From what I understand the current lockdown does not have an end date simply because the hopes of "Boris & Co" are that they can strike a reasonable balance between the numbers vaccinated and those not before mixing of any kind will begin again; and even then I think they'll opt for a slowly progressive release like they did from the first lockdown last year. So, in short, if you're waiting for a period in time like the one we experienced between the first lockdown in March and the second in November where for periods of the summer it was relatively "safe" and not frowned upon to partake in activities such as biking to other areas, or visiting restaurants to use the "eat out to help out" scheme then I wouldn't be holding my breath for very long.
I wouldn't say its illegal to ride in the current times, but not overly smart to go too far from home. Riding a motorbike is perhaps one of the few things you can do in the current climate with very little exposure to covid, but then you could say that if you get a puncture and have to get recovered home that sitting in a van with someone you don't know for 10, 20, 30 mins is potential unnecessary exposure (keeping in mind there's always a delay between catching and showing symptoms for covid, but of course with current testing times that is way faster than last year).
If I wasn't using mine for work I'd guestimate that for at least one day of a week I'd venture out for a 20-30 minuate round trip to keep some form of mental normality.
Ultimately you have to remember that there are people out there going shops in large groups, collecting items they really could do without from Argos; way more shops open this time round, and plenty of traffic on the road. So, in summary, riding a motorbike for a short period locally is not the worst thing you could be doing at the moment so long as you come back in one piece and stay well away from everyone else.
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On the other hand you have three bikes, and hopefully a garage (?). For me I'd be over the moon at that prospect, and ripping them apart one by one to clean and service within an inch of their life simply for something to do.
In terms of what to do to keep bike in a rideable state after being stored for a period of time:
> Put them onto the centre stand, and raise the front with a headstand or suchlike (keeping weight of the bike off one area of the tyre)
> Fill fuel tank as much as possible
> Disconnect battery terminals (I've had a battery sitting on a shelf for several months now from an old bike that I use as a spare / item tester and it still reads 12 v and works fine and has never been charged)
Beyond that, and providing the bike didn't need any work, then not a lot. I'd have to make sure they were thoroughly cleaned to prevent any corrosion, mind.
I'd use this time to tackle some of the bigger jobs like suspension rebuilds, coolant changes, swingarm lubrication, headstock lubrication, oil changes, brake rebuilds etc as there literally couldn't be a better time for it.
I hate when I can't use my bike for a short period for whatever reason so can share the frustration, but providing you put it away in good running order and don't leave it for an overly long period of time then there shouldn't be a huge amount to do when it comes to taking it back out on the road again.