2nd Build -- Fastest Legal Setup?

Discussion in 'Motorized Bicycle General Discussion' started by jji7skyline, Feb 6, 2013.

  1. jji7skyline

    jji7skyline New Member

    Joined:
    Jan 15, 2013
    Messages:
    114
    Likes Received:
    0
    I'm going be building my second bike, possibly over the Easter school holidays, or even before then if I can't wait :p

    I'm trying to get the fastest setup while staying under the (stupid Aussie) 50cc, 200watt limit.

    Note that the law does not limit torque, only power.

    Therefore I will be getting:

    Standard 48/50cc HT kit. -- $140
    Jackshaft (to take advantage of low-end torque) -- $160
    DIY 200watt limiting kit -- $89

    It's hideous how the prebuilt 200w engine kits are all $350+ :/

    With this setup, I think I'll be building the fastest legal motorbicycle in Australia, while staying under my $400 budget.

    What do you think? I can always save up a few extra dollars, but then my build will get delayed, which is why I'm staying under $400.

    Do you think it would be worth getting a skyhawk or rocksolidengines 50cc? That would add $100 to my total cost, and eBay kits seem pretty good anyway.

    What do you think my top speed would be?

    Due to the 200watt limiter, I would probably lose all my torque at around 3500rpm. That would mean a 25km/h limit with a 44T, but with a jackshaft, I hope to get at least 50kph :D
     
  2. SoThatICanRIdeWithTraffic

    Joined:
    Feb 6, 2013
    Messages:
    54
    Likes Received:
    0
    Just out of curiousity, how will the law enforcement know how much power your bike has? Because your 2hp motor can gain 1/2 horsepower just from screwing in an expansion chamber but your motor's spec will still be 2hp. I'm really confused about that
     
  3. jji7skyline

    jji7skyline New Member

    Joined:
    Jan 15, 2013
    Messages:
    114
    Likes Received:
    0
    I would carry papers and stuff to show that it is 200watts I presume...
     
  4. VIKTR

    VIKTR New Member

    Joined:
    Jan 10, 2012
    Messages:
    193
    Likes Received:
    0
    25km/h???

    That's less than my average speed when on a non motor assisted bicycle

    I say you get a 212cc predator and just outrun the fuzz if pestered

    lol jk
     
  5. 16v4nrbrgr

    16v4nrbrgr New Member

    Joined:
    Mar 17, 2012
    Messages:
    1,718
    Likes Received:
    1
    buy a road bike lol
     
  6. KCvale

    KCvale Well-Known Member

    Joined:
    Feb 28, 2010
    Messages:
    3,942
    Likes Received:
    29
    Hehehe, good one Viktr ;-}
    $400 US dollar total cost not counting the bicycle? Or some other currency worth like twice an American dollar?

    And what the heck does electrical Watts have to do with gas motor displacement size?
    Sorry, I am not the least bit familiar with the 'Down Unders' laws and regulations, all I can say is don't buy a thing until you save up another couple hundred bucks and share what you plan to mount this power plant on if you want real advice.
    OK, in a country larger than USA you want to make the fastest thing there is on a $400 budget?
    Think aerodynamics and weight to power ratio.

    Once you are over that dream I'd say a 48cc Skyhawk with SBP expansion chamber exhaust on a low profile if not semi-recumbent 2-wheeler with a 3 to 5 speed internal shifter.
    That will give you about 50% overdrive in high gear and down to about 50% under-drive with the other lower gears to get you from dead stop to your speed goal.
     
  7. jji7skyline

    jji7skyline New Member

    Joined:
    Jan 15, 2013
    Messages:
    114
    Likes Received:
    0
    $400 Australian dollar... would be about $420 USD.

    Power can be measured in metric and imperial. Imperial measurement is horepower, metric is kilowatts, and 1 kilowatt is simply 1000 watts. Therefore 200watts would be 0.2kilowatts and probably about 0.35 horsepower.

