Graham bell is an acknowledged expert on engine tuning, with many years experience in this field. For port work, one company that will help you is 2 stroke porting. Two stroke cylinder porting tips watch this before you start cutting. Quite a few good 2 stroke have been done that way in the past. What i did was i ground down the piston at a 40 degree angle to horizontal that gave the equivalent of. This is a villiers 9e engine but it has a sports conversion 250cc head piston and barrel made by marcelle. Measuring 2 stroke piston clearance tech helprace shop. A dremel or some old files will not yield good results. Piston diagnosis a rough guide 2 stroke maintenance. We have a legendary reputation for building the fastest, most reliable motors found anywhere. Closing the bottom of the piston cut right before the transfers open on down stroke playing some more i can get.
Bigger carburetors, higher compression ratios, altered port timings and expansion. When actual bore size is known then it is time to pick the right vertex piston to fit your bore size, respecting the clearance suggested with the cylinder i. After disassembling the cylinder head and the cylinder, its necessary to measure the actual cylinder diameter 1, using a dial bore gauge. To window a kx500 piston or not to window kx guru racing. Forum main tech helprace shop measuring 2 stroke piston clearance. When the coolant hits the piston crown the change in temperature makes the. Lets journey back to 1973 and read the book that was the two stroke bible of that. Piston size 47 to 52mm 54 tq 57mm 89 to 91 mm pisto towall recommended clearance size in thotsandtns.
We have now offered a small program that will provide the display of one, two or three crank anglepiston displacement tables for a 2 stroke engine on the same screen. In this video i explain why a higher port not necessarily is a good. That approach is a completely waist since port area dont give any information about port shape. In order to optimize an engine and to find initial settings for a tuned pipe exhaust system, on.
Calculates port heights from durations, or durations from port heights. The two stroke engine rotates internally through 360 degrees, naturally. We create high performance parts for 2 stroke race engines, based on our. Ring and piston life are shortened immensely at that figure, and max port width combined with a. Ktms new fuelinjected twostrokes could save the endangered engine. The top countries of suppliers are china, taiwan, china, and india, from which the percentage of. Enables all transfer port heights to be calculated automatically by just entering exhaust timing. And i made the transition curved somewhat at the beginning and end of the ramp. Used to pretty easy to do when the motors were piston port and rotary valve. Cleaningup the rough edges of the port windows inside of the cylinder bore is really all you need to do to the port windows, as anything further, and youre messing with the port timing keep in mind, were out to build a little twostroke screamer, not make a. 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. Assign fixed relationships between transfers and exhaust port. To this end, new clamping plates were devised to provide a straight line bending pivot surface and the piston received a non.
If you or your rider is on a 2 stroke, doing a top end rebuild periodically is something that should be done at scheduled intervals, as rebuilding the top end of a two stroke dirt bike is not difficult, and doing so can save other parts from destruction while also resulting in a profound difference in the output of the engine and overall performance of the dirt bike. After reaching the bottom of its stroke it proceeds to move up the cylinder throughout the secondary compressionexhaust stroke. I made this video long ago, but forgot to upload it. Tips on how to port a two stroke cylinder, what to donot do and how to do it right. You should only rely on the experience of the very best. Basic 2 stroke tuning by eric gorr changing the power band of your dirt. What happens if you put a 2stroke piston in backwards. How exhaust port timing affects two stroke performance. A twostroke or twocycle engine is a type of internal combustion engine which completes a power cycle with two strokes up and down movements of the piston during only one crankshaft revolution. For the same area of opening you can have more flow as if the piston had already moved farther down and out of the way. The piston continues its downward travel and the remaining charge in the crankcase is transferred at low velocity into the cylinder via the. Basic 2 stroke tuning changing the power band of your dirt bike engine is simple when you know the basics.
From five star rated high flow carb mods and cylinder porting, to cylinder head machining, piston antisieze mods and case matching. A wide variety of 2 stroke piston options are available to you, there are 8 suppliers who sells 2 stroke piston on, mainly located in asia. By taking your time an going through these steps you can insure a perfect and smooth transition of the piston ring into and out of the port windows. Organizing pallets repair science shelves solar tools woodworking. So, we clearly make aftermarket parts for 2strokes, and they are meant for engine tuning for. What is the reasoning behind windows vs no windows. Also remember, on a 2stroke, to position the ring ends to the peg in each ring groove.
The spark plug fires and the piston begins its powerstroke descent. When you want more 2stroke power, look no further than dicks racing. The descending piston also is causing pressure to rise in the crankcase. You should read about how the two stroke enigne works before you attempt this. The coolant is drawn into the combustion chamber on the down stroke of the piston.
