Carburettors, I shall miss you old friends - xBhp.com : The Global Indian Biking Community

Ganeshan · 07-08-2010, 07:46 PM

Seeing that carburettors are clearly on their way out, I thought that I’d write something in their defence, because I'm quite sad to see them disappear. Maybe I'm a bit biased because by now I know them quite well.

Apart from some 50cc mopeds, all road bikes in Europe today are fuel injected (FI). Only a few offroad bikes, up to 500cc, still use carbs, but not for much longer. Another year or so and they are history...

Why is this the case? As we have been told, one of the main reasons for swapping to FI is that it allows the engine manufacturers to reach better emissions standards, which are getting tougher. This is because injectors deliver just the right amount of fuel to the engine for its given running conditions. As a result they are more fuel efficient, and so pollute less. FI also has allowed the development of more powerful bikes, and because of the compactness of their systems, motorcycle designers have had more space to play with around the engine. This led to shorter wheelbases as well as better weight distribution. In a race environment, FI has taken out all the work of jetting and re-jetting the carb to find the perfect fuel mixture according to the track conditions, temperature, altitude etc., etc. FI does all this rather technical work automatically using sensors, which have allowed us to have all sorts of information on our instrument displays. Cool stuff. Sure that there must be a few more benefits.

Now what about carbs? I think we shouldn't forget that carburettors came in different designs, and were seriously developed on the later 1990s bikes. These high-performance carburettors (slide carburettors) are still used in some of today’s offroad bikes (up to 500cc).They have been developed to an extraordinary degree. A Keihin FCR-MX 41, for example, is an amazing carb, absolute state-of-the-art technology, great engineering, a 100% mechanical beauty.

Keihin, or Mikuni, carburettors got so highly developed that injectors didn’t have much more to offer. However, the demand for more powerful superbikes meant that engine designers needed straighter intakes with larger diameters. Slide carburettors could work well up to about 41mm and then struggled. Carburettors with bigger intakes were available, but not as efficient as the slide carb, and bigger in size, which in the case of a motorcycle, wasn't an option.

But really, in terms of performances up to say 500cc (per cylinder), these carbs are excellent in most riding conditions/situations. If the right mixture arrives in the cylinder, the engine doesn’t care if it comes from a carb or a FI system.

Carburettors do need more maintenance, and some parts will wear out with use, but they can easily be replaced and are relatively cheap. Also, if more than one carb is used then they need balancing from time to time. As far as reliability is concerned, I have found that they give little problems, if you make sure the fuel bowl is drained occasionally, and the fuel filter is regularly cleaned. Fitting another in-line fuel filter can also be a good idea. Carbs are less complicated than they appear. When they go wrong, it is mainly because of dirt blocking one of the jets, or that has accumulated somewhere. Cleaning them is again not such a big job, and it can be very rewarding... Just some organisation and an interest in mechanics will get you there. If you like mechanics, you should like carbs.

It's not like injection systems never fail, and when they do, there’s not much you can do with your toolbox, even less by the side of the road. It's more likely you’ll be stuck... I find that carbs are much more robust than FI systems, their sensors and the fuel pump. Dirty fuel is more of a threat to injectors because they work with minute clearances, and any change in the clearance can cause them to operate incorrectly. Injectors can get clogged (fuel residue build-up, dirt) and injection pump can give problems. Quite often injectors are sealed units, so you can’t repair them, and in this case mechanics just replace them (and they are not cheap...). And of course the computer can fail, the sensors or their wiring can fail. All sorts of sensors are needed to monitor FI systems, sensors to measure airflow, air temperature/pressure, throttle position, engine rpm, fuel pressure and so on. It is worth adding here that new cars have many problems due to failing sensors. It's likely to be the case with motorcycles too as the number of sensors continues to increase.

With carbs, on the other hand, you are in control, and personally, because I like to be as much in control as I can, and carburettors don't scare me, I would rather have a carburettor than a FI system. When a carb goes wrong it start running poorly but it won't leave you stranded... If I were to look for a bike to do some touring on, like crossing continents, it certainly would be on a carburetted bike (if they haven't been banned on our road by the time I get to do this trip!). To illustrate my point, a friend of mine in Africa needed to take the FI system out of his Toyota Hiace van and put carbs on because he had too many problems with his FI system. And he found that no one could repair his fuel injection system successfully!!

