Bicycle Question

[karlz]

I want to change an electrically modified mountain bike (26" wheel). I can't keep up with the motor pedalling! I think I can get a little extra by changing the front sprocket to 48 teeth (maybe 5mph). I have a '52 Rotrax Supercourse with a similar ratio and I've been clocked at 34.4 MPH in the past.
Currently there is the usual three gang front sprocket on the bike I want to alter but that's not a problem, a single sprocket would presumably mean a shorter spindle through the bottom bracket though?
there are lots of sizes to choose from, which one should I get?

[Answerprancer]

Wouldn't you normally be freewheeling when the electric motor is working?
It's probably best if you go into the local bike shop with the bike and ask to see the mechanic and see what s/he says. If you want to change to a higher ratio with a triple 'clanger' then IMO all three sprockets need to be proportionally bigger (not just one) you'll need a longer chain and a longer rear mech that can handle the differences.

[davebro]

//Wouldn't you normally be freewheeling when the electric motor is working?//

No, the motor assistance only operates when you pedal.

[davebro]

or *should only operate* - of course illegal mods can be made.