Two stroke tuning tips

Once you understand the basic functionality of one 2stroke carburetor, you. The piston crown opens and closes the exhaust and transfer ports. Two stroke cylinder porting tips watch this before you. C motor revs clean and crisp but runs really hot and lacks power. It clearly shows the air fuel mixture as a green mist while entering the engine through the intake track. Motorcycles, maintenance and repair, motors twostroke cycle. A number of things can go wrong within the workings of a 2stroke engine. So i thought why not post some basic info on how to set it up properly and alongside some tuning tips for those who want to get a little more out of their hpp engine. It covers my early days in the motorcycle trade, on to starting my own mc business then forming my tuning business. Motorcycle tuning twostroke 1994 edition open library. In the model tuning tips chapters of this book, all the head specs quoted have msv ratings designed for the intended power band changes. Like i said, these are just my findings, my mod motor is taking some tuning and i know there are a lot of other guys other building hot rods so this was ment to help out those guys. Two stroke moped tuning a tool to tune your two stroke. A myriad of different aftermarket accessories is available for you to custom tune your bike to better suit your needs.

The inlet port opens 30 after bdc and closes 79 after tdc. Two stroke cylinder porting tips watch this before you start cutting. I am very proud of the riders i helped and sponsored and there is an appendix. The difference in power between a dirty and clean filter is probably more than the difference in power between a stock and aftermarket pipe. This 2stroke carb tuning guide will give you all the information you need to tune your 2stroke carburetor for peak performance, no matter the make or model. Float height first make sure the bowl float turns off the gas inlet valve at the correct float height. Two stroke performance tuning back in europe two stroke engineers were battling excessive ring and cylinder wear, due to the exhaust port width being too great. When a motorcycle manufacturer builds a bike, they usually install jets in the carb that are too rich. Tuning and jetting mikuni carbs the vintage bike builder. Twostroke engines have lower velocity so the needle jet has a halfmoon shaped hood protruding into the venturi to produce a low pressure area that aids in drawing the fuel up through the needle jet. A narrow port reduced power but improved reliability. The pipe allows your 2 stroke engine to get rid of exhaust quickly and more efficiently than stock mufflers. Lots of experience and practice shows and knowledge of 70s and 80s twostroke racing engines is obvious.

A racing engine exhaust system uses an expansion chamber at the end of the pipe which is basically two cones that reverse themselves prior to the end stinger where the spent exhaust is allowed to. Two stroke engines have lower velocity so the needle jet has a halfmoon shaped hood protruding into the venturi to produce a low pressure area that aids in drawing the fuel up through the needle jet. The first thing you need to do when tuning a two stroke is to determine its characteristics. 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. Below is a number of turns that will get your rod set to a basic, ballpark, starting setting. Stroking means to increase the distance from the crank center to the big. A taller port restored lost power but made the power band unacceptably narrow. The pipe allows your 2stroke engine to get rid of exhaust quickly and more efficiently than stock mufflers. If you have no idea what these settings should be, use the needle starting point procedure in the next section below. In recent years the homebuilt rotorcraft industry has been exposed to a tremendous variety of engines, both offtheshelf and out of the salvage yard but little is known about engine tuning. Once you understand the basic functionality of one 2 stroke carburetor, you can apply that understanding to any carburetor.

Bigger carburetors, higher compression ratios, altered port timings and expansion. Two stroke motors are more efficient that four strokes for a few reasons. Lots of experience and practice shows and knowledge of 70s and 80s two stroke racing engines is obvious. These kits replace your cylinder and piston with a larger bore. Ktm exc and sx two stroke performance engine tuning. Oct 24, 2017 10 ways to gain power in a 2 stroke engine for free. Tips for air screw adjust on keihin pwk carburetor 2 stroke dirtbike motor many models duration. Back in the day, you know waaay back in the late 1990s and early 2000s, you would watch racers like ricky carmichael, jeremy mcgrath, and jeff emig and they all rode two strokes. They quickly developed a reputation for reliability. Two stroke aircraft engine tuning tips redback aviation.

Good resources on cylinder porting and tuning in general include jennings two stroke tuners handbook, and two stroke performance tuning by a graham bell. Bells fourstroke performance tuning book, this book goes into extreme detail regarding performance tuning a twostroke engine. Basic 2stroke engine tuning information joe hunt rc. You basically want the ports to be as large as possible, without going too high on its duration. Mar 02, 2009 differences in two stroke and four stroke carbs the difference between a two stroke and four stroke engine is intake velocity. Basic starting settings for 2 stroke dirt bike carbs running standard fuels. Generally, you will also need to rejet your carburetor to allow a greater volume of fuelair mixture to enter your.

