I have a bunch of SuperTigres and I like them... but there is a BIG caveat.

Some of the engines, and the .61 & .75 is prone to this, use the same size carbs for different displacements.

So the carb may be best matched to a particular size.

In turn this has made a percentage of the SuperTigres I've purchased somewhat problematic.

The problem manifests as an inability to get an accross the board smooth running engine.

You can tune the engine for a great idle, but then transitions will suffer.

You can tune the engine for a great transition and high end, but then the engine will bog down at idle as it will remain rich at idle to get the transition right.

SuperTigre advises you to turn the "cat-eye" opening in the carb to prevent this... and that suggestion only makes matters worst.

I've taken to grinding out a small half moon ( 2-3mm ) sliver on the closed part of the throttle opening to preven the idle problem when transition is adjusted properly.

The slightly enlarged opening permits more air to go in at idle, thereby richening the idle and preventing the engine from bogging down.

I've done this on three SuperTigre engines and I need to do it again on a fourth.

The fourth seems to be OK, but the idle is so rich that the engine continues to run with the barrel closed fully.

Yes air leaks around the barrel on all of the ST's it seems, which is why SuperTigres have that rubber boot below the needles.