All this makes me think about something that has little to do with carbs, but rather with how fast we are loosing control over our vehicles. And this has been so much the case with cars, and it all happened so quickly we didn't realise anything. With the newest cars, to mention one of many examples, it is now necessary to give the car computer a specific command so that it can release the brake pad pin!! In other words, we can no longer change brake pads ourselves unless we invest in some serious piece of dealer software… It makes me wonder what part of taking out a pin was so difficult that the computer has to do it for us now!? Personally I see this as useless progress, and a bit scary because it prevents us from doing things ourselves... Sometimes even dealers can't do things themselves and need to be connected to the manufacturer´s website to check the car computer online. Small independent garages are having more and more difficulties to survive. Although this is another issue altogether, similar developments are taking place in the motorcycle industry, and in my view, it is not all positive...

Anyway, as electronics are getting cheaper, and for the sake of convenience, motorcycle manufacturers will soon fit their smallest and cheapest models with FI too, but I am sure going to miss carburettors, my trustworthy old friends.

Aryan · 07-08-2010, 10:37 PM

General Biking Discussion Approved.

PRANAV D · 07-09-2010, 12:06 AM

Hmmm.... well written. I never ever thought that the FI system can have so many problems as pointed by you, and i always felt it was kind of flawless and amazing when compared to the carbs.
Although, here in India the fuel injected bikes available in the market are very few can be counted on fingers. So i guess its not goodbye to Carbs so fast, not in India atleast.

Ganeshan · 07-09-2010, 01:09 AM

Sorry I must correct something, although it has nothing to do with carbs. It's not to take out the brake pad pin that a dealer-only diagnostic tool is now needed on some of the latest cars (yet), but to wind back the caliper pistons. The same applies, though, in that a computer seems completely unnecessary to do either of these simple jobs.

aargee · 07-09-2010, 01:19 AM

Ganeshan sir, would like to spice up this thread & bombard you with lot of questions & hope you don't sharing the knowledge to keep this thread with new posts.

Lets start with basics, what's the difference between a regular & flat slide carbs?

jd666 · 07-09-2010, 04:11 AM

^^ good question Aargee..

But i feel that carburettors are being phased out for another reason.. they became too complex to tune and adjust, and to suit all requirements of an engine. It would need a mech 24/7 tinkering with the settings.

So alternatively, a computer does that tinkering real time, and delivers the best possible performance.

Though advances in circuitry and wiring/sensors etc, have made FI as robust and reliable as Carbs.

ravi@17bhp · 07-09-2010, 04:37 AM

I feel the FI system is as reliable as carburetters. All the cars in India are now Fuel Injected. I never heard of any issues with FI in cars. If at all, very very few and is acceptable.

Xenologik · 07-09-2010, 03:06 PM

Quote:

Originally Posted by ravi@17bhp

I feel the FI system is as reliable as carburetters. All the cars in India are now Fuel Injected. I never heard of any issues with FI in cars. If at all, very very few and is acceptable.

Quite true, the issue with bikes is that the FI units are reallly on the cheaper side. But still there havent been many issues with bikes with F.I ! Just that most of the mechanics don't even know what F.I is...

I'd go for an F.I bike provided there's someone who knows how to work / tune / maintain F.I units.

Ganeshan · 07-09-2010, 04:59 PM

Hi Aargee! There are quite a few things in the design of flat slide carbs that make them better. Going into all of them could be interesting, but a bit technical, and, I'm afraid, I'd have to get my books out! Maybe some other XBhpian can help.

But, off the top of my head, the main advantage is that they are more compact (but taller) and produce better control of the airflow. With a flat slide carb, when you open the throttle the slide goes up letting airflow into the engine. Once it is fully up, wide open throttle, there's nothing left in the air passage that would cause turbulence in the airflow, such as with carbs that have a butterfly valve in the way. Better control of the airflow makes them more efficient.

Injection systems actually also use butterfly valves, but I'm pretty sure I read somewhere that hi-performance FI systems are/have been using a flat slide too because of the same reasons. Can't find anything in my books but I've seen references to that. I wonder if anyone else can comment on this.

