Yamaha YQ50 Aerox - Leo Vince TT Exhaust Issue

I've worked on four-stroke sports bikes for years, but this is my first two-stroke, my first scooter 'mod' and there's a problem...

I've fitted a Leo Vince TT exhaust to a low mileage 2012 Yamaha YQ50 Aerox scooter. I removed the restrictor at the manifold, but apart from that, everything else is standard.

I'm planning on fitting the rollers and springs kit that came with the exhaust at some point, but after fitting the exhaust, I thought I'd do a quick test ride first, to see if all was OK.

The little Aerox was transformed! Pulled much stronger, sounded great and saw 40mph+ for the first mile. Then everything changed.

After what I assumed was reaching normal operating temp, it wouldn't pull at all and was barely getting to 25mph. Engine sounded bogged down (labored) and just wouldn't rev.

This Aerox is fitted with an 'air induction' system, but there's nowhere to connect this to the Leo Vince can. I'd seen on a forum that the hose from the carb (reed valve) can simply be removed, not blocked up and just tucked away somewhere in the belly pan.

Between letting it cool down a bit, I've tried three times and the pattern is the same each time. Great when it's cold/warm, terrible once it gets hot.

Any suggestion what the problem could be?

 

you have to fit a larger main jet when you fit a sports pipe, around 10% larger than standard...

the engine is probably running too lean and the cylinder is getting too hot.