to the axes of the main journals - no more than 0.02 mm along the length of the neck.

After checking, the crankshaft is assembled by turning Special attention on the correct installation of the connecting rods, and installed in the engine crankcase, as shown in fig. 2. When properly assembled, the shaft should rotate easily in the main bearings.

The engine pistons of Dnepr and Ural motorcycles are cast from heat-resistant aluminum alloy and heat-treated. The piston consists of a head with a spherical or flat bottom, a skirt and bosses. Piston rings are installed on the piston (two compression and two oil scraper). In the grooves under the piston rings there are through holes for oil drainage. The piston skirt is made in a special oval shape. The larger diameter of the skirt is located in a plane perpendicular to the axis of the piston pin. The piston skirt also has a conical shape. The difference between the larger and smaller diameter of the skirt is 0.015 mm. The diameter of the upper part of the skirt is less than the diameter of the lower part by 0.03 - 0.05 mm. The ovality and taper of the skirt are necessary so that, with a small gap between it and the cylinder, the piston, expanding from heating, does not stick in the cylinder. The pistons are the same for both cylinders. Depending on the diameter, the cylinders are divided into groups (Table 2.1).

To reduce the noise of the piston during its operation, the axis of the hole for the piston pin in the MT 10-32 engine is offset by 1.5 mm relative to the axis of symmetry. To correctly install such a piston in the cylinder, an arrow is stamped on the bottom of its bottom. During installation, the arrow on the pistons of both cylinders must point forward towards the centrifuge. In this case, when looking at the engine from behind, the pin in the piston of the right cylinder should be shifted down, and in the piston of the left cylinder - up.

The pin holes in the pistons of the K-750M and M67-36 engines are made without displacement of the pin axis from the diametral plane of the piston. The pistons of the K-750M and M67-36 engines have a flat bottom, and the MT 10-32 piston has a flat bottom with an ejector.

The finger holes are divided into groups at intervals of 0.0025 mm and marked with paint on the sidewall (Table 2.2). Permissible wear The hole for the piston pin must not exceed 0.02 mm. These bores contain grooves for circlips that assist in axial displacement of the piston pin. Pistons to cylinders are selected with the necessary clearance. To facilitate selection, pistons and cylinders are sorted through 0.010 mm. Their dimensions are stamped on inside piston bottom.

In addition, the pistons are grouped by weight, which matches the colored index of the piston pin hole. The difference in the mass of the engine pistons should not exceed 0.004 kg. The piston assembly with rings and pin is weighed. For selected pistons, the color marking of the holes for the piston pin must match the marking of the hole in the upper head of the connecting rod. The marking paint on the pistons is applied to the bottom

the surface of one of the bosses, on the connecting rods - at the top head.

