Monday, February 22, 2010

Something everyone with a license should know....

I have always believed that driving is an art and not just getting from point A to point B. Its something you are born with. I started driving from the age of 10 and I knew how to drive even before I got a chance to lay my hands over the wheels. Even as a child I would keenly watch how others drove and the had a pretty good understanding about why there are gears and what is the purpose of a clutch.

If you are one of the people who have been driving an automatic car since they got their license then chances are that you haven't learned how to drive a manual transmission car, or "stick" as most people say. For some people it's hard to understand how much gas to give it, how much to let off the clutch, how to get going, ect ect. I'll give you a few tips on how to drive stick and hopefully you can go out and learn something new.

First let's talk about how it basically works. When you push in the clutch, the clutch pulls off the transmission(read as the connection between the engine and the wheels) and is sitting there freely with no friction. As you release the clutch it closes down onto the gears in the transmission and starts to go because the gears are set in motion based on what gear you put it in with your hand. So think of it as if you have a record spinning and you put your finger on it slightly the record will slow down unless you turn up the speed on the record, and if you push down to hard, it just stops it because you have too much pressure without enough force to keep the record spinning. This is just like your transmission, you need enough force to keep the transmission working while allowing the clutch to sit on it. Lets start with the basics.

A good thing to do before actually starting the vehicle is to play around with the shifter and kinda get a feel on how to put it into the different gears. Make sure the parking brake is on so that you don't roll away. After you get a feel for it, put the car into neutral by moving the stick to the middle of the gears where it feels loose and free. Once there push down on the clutch (make sure the P-Brake is still on) and turn the key until it starts. I recommend you doing this on flat ground so that you don't roll away and it's easier to learn. After the vehicle is started, let go of the clutch and release the parking brake. Take a deep breath and push the clutch in and put the vehicle into first gear while holding the clutch in. Slowly release the clutch and you'll feel the vehicle start to move, once you feel that give it a little bit of gas to keep it from stalling. If you let the clutch out without giving it gas, the car will jerk and buck and then stall out. You want to release the clutch as you are giving it gas so that it equals out. This first part is usually the hardest and a good way to get a feel for it is just to keep practicing letting off the clutch and giving it gas so it moves. When I first learned how to drive stick, I would wait till I could feel the car start to move and then give it gas. After you give it gas it won't be long till you have to shift. You should shift gears around 3000 RPM or before it gets to the red area on your RPM reader. When shifting just push in the clutch all the way and let off the gas. Once you let go of the gas just shift from 1st to 2nd and release the clutch smoothly while giving it gas again. Continue to do so up to however many gears you have. Now comes for the stopping.

Stopping isn't your normal just push on the brake and everything is good. If you vehicle is any gear besides neutral then you have to push in the clutch all the way while you push the brake. If you have the car in a gear while pushing the brake and you stop then the car will jerk and buck and then stall out and you will look like a fool as you sit there at a stop light and have to turn your car back on. So when coming to stop just push in the clutch and hit the brake if you are in gear, or you can just put it in neutal and put on the brake. If the vehicle is in neutral then you can put the brake on without having to put in the clutch, this is because there is no gear for the clutch to rub up against and stall out on if it is in neutral. Another way of slowing down is to downshift, to downshift just put the car into a gear that is lower then what you're in, i.e. if you are in 4th then put it in 3rd gear. After it's in gear just slowly release the clutch. The RPMs will go up more so but you will slow down a little without putting on the brake. All you have to do is put it in a lower gear then slowly let off the clutch and the vehicle will start to change gears and slow down. This can be hard to get used to, so I don't recommend it to new stick drivers.

