New here from Australia. Just acquired 200w street legal motorised bicycle.

Discussion in 'Introduce Yourself' started by Devil's Advocate, Aug 23, 2015.

  1. Devil's Advocate

    Devil's Advocate New Member

    Hi all, I found this place when looking for ways to improve performance on a 48cc motor. I have not ridden a bicycle since I was a kid but recently picked up a pre-fab motorized bike from a guy who builds them. It's a $90 supermarket mountain bike with a 48cc 2 stroke motor that has been de-tuned to 200w to comply with Australian laws.

    It's been a learning curve for me just getting used to riding a bike again, let alone a motor powered one. I find the cars very daunting and can never hear them coming up behind me because of the exhaust noise. I've realized that becoming traffic savvy on a bike is an art in itself, motor or no motor. Fortunately in my area there are several miles of trails and tracks that cut through to all of the major parts of the region, i'm utilizing them almost 100% of the time, and only venturing into traffic when I have no other option. I've done about 30 miles in total so far, and really like it as a mode of transport, I just wish there were more bike lanes on the roads.

    The bike itself is okay for it's limited 200 watts I suppose, but it really struggles up hills and requires pedal assistance big time. I weigh 110kg (230lbs), so i'm really up against it. The manual says that the engine will increase in torque as it is run in, but I feel that I'm going to want more. The company that builds the engine can provide an upgrade kit which de-restricts the engine and gives it the power of a regular 48cc, but this would make it illegal to use.

    Rather than buy the upgrade kit (which appeared to be just an exhaust pipe and a carburetor) I was wondering what I could try on the existing combination to improve the torque and a little bit of top speed? The guy I purchased the bike from showed me a 200w inlet manifold gasket and it had a hole in it about a half or even maybe a third of the size of the carby and manifold throat, if I replace this with a gasket with a larger opening, will I gain power? I suspect that the exhaust might also just have a restrictor plate in it, and if I removed that as well, would I theoretically see an increase in torque or power, and is it likely that could I adjust my existing carby to work with the better breathing capability?

    Sorry to bombard you with so many questions, and I hope i'm posting in the correct forum.

  2. KCvale

    KCvale Motorized Bicycle Vendor

    An Expansion Chamber exhaust will wake it up.
  3. Wolfie65

    Wolfie65 New Member

    As a newbie myself, I can't tell you how to make your bike quieter, but as a very experienced cyclist, I can tell you that the best way to handle traffic is a mixture of passive-aggressive attitude.
    You need to be aggressive enough so they don't just run you off the road - which they will, given half the chance - but at the same time passive enough so you don't get flattened.
    Ease into it slowly, you're on the right track utilizing trails and side streets whenever possible and keeping your time on busier roads to a necessary minimum.
    If your ride counts as a 'bicycle' by local law, take advantage of bike lanes and such, but be courteous to cyclists, skateboarders, etc. who need those facilities even more than you do.
    Get a mirror if you don't already have one - maybe even 2 - but do ALWAYS look over your shoulder, there's no substitute for that.
    Wear something like a reflective safety vest and a helmet, makes you more visible and they might take you more seriously.
    Or, you could go the distracted history professor route and ride in an Irish fisherman's cap, tweed jacket (with leather elbow patches) and torn jeans, accessorized with glasses and long hair. They might give you a wider berth......
  4. Devil's Advocate

    Devil's Advocate New Member

    Thanks, would I do that and leave the rest of the engine as is? Or should I do it in conjunction with removing whatever the engine builder has done to reduce the power?

    My problem is that i've been a car driver for several decades, and riding a bike on the road just feels so alien to me. I feel like a sitting duck without all that metal around me, and enough horsepower to get out of most situations. I went for a 5 mile cruise today around the local area and up to my local shopping centre, and it was really enjoyable, the bike is currently restricted to about 20mph on a flat surface but once you get up there, it motors along really nicely. I'm slowly gaining confidence on the roads, but will always try to stick to the back streets and the bike trails where ever possible.

    I am really keen to build a project bike now, I love the whole concept of motorised bikes.​
  5. Wolfie65

    Wolfie65 New Member

    Bicycle commuting does take a while to get used to, motorized or not.
    ALWAYS look over your shoulder before changing lanes or turning and NEVER assume others (drivers) will do the right thing.
    Stop lights/signs may be ignored, they might cut you off, they might not see you - there are many drivers in whose world anything smaller than a 750 cc motorcycle simply doesn't exist - they might even autohate you simply because you're not in a car.
    Then there's the drunk, the drugged, the senior, the texters........
    Short trips to the supermarket on side streets sound like a good start, build up to busier streets slowly.
    One potential drawback of bike trails is that they could lull you into a false sense of security, making you freak out when the trail ends and you have to suddenly deal with traffic again.
  6. Devil's Advocate

    Devil's Advocate New Member

    I've been looking over my shoulder since you first mentioned it, and it helps a lot. It was just hard at first to force myself to turn away from the direction I was going in. It's definitely a completely different experience to anything I've done before.
  7. bluegoatwoods

    bluegoatwoods Well-Known Member

    Interesting thread. It's hard for me to imagine having an 'alien' feeling on a bike.