I cannot say that FI is worse than carburettors. Since the car/motorcycle manufacturers prefer FI to carbs, the advantages must outweigh the disadvantages, as far as they are concerned. But personally I prefer carbs for the reasons that I gave in my first thread.

The problem with FI and cars is more often to do with sensors or actuators failing than injectors getting clogged, although this also happens. The computer itself can also fail, but that's another problem, and a costly one. But really, today's car have got so complicated, full of electronics and it is a fact that these fail a lot, or their wiring... These problems are not necessarily related to FI as electronics do many other things, some I think unnecessary. We have at home a 27 year old carburetted car and a 10 year old diesel VW van with sensors (although not so many as the latest models). I have never had a problem with my car, and it's never let me down (touch wood), but the van has failed quite a few times leaving me stranded in the middle of the road, not nice... And it has been a very reliable van indeed compared to other makes. All these problems were to do with the sensors. Once the air flow sensor had failed, another time it was the water temperature sensor, and another time the crankshaft position sensor! Crankshaft sensors are known to fail regularly. Very often when a sensor starts failing it won't take long before if fails completely, or, if you are lucky, the car might go into what is known as the “limp-in” mode which basically restricts the engine performances until you make it to the dealer... With my 27 year old car, I'm laughing, I have none of all these problems.

rahulingle1 · 08-20-2010, 09:11 PM

guys i need to know some detail working and its explanation with pic of fuel injection.
1. how it work ?
2. where is the fuel pump ? and it runs on electric ? if yea is it AC or DC ?
3. where the sensors are located ? and how is the air flow maintain ?
4. good writeup with pics would be helpful !!

07-08-2010, 07:46 PM	#1 (permalink)
Ganeshan Member Join Date: May 2009 Location: Lisbon Posts: 64	Carburettors, I shall miss you old friends Seeing that carburettors are clearly on their way out, I thought that I’d write something in their defence, because I'm quite sad to see them disappear. Maybe I'm a bit biased because by now I know them quite well. Apart from some 50cc mopeds, all road bikes in Europe today are fuel injected (FI). Only a few offroad bikes, up to 500cc, still use carbs, but not for much longer. Another year or so and they are history... Why is this the case? As we have been told, one of the main reasons for swapping to FI is that it allows the engine manufacturers to reach better emissions standards, which are getting tougher. This is because injectors deliver just the right amount of fuel to the engine for its given running conditions. As a result they are more fuel efficient, and so pollute less. FI also has allowed the development of more powerful bikes, and because of the compactness of their systems, motorcycle designers have had more space to play with around the engine. This led to shorter wheelbases as well as better weight distribution. In a race environment, FI has taken out all the work of jetting and re-jetting the carb to find the perfect fuel mixture according to the track conditions, temperature, altitude etc., etc. FI does all this rather technical work automatically using sensors, which have allowed us to have all sorts of information on our instrument displays. Cool stuff. Sure that there must be a few more benefits. Now what about carbs? I think we shouldn't forget that carburettors came in different designs, and were seriously developed on the later 1990s bikes. These high-performance carburettors (slide carburettors) are still used in some of today’s offroad bikes (up to 500cc).They have been developed to an extraordinary degree. A Keihin FCR-MX 41, for example, is an amazing carb, absolute state-of-the-art technology, great engineering, a 100% mechanical beauty. Keihin, or Mikuni, carburettors got so highly developed that injectors didn’t have much more to offer. However, the demand for more powerful superbikes meant that engine designers needed straighter intakes with larger diameters. Slide carburettors could work well up to about 41mm and then struggled. Carburettors with bigger intakes were