Introduction:

As Tim Allen says "MORE POWER ARR ARR ARR"  there is noting in the world like more power and nothing better to have it on then a bike.

MORE POWER

I want more power:

The first question you have to ask your self is where you want the power. The typical RD power curve like any two stroke is as follows. You will notice that most of the power is made in a narrow RPM rage, this is called the power band. Alternatively you can just go for more power throughout the RPM range. But there's no such thing as a free lunch what ever route you chose there are choices to be made and pros and cons to be weighed. The long and short of it is 

Which is why you typically see the Indian LT can go for 20,000 Kms without touching the engine and most of the HT's will be needing a rebuild every 10,000 kms. 

The LT has an exhaust duration off  157.6 degrees and a redline off 6000 RPM. The HT has an exhaust duration off 177.2 and the original RD has a duration off 183.6. Its very easy for somebody to read the above statement and say all bikes that are faster than mine are less reliable dont fool yourself.  If that was the case we could design a RD sleeve with an exhaust duration off 100 Degrees or use the porting specs off a Vespa it would have a redline off 4500 RPM and it would last for ever.

So your thinking how do I chose. What is right. How do I strike a ballance. There are basically two things that can help you make up your mind. They are the present state off your engine as a whole. If its a weak engine with most off the components on their last legs. Local after market connecting rods. Poor quality parts & used parts. Then it would make sense to opt for the LT.  If the engine is in perfect condition with a good OE parts, a perfectly balanced crank  then it would make sense to opt for the power the RD was originally designed for. Which is 39 BHP with about 183 degrees off exhaust duration. So what power you chose should be based on the overall state off the bike in terms off engine and chassis setup. 

I can not stress this enough your decision should be based on the overall state off the engine and chassis. By this we mean every single nut, bolt bearing and moving part should be in good condition. Some off the more obvious items are carbs, crank, connecting rods, pistons, rings, bearings etc etc. This is one reason why some tuners refuse to tune only the ports. And only undertake work if the complete bike is give in to be redone.

 Don't be fooled into thinking that if you take your old connecting rods polish them and put them back that you are ok. The big end bearings and connecting rods are surface hardened. Polishing them turns your big end out off round and strips it off its hardest surface. If you must enlarge the size off your big end a sand papper mandrel on a lathe is the worst way to do it. You need to have your big end bored and then honed to a perfect circle. Most Indian workshops that reset cranks will have a chokra boy with a sandpaper mandrel which he runs thru your big end. The metal will get red hot and he will put it into a can off water to cool it.  So any hardness it had is gone.

Therefore on the quest to more power your fist stop should me getting your engine to perform at factory spec. By engine we mean the complete package. Or as it was originally designed.  It is only when you have reached this stage should one start to think off more power. So restoring your engine to as close to stock should be the first step on your journey towards more power. Otherwise your bike as a complete package will not be able to handle it. 

So Ok we now know why its important  to have a good engine and bike to have reliable power. What if we want more than stock power. Well if you want more than stock power then the condition off your engine has to be beefed up and made better than stock in all aspects. The first thing that needs to be sorted would be your connecting rods and bearings. Using RXG top end bearings and re-polished connecting rods or locally made rods will not cut it. As an example I state my own motor. The Connecting rods and crank was not lasting more than 100 Kms. This was with original connecting rods which had been polished. Solution was to get Wiseco Hot Rod connecting rods with heavy duty bearings. This has solved the problem. If you take this approach you can have performance and reliability. Make sure the parts you use are designed to work on machines that produce more power than your own.

In summary try and strike a balance between your engines performance and its overall condition.

What Makes the Power:

Firstly we need a clear understanding as to what make the power. Well the obvious answer is that the engine makes the power, by exploding a mixture of petrol and air and transferring the power of that explosion down through the piston head to the con rod to the crank which drives the primary & clutch basket which turns the gears to the sprocket.

Hence the most important aspect of the engine making power is the amount of petrol and air it can get into the combustion chamber. The study and optimization of how an engine breathes is a science in its self. The more petrol and air we can stuff into that combustion chamber the more power it will make.  Now it all depends on how radical you want to get. The compression ration i.e. how much the gases are compressed before they are ignited also contributes to how much power the engine makes. Your fuels octane rating decides how much you can compress the mixture.

