New to motorbicycling

Welcome to the forum.

I hate to be the one to break it to you, but just using a larger sprocket won't get you the speed you're looking for, you'll need the power to back it up. You can get a 50cc engine to do that speed, but you'll likely need a transmission of some sort and a heck of a bicycle motor.

If you want a bicycle for speed, you should drop it out of aC130 at 33,000 feet. I'm not sure what terminal velocity on a MB is.. So, Get a motorcycle. These are commuter bikes. Not even the most reliable ones, either.

Read the forum. Use the search option. Spend some time in here, and you can learn a lot.

Most bikes aren't for going 45MPH. They're not set up for it. And by that, I'm also talking about safety. Not rated for speeds like that, so vital components fail. Like brakes, gears, bearings, the crank...

So, again, want a fast bike, buy a Yamaha. Want a cool bike to ride around town/neighborhood and have a great time, motorize your bicycle...

Not trying to be rude, man. I just see people on here (newbies with 1 post) wanting to turn their Cranbrook into a land speed record holder. The problem with that is it's dangerous. These bikes are kinda fidgity (work sometimes, not work another). They're built to take you from here to there. You're trying to go 45 MPH on a bike you paid 79.00$ for? People aren't set up correctly, get in accidents or just piss the whole neighborhood off. It gives our hobby/sport a bad name.

i'd lower my expectations if i was you.
i'm very content with 35 kph cruising speed,its more than fast enough on a mountain bike.
all the brakes in the world arent gonna help you if a dog strolls out in front of you.
you will learn very quickly how vulnerable or frail a bike is when something happens at 70 kph.

I would be content with the normal kit doing 30kph because firstly its safe, and secondly you are only travelling 12km not a long travel time.

i dont think o.p. is interested in what we have to say.
besides,there's no room to add a larger sprocket to engine.
a jackshaft/transmission as mentioned earlier would be the only way to make it go.

If you plan to go that fast, I would install the wheels, tires and brakes from a downhill mountain bike, like an RM7.

OR buy a motorcycle that's built for the speed.

And ToolJunkie, you're right. He didn't care at all what we have to say. His first post is this is what I'm going to do. I'm going to buy a Cranbrook and want to go 40+MPH. I don't see a problem with it..

Well, I'm kinda not surprised. For starters this doesn't sound like a $79 Cranbrook;

Asjoc said:

My bicycle is a commuter style with 700c road tires.
It also has hydraulic disc brakes

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& then it went right to "buy a motorcycle" with little to no middle ground. 75kph/46mph is a bit much to expect, both safety & longevity begin to be compromised with such speeds and your typical in-frame kit hasn't a prayer of accomplishing that...

...but even those usually manage speeds of around 30-35mph/48-56kph sustained, as do other kit options including some of the rack mount kits - which may be an acceptable compromise in speed, reliability & preformance. Most bicycles other than the cheapest of the cheap box store bikes can safely deal with that type of use with no more than an increase in periodic inspection & maintenance... though I'd agree with wheelbender6 (appropriate name lol) & upgrade from the 700c road tires to a decent set of double wall rims w/1.95s if possible, to help absorb the inevitable rough road conditions.

Asjoc said:

Is the feasible?
Just let me know what you guys think.

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...it was asked, but I don't think this was meant as open season on sarcasm as it is quite feasible, he didn't even mention "kits" and there's a number of reliable 50cc engines w/the HP capable of reaching the speed desired & it's been done over and over - but those may be ill advised as a first build, or anything other than a dedicated track/racing bike given the attention it would draw.

I also wouldn't assume the OP "isn't interested" in what folks have to say - remember "been looking at these forums for about a week and i am ready to make a post" & they may simply not be a prolific poster, may not have constant access to the internet - or the may have simply been put off by the inferred hostility & assumptions *shrug*

Barely awake..

You are right. I was very hostile. I will appologize myself.

By the way, he joined 5-17 and posted one (and only one) post on 5-21. That was the last time he came onto the site. So, he didn't even read this yet.

I see brand new posters all the time that do not go to the "introduce yourself" section, and just go right to making the first post. They all say the same thing as every other newbie (no problem there) and ask the same questions. Then they all want to get a bike to go 45MPH.

The problem I have is that it gives the hobby a bad name. I personally have 2 cars, and a motorcycle. Plus I have the MB and in work on the next build. With that being said, I ride my MB slowly, and I don't try to tick off the neighborhood. Because of that, when I ride it, everyone smiles and waves, and puts out nice comments like: "wow, that thing is awesome" and "what is that, did you build that yourself?"

If you get someone who wants to get into this hobby, weather to just have fun, or to have a daily commute, that's awesome. But, don't be the loud abnoxious guy that zips down the road doing 40 upsetting everyone. It gives us a bad name. Also, it ends up ending in a bad wreck, since most of these bikes really can't handle 30+. I'm talking bearings, strucktural integrity, wheels and brakes. I know what is made to handle speeds like that though... Yep, Motorcycles (or scooters).

You are right, I know I personally was a little hard. But, I'm just defensive. I love both building these bikes and riding them. I love the interaction with others that this bike provides, and I love the look on their faces when I roll by. I just don't want anyone soiling that with expectations of spee. But, it's a free country (Even in Canada), and he can do whatever he wants to do. I just hope he's safe about it. I don't want to hear about a motorizedbicycle related injury/death.

My Appologies to ASJOC. Build whatever you want, but be safe and have fun with it...

I've built & re-built mine a couple of times & it's a never ending process of attempting to get it to a safe as well as fun ride but for me the fun stops at about 30 mph simply because any thing over that just doesn't feel safe. If you were riding it on new blacktop with no seams or bumps it would probably be OK but these bikes weren't made to go that fast on a regular basis on "normal" roads. I think mine may go well over 40 mph & I had it up to 38 mph once & it just wasn't comfortable. That's my input & you can consider my age into it also. I just turned 70 & am trying to put my daredevil days behind me.

Norm