171cc bbk for gy6 mods

[Snowmanhat]

New here, installing a 171 cc big block kit in my tao tao GY6 150 cc scooter to get Better top speed. I geared up to 14/38 tooth but need more power to make use of those gears. What is the best carburetor mods and exhaust mods to support the 171 cc for average conditions. i’d like to keep the pipe as quiet as possible Thank you very much for your help.

[ProDigit]

Nothing. Most amazon and Aliexpress exhaust slip-ons are for 50-125cc bikes.
You put them on a 150cc, and the silencer might fly out.
You have to modify them.
I needed to manufacture a baffle connected to the silencer tip, to make my bike about as quiet as a BMW or Honda, but still hear the single cylinder 'bop-bop-bop' sound.

You'd basically need to find a way to mount a baffle inside your exhaust slip-on.

[krat]

I am currently wondering how you have a 14/38 tooth gear setup on a GY6 scooter that uses a belt drive variator?

The "big bore kit" for the 150 gy6 is a waste of time. It is actually only a 161+- kit and not worth the effort or expense. Even the "200cc" scooters are only 160something. Not a large enough increase to notice over a well tuned 150cc unit. The real "big bore kits" for 125/150 scooters require drilling out the opening on the crankcase for a larger jug skirt and that takes some major machine work.

As for the carb and exhaust mods there is no need to worry. You can re-jet and tune the stock carb for plenty of performance.

The exhaust is no problem. Buy an aftermarket kit from E-bay. Mine has a full inch diameter tube and flow through glasspack and came with baffles if you want to use them. They will not blow off the bike or scatter muffler parts across the countryside.

After I tuned the carb and replaced the cat-restricted exhaust I was very pleased with my 150cc scooter. It will run at 65mph all day and I am fortunate to be in an area with excellent back roads to explore, and it is much more comfortable than my Chinese dual sport.