So there you have it, you now know how to drive stick...kinda. Just remember to give out equal gas to clutch pressure and put in the clutch when stopping. Getting to get going is the hardest part because that requires the most attention. Once you get going it's really just simple because all you do is switch gears and hit the gas. After driving stick for a while you'll find that it is a lot more fun to drive at times. When you have a fun small sports car it can be really fun because you can accellerate quicker and more precise that way. Also a lot of times you forget you're driving stick because it becomes so natural. I know at times I forget im driving stick and I almost stall because i forget to put int he clutch when i come to a stop. Hope this has been useful. Always wear your seatbelt, or else i'll pull the car over.

Thursday, February 18, 2010

Royal Enfield sees huge order backlog in its Classic 500 retro bike�-�WheelsUnplugged Automobile Industry News

Royal Enfield sees huge order backlog in its Classic 500 retro bike�-�WheelsUnplugged Automobile Industry News

There are reports that Royal Enfield's recently launched Classic 500, priced above Rs. 1 lakh, is witnessing a huge backlog in its orders. Globally, the Classic 500 was launched in European markets in October 2008 and has now been made available to Indian customers, while Classic 350 is a new launch mainly for the domestic market. The retro-look bike has been designed keeping in mind Royal Enfield's British character with the company's design team worked in close collaboration with Xenophya Design, UK. The engine was engineered in Italy while the fuel-injection system has contributions from Japan. It is to be mentioned that Classic 500, benefit from improved reliability and modern components (e.g. electronic fuel injection), stimulating demand in overseas markets. Its heavyweight models, which are homologated in Europe and the US to meet their specific rules and regulations connected to emissions and safety, is being tweaked to meet Indian conditions also.
"Orders have been beyond our expectations and we have a back-log of 3,000-4,000 bikes in the domestic market and around 2,000 for export. We will be able to clear up the backlog only by June-July," a senior official was quoted as saying to PTI, adding that the company has delivered over 1,000 units of the Classic 500 in the Indian market since the bike's launch in November last year.

Just when the model got rolled out during Nov’09, the company’s official spokesperson had stated, “We are in the process of attending to all enquiries which has come through the web, telephone, walk-ins and it is very early to predict the future bookings at this time and we can give the guestimate by month-end.”

Shaji Koshy, head, sales and marketing, Royal Enfield India, had earlier told reporters, “While other bike players are shifting gears towards mainstream our appeal is towards leisure, relaxation and travel. As of now, we have no plans to open other segments or capacity.”

According to Royal Enfield’s recent official release, “The reverence for motorcycle designs from the Royal Enfield stable is one of the reasons for its cult status. The ‘retro’ look of the Classic 500 is inspired by Royal Enfield’s –‘J2’- a model that shot to prominence around the early 1950’s. The colour ‘classic green’ – inspired by colours in vogue during the acme of the British motorcycling era – gives the Classic 500 a distinct yet timeless aura. The technology is avant-garde with enhanced combustion and tight caps on emissions. So, the ‘classic green’ also epitomises Royal Enfield’s commitment to a greener environment.”

Courtesy - WheelsUnplugged Automobile Industry News

Modify your ride - Part 4


1.Performance brake systems:
By the time you reach stage three, chances are that your current braking power is ineffective toward handling the additional engine punch. Upgraded boosters, performance discs and street / performance brake pads are available to improve your cars stopping power. Approximate cost = Rs.3,000 – 40,000.

Turbo's offer high power gains but don't exceed 6-8 psi on a stock motor. If you want to go higher than that, get ready for a seriously expensive investment in forged internals, sleeves etc. For a complete guide on turbo-charging, click here : Turbo-charging your car. Approximate cost = Rs.1,25,000 upward.

Super-chargers or "blowers" (as they are called in the tuner circle) are another method of forced induction. More expensive to install, they are driven off the engines crankshaft, unlike a turbo which is driven by exhaust gas energy. Super-charger kits are readily available for some engines, though Indian tuners prefer turbo-charging. For a detailed comparison, click here : Turbo chargers vs. Super chargers, and take a look at this link if you're considering supercharging. Approximate cost = Rs.1,25,000 upward.