Towards my search for more power I have studied and identified the following areas that can be tapped into for more power. Assuming we are the air and the fuel traveling through our engine this is the path we would take.

The Road Map to more power:

Intake / Air Filter

The original Yamaha micro paper air filter is very restrictive. The market is filled with hundreds of options, Uni filters, Pod filters, Y tube with single foam filter. Stand up filters etc. If you've got lots of money go for one of the fancy filters. My choice is the wire mesh air filter that is a slide in replacement for the paper filter. You then take a thin layer of foam and wrap it around the mesh filter sealing it closed with super glue or quick fix. Another popular route is to remove the stock air box leave the rubber Y tube in place and put in a cylindrical stand up filter. The idea is to make it as free flowing as possible while not letting any dirt in.

Carbs:

The next part we go through on our Journey through the engine is the Carburetor which handles the metering off fuel and air. To make the most power there is a certain ratio at which the fuel and air have to be mixed at. This has been accepted at around 12.5 to 1. 

The idea is to have a carb that can flow enough air and fuel to make good power. This is one place where bigger is not always better consider this the RZ350 came from Yamaha making 63 BHP with 26mm carbs. So how do we know what's the best size carb. 

We calculate our best sized carb for an engine based on the engine size and the max RPM the engine will see. I cant get into the mat involved here but as a rule off thumb you only need to worry about your carb size if your cc size has gone up or your RPM redline has gone up. 

So assuming you have ported your engine and have raised your RPM or cc then what are your options.

a. The Dale Alexandra mod of drilling out your carb . The Dale A Mod involves boring out your Carb to 29.4mm. There are other Dale A mods that involve drilling out your air jet and replacing it with a 2mm air jet. As well as modifications to your needle jet. Most of these modifications are not viable for us because we don't get the necessary parts here.

b. Fitting larger carbs. You can go from a 28mm to a 30 or even a 34mm carb. The best setup for the RD that has been tuned is 30-32 MM.

Reeds:

After we exit the carbs the next part we hit is the reeds. The original reeds are very restrictive. There are two aspects to extracting the max power from the reeds they are the reeds them selfs. And the amount the reeds can flow.

To start out here are the things you can try with your RD reeds. On the journey up the scale.

Reed Spacers:

You can try a 1/2" reed spacer to enlarge / lengthen the intake path. We have a complete range of reed spacers from 4mm to 14mm. The Project bike is presently running 10mm reed spacers. Which have been cut at an angle to point the gas flow downwards. 

Manifolds:

You have a number of options here. From the simple RZ style balance pipe to shared and independent boost bottles.  The cheapest and hottest trick is to install the RXG manifolds and connect both the pipes with a rubber hose. This is reported to give the LC an additional 2BHP. Should be the same for the RD. Another option is to install the RZ/LC manifolds and hook up a boost bottle go for 600cc per bottle. You have a choice of a common chamber or separated chambers. Notice the size of the Manifold intake its much much larger than the stock manifolds or even the RXG manifolds. These are RZ manifolds.

Ports:

Ports refer to the path that the fuel mixture takes after it passes through the reeds into the combustion chamber and out the cylinder. The porting setup on the RD is outdated and obsolete by about 30 years.  To get more power you can go in for a Stage I or Stage II or stage III port job. Not all porting refers to enlarging your port sizes. Porting is all bout Flow, Flow angles, both axil and radial. And lastly port size.

Stage I Porting:

This refers to taking the cylinder block off. Filling out any imperfections in the casting & lining up the casting with the barrels after removing any casting imperfections. The idea is to increase flow and remove casting imperfections. Ive noticed that even the brand new barrels from the factory / stock barrels are filled with tiny imperfections. And there is lot to be gained by doing a stage I port job without effecting the engines life.  

Stage II Porting:

Stage II porting refers to more radical changes in the ports. You can use any of the 2 stroke tuning software available. Alternatively you can study any  of the existing porting specs and adopt them for your bike. Stage II porting is best left to the experts because it involves detailed study of the time areas of the intake / exhaust & blow down. Unless you don't do it right 90% of the time you will loose power thru the RPM band only to gain marginally in a very narrow band.

If  you like you can review my porting spec collection. And see if you would like to try one of the combinations. If your feeling really brave you can try Dale Alexandra's porting recommendations. Or just shave 1.5 mm of the top of the exhaust port , widen the exhaust port. Make the booster port  deeper and bigger. This is a tried and tested porting setup for the RD. This does not apply to our Indian RDs though. Im working on some simple porting mods for the Indian RDs mail me and I share it with you.  

