i was wondering what do degree keys do

 

They advance your timing.

 

which does what

 

this is a damn good explanation... lots of good stuff on exriders.com

wilkin250r
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quote:
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Originally posted by Ryan
Im confused..... Can anyone explain to me how the Sparks timing key causes the engine to run hotter or even overheat?

In that matter, im not very sure what it exactly does .
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The timing of the spark is an important part of the power characteristics of your engine. Think about HOW it happens. I'm sure you know the theory, the piston is moving upwards compressing the fuel/air mixture, the spark fires, the fuel explodes, and it pushes the piston downwards.

Now, think about slowly, in full detail. Nothing happens instananeously. Imagine that the spark occurs right at Top Dead Center. The spark fires, and the fuel around the spark plug begins to ignite. Meanwhile, the piston has already started to travel downwards. Because the fuel has not fully ignited, and the piston is traveling downwards, the pressure is actually DROPPING inside the cylinder, instead of increasing like it should. The higher the pressure, the better the fuel/air burns, but your cylinder pressure is actually dropping. So the flame front moves outwards away from the spark plug, igniting more fuel/air as it goes, but it's moving slowly because the pressure is dropping and the fuel/air doesn't ignite as easily. Eventually, enough fuel/air will ignite that cylinder pressures increase and push the piston downwards, but you don't get a really efficient burn and not much power out of it.

Now, imagine that you install the advance timing key, so the spark fires 6 degrees BEFORE top dead center. The flame front travels outwards much faster because your cylinder pressures aren't dropping. The piston can still travel upwards because you haven't ignited all that much fuel yet, so cylinder pressures aren't too high. But the important thing is that your flame is traveling much faster. The piston reaches top dead center and starts moving downwards, but cylinder pressures don't drop. Why? Because you are already igniting fuel, you already have a high flame speed, to the cylinder pressures continue to rise and already begin to push on the piston, creating output power right away, instead of 10 degrees after TDC. You get a clean, efficient burn, and much more power output.

This is the basic theory. In reality, the spark doesn't actually occur at top dead center, but you get the idea and how it works.

The spark timing is controlled by a little trigger on the outside of the flywheel. By physically advancing the flywheel with the Sparks Key, you advance the timing.

Now, because the fuel is igniting quicker, and more efficiently, it will also create more heat. If you are running high compression to begin with, you could have detonation issues.

 

that is a very good way of saying it but long, in a short story it ups compression by firing earlier and no bike fires at top dead center thats because of combustion lag thats the time it takes for the fuel to burn and start making heat and force on the piston to send downward...the same thing as the post above but shorter...