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23-518: The Yezdi Roadking was the successor of the short-lived Yezdi Oilking. The Oilking was the first motorcycle in India to attempt to move away from pre-mixed fuel to a separate oil lube system via an oil pump. The box-like shape on the left hand cover housed the oil pump. Unfortunately this system had a very high failure rate resulting in piston seizures. This resulted in the discontinuation of the Oilking and

46-503: A drastic make-over in 1964 to conventional "wedge" combustion chambers, then modified again for stud-mounted rocker arms, and finally underwent an even greater re-design to become the modern 5.7 liter hemi. All of these engines retain the original 4.460" bore pitch distance set down in 1956. "Hybrid" is the term commonly used to identify an engine modified for high performance by adapting a cylinder head from another (sometimes completely different) brand, size, model or type engine. Note: using

69-497: A kicker and once started it automatically returns to the original position. The bike was silently launched in India in the late 1970s by Ideal Jawa. It had a prominent fuel tank and was finished in signature Jawa maroon and sometimes in black and gold pinstripe, priced slightly higher than the Classic and CL II models. The troublesome contact breaker ignition was replaced in 1993 with an electronic CDI unit. Until 1989, Roadkings had

92-463: A later head of the same engine "family" isn't a true hybrid, but mere modernization. In some cases, two heads from the donor (source) engine are joined end-to-end to match the number of cylinders on the subject engine (such as using three cylinders each of two V8 heads on a Chevrolet inline-six). Identical or extremely similar bore pitch is what makes this possible, or (almost) impossible. Sholavaram Cholavaram , also spelled Sholavaram ,

115-404: A main bearing. Since the start-up expense of casting an engine block is very high, this is a strong incentive to retain this dimension for as long as possible to amortize the tooling cost over a large number of engines. If and when the engine is further refined, modified or enlarged, the bore pitch may be the only dimension retained from its predecessor. The bore diameter is frequently increased to

138-430: A provision for adjusting the front fork dampers. During the late 1970s, another model known as Oil King was also launched which featured an oil pump for the 2T mix with petrol but later production ceased due to rampant issues with fuel pump failure. The prominent protrusion on the left hand side gearbox housing was the original location of the pump. Though the model was discontinued, the engine casing found its way into

161-478: A result of power glider efforts, during 1996 Somender Singh, a former Ideal Jawa road and rally racer developed a more refined engine, made from aluminium as opposed to the usual cast-iron, with increased power and fuel efficiency which was featured in Car & Bike magazine. The design was never put into production even though it ended up with Ideal Jawa. These motorcycles were also used by various police forces around

184-556: Is a single frame of motocross origin and was built out of square tube. The fork was more pronounced with a higher rake angle and came with adjustable shock absorbers . Rims were 16 inches. The motocross and ice racing origin frame and proper weight balance made handling very easy and agile compared to its rivals in India. The cylinder block was carried over from the CZ 250 motocross, which had an over-square stroke ratio. Carburetors were either Jikov (tickler choke ) or Pacco, wherein

207-632: Is a suburb 24 km (15 mi) north of Chennai , Tamil Nadu , India . It is popular as Sholavaram and is also known for the Cholavaram lake . Adjoining the lake, there was a defunct Air Force Airfield which was used as a motor racing track. It was an air strip used during World War II ; After the Madras Motor Sports Club was formed in mid-50s, it selected Sholavaram to conduct its racing events. Since then racing events took place every year and continued till late 1980s until

230-456: Is always larger than the inside diameter of the cylinder (the bore and piston diameter) since it includes the thickness of both cylinder walls and any water passage separating them. This is one of the first dimensions required when developing a new engine, since it limits maximum cylinder size (and therefore, indirectly, maximum displacement), and determines the length of the engine (L4, 6, 8) or of that bank of cylinders (V6, V8 etc.). In addition,

253-593: The GMC straight-6 engine , the Buick Straight-eight , and the Chrysler "Slant 6" ) the bore pitch is additionally extended to allow more material between the main bearing webs in the block. For example, in an L6 the first pair (#1 & 2), center pair (#3 & 4), and rear pair (#5 & 6) of cylinders that share a pair of main bearings have a smaller pitch than between #2 & 3 and #4 & 5 that "bridge"

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276-648: The Rajdoot Yamaha RD350 . During the early 1990s FMSCI , the sporting federation of India banned two-wheelers above 120 cc from rallies thus ending the Roadking's run in motor sports. The Roadking engines were a favorite among the hang-glider manufacturers in India. A Coimbatore based manufacturer headed by late motor racing driver and constructor, S. Karivardhan manufactured and exported several Power gliders using Roadking engines with modified aluminum heads, K & N filters and sleeved bore. As