4.Engine swaps:
When you have maxed out the power of your current engine, or simply want a bigger powerplant, engine swaps are a good option. Many tuner-friendly cars have a ready list of options available. D16 and B16 engines into Honda City’s, twin-cam Suzuki Swift GTi swaps into Maruti Zen’s and even Honda mills into Suzuki bodies are popular. Mitsubishi Lancers have various Mivec and EVO options. Swapping the engine is changing the "heart" of your car so consult only with tuners who have the necessary experience, knowledge and infrastructure; this is a very important consideration. Some swaps may not offer a bolt-on transition and will require heavy modifications to accommodate. Approximate cost = Rs.30,000 upward.

5.Upgrade clutch:
In stage three, a performance clutch may become a necessity to transfer the additional power effectively and quickly. Consider what the usage of your car will be before installing a performance clutch as varied options are available between street, drag and race applications. Some are a pain to use in bumper-to-bumper traffic. Approximate cost = Rs.10,000 – 50,000.

6.Lighter flywheel:
A lighter flywheel will improve throttle response at all rpms, since the inertia is lower. It works well with balancing the crankshaft. However, don’t add one to a stock engine else you will lose torque at low-rpms. Lightened flywheels are a good option for racing and make for a superb modification with a short (close-ratio) gearbox. Approximate cost = Rs.15,000 – 25,000.

The gearbox is one of the most important tools in extracting power from your engine, exactly where you want it (low, mid and high-rpms). You may choose to alter the final drive or go in for an entirely new custom gearbox. Your transmission may also require stronger drive-shafts to cope with the additional power. Approximate cost = Rs. 6,500 upward.

8.ECU replacement:
The ECU (engine control unit) is the brain of your car and controls various engine parameters and functions. Custom ECU's can be tuned for specific engines where power gains vary from 5%(stock engine) to more than 30% (heavily modified engines). A stand-alone engine management system (Link, AEM, TEC-II etc.) allow great flexibility. With that flexibility comes complexity, custom fitting, and cost. As you progress within stage three, a replacement ECU will become necessary. A great feature of some stand-alones (with a toggle switch) is that they can be switched between performance and stock modes. Approximate cost = Rs.25,000 upward.

Modify your ride - Part 3


1.Performance suspension kits:
With the additional power that your engine is churning out by now, increased grip levels are a must. There are plentiful branded options available for performance struts, coils, coil-over springs, dampers (shock-absorbers) and camber kits (Polyurethane bush kits). Approximate cost = Rs.10,000 – 1,00,000.

2.Head Porting & polishing:
Cylinder head porting and polishing refers to enlarging and smoothening of the ports on the intake and exhaust. This results in better quality and quantity of gas flow-rates. Power gains are very noticeable from a high-quality porting and polishing job. Remember that the intake ports need to be finished rough while the exhaust ports should have a mirror finish. Approximate cost = Rs.9,000 – 15,000.

3.Removing the revv-limiter:
A fairly simple modification which any ECU specialist can implement in a very short time. Your cars manufacturer-set rpm limits will be raised but you also need to check if your engine internals can take the additional stress. It wont lead to a power increase with all engines; yet can be a useful tool in improving lap times (holding a gear longer) and acceleration (one less up shift for 0 - 100). Approximate cost = Rs.3,500 upward.

4.Nitrous oxide systems:
NOS, as they are popularly called, are cheap power shots and a favorite with drag racers. Due to the inherent nature of the gas, it is a very risky installation. Don’t go overboard with the dose else your engine will end up blown. Also make sure that you back the timing off by a few degrees. Take a look at this guide on setting your car up with nitrous. Approximate cost = Rs.22,000 – 75,000.

