Can any of you explain why a lean bike runs hot?
Any chemistry gurus out there?

Offhand I would think the opposite, but I know that's not true.

Yes, I'm posting more and asking these questions b/c I'm at home with sinus infection and cold. Weather sucks anyway so no riding.

Inside the cylinder, its because a rich mixture's higher amount of fuel droplets cools the walls of the chamber. On the exhaust side and into the pipe, its because a lean mixture burns more completely and generates a greater amount of energy (which is why it produces more power), and all that hot gas streams past the exhaust valve and port.

That makes sense.  Thanks for the info!

so let me see if i've got this straight... you actually want incomplete combustion for a bike to run optimally?!?!

wow... that goes under the 'what I learned today' column for sure.   :mrgreen:

Maybe it is a case were reality and theory diverge a bit.
I guess the equation at the bottom of your page gives the theoretical combustion process. Since that can never happen due to incomplete combustion, etc. you end up with a particular mixture to get the most power. To get the least emissions you run lean, like on the stock GS.
I'm just pulling this out of my a$$ but it sounds good. Besides, we wouldn't need catalytic convertors if it wasn't for incomplete combustion.

Quote from: vtlionso let me see if i've got this straight... you actually want incomplete combustion for a bike to run optimally?!?!

Yes because otherwise the material that makes up combustion chamber will rapidly reach the same rediculously high temperature of the burning hydrocarbons (something like 2600 degrees IIRC) This will burn off you lubricant, vaporize coolant, and start to melt aluminum. In other words, bad things will start to happen.

jamesG wrote:

QuoteYes because otherwise the material that makes up combustion chamber will rapidly reach the same rediculously high temperature of the burning hydrocarbons (something like 2600 degrees IIRC) This will burn off you lubricant, vaporize coolant, and start to melt aluminum. In other words, bad things will start to happen

.
now that would be interesting to watch. (from a distance of course),

anyone care to donate an engine to  "the cause?"    :mrgreen:  :mrgreen:  :mrgreen:  :mrgreen:  :mrgreen:  :mrgreen:  

Quote from: vtlionso let me see if i've got this straight... you actually want incomplete combustion for a bike to run optimally?!?!

wow... that goes under the 'what I learned today' column for sure.   :mrgreen:

You need incomplete combustion for the engine to run coolest and there fore last the longest, you need complete combustion (almost lean) to make the most power, and you need faar too complete combustion (very very lean) to satisfy emissions. Hence from the factory bikes run like crap and have exhausts that are so corked up they dont let the bike even take a breath.
Cool.
Srinath.

Quote from: yamahonkawazuki
anyone care to donate an engine to  "the cause?"

Already have! I can send you the smeared piston if you want...

For performance, and fuel economy, you want to run as lean as you can with decent throttle response and without cooking the engine.

ive blown up an atv engine, (at mmi), was fun, made a perfect smoke ring :lol:

i don't want to start a new topic because i have a question about this "lean and rich"

how do you know if your engine is lean or rich?
how is the engine suposed to run when it's setup right?

well, (lo-tech answer), if running rich excessive gas smell in exhaust, reduced fuel economy, occasional puff-o-black-smoke when running hard :dunno:

Quote from: yamahonkawazuki...ive blown up an atv engine, (at mmi)...

Running 2-stroke motors at MMI usually don't last as long as Britney Spears marriage.