Table 2.3 Repair dimensions of cylinders and pistons

Brand move	Cylinder and piston size	Diameter cylinder,	Piston designation according to the catalog	Piston diameter, mm
MT10-		78,20-78,24	KM3-8.15501237-P1	78,18-78,14
mtu-		78,50-78,54	KM3-8.15501237-P2	78,48-78,44
750M	1st repair (increased by 0.2 mm)	78,20-78,24	72Н01237-Р1	78,15-78,11
750M	2nd repair (increased by 0.5 mm)	78,50-78,54	72Н01237-Р2	78,45-78,41
M67-36	1 repair (increased by 0.2 mm)	Four-stroke two-cylinder power unit consists of separate mechanisms placed inside the crankcase. The gearbox 4 is attached to the engine 1 with the help of three studs and a bolt. The generator 3 is mounted on the upper part of the crankcase, and the ignition devices are placed in front of the engine under a removable cover 2. Carburettors 5 are attached to the cylinders. By design, the K-750 motorcycle engine is basically similar to the M-72 engine, but has the following features: the crankcase has holes of a different size for the camshaft bearings; cylinder heads are made in such a way that they have a smaller combustion chamber, due to which the compression ratio is increased, and hence the power of the unit; camshaft rotates on two bearings: radial single-row and plain bearing; pistons have two oil prefabricated rings; the distribution gear cover is made in a slightly different configuration; changing this cover from M-72 to K-750 or vice versa is possible only together with a breather. Assembled motors are interchangeable; with an increase in the compression ratio and power increased slightly temperature regime, therefore, the engine oil reservoir is made with fins, which replaces the oil cooler, reduces the oil temperature in the sump, and keeps the engine temperature at the same level; significantly increased the efficiency of the crankcase ventilation system. The table shows comparative data on the parameters of the engine ventilation systems of both motorcycles. Video. Engine K-750 The heavy motorcycle K-750 appeared as a result of the modernization of the famous motorcycle of the Great Patriotic War M-72. Initially, the M-72 was planned to be produced at factories in Moscow, Leningrad and Kharkov. Probably, the letter M just meant the Moscow Bicycle Plant, located in the Kozhukhovo district in the southern part of the capital. With the outbreak of war, the factories had to be evacuated. Moscow - in the Ural Irbit, Leningrad and Kharkov - in Gorky. As a result, the Gorky Motorcycle Plant arose on the territory of the Krasnaya Etna plant. He successfully produced the M-72 at the end of the war and the first years after the Victory. But in 1949, the government decided to re-profile the Gorky Motorcycle Plant, and transfer the production of the M-72 needed by the country to Kyiv. Since 1945, a motorcycle factory has been operating in the capital of Ukraine on Kagatnaya Street. He produced a light motorcycle K-1B "Kievlyanin" class 125 m 3 , a clone of the German Wanderer. They decided to sacrifice this model for the sake of the former Gorky M-72. However, the restructuring of production took several years. The first heavy motorcycles left the Kyiv assembly line in 1951, but they were assembled from imported parts. First, from the stock of Gorky, and when it ended - from Irbit, and in parallel with the assembly of the last batches of "Kiev". By 1955, they managed to master the full production cycle, but the M-72, created before the war, was completely outdated by that time. The result of the phased modernization of the motorcycle was new model K-750 of 1958, the original Kyiv design, which was not a copy of the Ur al motorcycles, obtained by a separate modernization of the M-72, carried out in Irbit. As a result, the country has two independent manufacturers of heavy motorcycles of the same class. In order to reduce competition, the planning authorities tried to distribute and sell Kyiv motorcycles in the European part of the country, and Irbit ones - beyond the Urals. The K-750 engine was equipped with new cylinder heads: the shape of the ribs changed and the compression ratio increased. Another was the front cover of the engine with a breather. Two oil scraper rings appeared on the piston, and ribs were made on the oil sump for better cooling. The rear wheel suspension became pendulum, spring, with telescopic hydraulic shock absorbers, which were absent on the M-72 and its modifications. Finally, the K-750 differed from its predecessor in a new sidecar with a spring (not torsion) wheel suspension and a hydraulic shock absorber. In 1963, the modernized K-750M appeared. On some machines, an ignition timing device and a paper element were introduced in air filter. Instead of a gearbox of the M-72 type, a modernized one began to be installed, the front fork also changed: it was distinguished by hydraulic shock absorbers double action and increased wheel travel. Motorcycles K-750 were widely used in the police. The 50s and 60s were a time of mass use of sidecar motorcycles as patrol vehicles. Police K-750 was filmed in the famous film by Eldar Ryazanov "Beware of the car." On it, the traffic police inspector, played by Georgy Zhzhenov, is chasing Yury Detochkin's Volga, and before that he starts the motorcycle itself from a tow using the same Volga: "With an old battery, this is not life." Motorcycles K-750 met with private owners back in the 60s, but many of them were decommissioned from the army and the police and "privatized" in the 70s. Currently occurs quite often. The Museum presents the restored K-750. Technical specifications Number of places 2-3 dimensions 2400x1600x1060 mm (with side trailer) Width and track with sidecar 1700x1110 mm Wheelbase 1450 mm Engine gasoline, carburetor, two-cylinder, four-stroke, boxer, lower valve Working volume 746 m3 Power 26 at 2900 rpm Dry weight 315 kg Max speed 95 km/h Average fuel consumption 7 l/100km PISTONS AND VALVE SPRINGS FOR OPPOSITES · Engine With enviable frequency, Opposite questions arise: what pistons to choose, whether it is possible to put Ural ones on the Dnieper or Dnieper ones on the Urals, how to distinguish pistons for 80th gasoline from pistons for 92, etc. etc. There are also questions about valve springs - is it possible to install non-standard ones, if so, which ones and how? What can be put in place of weak clutch springs? This article will help to understand the existing