[Seacat]

Hello ! I need some help regards my Bajaj Avenger 220 .
I find that every time when at cold start or idling immediate after a cold start, the engine cuts off.
Even whilst riding the bike say for five minutes if I hold the clutch briefly and roll, the engine cuts off. This is scary as twice I have got caught in a near accident situation as the engine cut off just when i needed power.
I have to keep fiddling with the throttle screw to adjust the fuel .
I gave the bike to the Bajaj Service center at Mahim in Mumbai about 3 weeks ago and now that the Mumbai weather has turned little cool (Mumbai winter), the problem persists. And this just does not happen because its cold but also happens during summer.
I have tried to have this sorted with different mechanics in the past but this issue just does not get resolved.
Do I need to get the carb replaced.??
Any advise welcome.
regards,
Seacat

[adrian]

Originally Posted by Seacat

I have to keep fiddling with the throttle screw to adjust the fuel .
Seacat

Lean pilot circuit in your motorcycle (assuming it not to be EFI). Identify the fuel screw (not the throttle / idle adjustment screw) in your carburetor and give it 1/4 a turn in the anti clockwise direction. Posting a picture of the carburetor can help us pinpoint it for you.

More help in the following thread

https://www.team-bhp.com/forum/motor...-properly.html (How to tune your carb properly)

[Seacat]

Originally Posted by adrian

Lean pilot circuit in your motorcycle (assuming it not to be EFI). Identify the fuel screw (not the throttle / idle adjustment screw) in your carburetor and give it 1/4 a turn in the anti clockwise direction. Posting a picture of the carburetor can help us pinpoint it for you.

More help in the following thread

https://www.team-bhp.com/forum/motor...-properly.html (How to tune your carb properly)

Thanks Adrian,
I will try this for sure. Was hesitant to mess with the carb but now i think I have no alternative but to do so. Will keep you updated.
regards/Seacat

[swissknife]

The fuel mixture may be a little lean. You could try using the choke. If that helps, you may want to increase the fuel in the mixture by a little bit so that it isn't starved during cold starts.

[ani_meher]

Don't worry about messing the carb setting. It is simple to tune, just watch some youtube videos. This is very easy to fix, infact you will fix it better at home by using both air and fuel screw, than a mechanic who may adjust only one screw.

[ashwinprakas]

Originally Posted by Seacat

Hello ! I need some help regards my Bajaj Avenger 220

First determine what the issue at hand is, for that first you'd have to ensure that all consumables have been adequately replaced.

If the issue still persists you should determine whether the tuning is off;

Determining whether Rich:

Starts up easy, but runs like crap once hot, fails to idle when hot, at higher rev's you'll notice black smoke from exhaust.

Determine whether Lean.

Hard to start, but runs nice for a while when hot, then RPM starts to stick/float i.e when you blip the throttle it would rise and then come down slower than it would ideally do, the motorcycle would also be idling higher the hotter it gets, when it gets really hot the idle RPM would be noticeably erratic.

If Rich, you should suspect the Air Filter and Air Filter box, if lean you should diagnose for an air leak.

To diagnose for an air leak you need to raise idle and then spray carb-cleaner/WD40 on the intake route and observe for the RPM to spike, the RPM would spike when you spray on the part that has the leak.

The manifold between the carburetor and head is the usual suspect, so personally rather than do a leak test I directly replace the manifold and 2/3 times that solves the issue at hand.

You should never mess with the carburetor unless it is being rebuilt.

Do I need to get the carb replaced.??

Can't say, as you've let many people mess with your carburetor.

Any advise welcome.

As a lot of hands have worked on your carburetor it would be best to reset things to factory settings or rather re-tune to optimum, to do that you would have to replace all consumables i.e SP, AF etc and then re-tune the carburetor going by the following steps I'd shard in an earlier post;

Originally Posted by ashwinprakas

Good call, never let anyone touch your carburetor, first rule of Fight Club!

Ideally a CV's optimum range is 3~3.5 turns, you can set it at 3 turns blindly or you can re-tune it once you have a new spark-plug and air filter in place.

The procedure is simple, with the motor moderately warm and SAI temporarily disabled with a ball bearing, start at 0.5 Turns with the idle raised, open the AFR screw 0.25 turns at a time and stop at the point where you get the highest RPM, then fine tune it such that you reach the spot just after the RPM is the highest and it settles to a lower speed and you're good to go after setting idle back to normal and unblocking SAI plumbing.

Once AFR is set it should not be fiddled with unless the carb goes for a complete overhaul.

You should not worry about SAI if your motorcycle is a BS3 variant as Bajaj motorcycles only came with SAI recently after the BS4 mandate unlike the rest.

Had also shared the reason why you should not fiddle with the carburetor;

Originally Posted by ashwinprakas

These carburetors have a Fuel Screw for controlling AFR(Air Fuel Ratio);

Attachment 1829222

Which is the only brass screw on the carburetor, the ideal setting is 3~3.5 Turns for a factory dialed setup.

