I will be on SQ26 FRA/JFK on a Monday in September arriving JFK T4 at 10.50. I then will transfer to JFK T3 to take Delta 5356 to YYZ departing at 13.40. Is this sufficient time given the following variables:

[1] I am a UK citizen arriving in the US and transiting to Canada.

[2] As such I will have to go through Homeland Security at least twice.

[3] I may have to re-check-in hold bags.

Regards

No problem. Piece of cake. Travel between terminals via the AirTrain will take a couple of minutes.

Welcome to Flyertalk globalnomad888.

Luggage:
You can re-check your luggage as you leave the customs.
When you leave the customs through the automatic doors
there is a small passage to your left just before the meet and greet area.
You will find the luggage re-check facility here. They will accept
luggage for flights leaving from any terminal as long as you have
enough time before the flight. (Not sure how much.. but probably over
an hour or so)


you could walk to terminal 3 if you like. its probably about 5 minutes
of walking from terminal 4 arrival area.

As you leave the terminal 4, walk left towards terminal 3. Probably
faster than Airtrain in this case.


Welcome to FT!! :)

Of course, this being NYC, you'll probably want to budget at least an extra 3 hours' padding in case there is traffic. (kidding, of course)

No problem. Piece of cake. Travel between terminals via the AirTrain will take a couple of minutes.

Welcome to Flyertalk globalnomad888.


Just make sure you take the AirTrain in the right direction.

Luggage:
You can re-check your luggage as you leave the customs.


Only if it is a single ticket and the bags are tagged all the way through. Otherwise I would expect difficulty with trying to get the bags over to DL, as the OP will likely not have a BP yet. Not a very big deal to take them up on to airtrain and over to T3 nor to walk it.

By the way
provided the baggage recheck accepts your bag
and you already hold a boarding pass for your delta flight, use terminal two to clear security. line is much shorter, and at this time they are not enforcing the security line for elites only, though it is the elite terminal.

EDIT It will also be easier to reach your Comair flight, since 90% chance it will be leaving from Terminal 2, Gate 23/25 at the end of the terminal.