    All the same, though, it does sound as if you're doing it right. Get your footing in traffic nice and slow. There's no rush.

    Wofie's advice about high-vis clothing is good. If nothing else, you want to take away any excuse for them to say, "But I didn't see him". And autos do give reflective vests a bit of respect.

    I strongly advise two mirrors. Maybe it sounds like overkill. But having two different rear points of view gives you a better notion of what's going on behind you. Personally, I don't turn my head much. (Though I would not claim that it's bad advice) I do watch both of my mirrors a good deal. And I especially look them over thoroughly when I'm about to cross traffic.

    I won't claim that a car can never, never sneak up on me. But it happens only very rarely.

    I'd actually advise you to leave your motor just the way it is and not even try to get more speed out of it. But I'll admit that I'm a bit more conservative than most on the issue of top speed. But I do think that twenty is more than enough. Anyone who wants to go faster really shouldn't be doing it on a motor assisted bicycle. They should be moving up to scooters. Plus this way you'll stay legal. And that don't hurt things one little bit.
    DMO-1291 likes this.
  8. KCvale

    KCvale Motorized Bicycle Vendor

    An NGK 5944 (BPR7HIX) Iridium spark plug IF you have a slant head stock engine will help too.

    Chances are little else was done to hamper performance other than maybe a restricted (smaller) intake gasket.
  9. libranskeptic

    libranskeptic Member

    Re the newbies looking behind them is good but scary thing:

    A game changer for me was realising how stable standing fully upright with most weight on one pedal is. I find it gives me similar confidence to take my eyes off the road as i would have when walking. It wasnt that i couldnt see the road was clear ahead, but that i didnt trust myself not to wobble while looking behind.

    also, as u can twist your body much more easily, the head twist is less extreme.
  10. skyash

    skyash Active Member

    Just putting it out there but I don't think the motor is 200w. Cops don't care enyway as long as you pedal thay can't say enything. I think it's a big lie 200w enyone know of this
  11. skyash

    skyash Active Member

    I live in Melbourne City Australia where are you?
  12. Steve Best

    Steve Best Well-Known Member

    Excellent thread Devil! Great advice from Wolf and all.

    I have been a motorcyclist for 40 years but found the transition to bicycle difficult.
    Careful "seat time" will change that and I found all Wolf's advice very true.

    As for general de-restricting and getting up to speed and fuel efficiency:
    1) match the intake gasket (but not the port, a step here is good)
    2) sand or cut a "Squish Area" into the cylinder head and sand its gasket surface to get 1mm clearance
    3) Some careful widening of the cylinder ports will help. Don't make them taller.
    4) port match the exhaust pipe and gasket to the cylinder
    5) Tuned exhaust pipes are "Da Bomb" but I found this worked well and is quieter than stock:
    (quieter, inoffensive looking and made good power compared to other stock exhaust systems)

    As well, I'd suggest
    1) pedaling at all times while riding
    2) shutting motor off and pedaling around pedestrians on shared use trails and in residential areas
    3) keep the speed down in appropriate areas.

    It is our behaviour that gets us noticed by the police.
    Loud pipes, engine only riding, excessive speed, no safety gear, and aggressive driving will get us noticed and pulled over.
    It is only at this point that most police will start picking the bike apart for legalities.
    Unless of course some previous motorized biker has already soured his attitude toward us.
    We are all in this together folks...

  13. libranskeptic

    libranskeptic Member

    Re the urban noob on a bike, been there recently too.

    my 2c, muck around in quiet a parking lot, take u time, repetition, simulate as many situations as may happen on road, fears, brakes, observe behind, pretend car doors open in front etc. play soccer w/ u self?

    get it all familiar and reflex, or risk getting muddled in a crisis

    read the road. if a tricky bit approaching & am as fast as cars, NO AMBIGUITY. I ownthe lane. Dont trust the judgement of morons.

    at all other times, i am courteous & happy to go last. I dont even have a bell & would feel rude asking. i doodle around them somehow at their speed til it clears.

    if u love the petrol bike, u will swoon over electric if it suits. so much nicer. get a mid-drive

    roads are safer and preferred, but if an unused path is free, i get out of the way and use it - a busy grade e.g

    ride the wrong way works for me often. u can see whats coming & avoid - + i have a dog running along so i consider his needs too when deciding - best we stay on same side, & i share w/ pedestrians more also cos o this.

    yeah look behind is scary, but get over/familiar w/ it. I dont have mirrors, not tried, but i get by fine?

    a revelation and godsend for me, especially in busy lower speed traffic, is how cool standing on one leg, fully upright is, on my pedaling optional ebike (just work the throttle).

    I see over the cars, around corners, stability at a crawl speed like u r walking, turn on a dime. Looking behind/twisting is a snack. Any bumps are perfectly shared by both wheels and leg.

    my bike is 30kg & i am 75kg, so how good is having that weight majority, centered, shiftable ballast, and low?
  14. skyash

    skyash Active Member

    Eny one on the wrong side of the road is a idiot. If can't go with the traffic then get off the road. Or if you can't imagine what might happen up a head then you are the unsafe one. Some times worrying to much makes you dangerous.