Last time I was in a geared bike was 12 years ago in Brazil, than 5 years without any bike and for the last 3 years I've been riding a 50 scooter and yes you can get really bad habits.
I did my Module one last week, 1st day training and 2nd day was a morning training and test after lunch. (had 2 fault out of 5, both for riding too fast on the slow riding
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Did Module two this week, 1st day training and 2nd day was a morning training and test after lunch. (had 2 minor faults out of 10)
I really had to take an extra care on shoulder check, positioning and switching off the indicators.
I think you would be ok with a 3 days course, but you could do a 4 day just to be more relaxed and lose the bad habits.. funny is that after you pass the test, the bad habits comes back in less than 10 minutes
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coming back to the topic, I ordered a new sump plug for my scooter as the original is rounded and I cannot remove it