The screw is sensitive and hence should not be fiddled with for no apparent reason which is the usual case with local mechanics, if you do fiddle with it frequently then it will develop a really inconvenient air leak which if you're lucky would get resolved my replacing the AFR screw;

Attachment 1829223

As for SAI, it is the Secondary Air Injection system used for emission compliance, on your manifold/sleeve/(Word Starting with 'D' which I cannot recollect at the time) is a small port on which a tube is connected which goes to the SAI unit, when tuning the AFR it is recommended to temporarily disable it, either by pulling the tube off and plugging the hole on the manifold end with your finger or by introducing a ball bearing into the tube and reconnecting it, I'd recommend the ball bearing as manually blocking it would be one more thing to be bothered about.

The reason for temporarily blocking the SAI is so that you get a more accurate read as with the SAI system connected you tend to get a more erratic idle which makes it hard to fine tune.

That's all as far as the basics go, and yes, unless an actual need arises I'd suggest you ignore the carburetor, as on the 220 which is about 4 years old I've yet to touch either the AFR or Idle Screw to date, reason being if an issue arises out of the blue then blindly playing with the AFR screw is not the right way to resolve the issue as it is simply a band-aid fix which would simply be inviting unnecessary inconveniences in the future.

Then again, a carburetor is like your privates, you don't let another man touch it unless a life-altering need arises and its being worked on by someone whose simply a specialist.

YouTube videos are mostly made by people who seek attention and hence they lack the adequate know-how of what affects what, I've seen a good number of videos on YouTube regarding carburetor tuning and none of them is any better than what you'd expect from a road-side mechanic, so I'd suggest you keep safe distance from such jokers.

Originally Posted by ani_meher

Don't worry about messing the carb setting. It is simple to tune, just watch some Youtube videos. This is very easy to fix, infact you will fix it better at home by using both air and fuel screw, than a mechanic who may adjust only one screw.

I would suggest you not go ahead with what you know, simply because a Carburetor does not have both an Air Screw and a Fuel Screw, it has either one depending on the carburetor type.

You'll find more info on the following quoted post;

Originally Posted by ashwinprakas

Carburetors are more or less the same in function with minor differences depending on type.

The type on your Shogun was a cable operated round slide carburetor like the one on my CT100B,

Attachment 1829216

Which as the name suggests has the throttle cable directly attached to the slide, on these carburetors you have an Air Screw for tuning the AFR(Air Fuel Ratio), the ideal setup for these carbs is between 2~2.5 Turns for a factory machine, unless its a Bajaj(Don't ask!).

On your UCE Bullet 350, you have a CV(Constant Velocity) carburetor as in most modern motorcycles, here's a snap of the Keihin CVK 30 on my ZMA.

Attachment 1829218

On these carburetors the slide is operated by vacuum which is modulated with the help of a butterfly valve which is controlled by a pulley on which the throttle cable is connected.

These carburetors have a Fuel Screw for controlling AFR(Air Fuel Ratio);

Attachment 1829222

Which is the only brass screw on the carburetor, the ideal setting is 3~3.5 Turns for a factory dialed setup.

For those who'd like to know more about carburetors I'd suggest you go through the following post of mine;

Carburetor Types (The Drama of buying & owning a Royal Enfield Bullet 350ES (Electra))

[Seacat]

Hi Ashwinparkas,
Many thanks. Much appreciated. Going through your post I feel mine is still a Lean mix.
Just so that there is clarity please be guided I had got the air filter and spark plugs renewed when I last took it to the bajaj service center.
The bike is running much better after I adjusted the idle screw myself but what I notice is that after a moderate run of about 5- 7 kms and when she is nice and hot, the idling is little erratic. So I feel it may still be a case of too lean a mixture. Not too certain if I should adjust the idle screw further or the Fuel screw (Brass one).
The problem is the Avenger 220 DTSI does not have a tacho so difficult to get a exact RPM readout. The manual says idle rpm is 1400 revs.
Im learning :-)

[ashwinprakas]

Originally Posted by Seacat

Hi Ashwinparkas,
Many thanks. Much appreciated. Going through your post I feel mine is still a Lean mix.
Just so that there is clarity please be guided I had got the air filter and spark plugs renewed when I last took it to the bajaj service center.
The bike is running much better after I adjusted the idle screw myself but what I notice is that after a moderate run of about 5- 7 kms and when she is nice and hot, the idling is little erratic. So I feel it may still be a case of too lean a mixture. Not too certain if I should adjust the idle screw further or the Fuel screw (Brass one).
The problem is the Avenger 220 DTSI does not have a tacho so difficult to get a exact RPM readout. The manual says idle rpm is 1400 revs.
Im learning :-)

That is a good start, now that we have determined that the motorcycle is running lean, we need to find what is causing the lean state.

The carburettors AFR setting would not go out of tune without anyone fiddling with it, hence the reason why its adviced against tweaking the AFR setting unnecessarily, so you have two alternatives;

1. If you feel the carburetor has been fiddled with, properly retune the carburetor as already advised.

2. If you feel the carburetor has not been fiddled with then do an air leak test as already advised.

A new carburetor costs you around 2.5k and would solve all concerns in one go, provided that you replace the manifold as well if your motorcycle is about 5 years old, or simply replace it for the heck of it as it costs peanuts to begin with.

If you're not into spending the moolah, then you'll learn a lot at the expense of time and patience, and would only spend about a few hundred to replace the manifold if a leak is found.

Ideally it is recommend to replace all plumbing including the manifold once in a couple of years, the fuel line, more frequently due to obvious reasons.

The choice is yours, power to the rider!

Cheers.