Royal Enfield Bullet Electra X AVL


shall I lower the needle as well as use lower jets? Or do one at a

time alternatively as the bike gets crazier.

It won’t get crazier, as you climb it will come to run richer due

to the relatively lower air pressure. Richer will mean possibly

fouling plugs (although probably not as you’re pulling fairly hard up

hill, I’d think) On the way back down, though, it will run leaner,

Carburetor Jetting

Carburetion adjustment affects the proportion of fuel to air

enteringthe engine. Too rich a mixture can result in poor fuel

economy,carbon-fouling of spark plugs, and wooly or sputtery running

The Float Circuit

The gasoline is mixed with the airflow through the carburetor by

The Pilot Jet

The pilot jet affects idle mixture. Setting your pilot jet involves

getting the machine warm, and then adjusting the idle stop screw for

slowest possible clean tick-over, or idle speed. First, be sure

your throttle cable has at least 1/8-3mm slack at full closed.

Before startingthe engine, ensure that shutting the throttle full off

from 1/2 or so results in an audible clack as the slide hits the

stop. If not, look to your cable routing and condition. Later, with

engine warmed and running, adjust the pilot jet screw for fastest

engine speed. Reduce the speed with the stop screw once again, and

repeat the pilot jet adjustment. Do these until you get the best

possible idle adjustment. Sudden increases of throttle should not

cause the engine to go flator die. The pilot jet is an air bleed

– tightening it makes for richness, loosening leans it out.

Since it is the pilot circuit which provides the fuel during

Plug Checks

By a fortunate coincidence, the insulator for the center electrode

tip, at the business end of the spark plug, changes according to the

mixture. You will need good light and likely a magnifying glass to

see it. At the very bottom of the insulator tip (the top when the

plug is in place in the engine) will be found a soot ring – just

where the insulator begins to project into the well at the plug

bottom. This soot ring will vary in width according to mixture at any

given throttle range. The wider the ring, the richer the mixture. You

want to richen until such a ring is just discernable. For more

specific information, see the

appropriate section of the

Jennings Article, elsewhere in this manual.

Mid-Range Carburetion Check – The Plug Chop

This is a road-test exercise. Put a plug wrench in your pocket or

toolbox. Put on your hat and gloves, start the bike, and take it for

a warm-up cruise to your test site. This will be a place where you

can ride at half throttle for 30 seconds or more – at the proper

throttle opening for the jet circuit you’re checking – before

suddenly cutting off the ignition as you pull in the clutch and come

to a full stop at the roadside, in a place safe to do a little

work.(You will likely need a slight uphill in order to be able to

maintain half throttle for 30 seconds, and even steeper grade for the

full throttle check.) The last thing you should do before commencing

your test runs is to switch to a new plug – a new one will give you

the best readings, although you may find your present one

satisfactory. Be sure to use the proper gap and heat range.


Be VERY Careful! If any other motorists are present, there is heavy

danger they won’t understand your reason for the sudden stop, and

will run over you. Also, you must be in a safe place for working on

your engine when stopped. Be well off the shoulder and stay aware of

traffic coming toward you at all times!

Then, pull the plug and look for the soot ring. If it’s barely there,

you’re good for that jet range. If it’s more than a mm or so wide,

you’re heading into the territory of richness, and if it’s not there

at all, you’re too lean, and need desperately to raise your needle,

In times of leaded gasoline, it was also possible to read the plug

insulator by the colour of the entire cone. If it’s white, you’re too

lean, and the needle must be raised a notch (the clip lowered.) If

it’s black, you’re too rich, and the the needle must be lowered (the

However, to reiterate: with modern fuels, you may not find the

chocolate brown plug to be attainable with some modern fuels,

especially if they’ve been adulterated with such things as ethanol.

In these cases, you’ll be dealing with varying shades of grey, and in

some cases the best you’ll get will be a thin ring of carbon around

the tip of the insulator. If this is you, you’re looking for a thin

ring of carbon just above the tip (from which projects the electrode.)

The Midrange-Highrange Circuit:1/4 to Full

The needle and main jet circuits – 1/4 to 3/4 and 3/4 to

FullThrottle. Raising the needle relative to the throttle slide

richens the mid-range; a larger mainjet richens the top range.

To adjust the needle setting, you must unscrew the carburetor top

cap, remove the complete top cap/spring/slide assembly, pull the

needle clip, move the needle, replace the clip, and replace the top

cap assembly. With some models, this may require removing the fuel

tank and/or loosening the spigot clamp and turning the carburetor to the right.

The fuel flow is from the bottom of the floatbowl and into the jet

block, through the main jet upward into the needlejet, where it is

regulated by the tapered needle. At full throttle, the needle has

little effect; the actual size of the preceeding main jet is what

determines mixture ratio at the upper end – starting about 3/4

throttle. So the size of the main jet determines where the fuel flow

peaks out at wide open. If you don’t ever ride wide open, you’ll

never have to worry about this one – although too small a mainjet can

restrict needlejet flow.

For full throttle tuning, do the plug chop, although you may need a

slightly steeper hill. Run at full throttle for about 30

seconds,pulling in the clutch and turning off the ignition quickly,

then coast to a safe stop in a safe spot. If there’s no soot ring at

all, you’ll need a larger main jet, if it’s too wide, a smaller.