    I'll be mounting it on my dad's apollo mountain bike... it has 7 speed rear derailleur, and 3 speed at the front, though I guess with the shifter the front speeds wouldn't be used.

    I'm hoping to get quite a good range of gear ratios with the shift kit.
     
  8. VIKTR

    VIKTR New Member

    Joined:
    Jan 10, 2012
    Messages:
    193
    Likes Received:
    0
    I have a jack shaft kit on one of my bicycles... I don't think it will give you the top end speed you are hoping for.

    I like it because it lets me climb hills but in the highest gearing it's obvious to me that the bike could go faster but the engine won't permit

    With the 200W limiter I would estimate a top speed of 18-20mph (28-32kmh) not pedal assisted
     
  9. jji7skyline

    jji7skyline New Member

    Joined:
    Jan 15, 2013
    Messages:
    114
    Likes Received:
    0
    I guess I would have to make some torque mods then... I heard you can unscrew your endcap slightly for better low end torque, and it's safe as long as you keep it at low revs?

    Any other torque mods?
     
  10. DaveM

    DaveM New Member

    Joined:
    Aug 22, 2010
    Messages:
    86
    Likes Received:
    0
    Hi jji7skyline,

    The biggest problem we have here in Australia is people losing their license for drink driving, buying a cheap kit and going flat our everywhere and wondering when pulled over, why the police take such a dim view of motorized bicycles.

    When I built my bike I made my own tank to place it on the left hand side of the frame so it is hard to see, a friend runs his tank in a open box mounted on the rear carrier.

    The reason for this is I believe the police when looking at you and your bike they will see and maybe looking out for the stock peanut tank because it is very obvious and going flat as well draws attention to yourself.

    So many people say to me because I cruise everywhere, using the stock exhaust that they did not realize it was motorized until I got very close to them.

    Try to fly under the radar!

    What ever kit you buy remember that none of the castings have been washed and there is a lot of swarf/aluminium pieces floating around.

    The minimum I have done to my motors is remove the barrel and wash out the crank case area with fuel and two stroke mix when the fuel evaporates it leaves a trace of oil behind to lubricate everything. But be very careful, if you are concerned using fuel use straight kerosine instead it is less volatile!

    While the barrel is off check all gasket surfaces none will be flat and level, this includes the inlet manifold and exhaust manifold.

    Doing this work first, both of my Grubee motors, GT-2B and GT5 have been very reliable.

    Only problems in over two years -

    GT-2B - float had a small hole from new.

    GT-5 - inlet manifold was badly made and where the carby bolted on was not perfectly round and one of the tabs on the carby broke. I bought a aluminum manifold, the surface is machined where the carby bolts on.

    That's it!

    There is a lot of good information on this site on cleaning up and changing things on your motor before fitting it to the frame to ensure you have less problems in the future.

    I just can't find the page I am looking for, maybe someone else has the link for it.

    Cheers,
    DaveM.
     
    #10 DaveM, Feb 7, 2013
    Last edited: Feb 7, 2013
  11. SoThatICanRIdeWithTraffic

    Joined:
    Feb 6, 2013
    Messages:
    54
    Likes Received:
    0
    I tried a lot of different stuff to get enough high end speed to ride with the traffic. I believe 1 tooth off a sprocket gave me approximately 1 mph top speed and made me lose acceleration. 1mph is about 1.6 kph.

    If you can some how get away with your motor's actual power, invest in an expansion chamber that will get you 1/2 extra hp and way more torque. Then your motor will be comparable to a 66cc. Stock 66cc kit with no performance mods with 44 tooth sprocket does about 30 mph which is 48 kph. Since your 50cc with expansion chamber will more or less be the same as a 66cc putting on a 36 sprocket will also get you about 13 kph more without any accelleration loss since 36 tooth are designed to be the "stock" sprocket for a 66cc.

