On average, manufacturers tend to look at a ratio of 1. Tuning and jetting honda, ktm, kawasaki, yamaha, suzuki, husaberg, husqvarna, tm, gas gas. The morbidelli 125 twin road racer is a rotary valve engine. This range of stroke to bore ratio values allows us to create a highly efficient internal combustion engine while still having mean piston speeds comparable to engines currently available in medium and. Consider two engines having same swept volume but one having bore to stroke ratio greater than 1 and the other having. I have been dreaming of proper big bore 2 stroke for 8 years now and i even attempted to build my own and it works pretty well. Detailing for any one interested in increasing the performance of their machines.
Standard bore two stroke performance engine tuning. Some rearwheeldrive cars that borrow engines from frontwheeldrive cars such as the mazda mx5 use an undersquare design. The larger the bore and stroke, the bigger the displacement and thus a more power engine an engines bore and stroke are generally chosen to keep the piston speed to a reasonable level around 20ms maximum for a road car, while race engines can generally sustain 27ms or so a bigbore, shortstroke engine will. In a reciprocating piston engine, the stroke ratio, defined by either borestroke ratio or strokebore ratio, is a term to describe the ratio between cylinder bore diameter and piston stroke length. On a stroker things like matching the ports to the liner, crankcase to transfers etc. There is quite a large section on changing the face of production racing and into the marlboro series and the lc era and through the kr1s and rgv eras. Other books to his credit are modern engine tuning, twostroke performance tuning and forced induction performance tuning. Finally, we have engines where the stroke is considerably. Anyone interested in doing their own engine porting, or taking the time to learn the intimate secrets of 2 stroke engines should take the time and read each of these books. Everyday low prices and free delivery on eligible orders. He really talking abour a mixwre of fuel and oil if yoll rjchen rhe premix ratio 20. World exclusive brc racing 500cc 2 stroke the big bore. Contents chapter 1 introduction 9 chapter 2 the cylinder.
The website does not intend to compeed with any other website dealing with 2 stroke tuning, and the information shared is not at all as thorough as what you can get from reading the books. In comparison, the achates power opposedpiston, twostroke engine is being designed with a stroketobore ratio in the range of 2. This range of stroketobore ratio values allows us to create a highly efficient internal combustion engine while still having mean piston speeds comparable to engines currently available in medium and. It is not intended as a tuning reference so the settings and timings are for example only, but. Wallace racing back to calculators todays date is 5122020 this is just an approximation. Apr 04, 2015 an introduction to tuning 2 stroke motorcycles for those who want results straight out of the box. I am very proud of the riders i helped and sponsored and there is an appendix. Bell covers all areas of engine operation, from air and fuel, through carburation, ignition, cylinders, camshafts and valves, exhaust systems and drive trains, to cooling and lubrication. An introduction to tuning 2 stroke motorcycles for those who want results straight out of the box. I usually recommend this book along with gordon jennings two stroke tuners handbook, because this book has what the first one doesnt and vice versa. Drawing on the authors many years of experience in tuning and modifying highperformance road, rally and race units, every aspect of an engines operation is explained and analyzed. The bore and stroke of the engine decides the displacement of the engine. Anyone interested in doing their own engine porting, or taking the time to learn the intimate secrets of 2 stroke engines should take.
It covers my early days in the motorcycle trade, on to starting my own mc business then forming my tuning business. Goofit 44mm big bore 53cc 54cc top end kit for 2 stroke. An excellent academic book on the theory behind performance tuning for 2stroke motorcycles. I think ktm is bringing back the big bore 2 stroke.
Two stroke performance tuning a disc partially cut away and attached to the end of the crankshaft opens and closes an inlet port in the side of the crankcase. This fully revised and updated edition is one of the most comprehensive references available to engine tuners and race engine builders. Balancing the crank dynamically, getting correct piston to bore clearance, using good rings with correct end gap, matching piston weights. Other books to his credit are modern engine tuning, two stroke performance tuning and forced induction performance tuning. With larger turbo, exhaust, forged internals, oil pump gears. By dividing the bore by the stroke, a ratio is obtained which characterizes the engine of the bike. About the same price ranges for the motorcycle big bore kits and the atv big bore kits can be found for the suzuki and the yamaha models. We sat down with one of the creators of the brc500 built right here in our hometown of calgary, albert, canada. In comparison, the achates power opposedpiston, two stroke engine is being designed with a stroke to bore ratio in the range of 2.
Two stroke cylinder porting tips watch this before you start cutting. Geared specifically for gp and kart racers, this hardcover treasure has turned out to be a great reference source for questions on the logic and concepts that pertain to tuning a 2stroke for maximum performance. Buy 2 stroke big bore kit 10mm wrist pin 70cc scooter minarelli jog 1e40qmb. We do have a wide range of big bore kits, including for 2 stroke off road motorcycles, 4 stroke off road motorcycles, 2 stroke atvs, and 4 stroke atvs. Ill try and get the ball rolling in here with a list of books i currently own on 2 stroke engines, and 2 stroke engine performance tuning. I started reading these about a year ago now and ive learned so much in just the short time already its mind boggling. We do have a wide range of big bore kits, including for 2stroke off road motorcycles, 4stroke off road motorcycles, 2stroke atvs, and 4stroke atvs. In australia we have the xr6 t which is 4 litre engine. New material on electronic fuel injection and computerized engine management systems. Two stroke performance tuning chapter 3 porting and cylinder scavenging today, when we take a look down the cylinder of a twostroke engine, we find its walls literally filled with ports to handle the induction, transfer and exhaust phases of gas flow through the engine. A reference book for the enthusiast engine tuner and race engine builder. Graham bell second edition this is the moped performance tuning bible as far as im concerned.
