but 12k rpm
How else do you expect them to get 20bhp out of a 150cc engine? Since you are quite into motorsport, I believe you understand how the relation between rpm and bhp exists. Take for instance Formula1 engines, they are just around 4K-5K cc, like any normal C Class Merc benz, but the difference is, F1 cars rpm are at insanely high 22K-30K compared to the 5-8K for the same engine cars, that's how they get almost 5times more bhp. But yeah, increasing rpm seriously reduces engine life, and that's when you need to make an engine with really good components to last longer and Yamaha has the knowledge, expertise and money to do that. 20bhp for a 150cc engine is pretty much the max you'll see.
However, comparing the price, I would go for a Pulsar220 which has better milage, higher cc and same bhp at 8500rpm instead of approx 1000rpm for yamaha. Same fuel injection, same front and back disc brake, oil cooled and ofcourse, expected to be cheaper and finally not to forget, HAMARA BAJAJ
Wait, am I forgetting something? Oh yeah..
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PULSAR MANIA