What size sprocket should I get?

[cdevidal]

I’m planning to get a Dax F50 49cc two stroke (the state limit is 50cc) for a daily eight mile (one way) commute that is almost entirely flat except one hill over the interstate. I weigh about 280lb fully clothed so I want to pedal assist (to lose some weight) getting up to 30mph, the state maximum. I will be mounting it on a steel Walmart mountain bike (no suspension). It weighs around 30lb. I have a 25lb backpack that will ride in a basket on the rear rack. Getting to work on time is the most important consideration.

With these factors, what size rear sprocket should I use? I will be getting a CNC milled sprocket mount — not the rag joint donut as supplied by Dax.

 

[crassius]

I don't worry much about traffic laws with 49cc stickers so readily available, so won't comment on this at all.

 

[cdevidal]

I noticed that in Florida it is a requirement to register gas bikes, which costs $225 + 5. That puts the price about the same as an electric motor... hmm.

 

[bakaneko]

I want to mention and I hope no one takes this personally. But, you are not going to get a workout on a gas bike. If you want to workout go electric and draw all the juice going to work (8 miles) and then do 50W or eco mode going home. This is a workout and a lot of commuting folks do this for a workout. With the gas bike, you are going to pedal to 5-8 mph then gas it to mid 20s. Pedaling then is worthless.

Also, an electric with good wires and connections is almost 100% fail proof so you won't have mid trip breakdowns or no starts. No need to decide right away. There are benefits and concerns with both.

 

[motorizedbikeguy]

I agree with Bakaneko; An e-bike has a lot of strengths in your situation. Low maintenance, you won't smell like gas or get oil on you, less attention by the police, can ride it more places and it's probably cheaper in the long run.

 

[Will'smotobikes19]

I noticed that in Florida it is a requirement to register gas bikes, which costs $225 + 5. That puts the price about the same as an electric motor... hmm.

Wow in pa I've heard it's $9 a year to register as a moped. Try a 40 tooth

 

[cdevidal]

I can’t pedal on top of the gas motor?

 

[bakaneko]

Sorry, what I meant is at 20 mph+ and especially at 25 mph+ you will just be spinning the cranks and not really providing any power especially for you since you mentioned that you have a flat terrain. The motor doesn't need you to pedal it up to cruising speed (25-30mph) after getting it to 5-7 mph though you definitely can. What I am trying to say is that you will eventually find yourself using the gas bike as a moped rather than a workout bike.

 

[rwaterman00]

will " Wow in pa I've heard it's $9 a year to register as a moped. " do you know anyone or how one can register a MB in pa? I would like too but I was under the impression it is almost if not impossible

 

[Will'smotobikes19]

will " Wow in pa I've heard it's $9 a year to register as a moped. " do you know anyone or how one can register a MB in pa? I would like too but I was under the impression it is almost if not impossible

If it is within the requirements of a moped it should be able to be registered the only thing is you need a vin # lights and that stuff that regular mopeds have. I dont know if you can have a vin made or not. I just got a 49cc mini chopper with a charging system and electric start I might try adapting to a bike frame.