The larger the bore and stroke, the bigger the displacement and thus a more power engine an engines bore and stroke are generally chosen to keep the piston speed to a reasonable level around 20ms maximum for a road car, while race engines can generally sustain 27ms or so. The first issue to address is jetting and carburettor tuning. Uses just bore and stroke to calc what your hp could be on average. A great buy for any racer who runs any 2 stroke engine. An excellent academic book on the theory behind performance tuning for 2 stroke motorcycles. Detailed modifications and improvements are described. Enough to get you started and hopefully lead on to growing your own knowledge and skills. Graham bell steers you through the various modifications that can be made to coax maximum useable power output and mechanical reliability from your twostroke. Pistons free delivery possible on eligible purchases. The piston crown opens and closes the exhaust and transfer ports. What is the best big bore 2 stroke what motorcycle. I have the book, but its nice to have as a pdf as well and a good reference for those who dont know about it. A bible for building a high speed and high power 2 stroke machines.
Geared specifically for gp and kart racers, this hardcover treasure has turned out to be a great reference source for questions on the logic and concepts that pertain to tuning a 2 stroke for maximum performance. How far the piston travels back and forth, defines stroke. The website does not intend to compeed with any other website dealing with 2stroke tuning, and the information shared is not at all as thorough as what you can get from reading the books. The inlet port opens 30 after bdc and closes 79 after tdc. Basic 2 stroke tuning by eric gorr changing the power band of your dirt bike engine is simple when you know the basics. It fits on your pocket bike effortlessly and adds plenty of speed. Bigger carburetors, higher compression ratios, altered port timings and expansion. Those of us who have grown up in the japanese two stroke. A detailed explanation of engine displacement and the relationship of bore x stroke to the power production of your engine.
First rule of 2 stroke or any tuning is to make it like it should be, i. The regulations for 2002 season are used as a guideline. Finally, we have engines where the stroke is considerably longer than the bore diameter an under square engine. Engine, turbocharger, rotary engine, torque, specific impulse, crankshaft, piston, twostroke engine, flywheel by books llc and a great selection of related books, art and collectibles available now at. Graham bell is an acknowledged expert on engine tuning, with many years experience in this field.
Bell covers all areas of engine operation, from air and fuel, through carburation, ignition, cylinders, camshafts and valves, exhaust systems and drive trains, to. There is a whole chapter just on the piston ring and a lot of go faster info. The power listed on this guide is from experience not claims. What is the best big bore 2 stroke what motorcycle should i. If your cylinder kit included its own specifications, use those. Genibels books have always been very informative and to the points. Bmw took a similar approach with the design of the s85 v10, which utilised a bore of 92mm and a stroke of just 75. Jun 25, 20 one of the most famous books on 2 stroke tuning. Your engines bore and stroke dimensions play a vital part in the way it produces power. Fully revised with the latest information on all areas of engine operation, from air and fuel, through carburation, ignition, cylinders, porting, reed and rotary valves, and exhaust systems to cooling and.
Undoubtedly, the virtue which has most contributed to the widespread use and varied application of the twostroke engine is its mechanical simplicity. The author approaches every part of the kt100 in great detail. Ktm is bringing back the 2 stroke big bore for 2016 moto. Here im not going to speak about swept volume instead im going to directly relate bore and stroke with engine performance. So whether youre assembling your mini bike or discover that you have other problems. This can be used for either an internal combustion engine, where the fuel is burned within the cylinders of the engine, or external combustion engine, such as a steam engine, where the combustion. List of 1980s, 90s, and early 2000s big bore 2 stroke dirt bikes these are the classic 500cc bikes such as the cr500, kx500, cr480, yz490, ktm 495, and. A myriad of different aftermarket accessories is available for you to custom tune your bike to better suit your needs. For sheer power for money and driveability the best setup would comprise of. Those of us who have grown up in the japanese twostroke. Two stroke tuners handbook 2 another mistake commonly made, sometimes even by those who have enjoyed some success in modifying twostroke engines, is to believe in a kind of mechanistic magic. Many ignore the oil rails, those thin rings for oil control, but you may wish to check and set it to 0. Two stroke performance tuning chapter 3 porting and cylinder scavenging today, when we take a look down the cylinder of a two stroke engine, we find its walls literally filled with ports to handle the induction, transfer and exhaust phases of gas flow through the engine. Bells four stroke performance tuning book, this book goes into extreme detail regarding performance tuning a two stroke engine.