XJet

I've tried a less-restrictive muffler (in the form of a mousse-can pipe) and, while it improves the throttling and power somewhat, the carby still provides very poor midrange mixture-control, resulting in poor transition and loading up at throttle settings from 1/3-2/3.

All ST has to do is use a decent carby and they'd have an engine that was even better than an OS.

The only reason I can think of to explain why they don't fix their carby designs is that they simply don't have any design-engineers on staff. I get the impression that ST is (now) just a company which has bought the rights for the current design, commissioned their manufacture in China, and don't have a clue themselves how to fix or improve things.

This would also explain why the long-awaited and long-rumored replacement for the G4500 (the G3750?) has never actually eventuated.

The STs are good engines but their carb design is two or three decades out of date and it's now really hurting them as the other Chinese manufacturers start to roll out some very nice engines which are lighter, stronger and much better suited to today's modern highly-powered models.

ST maybe able to squeeze a few more years out of the current line-up but, unless they update those carbs, they're going to find themselves with only a few totally brand-loyal customers left. As it is, they sell mainly on price but, with other Chinese engines now undercutting them, that can't last either.

I've designed my own carby for my G90s (with responsiveness even suited to 3D) and I'd gladly *give* the design to SuperTigre if they wanted to manufacture them -- but it seems they just don't care. So long as folks keep buying them, they won't change a thing -- which is a shame.