5.Performance camshafts:
Performance cams are a superb modification and can add upto 10% - 20% more power, with options available for low, mid and high-rpm gains. An increase in compression ratio is highly recommended. Also insist on a cam adjuster (variable cam pulley for adjusting cam timing) to realise the full gains of the cam. It is important to avoid over-cam'ing while the more extreme profiles will surely require head work. High lift cams cost a packet and are not recommended for daily-driven cars since the low-end response is compromised, fuel-efficiency takes a beating and you will need to fiddle with idle settings to get it right. Approximate cost = Rs.12,000 – 35,000.

6.Map sensor signal modifiers:
These can improve part throttle performance, but will result only in marginal performance gains. Approximate cost = Rs.12,000 – 25,000.

7.Valve angling:
A multi-angle valve job can lead to noticeable street performance gains by improving the head flow. Note that this is a highly precision-oriented task. Approximate cost = Rs.3,500 upward.

8.Over-boring / Stroker kits:
Over-boring is increasing the CC (cubic capacity) by changing the piston size and stroke of the engine. Pistons, connecting rods and the crankshaft will need to be replaced. Simply put, bigger engine size = more power. For e.g. a 1.3 liter can be overbored to 1.5 liters in capacity. Approximate cost = Rs.12000 upward.

9.Piggy-back ECU's:
Piggybacks are additional engine control units that work along with the standard ECU. They enhance engine performance and leave the non-engine electronic work to the standard ECU. A piggyback modifies some signals (sent back to the ECU) and plays around with the performance parameters only (fuel injection, timing etc.). Fuel controllers adjust the fuel mapping and allow the engine to increase its power output. An example of a fuel computer is the ApexI S-AFC. They offer a multitude of adjustments whereby you can run rich or lean, depending on the driving conditions. It is imperative for the piggy-back to be compatible with your ECU. Remember that the AFR signal adjustment is to be done only in tandem with a wide band AFR kit. Leave the tuning part to an expert. Approximate cost = Rs.12,000 – 35,000.

10.Engine remaps:
An ECU flash will give you higher power gains than a piggyback, by changing the entire characteristics and settings of the factory software. There are ready performance remaps available for a wide range of Indian cars and the installation procedure is fairly simple. If you plan on going further to stage three modifications, do the remap at the very end. Any reputable company is going to account for your full mod list in order to give you the best remap. Do the remap last, unless you want to do it twice. Approximate cost = Rs.23,000 – 60,000.

Modify your ride - Part 2


1.Upgrade tyres and alloy wheels:
Before adding more power to your car, it must have the adequate grip levels for current & future power delivery. Alloy wheels are not always necessary for a tyre upsize. A detailed guide on upsizing your tyres is available here : Choosing the right set of tyres for your car. Approximate cost = Rs.12,500 – 50,000.

A stock replacement performance filter requires no modifications and is very simple to install since it fits exactly in place of your factory filter. The performance gains are marginal. Approximate cost = Rs.2,000 – 7,500.
A Cold air intake (CAI) is the more serious of performance air-filters. With a CAI, proper installation is very important and it should not suck in hot air. The colder the air available to it, the better will be the gains in performance. A true CAI sucks in outside air, while short rams and most CAI applications take air from under the hood. Even if it's 35 degrees outside, that is still significantly cooler than the air under your hood. You can also opt for a good conical / universal filter without CAI. The plumbing needs to have minimum restrictions with most experts recommending mandrel bent aluminium pipes. The diameter of the pipe through its entire length should be uniform and greater than that of the throttle body. Do note that the sound levels with significantly increase with a CAI, and some precautions must be taken when driving in the monsoons. K&N recommends a shroud for use in dusty conditions. Approximate cost = Rs.5,000 – 17,500.

3.Free-Flow Exhaust:
A well-designed free flow exhaust system improves the breathing abilities of your engine and can lead to good performance / fuel-efficiency gains. It is important to get a complete free-flow kit (including headers) and not a muffler / end-can kit only. A good header design is very important and you may specify to your installer a preference of low, mid or high-rpm gains. Very little time is actually spent at high-rpms so you might be better off asking for a low to mid-range power gain. The appropriate back pressure must be maintained else you will lose out on torque. An exhaust system is like a chain and only as strong as its weakest link. The most restrictive part is usually the cat-con or the mid-muffler. Some tuners will remove the cat-con, which will result in difficulty toward meeting the emission norms. Also, try and insulate the exposed part of the exhaust system within the hood with asbestos wire (cheap) or ceramic coating (expensive). Approximate cost = Rs.7,500 – 25,000.

