Yamaha aerox 50cc starting and top end speed bogging out.

Hi. Just bought a 2013 yamaha aerox 50cc which has had a 70cc kit fitted but i bought it as a spares or repair project. Its a nightmare to get started and when it does start it trys to stop and bogs out at top end speed. There is plenty of compression and no water getting jnto the barrel. I was looking for for advice on what could possibly be the problem.
Cheers in advance.

 

Welcome in.
Have you checked the jetting on the carb? If it's had a 70cc kit fitted the carb could need upjetting.

 

Good idea i will try that in the morning. Thanks. I just had a google and read that when a 70 kit is added a long reach plug is recommended, the plug that is currently in is a medium length. Would this also cause the issue with bike?

 

I'll leave someone else to answer the plug question. I'd have thought if it uses the stock head it'd use the stock plug, but if it's a head specifically for the 70cc kit it's anyone's guess.