299-477: The Roadking and hence all Roadkings have this protrusion even though the oil pump is not included. In 1993, in an effort to increase fuel efficiency and to solve starting problems the CB or contact breaker ignition units were replaced with CDI electronic ignition units. The livery was also changed. Fuel efficiency was increased by 30%, however the motorcycle's competitors were getting better and with rising fuel prices

322-547: The Yezdi Classic/Model B in appearance. Also the CZ original had a "Porcupine" cylinder head, which was used only in the initial models; the cylinder head later reverted to regular straight fin design. The cylinder block (Type 980.5) was from CZ. Just like in the older Jawa 353 Kyvacka and the Yezdi Model B, the Roadking also came with an original Tesla (Czechoslovakian) headlight bulb as standard. The frame

345-430: The birth of the Roadking. The Roadking though, still retained the protuberance on the left engine cover that housed the oil pump in the Oilking. The Yezdi Roadking was based on the 1974 CZ 250 Falta, where the original bore and stroke of 70 mm × 64 mm (2.76 in × 2.52 in) was retained, but detuned for lower power than its Motocross original. The engine block is smaller than and different from

368-454: The bore of a locomotive cylinder or steam engine pistons . The term bore also applies to the cylinder of a steam locomotive or steam engine . Bore pitch is the distance between the centerline of a cylinder bore to the centerline of the next cylinder bore adjacent to it in an internal combustion engine . It's also referred to as the "mean cylinder width", "bore spacing", "bore center distance" and "cylinder spacing". The bore pitch

391-748: The factory after the Twin was discontinued. In road races at Sholavaram , the Roadking ran in its own 250 cc class, while in the Indian open class category its main rival was Royal Enfield Bullet and later the much more powerful Rajdoot 350 . Power was usually increased to 25+ bhp or beyond for Group E categories where the engine was bored up till 300 cc and over-engineered in stock trim. Among prominent racers were C.K. Chinnappa and Somender Singh. In rallies, N. Jagadeeswara Reddy won many rallies until 1980. Then racing couple Jagat and Anita Nanjappa and Thirumal Roy won several victories before switching to

414-486: The former was exclusively for the Roadking while the latter was used for the Classic D250 model. The spark plugs were cold and the bike also featured a semi-automatic clutch , where a mechanism by the name cam and roller connected to the clutch push rod to engage/disengage the clutch which is unique to this and other Yezdi/Jawa models. The cam and roller is mechanically coupled to the gear selector thereby eliminating

437-422: The limit of minimal wall thickness, the water passage is eliminated between each pair of adjacent cylinders, the deck height is increased to accommodate a longer stroke, etc. but in general if the bore pitch is the same, the engines are related. As an example of development, the Chrysler 277" polyspheric V8, first introduced in 1956, was gradually increased in size by bore and stroke to 326" by 1959, then received

460-408: The need for a hand-clutch while engaging the gears. The motorcycle featured dual exhaust ports with dual silencers akin to most Jawa motorcycles, but unlike the CZ 250 on which it was based, which featured a single exhaust port. Another unique feature of the bike was that the kick-starter and the gear shared the same shaft as with all Jawa/CZ/Yezdi motorcycles. Once the gear rod is reversed it doubles as

483-481: The positions of the main bearings must be between individual cylinders (L4 with 5 main bearings, or L6 with 7 main bearings - only one rod journal between main bearings), or between adjacent pairs of cylinders (L4 with 3 main bearings, L6 or V6 with 4 main bearings, or V8 with 5 main bearings - two rod journals between main bearings). In some older engines (such as the Chevrolet Gen-2 " Stovebolt " inline-six,

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506-474: The sales plummeted until finally it ceased operations in 1996. At the 1996 Auto Expo, Yezdi displayed a model which used the Yezdi 350 Twin frame & fuel tank, and the Roadking engine. The rims were 18 inch as opposed to the regular 16 inch. However, it sold only in few numbers. Although some attribute its low sales volume to the company's need to get rid of the surplus Yezdi 350 frames that remained in

529-528: The world, examples being Guatemala, Sri Lanka, Egypt, Turkey etc. Bore (engines) In a piston engine , the bore (or cylinder bore ) is the diameter of each cylinder . Engine displacement is calculated based on bore, stroke length and the number of cylinders: The stroke ratio , determined by dividing the bore by the stroke, traditionally indicated whether an engine was designed for power at high engine speeds ( rpm ) or torque at lower engine speeds. The term "bore" can also be applied to

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