available, but not as efficient as the slide carb, and bigger in size, which in the case of a motorcycle, wasn't an option. But really, in terms of performances up to say 500cc (per cylinder), these carbs are excellent in most riding conditions/situations. If the right mixture arrives in the cylinder, the engine doesn’t care if it comes from a carb or a FI system. Carburettors do need more maintenance, and some parts will wear out with use, but they can easily be replaced and are relatively cheap. Also, if more than one carb is used then they need balancing from time to time. As far as reliability is concerned, I have found that they give little problems, if you make sure the fuel bowl is drained occasionally, and the fuel filter is regularly cleaned. Fitting another in-line fuel filter can also be a good idea. Carbs are less complicated than they appear. When they go wrong, it is mainly because of dirt blocking one of the jets, or that has accumulated somewhere. Cleaning them is again not such a big job, and it can be very rewarding... Just some organisation and an interest in mechanics will get you there. If you like mechanics, you should like carbs. It's not like injection systems never fail, and when they do, there’s not much you can do with your toolbox, even less by the side of the road. It's more likely you’ll be stuck... I find that carbs are much more robust than FI systems, their sensors and the fuel pump. Dirty fuel is more of a threat to injectors because they work with minute clearances, and any change in the clearance can cause them to operate incorrectly. Injectors can get clogged (fuel residue build-up, dirt) and injection pump can give problems. Quite often injectors are sealed units, so you can’t repair them, and in this case mechanics just replace them (and they are not cheap...). And of course the computer can fail, the sensors or their wiring can fail. All sorts of sensors are needed to monitor FI systems, sensors to measure airflow, air temperature/pressure, throttle position, engine rpm, fuel pressure and so on. It is worth adding here that new cars have many problems due to failing sensors. It's likely to be the case with motorcycles too as the number of sensors continues to increase. With carbs, on the other hand, you are in control, and personally, because I like to be as much in control as I can, and carburettors don't scare me, I would rather have a carburettor than a FI system. When a carb goes wrong it start running poorly but it won't leave you stranded... If I were to look for a bike to do some touring on, like crossing continents, it certainly would be on a carburetted bike (if they haven't been banned on our road by the time I get to do this trip!). To illustrate my point, a friend of mine in Africa needed to take the FI system out of his Toyota Hiace van and put carbs on because he had too many problems with his FI system. And he found that no one could repair his fuel injection system successfully!! All this makes me think about something that has little to do with carbs, but rather with how fast we are loosing control over our vehicles. And this has been so much the case with cars, and it all happened so quickly we didn't realise anything. With the newest cars, to mention one of many examples, it is now necessary to give the car computer a specific command so that it can release the brake pad pin!! In other words, we can no longer change brake pads ourselves unless we invest in some serious piece of dealer software… It makes me wonder what part of taking out a pin was so difficult that the computer has to do it for us now!? Personally I see this as useless progress, and a bit scary because it prevents us from doing things ourselves... Sometimes even dealers can't do things themselves and need to be connected to the manufacturer´s website to check the car computer online. Small independent garages are having more and more difficulties to survive. Although this is another issue altogether, similar developments are taking place in the motorcycle industry, and in my view, it is not all positive... Anyway, as electronics are getting cheaper, and for the sake of convenience, motorcycle manufacturers will soon fit their smallest and cheapest models with FI too, but I am sure going to miss carburettors, my trustworthy old friends. __________________ Ride with your head, not your emotions.