4.Spark Plugs:
Performance plugs are pointless on a stock / marginally modified car. Iridium plugs have hardly any benefits and you will never notice them anyway. In case you do install the same, ensure that you pick up plugs with the correct heat range for your engine. Approximate cost = Rs.800 – 3,500.

5.Plug wires:
Same as above. After-market wires don’t add any performance to a stock or marginally modified engine. Only if your eventual modifications require an upgrade to a custom engine management system (or a high-performance ignition system) will your plug wires have some benefit. But at this stage, don’t opt for plug wires as you will only waste your money. Approximate cost = Rs.1,500 – 6,000.

6.Temperature signal modifiers:
These devices are fairly simple to install and result in marginal (if any) performance gains. They modify some signals that are delivered to the ECU, which results in altered fuel / ignition maps. Approximate cost = Rs.900 – 9,000.

7.Synthetic Oil:
Synthetic lubes are highly recommended by Team-BHP for the superior protection and enhanced lubrication on offer. For a detailed explanation, click here : Synthetic oil vs. Mineral oil. Approximate cost = Rs.500 – 1300 per liter.

8.Strut braces:
Strut braces / tower bars reduce flex, and help in increasing the grip levels / stability of the car through corners. However, it’s only under hard cornering that the difference is noticeable. Approximate cost = Rs.1,500 – 5,500.

Short-shifters shorten the throw of your gear-lever, and result in quicker gear shifts. Be advised that there is an optimum length of the shifter depending on the throw, ergonomics and your preferences, and it will take some getting used to. Most drivers are better off with a stock-shifter! Approximate cost = Rs.4,500 – 7,500.

Modify your ride - Part 1

BEFORE you modify your car

• Remember to practice SAFE DRIVING on public roads! With additional power comes the need for additional responsibility. Keep the racing restricted to track days and in other forms of competition (within a controlled environment).

• Enroll with a professional rally / racing / driving school. This will not only make you a faster driver but also a safer one. To quote a popular Pirelli tagline : Power is nothing without control.

• Ensure that you are with the right tuner. The quality of install and product is most important. Get your work done only by a tuner who has the relevant knowledge, infrastructure and dedication to carry out a high quality installation. The product quality is equally important and it is generally recommended to stick to reputed brands (wherever available). A bad modification can actually make your car slower than in stock tune. Poor reliability may also result from a bad installation, causing a great amount of heart-burn to you.

• Remember that the engine is a very complex system and each component has to work in harmony with everything else. Only then will you benefit from the performance modifications.

• Tune your car via a step-by-step method. This will allow you to gauge improvements in an incremental manner and fine-tune one modification before moving on to the next.

• Choose a “mod-friendly” car to start with. Most Japanese brands like the Hondas and Suzuki’s have tremendous after-market support in terms of parts availability and tuner capability. Simply put, there are some cars which inherently respond better to performance tuning. On the other hand, it is a pointless exercise trying to make heavy cars like the Contessa or a Mahindra Jeep go any faster! Pick your car based on what you want to achieve.

• Beware of cheap “go-fast” gimmicks like the Surbo and electric superchargers, which are nothing but an absolute waste of money. Common sense plays a vital role out here; why would you need a DTM corner slammer on a front wheel drive car that spends most of its time below 120 kph.

• Remember that Vitamin M (or Money!!) runs the show. Tuning your car can be an expensive proposition, so outline a detailed budget before moving on from stage to stage. Not only will the modifications cost you big $$$, but lowered fuel efficiency (almost certain) will cause another dent on your wallet. Some highly-modified cars or engines running an increased compression ratio may also require high-octane fuel to run efficiently.

