Err...Ji...I think I confused you; or...are you saying if the emission test outcome is higher (say like 4.0 etc) the CO is high. Is that what you're trying to say?

OR...is there altogether a different emission test you're saying? Because, I'm talking about the regular emission test centers that we see around fuel stations in Chennai. Over there, we don't get the graphs or any detailed output. All we see is just a number indicating lower the better. How do we deduct from that is what my confusion. Pls help me understand Sir.

so, maximum power happens at between 14-to-15 AFR, as can be seen from graph.

now forget emmissions, and say "i care more about my bike's performance rather than environment" so i will tune for max. performance.

so, obviously zero CO point is not what i am looking for, i am looking for the shaded part of graph, and more easier way of achieving it is tune for maximum CO2.

am i correct.

now if see the graph, on the lean side, power tapers off very fast, so any little bit too lean will result in drastic drop in power, on the other hand, if you go to rich side the power holds up right upto 12, so it is somewhat flat, so it is less risky to tune is rich then lean, if you are looking for power and not cleaner environment. right..???

If you do not care about environment then a little rich will be preferred ...around 12~13:1 like you said.

Uff, lot of useful informative discussion going On here, and PSR sir - You are always at your super best.
My Question is
1)why the Power graph is Double lined??
2) Is this graph common for all gasoline engines, irrespective of the Displacement, Bhp, Gearing ratio, etc??

Thanks for kind words of appreciation...to answer the points you had raised..1. The chart is generic for all Gasoline(Petrol) engine.and hence can be used to get at proper AFR tuning..2. AFR ratio is the ratio of Air to Fuel in the engine....The ideal one is supposed to be 14.7 of air to 1 part Fuel..note in the chart the center area of 14 to 15 is shaded to denote this.3. The emission check unit is periodically calibrated. There is no way a common man can check the machine's accuracy.4. The most toxic gas in the burnt fuel is the CO..to keep it low either 14.7:1 or a slightly lean mix at 16 :1 will suffice.5. The preferred tuning is to get 14.7 : 1 ratio..6. A rich tuning may give you better power from engine....If you tune a bit Rich the CO is rising at a faster level , and it is the most toxic by product of ICE. At 14.7: 1 or slightly leaner, it is almost at Zero level....Max power is at AFR of 14:1.Individual preferences in tuning is a personal preference..The chart clearly shows where an engine emission based on it's tuning becomes a threat to the environment in which we live..There is lots more I don't know and hope to learn at least a tiny bit before going off from this world.

would have loved if this graph can be related with engine temperatures. but none the less, it has taught me and served very very well.And can you relate this graph with spark chops.. it will help guys who can't go for emission checks. had done some digging about the topic few years back and came to know that stoichiometric mixture of 14.7:1 can overheat an ICE under load.So according to it with stoichiometric mixture, which gives max power + min pollution can be dangerous.. And i think 16:1 can kill the engine.. (just my thoughts based on earlier research)plz help me understand correctly if I'm missing something. Note to Mods: I'm unable to like & multi-quote above quoted posts (I managed to copy paste) , is it because of slow net speed?? I'm using GPRS.. Awaiting PM or something, wanna keep this thread clean.

would have loved if this graph can be related with engine temperatures. but none the less, it has taught me and served very very well.And can you relate this graph with spark chops.. it will help guys who can't go for emission checks.

Hi,

I recently converted my 220 Fi into carb. I have been facing a problem of engine shutting down abruptly at higher speeds ~post 80Kmph. Also bike is not as responsive as it was before. Not sure if its problem with carb running lean or rollover sensor. Noticed biked did not shut itself off when it toppled flat on ground.
Any help will be highly appreciated.

Regards,
Ashish

Ashish The Fi will control not just the fuel in to the engine ...the Ignition timing is also controlled....Technically the Advance or retard of Ignition timing of any Fi engine,and it's shut down, will be dynamically controlled based on sensors, by the Engine Control Unit...So go back to the person who changed the Fi to carb in your bike and find out what all had been done...then post it here..

Hi PSR, This is the bill stating the parts changed at the time of FI to carb conversion. I was expecting a CDI unit in the list. Not sure how is ignition timing being taken care in my current set up. If ECU is still controlling sparks how is it doing it without TPS on carb's butterfly ? By the way, this job was done at a famous pro-biking service center.

From the BOM it is clear that the ECU and CDI had not been changed and it is in place.....
But the first Item on the bill is a Roll Over Sensor...this is fitted only in a Fi bike and not in a Carburetor bike, since there is no need for it...rest all are for the conversion and some other work connected with maintenance...
So still the ECU is controlling the CDI, and most probably the TPS on the Fi Throttle body had been shifted to the carb., take a look at the right side(petrol tap side) and see if any black thing with wires from it is attached to the carburetor...since you are knowledgeable in this , you will be able to identify it...
After seeing the Bill of Material, did you ask them on how the conversion was done ?retaining the ECU and CDI ? did they return the changed parts like throttle body,injector etc ?