F-12 timing gears

Fritz Maurer

Well-known Member
Many years ago, when I was overhauling my F-12, someone was making new crankshaft gears. Since the teeth on mine were razor sharp, I purchased one. After trying to start it for two days, I eventually figured out the timing mark was stamped in the wrong place. After timing it by trial-and error, I got to a point where it was close, but one tooth in either direction was too much or not enough. Flip the gear over,same deal. Out of four possible choices, I picked the closest one, but the piston is well down the cylinder before the intake opens. (In this setting, the original timing mark is about 45 degrees away from the cam gear). It is hard to start and sounds like crap on the rare occasion that it does start. I want to try this again, by cutting a new slot in the gear. I figure I can position the cam between exhaust and intake on No. 1, install the gear on the crank without a key, turn the crank to the desired timing, and transfer the position of the keyseat to the gear. The question is, do I want to be top dead center halfway between exhaust and intake, or do you recommend a number of degrees one way or the other?Thanks, Fritz
 
Here is what I would to if I were you, get a good used gear to replace the one you have, or here is another idea, get some old worn out junk original gear and use it to determine the location of the keyway in relation to the timing mark. I have a junk F12 crankshaft gear that you can have, the teeth are badly damaged from rust, you can have it for the cost of shipping. [email protected]
 
The intake valve should start to open while the piston is on it's way up and just before top dead center. That is so the escaping exhaust gasses can help pull the fuel air mixture in. It sounds like you're 90° or 180° off time! The cam only turns half crankshaft speed and only travels half as far as the crank. Just thought I would throw some pointers your way. Hope you get it figured out.
 

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