• Invest in a popular timing device like the G-Tech series. This range of timing equipment will help you to gauge the benefits of your modification, and whether that actually translated into making your car faster.

• Remember that your warranty will almost certainly be nullified, if your car is within the coverage period.

• Think before you try to alleviate the visual appeal of your car via body kits and spoilers. Be warned that a badly-designed body kit will ruin the aerodynamics of your car and may cause it to become unstable at high speeds. Also, spoilers are merely for looks and, in any case, work only above 175kph.

Turbo charging your ride

So, you want to turbo-charge your car and you dream of sub-seven second dashes to 100km/h. There are many hatchbacks and sedans in India that have had successful after-market turbo jobs, but each one of them required a huge investment in time and money. Adding a turbo-charger to your car is a serious modification and lack of knowledge, expertise and appropriate parts can lead to disaster. This compilation covers some things to look for before you buy a turbo and the simple ways to check a turbo install job.

Before you choose a turbo make sure the following is checked:

- That the ECU has the ability to handle turbo-boosting;
- That the injector has enough size to supply extra fuel;
- That you use fuel of the proper quality, pressure and volume;
- That knock sensing apparatus is equipped;
- That there is available space in the engine compartment; and
- Whether the compression ratio has been brought down to at least 8.5.

How to choose the right turbo:

- Pick one that is designed for the engine capacity of your car. The chart below can be used as a rough guide;
- Make sure that the exhaust side (or turbine trim) is designed for your engine capacity and that the intake side (or compressor trim) is larger;
- High-quality turbos have ball bearings and water-cooling while lesser ones use roller bearings and have no water cooling;
- Does the turbo have an external/internal waste gate and at what boost does it open?

Here is a chart to help you choose your turbo trim, assuming you know how to calculate your engine’s CID:

Engine Displacement Compressor Trim Turbine Trim Turbine Hsg
60-100 CID T3-50 Trim T3 Standard .36/.48
100-150 CID T3-Super 60 T3 Standard .48/.63
150-200 CID T3-Super 60 T3 Standard .63/.82
200-250 CID T4-S3 Trim T4 "O" Trim .58/.69
250-300 CID T4-V1 Trim T4 "P" Trim .69/.81
300-350 CID T4-V1 Trim T4 "P" Trim .81/.96
350-400 CID T4-H3 Trim T4 "P" Trim .96/1.30
400-450 CID T4-H3 Trim T4 "P" Trim 1.30
(Source: Toysport)

Additional parts you will need:

- An intercooler, as the intake temperatures will be above 40°C;
- A radiator able to handle higher engine temperatures;
- Exhaust pipes the size of the exhaust port on the turbine;
- A BOV if you do not want to stress the turbo;
- A rising rate fuel pressure regulator to linearly increase fuel pressure, though this may not be required if you have a good fuel pump and an aftermarket ECU;
- Forged internals are required for anything above 6 PSI, though some stock internals can handle higher boost – check with your tuner;
- Ported and polished heads for increased power; and
- A milder cam to reduce valve overlap.

How to check your install:

- The easiest way to check is by applying the throttle while in second gear and letting the engine reach 60% of the rev range. If your ECU's warning lamp does not come on, you are ready to go;
- There should be no smoke from the exhaust;
- Make sure your water temperature needle is at its usual position and does not climb rapidly;
- There should be no sudden sucking noises from the turbo. This noise means you are running a small turbo;
- Lift you foot from the accelerator and check to make sure your BOV engages; and
- Learn how to slip your clutch. It is almost mandatory for driving turbo cars.

Things that will harm your turbo:

- Contaminated or dirty oil;
- Lack of lubrication;
- Low oil pressure;
- Blocked air filters;
- Collapsing plumbing;
- Undersized plumbing;
- Prolonged engine idling;
- Over-fueling the engine;
- Hot engine shut-down;
- Improperly installed gaskets; and
- Nuts & washers dropped into the exhaust system.
- Higher-rated spark plugs (for the engine).