diversity. So, PISTONS. Pistons are manufactured using different technologies (photo 1). Usually this is casting (for lower valves, as well as standard Ural and Dnieper ones). There is another technology called isothermal stamping (colloquially they usually say "forging", although this is not entirely correct). Both technologies have their pros and cons; in addition, the sizes differ, so we will consider all the options in order. We look at table 1 and at figure-scheme 1. PISTONS FOR M-72 and K-750 of interest primarily to lovers of antiquity. They are not suitable for use in more modern motors due to the large distance from the pin axis to the bottom and the large mass. The pistons are interchangeable, they are distinguished by the presence of a groove for the second oil scraper ring in pistons for K-750 (photo 2 and 3). STANDARD PISTON FOR 650 IMZ ENGINE(photos 4 and 5). Cast piston with a flat bottom, with two oil scraper rings. Provides a low compression ratio requiring the use of gasoline with an octane rating of 76-80. PROS: affordable price, widespread (in case of a breakdown, you can find a spare piston or rings in any village), the use of inexpensive fuel. Available repair dimensions. CONS: higher coefficient of thermal expansion compared to forged pistons, and, accordingly, a greater tendency to jam when overheated. Poorly resists burnout. Large weight compared to forged pistons. Wide piston rings create increased liner friction, increasing mechanical losses. Partially, losses can be reduced by removing the lower oil scraper ring, which at the same time reduces the mass of the piston. However, an increase in oil consumption is possible. STANDARD PISTON FOR IMZ 750 ENGINE(photos 6 and 7). Forged piston with spherical bottom, short skirt and one oil scraper ring. It is allowed to be installed on both 750 and 650 cc engines. Provides an increased compression ratio, which requires the use of AI-92 gasoline. The pin is offset relative to the piston axis, which makes the engine run smoother and reduces wear on the CPG. PROS: lighter than a standard cast. Less prone to burnout. A lower coefficient of thermal expansion reduces the likelihood of a thermal wedge. Thin piston rings reduce mechanical losses in the ring-cylinder mirror pair. CONS: high price. Low prevalence in spare parts. Use of Hastings rings of rare dimension. A reduced skirt can THEORETICALLY cause increased piston or cylinder wear. There are known cases of burnout of the pistons in the center with a strong over-depletion of the mixture. There are no repairs. PISTON MANUFACTURED BY AUTOTECHNOLOGIA, STANDARD DIAMETER 78 MM(photos 8 and 9). Forged piston with spherical bottom, standard long skirt, one oil scraper ring. The dimension of the rings is the same as on the forged Irbit piston. It is installed on 650- and 750-cc engines. Provides an increased compression ratio for 92 gasoline. The finger is offset relative to the piston axis. PROS: with a full skirt, it has a mass as small as that of the Irbit forged pistons. Exclusively high quality material (from a finger strike it rings like crystal) and processing. Optimum skirt shape (barrel-shaped), providing improved skirt lubrication conditions. The price is at the level of Irbit forged pistons. CONS: it is almost impossible to buy them somewhere other than Moscow. It is believed that the harder material of these pistons can cause accelerated cylinder wear. There are no repair sizes. PISTON MANUFACTURED BY AUTOTECHNOLOGIA, INCREASED DIAMETER 79 MM Piston manufactured by Avtotekhnologiya, enlarged diameter 79 mm (photos 10 and 11). Structurally repeats the piston under the size of 78 mm. Differs in the use of standard piston rings from the VAZ engine. PROS: Same as size 78 pistons. Use of easily accessible rings makes these pistons ideal for long distance travel. Some increase in working volume (up to 666 cubic meters). A good option to restore a badly worn motor. CONS: Same as size 78 pistons. Some increase in weight can reduce the maximum engine speed. PISTONS FOR MOTORCYCLES OF THE Kyiv PLANT I did not have a chance to examine personally, so the information is given from a third-party source: motodrive.com.ua The difference between them is in the design of the bottom, mass. All are equipped with standard opposed rings - 2 compression and 2 oil scraper rings per piston. The disadvantages and advantages are the same as for cast pistons for 650 cc IMZ engines. PISTONS PRODUCED BY AUTOTECHNOLOGIA FOR DNEPR MOTORCYCLES(photos 12 and 13). They come in a diameter of 78 mm - for Hastings rings, and 79 mm - for VAZ rings. Forged pistons, structurally repeat the piston for the MT-10-32 engine with a trapezoidal displacer, but with one oil scraper ring. ADVANTAGES are the same as for Avtotekhnologii products for IMZ motors: low weight (much less than the lightest cast ones), low thermal expansion coefficient and tendency to jamming, exceptionally high quality. MINUSES similarly - low prevalence, fears of accelerated wear of cylinders. Separately, I want to say about pistons with a diameter of 82 mm. The need for such details is experienced by owners of 720 cc Voyages, as well as tuning enthusiasts who want to bore their 650 cc engine to 720, or 750 cc engine to 825. Factory pistons for a 720 engine cannot be found on sale - “no, son, this is fantastic!”. The way out is to remake automobiles. For example, a standard cast piston FROM THE VAZ-2112 ENGINE(photos 14 and 15). Remaking it is simple: make additional recesses for the valves in the bottom, bore the holes and press in the bushings for the opposite pin with a diameter of 21 mm. PLUSES: high prevalence of workpiece parts, ease of rework. Use of common inexpensive rings. There are repair sizes. CONS: VERY large mass - almost 100 grams heavier than a forged piston with a diameter of 78 mm. Such a mass can negate all other forcing work: the maximum engine speed will drop, the load on the crank and connecting rods will increase sharply. A cast piston will have a tendency to seize when overheated. Insufficient height of the sphere will reduce the compression ratio, which will have to be compensated by trimming the cylinder. In short, this option is only suitable for resuscitation of a 720 cc engine. It is not categorically suitable for forcing, as blanks you need to look for lightweight, probably forged, pistons. koreada.ru - About cars - Information portal