still confused

[81 clark racing]

im still greatly confused on weather you can run a timeing key with a rev box? does anyone no? is anyone runing both right now? i hear it will be to muc timeing adv and cause my motor to blow due to 2 much heat is this true also how do u no if you hav to much timeing adv? thanxs

[2004exrider]

Just try it and see how you like it. If it starts getting spark knock then you have two choices you can either take the rev box or key off or you can run a higher octane if 93 just wont cut it.

Jimmy

[81 clark racing]

yea im runing 93 now. thanxs tho

[wilkin250r]

Ok, let's start at the very beginning, so you know exactly what you are working with. This is a long post, but don't ignore it. Read it all the way through, probably more than once.

In theory, the piston travels upwards and compresses the fuel/air mixture. The spark plug fires at TDC (Top Dead Center), and pushes the piston down. Simple, right?

Well, that works up until about 1000 RPM, which is just barely above idle. Beyond that, and you're not going to be making very good power. The spark doesn't fire instantly, the fuel doesn't ignite instantly. NOTHING in nature happens instantly. If you actually fire your spark at TDC, then your piston will already be moving downwards when the fuel really starts to burn, and by then it's too late to make power.

So what's the answer? Fire the spark plug BEFORE the piston reaches the top. That way, the flame begins while the piston is still moving upwards, compressing everything. Because the fuel/air is compressed and tight, the flame front travels quickly. It spreads out while the piston passes up and over TDC, and you get a complete burn and maximum pressure just as the piston starts traveling downwards. You get the maximum bang for your buck, so to speak.

This is called spark advance, or timing advance. But there is a limit. If you fire TOO soon, you get a problem called detonation, which is really bad. It's when the gasses near the edge of the piston get compressed so much that the ignite all by themselves, before the flame front reaches them. Now you have TWO flame fronts, one going outwards away from the spark plug, and one coming inwards. When they collide, it's enough force to actually blow apart little pieces of your piston. This can literally destroy your piston within a matter of minutes, and kill your motor along with it, causing thousands of dollars in damage.

So how does that relate to your CDI (rev box) and timing key? The manufacturers left a little extra room. You can advance the timing a little bit more, but not a lot. This is where the timing key comes in, it advances your spark a little bit, making your spark plug fire a little sooner. But many aftermarket rev boxes ALSO advance your timing a little bit. They add up. A little advance from the rev box, and a little advance from the timing key, and the result is a LOT of advance.

You'll know you have too much advance when it sounds like somebody is knocking on your engine with a hammer from the inside. That sound is your piston being blown to pieces, literally. It's not a matter of overheating, it won't get better if you just let it cool down.