Things to keep your turbo running smoothly:

- Replace engine oil frequently;
- Keep the air filter clean and unrestricted;
- Check that the plumbing from the air filter is free of holes;
- Check that plumbing connections are tight to prevent leaks;
- Warm up the engine for two to five minutes prior to driving; and
- Let the engine idle for approximately 2 minutes prior to shut down;

Car Tuners in Chennai

Ever wondered where you can find a good tuner in Chennai.
Even I did... So here are some of them which you might be interested in:

1. Electra Performance
2. Hi-Rev Automotives

Please feel free to add others if its worth mentioning in the comments.

Friday, February 5, 2010

How to: Fit a K&N Filter and Rejet a Carburetor

How to: Fit a K&N Filter and Rejet a Carburetor

This post is for all my fellow bike riders who wish to extract the last possible juice out of your ride. This post is regarding to the fitting of free flow air filters, its effects and how to rectify it using the method of re-jetting.

You need to consider re-jetting your bike whenever there’s been a major change to the air intakes (like installing K&N filters which allow more air to pass to the carburetor), or adding drag pipes. Both modifications will lean out the air-fuel mix. The stock jet can only allow a certain amount of fuel to pass through and is designed according to the specification of the vehicle. Installing larger jets increases fuel to the carburetor to restore the 14 parts air to 1 part fuel optimum mix. This mixture is called stoichiometric ratio. Whenever the amount of air intake is increased, the fuel part is also to be increased. In all other cases, the stock jets will take you through 95% of your riding requirements.

Since the main jet effects all speed ranges after idle, you need to get the main jets right first, and then tune the mid-range and low end. All tuning should be done on a fully warmed up engine because that’s the way you usually ride; the spark plugs should have been previously checked and cleaned; the gas tank should be at least half full; a new or recently installed fuel filter if present; the air intake filters checked for holes, and cleaned; and all air intake and manifold connections tight and secure; the battery fully charged; and the carburetors synchronized, if it’s a multiple cylinder engine (more than one cylinder, eg: kinetic comet ) for optimum results.

We are now going to tune the carburetor without the help of a tachometer (engine speed). High speed or top end main jet sizes are determined by full open throttle performance. Low and mid-range tuning is determined mainly by how the bike feels to you as you roll the throttle. Mikuni CV carburetor is different from the Keihin CV. So is the difference with other carburetors. So tuning will be different in different vehicles.

Note: If you do sense a loss of power, or rough running on a stock vehicle, it may due to some other reason. In this case re-jetting is not the solution to the current problem. Please take the bike to an authorized mechanic and rectify the problem.


High speed performance (80 KPH and up) is controlled by the main jets. To make sure you have the right main jets, take your bike out to an open highway where you can safely (and legally) open the throttle all the way in top gear. Ride the bike full open and let the bike get to top speed. Again, do this only if you are experienced and comfortable running at top speed and you are not in danger of injuring yourself or someone else.

A. If at top speed or before, the bike runs rough, heavy throttle feel or begins to hesitant and buck, your main jet is TOO BIG. The mix is too rich (more fuel than the optimum 1 part fuel to 14 parts air) and you are getting an uneven burn and poor performance. Install smaller main jets and take the bike for another test run. Another way to determine rich mixture is, when u cold start the vehicle and if the bike starts in the very first crank the mixture is rich (no need to use the choke in this instance). Low fuel efficiency and more smoke in the exhaust than usual are some of the characteristics of a rich mixture.