Stage III Porting

Normally refers to all out race bike porting . Which is rather radical and due to the large size's of the ports. Engine life is drastically reduced. Dont expect to get more than 5-6 races out of the bike before the top end needs to be fixed.

New Porting  ideas:

After studying a number of the latest trends in GP 2 stokes. And trying my best to adopt them to the RD. I think Ive hit upon a combination which can give you the most power while still giving you exceptional engine life. You can try too. The secret lies in get the desired TA values while ensuring good ring support for the Pistons and rings. You may want to look at bridged Exhausts and Intakes.

Squish Band  / Compression:

Getting the squish band right at around 1mm. Can help you  tap into more power and run cooler. Getting the squish band right ensures you get good compression. Avoids detonation and ensue you get the best transfer of power. There has been some debate as to whether it really helps the bike run cooler or not. Maybe it really doesn't result in cooler running but getting it right is critical. Its a lot more than shaving your heads and checking with solder. It involves calculating the thickness of your Squish band and working out the MSV of your mixture.  

PIPES / CHAMBERS:

We have found that a well designed set of chambers offers the best value for money improvement to the power. There are some great s/w packages out there to help you design a set of pipes best suited to your riding style and requirements. You can expect to see anywhere from 10-20 BHP increase in power with the right pipes.

The pipes are designed based on your porting setup. Most of the ready made pipes have been designed for stock engines. So if you have a modified engine you really need to have a custom set made up. 

Results of My Porting:

Ok After doing a Stage I porting Job. I raised the Exhaust Port that is measuring from the top of the cylinder. The measurement should be 28mm depending on the type of RD you have the original measurements can be anywhere between 38mm and 29.5 MM.  Open up the exhaust port. Widen or knife edge the transfer ports. Open up the 7th port by removing material. Improve the compression ration by putting the heads on a lather and shave off 5mm (For Indian RDs). Take the barrels to the lather shop with a piston so that you can check the squish band with some lead. I found that getting the squish band right and increasing the compression, cleaning out the ports, jetting right and geting a good set of chambers  is the best route to more power.

Of course if your totally crazy and want something like a 80 BHP motor that does the quarter in under 12 seconds you can read. You will see that making power is more about the Ignition system, Carbs, clutch system, crank, bearings  and various other parts. That are needed to support a give power output.  http://eindiancompanies.com/unsorted/

 

FAQ

Is bigger better:

No too many people think they can increase power by boring out the cylinder to Max and fitting larger pistons. This is the wrong approach. There are much smarter options refer list above. Though once you've tried everything then the only option is more cubes. Which is why Im running a big bore kit on my motor. But taking a stock bike and boring it out to 2mm over size and expecting big results will result in a disappointment.

I want more Mileage:

This issue has been discussed to death over the ages. The best mileage you can expect from a RD350 is about 25 Kms per Ltr. In India a special Low Torque model was made with delayed port timings that increased mileage, provided more power at lower RPM while sacrificing top end power. The best way to get more mileage is to ensure you ride smoothly. No sudden acceleration keep the RPM down, switch to 6th gear as soon as possible.

A last drastic measure that you can try is to switch to 110 mains that too only if you are using a paper filter. But be warned that this will destroy you engine. The engine uses petrol to cool. Starving it of petrol results in over heating and you will blow your engine.

Do I Premix or use the Oil Pump:

This is a personal dissension. The bike was designed to use the Auto Lube the only reason people switch to pre-mix is because they have better control over the mixture as well as the fact that a failure doesn't result in the Engine being blown.

You will find that some people follow the middle route. i.e. they use the auto lube as well as a very low ratio of pre-mix this way even if the auto lube oil pump fails the engine wont seize. As to what ratio one should use this depends on the condition of your engine. Just remember that the more oil you use the leaner the petrol mixture gets.

The Oil / Heat Trap:

Most people react to engine heat by adding more oil. They figure that with more oil the engine will be better lubricated and less prone to a seizure. This is dangerous as beyond a certain temperature around 400 Deg C oil stops working. Also by adding more oil the petrol mixture leans out further contributing to the heat. So be careful of this trap.

More to come soon .........

 

MORE POWER

Check out this space soon for all the power tips.