Hi, thanks for the pics!
(I actually learned that comet now print's "engine this way" on symmetric belts... who'd thought)
Now, from the pics it seems like your belt is a bit tight and your chain a tad lose...
but let's get to the creeping kart..
first make sure that your Center-Center-distance is set correctly, if the belt is too tight the bronze bushing is not enough to get rid of the friction;
this could be the issue already.
I'm quite convinced you bought the exact same belt that was on there so it "should" be good.
but IIRC you removed the engine recently.. for governor removal and such..
so double check that and if necessary move the engine back a bit (towards the jackshaft).
if you did check that already double check the driven unit (the spring)
make sure it's properly preloaded.
(and the spring is tightened [i.e. sheave moved CCW] before pushing the cam down)
look from the left rear wheel (cam on the back of the driven unit);
the rubber button must be coming from the right side touching the cam!
that's the only thing I cannot see on your pics
And if you checked that as well;
make sure you set the engine idle speed correctly.. sometimes it just want's to rev a hair too high engaging the driver.
best: unhook the throttle cable from the butterfly, to make sure it's not a sticking cable or messed return spring or such.. then check your idle speed to be indeed 1800 +/- 50 rpms
After checking/adjusting the carb reconnect the throttle cable and see if that helped.
if not.. the last thing I could think of ATM
is worn out garter springs (or a wrong set)
so open up your driver again, unhook the garter springs and check.
they MUST NOT BE longer than 7 7/8" and the correct ones should have blue ends.
They determine the engagement speed, which for a series20 and 30 can be set as low as 1200 rpms (with the zinc weights) and black springs
which is too low for your current idle speed.
2200 rpm eng. speed for the blue springs is what you're after.
'sid