B. If before top speed the engine is running smooth, but has no power, seems to be running hot or knocking from the engine and you can’t push the bike to top speed, then your main jets are too SMALL. You are running too LEAN a mix (less fuel than the optimum 1 part fuel to 14 parts air) for maximum engine performance. Put in LARGER main jets and take the bike out for another test run. Another way to determine lean mixture is the difficulty u feel when cold starting. Even after repeated cranking, if the engine does not start, the mixture is lean. When u closes the throttle in a downhill, if u hears popping or cracking sound from the exhaust, it is again due to the lean mixture.


The carburetor needle controls mid-range performance. The needle tapers down to a point that fits into the main jet. The needle is lifted upward (along with the slide) by the carburetor diaphragm as the air flow increases through the carburetor. As the needle moves upward it is withdrawn from the main jet, allowing more fuel to mix with the increased air volume. All that is needed to modify mid-range performance is to place (or remove) one or more small, thin washers between the diaphragm and the head of the carburetor needle where it’s held in the diaphragm. Adding washers effectively raises the tapered needle further out of the main jet at all engine rpm’s and allows more fuel to mix with air to create a richer mix. Removing a washer effectively leans out the air-fuel mix.

There’s usually no need to replace the stock needles since they have proven over time to provide good performance and good gas mileage. If you do use a third party needle for increased performance, then anticipate lower fuel efficiency.

Mid-range tuning is accomplished mainly by how the bike performance feels to you. If there’s a smooth increase in power as you roll the throttle, then you’re there. If there’s a slow response or there’s no power, then the mix may be too LEAN and you may need to add one or more washers to richen the mix. If the bike accelerate with power, but feels rough, you may be too RICH and need to remove one or more washers to lean out the mix. Now take the bike out for a test spin.


Now you can tune for low end performance. If you are getting a poor pickup or hesitation off the line, or a lot of backfiring on deceleration, then you need more fuel through the pilot jet. You increase fuel flow through the pilot jet by turning the pilot jet screw OUT a half turn. It’s best to start at 2 1/2 turns OUT on the pilot screws and then increase the turns OUT 1/2 turn at a time, and go for a test run. Do these until you get the performance you want and/or there are no back fires on deceleration. If you go more than 5 or 6 FULL turns out, you will probably have to install a LARGER pilot jets. Larger pilot jets are usually needed if you have removed the stock air intakes, air box and installed K & N filters which dramatically INCREASE air intake volume.

I am not posting how to successfully repair the carburetor because of its complexity for a normal person. And friends, please make sure that a professional mechanic is always nearby if anything goes wrong.


If you get inconsistent running, fluctuations in power, you are probably running rich. Lean running is more likely to cut power completely. If you have poor power at small throttle openings and a surge at wider throttle then you may be running lean. Quick ways to see if you are running rich or lean.


If you bike runs better with the choke on even after a few minutes of warm – up, your original mixture might be lean in the lower rev range. This test does strange things to the upper rev range, so don’t use it at highway speeds.


Temporarily remove the air liter cover (to INCREASE air to the mixture), and go for a test ride. A well tuned bike (where the air and fuel mix is right on) will run pretty badly (i.e. mixture too lean) when you do this. But if the mixture was originally too rich, the bike will run better. Then u can fix the air filter cover and lean the mixture.

If your bike’s performance has a hitch or hesitation at certain speeds or you can’t tell if it’s rich or lean, experiment by leaning out the mixture which is the easiest way to find out – if the mixture was originally too rich, the bike will run better immediately. If the mixture was originally too lean, your bike will run worse immediately

(Use the tuning techniques listed above to adjust the low, mid- and high speed ranges).

Now u might also understood why manufacturers stick to a particular setting and not going for extreme tuning. Extreme tuning will call the need for extreme keeping up of it. Friends, it’s all about experimenting with different settings. Also if found a good setting, don’t forget to check the fuel economy too. And always ride safe!

Courtesy - Abiram Menon

How To Tune Your Motorcycle For Performance and Fuel Efficiency

How To Tune Your Motorcycle For Performance and Fuel Efficiency: "Tuning Your Carburetor For Optimal Performance And Fuel Efficiency"

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