Soo.. why not tell us earlier where we could find them then?
Anywhoo.. good.. two things I recognize, both might be an image issue more than a mechanical thing,
but check em:
1) make sure the belt runs perectly straight and perpedicular to both the jackshaft and more importantly the PTO (your crankshaft)
It appears your driver is too far out, which can be caused by the fisheye effect of phone cameras.. but it might be a mechanical misalignment.
Check that (and if necessary fix that)
a crooked belt heats up more quickly and more drastically than a straight running belt.
2) that chain tensioner is hopefully spring loaded and can move away from the chain, else that chain looks to be too tight.
a too tight chain fails quickly it also puts stress on all linked parts.
btw: bearings work best if they sit as close as possible to the load
(in your case the sprockets)
the further they are from the load the bigger the lever (and bigger the force) to bend the shaft.
that together with a tight chain can cause the bearing to heat up quickly..
boil off the lubrication and finally seize up.
So take care, and if possible imporve pillow block location.
Now, since that's out of the way..
jack up the rear frame securely so that the wheels are off the ground [and away from anything they could propell in your direction
];
start the engine, and use the twist throttle to rev the enige up
(better ask someone else to do so since your eyes will be needed on the opposite end of things)
observe the uncovered TC.. the belt should almost immediately drop all the way down on the driven, and the belt should peak above the outer rim of the driver slightly.
as soon as the rpms are not climbing any longer you can kill the engine again.
Now touch the driver bell (as soon as it stopped rotating of course)
it must not be hot.. barely above ambient temp is okay.. warm is almost not.
same goes for the belt.
It should get hot in such a short amount of time, not even warm really.
that would lead me to assume your driver weights are not engaging properly
(too low rpm.. likely a throttle connection error)
so that the driver isn't providing enough clamping force on the belt.
(wait.. you haven't lubed the sheaves, have you?? that'd be the exact opposite of a good idea
If you had by accident.. clean them with acetone)
Best: take a video of that short rev up and show us.
(we need to see the TC driver and driven at least)
If you're unsure about the rpms your engine provides, get a small tach and attach it,
for now (if you have an android phone) I think there's a audio tach on the google play store IIRC [IDK if it's free or not though]
that could at least give you an idea for now.
Also, after checking the belt and driver bell for overheating (or the hint thereof)
check the JS bearings as well... I still have a feeling that final chain is a hair too tight and heats up at least one of the pillow blocks..
while you're at it, you can quickly check that too.
Any squeaking, squealing, scratching noises?
find the origin and fix that as well.
Work your way away from the engine
ie. remove the TC -> JS chain and give it a try.. if everythign's fine
(rpm hits 3600, TC belt is climbin happily above the driver edge, belt and bell stay cool),
reinstall and remove the JS->axle chain.
jackshaft bearings stay cool as well, no odd sounds...
manually spin the wheels with the chain still off
bearings make no sound at all, no wobble, no misalignment, no binding?
reconenct the JS-> axle chain (check for enough play)
if you came this far without finding any issue whatsoever,
your engine is the one thing unchecked.
maybe it's not running properly (serious lack of compression or something) and isn't providing the power you'll need (I expect it to be 6.5hp at least, right?)
'sid