    I found that putting on a higher performance motor with performance mods and using direct drive with smaller sprocket to be more cost efficient than putting on a jackshaft. But if there's a lot of different types of terrain at where you live go with jackshaft. I believe if you used 8 speed cassette it'll have the top speed of a 27 tooth sprocket which would be somewhere around 70kph. But if where you ride has whole bunch of stop signs or traffic lights you would be at that speed for like less than a minute and would have to start shifting back to the highest gear after you take off again if you care about the top speed that much
     
  12. jji7skyline

    jji7skyline New Member

    Joined:
    Jan 15, 2013
    Messages:
    114
    Likes Received:
    0
    I'm pretty sure that even if I did get pulled over, I'd get away with a warning (As long as I don't get pulled over by the same cop twice :p), and I only ride on surburban streets anyway (though soon I might have to commute somewhere to a part time job), but my main concern is actually staying legal.

    I've been riding a 70cc unmodified bike everyday around the neighbourhood with no problems, but that thought of getting pulled over still lingers in my mind, and I'd rather be sure than sorry.

    Therefore I am building a legal build, and who knows, one day I might undo the 200watt conversion (if that's possible???), and zoom around at 80kph :p

    EDIT: I was outposted by Sothaticanridewithtraffic... :p

    I might look into the expansion chamber exhaust (is it very loud?), but my main objective with the jackshaft is being able to cruise at top speed, rather than burning out my motor at top speed.

    I've considered getting a 36tooth before I found out about the 200 watt limit, but with the 200 watt limit, I think the bike would be too slow off the line.
     
    #12 jji7skyline, Feb 7, 2013
    Last edited: Feb 7, 2013
  13. KCvale

    KCvale Well-Known Member

    Joined:
    Feb 28, 2010
    Messages:
    3,942
    Likes Received:
    29
    A stock 48cc 2-stroke motor has 1.95 HP or 1454 Watts.
    200W = 0.27HP

    What exactly is this $89 '200W Limiter' and how does it work on a 2-stroke gas motor?

    1/3rd HP with all the human power you can muster (1/10 HP for an athlete) added in is a completely laughable power restriction, heck I have cordless drills with more power than that.
    Heck some gas powered RC planes have more than that and they can barley make 30MPH.

    You have to decide if want legal or fast because with a 200W total power assist you'll need to defeat the laws of nature with the bike itself or start doping like Lance Armstrong.

    http://www.fogonazos.es/2007/06/worlds-fastest-bicycle.html

    [​IMG]

    Drop a 200W electric assist on that 'bullet' bicycle and you could run with cars on the highway, just add another 0 to the end of your $400 budget ;-}
     
  14. Genisisonyx29

    Genisisonyx29 New Member

    Joined:
    Jul 8, 2011
    Messages:
    207
    Likes Received:
    0
    you do realize that no police office on earth is gonna be able to tell the difference between a 66cc and a 48cc. just get a 66cc kit. i own a 66cc kit, and have fooled every officer that its 49cc and is under 2 hp, and does only 25mph.
     
  15. Gawdzahh

    Gawdzahh New Member

    Joined:
    Feb 11, 2013
    Messages:
    52
    Likes Received:
    0
    This, Seriously ha
    auflg
     
  16. Mr. OrangeConeRacing

    Joined:
    Feb 19, 2013
    Messages:
    26
    Likes Received:
    0
    Just get the 66cc kit and get a speed carn and build an exhaust for it. Also get a 32 Tooth sprocket for your top speed. Build a fairing to help hide the motor from eyes sight. If you rilly hate pedaling, get a electric hub motor and use that to get going then use the gas motor for speed. Just make a cover for the wheel to hide the fact that you even have an electric motor on the bike at all.
     
  17. jji7skyline

    jji7skyline New Member

    Joined:
    Jan 15, 2013
    Messages:
    114
    Likes Received:
    0
    No matter how much you hide the engine, it's going to be pretty obvious to anyone who isn't stone deaf :p
     

Share This Page