Mainly aftermarket cylinder heads, aftermarket pistons, crankshafts. The piston crown opens and closes the exhaust and transfer ports. Many people talk about a port area as a target value and indirect refers to a header area with an area factor for the port. Setting the correct piston protrusion and squish volume is imperative to tuning the modern 2 stroke race motor. Can anyone explain why some pistons have windows and others dont. If the cylinder is a big port 2stroke you may have to reach in through the intake port, with a long thin screw driver, and push the ring so it does not get caught in the port. When actual bore size is known then it is time to pick the right vertex piston to fit your bore size, respecting.
My porting setup affordable and functional 2 stroke tuning. A myriad of different aftermarket accessories is available for you to custom tune your bike to better suit your needs. 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 top of the piston begins to open the exhaust ports, allowing combustion gases to escape. A twostroke, or twocycle, engine is a type of internal combustion engine which completes a power cycle with two strokes up and down movements of the piston during. An introduction to tuning 2 stroke motorcycles for those who want results straight out of the box. The 2port linear piston is a new item available from penske racing shocks. What is the use of transfer ports in a twostroke engine. This increased the pistons heat gathering area and. Two stroke exhaust systems are dynamically very complicated yet also very effective tuning tools to manipulate, adjust and capitalize upon an engines power characteristics. John i believe you have it correct in the cooling benifit for the piston crown.
Customizationoptions including bodywork, suspension tuning and cylinder porting. As promised last week, here is the instructable inspired by. Porting and polishing twostroke motorcycle engines. As the piston descends, its skirt quickly closes the third port. There are a multitude of variables and their effects on the individual powerband targets to be analyzed and considered. Easy to use mounts securely for consistent measurements all metal construction will work with any standard dial indicator. The most common mistake is to choose the wrong combination of engine components, making the engine run worse than stock. The theory behind this piston stems from optimizing shim deflection efficiency by promoting a more natural bending moment. When tuning 2 stroke engines raising the exhaust port is common practice. The morbidelli 125 twin road racer is a rotary valve engine. The timing of the transfer and exhaust ports is a key factor controlling the performance characteristics of a two stroke engine. Other books to his credit are modern engine tuning, twostroke performance tuning and forced induction performance tuning. Try out the new zeda 80cc performance, dual windowed piston for our 2 stroke motor today and you will be impressed with the results.
Exhaust and main transfer timing can be entered by mouse click on graph, or typed in. Once the piston uncovers the side transfer and rear boost port, the arriving lowpressure vacuum pulse from the exhaust draws airfuel up into the combustion chamber. 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. If you are aiming for these qualities, modifying your 2 stroke engine is a great strategy. If you are going to run a two stroke to the limit my advice would. I called weisco and asked them if their racers choice piston had a window. When the coolant hits the piston crown it makes the aluminium brittle and it eventually cracks. I have seen both closed port and open port cylinders that have pistons with and without windows. I tested the rse reed valve against a piston port intake with extended intake and the latter gave the best low rpm power and would be my. I like to put the piston with rings and one circlip installed, in from the top of. 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. Piston diagnosis the process of examining used pistons can tell us a lot of helpful information on the condition of an. Many modern reedvalve 2strokes have a rear boostport running up from the intake port to the same height as the transfers. Toward the end of the stroke, the piston exposes the intake port, allowing the.
One complete stroke consists of the piston starting at the top of its cycle, moving down the cylinder on the inductionprimary compression stroke. Piston port intakes are just fine if the engines main use is within a powerband of 4000 rpm. This is in contrast to a fourstroke engine, which requires four strokes of the piston to complete a power cycle during two crankshaft revolutions. By riphonda, march 28, 2005 in general dirt bike discussion.
Two stroke tuners handbook 2 another mistake commonly made, sometimes even by those who have enjoyed some success in modifying two stroke engines, is to believe in a kind of mechanistic magic. 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. However, you shouldnt just pick any business that you can find anywhere. Simple twostroke cylinder porting tutorial youtube. Doing the finishing touches on the spx cylinder and wanted to give you a quick tour of my porting setup. I am looking for easy, and inexpensive piston ported low compression tuning tips. Reason main causes are general overheating, the bike. And would your tv and family photos also have a place in the wall cabinet of your dreams. Geoff batticks notes on 2 stroke engine modification. Ten motorcycles that remind us why we miss twostrokes new atlas. The windowed piston creates more intake flow and volume allowing trapped fuel to escape from underneath the. I polish the exhaust port and the head so that carbon doesnt adhere to them, but if it does, its easier to clean off. If your looking for the best from your 2 stroke mad biker designs has its own dedicated tuning arm under mad biker developments not content with being one of the premier parts suppliers in the uk from world renowned companies, such as brembo, dymag, samco to name but a few. An anonymous donor has provided the twostroke handbook in word so it is very usable and printable.
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