Riding is it's own high, I don't need anything else to augment that experience.
When I am feeling nervous about riding, such as I was the other night, I don't want to add complications.
What makes me nervous when I ride is the cars on the freeway that have absolutely no respect for the fact that it's my life on the line. The other night I rode from Santa Rosa to Berkeley well after dark. It was not the most enjoyable ride I've been on but, I managed it safely. Eventually I became somewhat accustomed to the not so occasional piss poor road conditions I could not see coming. Smoking pot might have calmed my nerves or it may have caused me to be paranoid and even more uncomfortable. It's a mute point because I don't smoke and ride. To be honest, I don't smoke and anything.
As someone pointed out in a thread I started about mixing alcohol and riding, in any amount, it's a big risk. Even if you do have the skills to minimize the personal risk, you would be unwise to overlook the liability.
Let's say you took a toke or had one beer like two hours ago. Then you go on a casual cruise home and some idiot runs a red light and knocks you off your ride. Now you are on the way to the hospital in an ambulance. Next thing you know they are taking blood and the CHP is ordering tests. Two years later, when you option to sue expires, your insurance company still refuses to pay and his lack of insurance leaves you without a ride and deep in debt. At that point in time you may thank your lucky stars you are still alive and take it all with a grain of salt, or you may wish you had never put yourself in the position.
The fact is that insurance companies are in the business of finding loopholes. Do you think for a moment they will overlook the presence of an illegal or questionable substance in your blood?