Got a stand up scooter, it's half as fast as it should be based on gearing??

Status
Not open for further replies.
R

rudyauction509

New member
Messages
21
Reaction score
0
I recently bought a generic gas scooter from a friend. I fixed it up, but it maxes out at 10mph because of the engine's redline. I calculated all of the gear ratios and I should be getting minimum 25mph.

The transmission is 5:1 (unless they have other gear ratios in the exact same case?), chain drive is 2.5:1, wheel is 8 inches in diameter (measured). The engine is running well above 5,000 rpm, but based on those gear ratios and an internet calculator, I should only need 1,000 rpm to get to 10mph.

Any ideas? The engine and transmission are just the basic one sold on all of the cheap scooters.
 
R

rudyauction509

New member
Messages
21
Reaction score
0
Never mind, turns out I had the final drive typed in backwards. Still, any ideas on how to make this as fast as the others I've had??

Side note, rear sprocket is the smallest available, front is the largest available. I may be able to fit a 10 inch tire on, but that will only get me an extra ~3-4mph.
 
R

rudyauction509

New member
Messages
21
Reaction score
0
That's going to be hard, my camera is at my second home 150 miles away. I should be able to get some pics on the internet.

Engine is http://www.monsterscooterparts.com/49enwimapust.html with different muffler,

transmission is http://www.monsterscooterparts.com/trfor3336434.html with 25 tooth #25 chain sprocket,

rear sprocket is 42 tooth.

tires are 9x3.5-4, measure 8.5 inches in diameter.

I'm thinking about converting to bike chain, then I'll have many gearing options, with only a bit of welding needed to change them.
 
itsid

itsid

Moderator
Staff member
Messages
11,563
Reaction score
247
Location
Ruhrpott [Germany]
wait.. what?

you have a gear reduction installed (5:1)
gear sprocket runs 1300rpm max. wheel currently 520 rpm with your 2.5:1 ratio
leaving you with 12.5:1 overall ratio

and now you want to counteract that by mounting a larger front sprocket than your wheel sprocket?
I can't see the point in that..

just get a std clutch like this:
http://www.monsterscooterparts.com/clutch.html

And work your way from there...
with that 7T clutch sprocket you should get away with 45T wheel sprocket to hit roughly 24mph (6.43:1).
maybe a 40T would still provide enough power (5.71:1).. I'm not too sure *shrugs* that'd give you ~27mph in Top Speed.

And you don't loose as much power as you would gearing up and then down again for no reason ;)

Or if you want to keep the reduction box, get a 30T axle sprocket, that (30/25 is 1.2:1) with that GRB you'd end up with exactly 6:1 overall ratio
I'm not sure that this is enough for a small engine like that... maybe you're better off with a 35T wheel sprocket *shrugs*

you need to try I'm afraid (or let us know your weight :D)

'sid
 
R

rudyauction509

New member
Messages
21
Reaction score
0
itsid said:
wait.. what?

you have a gear reduction installed (5:1)
gear sprocket runs 1300rpm max. wheel currently 520 rpm with your 2.5:1 ratio
leaving you with 12.5:1 overall ratio

and now you want to counteract that by mounting a larger front sprocket than your wheel sprocket?
I can't see the point in that..

just get a std clutch like this:
http://www.monsterscooterparts.com/clutch.html

And work your way from there...
with that 7T clutch sprocket you should get away with 45T wheel sprocket to hit roughly 24mph (6.43:1).
maybe a 40T would still provide enough power (5.71:1).. I'm not too sure *shrugs* that'd give you ~27mph in Top Speed.

And you don't loose as much power as you would gearing up and then down again for no reason ;)

Or if you want to keep the reduction box, get a 30T axle sprocket, that (30/25 is 1.2:1) with that GRB you'd end up with exactly 6:1 overall ratio
I'm not sure that this is enough for a small engine like that... maybe you're better off with a 35T wheel sprocket *shrugs*

you need to try I'm afraid (or let us know your weight :D)

'sid
Click to expand...



I have to keep the reduction box, or the sprocket would spin backwards, and I'm not going to completely redesign the motor mount yet.

Where can I find a 30t or 35t wheel sprocket? I could just weld it to my 25 tooth drive sprocket for 30/42 or 35/42.

Right now I'm leaning towards using an 12 tooth bike sprocket in front and a 20 tooth in back. That should get me near 20mph and still leave me a decent amount of torque. By the way, I can pull a wheelie using the engine alone without even leaning back. I don't need that much acceleration.

At some point I may weld the back of a bike's frame to the back of the scooter, complete with 5 or 7 gears and derailleur. That would give me everything I need in terms of torque and speed.
 
R

rudyauction509

New member
Messages
21
Reaction score
0
I ended up doing a bike chain conversion, 17 tooth front 28 tooth back. Gets me the extra speed I was looking for yet I still have enough torque to get up hills. I also noticed that I have the 33cc engine, I now plan on upgrading to 49cc soon, and will likely change the gearing again when I do. In the end I gained about 7mph, and I'm happy with it.
 
Status
Not open for further replies.
Top