After main jet tuning, check the mid-range again, although only very

large mainjet changes generally affect mid-range. The mainjet is

screwed into the bottom of the jetblock, which may be removed on some

models by unscrewing the carburetor base plug, and reaching up in

there with a socket of the proper size. On others, or if you’re

unfamiliar with the territory, best to remove the entire float bowl.

It will be held in place byeither a spring clip, or screws running

from the bottom through the bowl flange into the carb body, or vice-versa.

A Note On Plug Colours

In earlier times, the entire insulator tip of the plug could be

Cleaning Specific Circuits

If a problem occurs which can be traced to a specific circuit, eg

poor starting pointing to possibly plugged starting enrichment

circuit, or poor but undadjustable idling pointing to possibly

plugged pilot circuit, the carburetor should be removed, stripped,

and cleaned, using carburetor cleaner, or even just washing solvent.


The Indian Bullet is shipped, as are most vehicles in these

EPA-troubled times, with the carburetion set on the side of the EPA

angels, that is to say, very lean. Consequently, it is very common

for owners to find that white spark plug insulators are the order of

the day in the all-important mid range, even with the needle set as

high as possible(clip in bottom groove.) If you have fitted a less

restrictive air cleaner and/or silencer, this will be particularly

apparent; in fact your machine will be dangerously lean in this

instance with the stock jetting. This means installing a larger

needle jet – for the 500, for example, the original will most likely

be an O-8, and you will likelydo better with a P-8.

While in there, check your pilot jet – if a 30 is not already in

there, you’ll likely find it best, too. Most likely main jet has been

Royal Enfield Bullet Electra X AVL
Royal Enfield Bullet Electra X AVL

Float height/level is measured with the float bowl removed, and the

carb held upside down. Spec for distance from top (bottom) of float

to the top of the float chamber (on the carb body) is 22 – 24mm.

A Word On Idling

It seems to be a recurring problem with new riders that their

motorcyclewon’t idle. Although it is simply to be expected that you

can release the throttle on an automobile, and the engine will drop

down toa happy burble, it is not always the case with motorcycles,

particularlywith lo-tech big singles. And it has been my experience

that making my motorcycles do this is often just more trouble than

it’s worth. In fact, it is much more important to me that the power

drops off suddenly and completely when the throttle is shut, with no

run-over, as this is important to proper engine braking. Even if it

is sometimes possible to get a big single to idle, or tick over

when the throttle is rolled off, it can sometimes be very difficult

to get it to do both. Consequently, I have always considered the

primary reason for proper pilot jet adjustment to be to effect a

smooth transition up onto the cutaway and the needle, rather than as

a means of bringing the machine to a point where it will happily putt

away all by itself when I let go of the throttle.

It is, I think, to be preferred to learn to keep the engine running

withthe throttle while simultaneously using the front brake. The

process is easily learned, and like proper gear changing or other

at-first-new things to the beginning motorcyclist, soon becomes

second nature. The thumb and first and second fingers of the right

hand are for controlling the front brake lever, and the rest of the

hand, with the 3rd and 4th fingers, will be found sufficient to

control the throttle to keep the engine running when pulling up to a

stop, or holding the vehicle on a hill with the front brake. This

must be difficult for those circus chimps on the mini-bikes, but for

The Induction Pipe

A common problem with the Indian Enfield is the Induction Pipe

between the carburetor and its spigot on the cylinder head. North

American and European Fuel appears to have additives not common in

India, and the genuine rubber spigot pipe (Indian Rubber!) soon

cracks in most places outside the home turf – rotting, cracking, and

leaking are a common problem. The best fix for this one is to use a

straight piece of radiator hose – you will find you can buy a length

of the proper diameter at your local auto supply house, enough to

make a number of induction pipes, for less than the price of one new

one from the factory – and this one will likely last the life of the

machine. (The induction pipe is sometimes called the manifold,

although this is obviously a misnomer.)

When the pipe is leaking air, a lean mixture is the result. This can

damage the engine at worst, and at minimum will bring about uneven

running, especially at slow speeds, and hard starting, sometimes also

resulting in inlet blowback sufficiently violent actually to blow the

carburetor off the motor! If this occurs, replace the pipe when you

replace the carburetor.

Dirt in Carburetor: No Fuel Flow – Or Bad Flooding

Dirt from the fuel entering the carburetor can cause problems,

rangingfrom no fuel flow at all to excessively-enhanced fuel flow due

to the float valve being stuck open or closed. Either of these

conditions can be brought about by dirt fouling the float needle, or

an excessively worn needle valve orseat. First, remove the float bowl

and carefully take out the float lever hinge pin,(DON’T let it fall

into the dirt!) and then remove the float and lever. With a suitable

container, such as an empty tuna can, under the carburetor, open the

fuel tap and allow some fuel to run through the now-unimpeded float

valve. This should wash out any dirt particles. If dirt is obviously

a problem, the fuel tank may have to be removed and cleaned. Test the

float valve closure after reassembling the float and lever into the

carburetor, by turning on the fuel (tuna can still under the carb)

and gently raising the float asssembly – use a screwdriver of similar

tool to avoid getting gasoline on your skin – to ensure that the fuel

Royal Enfield Bullet Electra X AVL
Royal Enfield Bullet Electra X AVL
Royal Enfield Bullet Electra X AVL
Royal Enfield Bullet Electra X AVL
Royal Enfield Bullet Electra X AVL

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