Yes it will, not worth the effort of the 140cc motor with such a restricted exhaust. Biggest mistake people do on a big motor swap is cheap out on an under sized carb setup and home made exhaust system. These alone are almost again the cost of the engine upgrade but are necessary for optimal performance. Also highly recommended a Z40 camshaft and a thin head gasket to increase compression as these cheap mods really wake up the top end of the Honda based 140 and 150cc motors.
Best fitting exhaust system is from Spangler's however it appears to be out of stock right now. Exhaust
Tbolt does have it in stock though >>>> https://tboltusa.com/store/piranha-full-exhaust-system-for-honda-atc70-trx70-p-9663.html
Another (expensive) option is the Two Brothers Exhaust as it looks and fits beautifully.
I have one of each and love them both.....
Two Brothers Exhaust on my orange 150cc trike.... click twice on each photo for a full screen view...
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