Carb theory questions (stoichiometric)

[pistolclass]

So I hear how Lean these carbs are on certain bikes which leads me to a fer questions:

1) is the target a 14.7:1 AFR?
2) how does ambient temp effect this? Does the bike want a leaner or richer ratio on hot days?
3) How does Altitude effect this? Does the bike want a leaner or richer ratio the higher you go?

[mq1991]

(I should preface this warning you that I am NOT a carb expert, this is just what I've learned from the awesome people here, and through my own experimentation)

1) Yes, I think that is correct.


2) Cold air is more dense, so it would need more fuel to keep the same mixture. Warm air is less dense, so it would need less fuel.
Its not so much about trying to be richer or leaner on hot days/cold days, its more that your bike will end up running rich or lean due to temperature and elevation changes. You would want to adjust your mixture according to your elevation.

I feel that trying to tune for a specific temperature would be crazy, as that fluctuates so much.(especially in the northern states!) You want to tune for your average temperature that youd be riding in.


3) The higher you go, the less fuel you need to maintain that ratio. So if your engine is running rich at a high elevation, moving down to a lower elevation would make it run better.

Hope that makes sense!

[pistolclass]

yeah I'm just talking theory. Rejetting because of the temp is crazy, more of a how things work question.


But if Iwere to say climb MT washington at 6K feet do I want to richen the mixture or make it leaner?

So next thought is when do you think China will start putting Fuel injection on their bikes

[mq1991]

Originally Posted by pistolclass

yeah I'm just talking theory. Rejetting because of the temp is crazy, more of a how things work question.


But if Iwere to say climb MT washington at 6K feet do I want to richen the mixture or make it leaner?

So next thought is when do you think China will start putting Fuel injection on their bikes

You would want to lean it out a bit, the thinner air now coming into the engine would cause the mixture to richen.

Im kinda jealous because the bikes like the RX3 and RC3 are fuel injected and water cooled!
http://www.cscmotorcycles.com/RX3-CYCLONE-s/108.htm
I hope they bring a bike like the hawk, with the engine of the RX3/RC3.

Talk about a killer machine!

[BlackBike]

Originally Posted by mq1991

You would want to lean it out a bit, the thinner air now coming into the engine would cause the mixture to richen.

Im kinda jealous because the bikes like the RX3 and RC3 are fuel injected and water cooled!
http://www.cscmotorcycles.com/RX3-CYCLONE-s/108.htm
I hope they bring a bike like the hawk, with the engine of the RX3/RC3.

Talk about a killer machine!

And there goes the neighborhood along with the price, sky high. Sure is nice though.