Back in the day, you know waaay back in the late 1990s and early 2000s, you would watch racers like ricky carmichael, jeremy mcgrath. Mar 10, 2014 c motor revs clean and crisp but runs really hot and lacks power. Do you want it to be full range, still strong at low rpm or do you want it for higher power at rpm even if that means you will loose some low rpm. Racingsm software has features for many different areas 2 stroke exhausts development, drag racing features, simulators, carburetor tuning, connectingrod analysis etc with all this knowhow along with lufo racing heritage, we believe this is a very fair price. How to trim a 200820 ktm air boot not required carburetor detailed views. The bbr tuning high performance f2 thrust exhaust muffler will give your 2 stroke motorized bicycle a boost in power and speed while giving you a smoother ride.

The power listed on this guide is from experience not claims. The height of the gas in the bowl is important to maintain stability when going over bumps and also has a slight effect on the jetting. For the models up to 2017 the most popular setup is to machine the head, bore and rejet the carb, set the ignition advance to our tsp spec and fit a new pipe. For sheer power for money and driveability the best setup would comprise of. However, with the proper maintenance and diagnostic ability, many of these issues can be prevented. This is the most common misconception about two stroke jetting. 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. You would burn about a gallon of oil every 1,000 miles if you used a twostroke engine in a car. The new mikuni roundslide carburetor started hitting us and european shores in the mid 1960s mounted on twostroke, japanese motorcycles. When a motor runs excessively hot and lacks power, it is on the verge of seizing. It makes some very sensible, easily readable, tuning tips and ensures that you tackle the obvious ones first, ie easiest with best performance improvement. Be careful not to gouge the aluminum, just trim the gasket, and easy does it. Bells four stroke performance tuning book, this book goes into extreme detail regarding performance tuning a two stroke engine.

Take your time doing this, i recommend using a utility knife with a new blade. The exhaust tuning of a 2stroke is designed to preserve the positive pulse going down the pipe and reflect that positive pulse back up the pipe. Contents chapter 1 introduction 9 chapter 2 the cylinder. The difference between a twostroke and fourstroke engine is intake velocity. This 2 stroke carb tuning guide will give you all the information you need to tune your 2 stroke carburetor for peak performance, no matter the make or model. Basic 2 stroke tuning by eric gorr changing the power band of your dirt bike engine is simple when you know the basics. Turbo and even supercharger setups of various configurations can be very useful, however, they are often more complicated with 2 stroke tuning than with 4 stroke applications on a tangent, i did witness a 50cc turbo 2 stroke bike that would do over 150mph, but i digress.

Keep your twostroke running well on the track andor trail with these 12 tips. The morbidelli 125 twin road racer is a rotary valve engine. Twostroke oil is expensive, and you need about 4 ounces of it per gallon of gas. The ageold debate of between getting a 2 stroke vs 4 stroke dirt bike is still going strong although not quite as strongly as before. 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. On one hand, jetting changes can give you an inexpensive means to instantly increase horsepower, throttle response and power characteristics. During the 1930s they were reproducing carburetors under license by amal. Carburetor tuning has the greatest effect on engine performance. Two stroke performance tuning back in europe twostroke engineers were battling excessive ring and cylinder wear, due to the exhaust port width being too great. The bbr tuning high performance f2 thrust exhaust muffler will give your 2stroke motorized bicycle a boost in power and speed while giving you a smoother ride.

Crankshaft there are two popular mods hopup companies are doing to crankshafts. The manufacturers sell the same model worldwide, so they couldnt afford to install different jets in the carb to suit all the different. Clean the air filter sounds stupid, but you can be sure there are a lot of bikes at the races with expensive racing parts and a dirty air filter. Prox put together a list of 12 key things to keep your 2stroke running strong. 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 did do 6 months of riding on dirt with this carb on my stock 250 so i could see what just the carb was doing, and i will have to disagree about the q11 rod being. Just think of how many people pay good money to have their 2 stroke ported and leave an oversized gasket sticking in the ports blocking the flow.

Racingsm software has features for many different areas 2stroke exhausts development, drag racing features, simulators, carburetor tuning, connectingrod analysis etc with all this knowhow along with lufo racing heritage, we believe this is a very fair price. If you dont know how, see our tutorial on how to start the engine. There are different phases taking place in the crankcase and in the cylinder bore at the same time. Performance engineering 2stroke tuning we specialise in honda 2strokes, covering the cr range of motorcross bikes, the nsr250 street bikes, and hrc grand prix 125, 250, and 500s. 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. Twostroke principles although a twostroke engine has less moving parts than a fourstroke engine, a twostroke is a complex engine because it relies on gas dynamics. Twostroke engines do not use fuel efficiently, so you would get fewer miles per gallon. This symptom indicates a lean main jet andor needle. In the model tuning tips chapters of this book, all the head specs quoted. The best 2stroke motorized bicycle upgrades bikeberry blog.