Pradeepbhat92.
I would spend some more time in this forum. I mean really spend some time. Go through pages and pages of posts. I'm personally not a big fan of friction drives. Dunno why, I just don't want one. I like the infram design. Again, dunno why??? You can get a jack-shaft kit (allows the bike to run off the crank (where you pedal) but with freewheel where you're feet aren't moving, just the chain. You can just install a regular chinese engine (a regular 2 stroke in frame). they're not built from the best material, but if you know what you're doing (because they're pretty simple), you can get a lot done.
Also, there are many 4 stroke options.
So, if you take a few good hours, and look at people's posts, you'll have a lot of fun learning, and pretty much know what to expect, and what to order.
You'll get one main thing from almost everyone in this site, though. Stay away from Kingsmotorbikes and gasbikes. Those are websites that sell the engine kits, and are known for pretty lazy customer service.
All these kits are pretty much the same. I can't tell you this kit is better then this kit. But, the customer service is where the the real advantage is.
Also, I wanted my first build (a 100$ walmart bike) to go 45, too. Now, doing 25-30 is pretty scarry to me. Because it's a bicycle. It's made to go from your house, to a place pretty close by and back. Not to haul butt down any street. With that being said, be happy that you have a bike that works and that is safe. I can go over 30 on my bike, but I am very comfortable with 10-15. I know if I hit the brakes, I can stop in enought time not to kill myself, or others.
The real joy, though, isn't just riding. It's building. So, get a good bike, get a good motor kit, and have fun building it.
Cheers.