07-08-2010, 10:37 PM	#2 (permalink)
Aryan Senior Member Join Date: Jan 2006 Location: New Delhi/ Shillong Posts: 18,275	General Biking Discussion Approved. __________________ ...in search of that perfect world - My Travel Blog :)

07-09-2010, 12:06 AM	#3 (permalink)
PRANAV D Jack the Ripper!!! Join Date: Feb 2010 Location: Mumbai Posts: 178	Hmmm.... well written. I never ever thought that the FI system can have so many problems as pointed by you, and i always felt it was kind of flawless and amazing when compared to the carbs. Although, here in India the fuel injected bikes available in the market are very few can be counted on fingers. So i guess its not goodbye to Carbs so fast, not in India atleast. __________________ RIDE IT LIKE YOU STOLE IT!!!

07-09-2010, 01:09 AM	#4 (permalink)
Ganeshan Member Join Date: May 2009 Location: Lisbon Posts: 64	Sorry I must correct something, although it has nothing to do with carbs. It's not to take out the brake pad pin that a dealer-only diagnostic tool is now needed on some of the latest cars (yet), but to wind back the caliper pistons. The same applies, though, in that a computer seems completely unnecessary to do either of these simple jobs. __________________ Ride with your head, not your emotions.

07-09-2010, 01:19 AM	#5 (permalink)
aargee My world changed from smoke & 2T to ECM & 4 joke!! Join Date: Jan 2010 Location: Chennai Posts: 6,612	Ganeshan sir, would like to spice up this thread & bombard you with lot of questions & hope you don't sharing the knowledge to keep this thread with new posts. Lets start with basics, what's the difference between a regular & flat slide carbs? __________________ Be who you are and say what you feel, because those who mind don't matter, and those who matter don't mind - Dr Seuss

07-09-2010, 04:11 AM	#6 (permalink)
jd666 Senior Member Join Date: Sep 2009 Location: Gurgaon/Faridabad Posts: 3,320	^^ good question Aargee.. But i feel that carburettors are being phased out for another reason.. they became too complex to tune and adjust, and to suit all requirements of an engine. It would need a mech 24/7 tinkering with the settings. So alternatively, a computer does that tinkering real time, and delivers the best possible performance. Though advances in circuitry and wiring/sensors etc, have made FI as robust and reliable as Carbs. __________________ The latest RXZ rebuild pics, updated July 2011 - http://www.xbhp.com/talkies/thumpers...tml#post669927 My offerings to the gods of speed - - Yamaha R15 - Yamaha RXZ 5 speed

07-09-2010, 04:37 AM	#7 (permalink)
ravi@17bhp The Explorer Join Date: Dec 2006 Location: Hyderabad Posts: 3,688	I feel the FI system is as reliable as carburetters. All the cars in India are now Fuel Injected. I never heard of any issues with FI in cars. If at all, very very few and is acceptable. __________________ Honda CB Unicorn Dazzler (Current) \|\| CBF Stunner PGM-FI \|\| HH Karizma Honda Aviator \|\| Kinetic Flyte \|\| Kinetic Blaze \|\| HH Splendor

07-09-2010, 04:59 PM	#9 (permalink)
Ganeshan Member Join Date: May 2009 Location: Lisbon Posts: 64	Hi Aargee! There are quite a few things in the design of flat slide carbs that make them better. Going into all of them could be interesting, but a bit technical, and, I'm afraid, I'd have to get my books out! Maybe some other XBhpian can help. But, off the top of my head, the main advantage is that they are more compact (but taller) and produce better control of the airflow. With a flat slide carb, when you open the throttle the slide goes up letting airflow into the engine. Once it is fully up, wide open throttle, there's nothing left in the air passage that would cause turbulence in the airflow, such as with carbs that have a butterfly valve in the way. Better control of the airflow makes them more efficient. Injection systems actually also use butterfly valves, but I'm pretty sure I read somewhere that hi-performance FI systems are/have been using a flat slide too because of the same reasons. Can't find anything in my books but I've seen references to that. I wonder if anyone else can comment on this. I cannot say that FI is worse than carburettors. Since the car/motorcycle manufacturers prefer FI to carbs, the advantages must outweigh the disadvantages, as far as they are concerned. But personally I prefer carbs for the reasons that I gave in my first thread. The problem with FI and cars is more often to do with sensors or actuators failing than injectors getting clogged, although this also happens. The computer itself can also fail, but that's another problem, and a costly one. But really, today's car have got so complicated, full of electronics and it is a fact that these fail a lot, or their wiring... These problems are not necessarily related to FI as electronics do many other things, some I think unnecessary. We have at home a 27 year old carburetted car and a 10 year old diesel VW van with sensors (although not so many as the latest models). I have never had a problem with my car, and it's never let me down (touch wood), but the van has failed quite a few times leaving me stranded in the middle of the road, not nice... And it has been a very reliable van indeed compared to other makes. All these problems were to do with the sensors. Once the air flow sensor had failed, another time it was the water temperature sensor, and another time the crankshaft position sensor! Crankshaft sensors are known to fail regularly. Very often when a sensor starts failing it won't take long before if fails completely, or, if you are lucky, the car might go into what is known as the “limp-in” mode which basically restricts the engine performances until you make it to the dealer... With my 27 year old car, I'm laughing, I have none of all these problems. __________________ Ride with your head, not your emotions. Last edited by Ganeshan; 08-23-2010 at 06:53 PM.

08-20-2010, 09:11 PM	#10 (permalink)
rahulingle1 Senior Member Join Date: Apr 2010 Location: pune Posts: 109	guys i need to know some detail working and its explanation with pic of fuel injection. 1. how it work ? 2. where is the fuel pump ? and it runs on electric ? if yea is it AC or DC ? 3. where the sensors are located ? and how is the air flow maintain ? 4. good writeup with pics would be helpful !! __________________ my dreams won't let me sleep.

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