Why doesn't it start?

What brand of motor? Briggs has a dimple on the cam and has a timing gear ring on the crank. I position ny piston to TDC of, well, it doesnt matter. Position the piston at TDC and put on the ring gear (if applicable) back onto its keyway. Rotate the crank clock wise until the black dimple is 90° to the right. You can then line up the camshaft dimple to the crankshaft dimple accordingly. What motor model numbers do you have. That will help.

Dean Hi there, is it possible that you have got a blockage in the fuel line or maybe just put one of the gaskets back wrong. It needs everything airtight to suck the fuel through.

Possible solution - This happened to me and my battery was dead in my key fob and also I needed an ignition switch because a piece on it was broken which therefore wouldn't turn to start the engine.

The damage is already done before you put the fuel filter in. (dirt in Carb)
Remove your carb and dissesemble it and clean everything out and then put back on the machine with FRESH gas and you will be fine...run like a top !

take out the battery, then take out the memory. Put one of the two memory modules back in, and turn it on. If everything looks ok, shut down and put the other one back and try again...if everything is ok...then ok. If it doesn't work after the first one, let me know...

There may be an air lock in the fuel line or fuel pume.
Pour some fuel in the carby and start the engine. You may need to do this a few times to get the air lock out of your fuel line/pump.

your getting air into the system,, change that primer bulb and you should be fine

It's a sign of RAM failure. Replace your RAM.

intake cam gear line the "i" up with the dimple in the rear timing cover
exhaust gear line up the e with dimple on rear timing cover above letters there should be a mark on one of the teeth line it straight up with the coorsponding dimples in the black steel cover behind gears

usually that means somethings up with your cpu it may not be in place properly or may be defective