Crazy Speeds

Discussion in 'Motorized Bicycle General Discussion' started by ferball, Apr 5, 2011.

  1. ferball

    ferball New Member

    Joined:
    Apr 8, 2010
    Messages:
    599
    Likes Received:
    0
    I just thought I might fan the crazy speed claim flames here with this thought. I found the factory specs for my motor. It says that my engine can put out 5-6 hp at 6000rpms, and is good for up to 42 mph. I know that it is wishful thinking that these little motors are that strong out of the box, but claims of speed around 30mph are not unrealistic for a stock motor if those specs are even half true.

    I do realize that as your speed increases your power need increases at an exponential factor, so 45mph maybe possible but very unlikely. But 30ish MPH should not be considered a fantasy or crazy talk for these things. I personally never ride that fast and when people start claiming 35+ I don't often question if the bike can do it, I question if the rider can, considering the vibrations of the bike at the speed, the lack of decent suspension to handle those speeds, and what you have to ignore when your brain starts shouting to the rest of you what a bad idea it is.

    Just a thought, not trying to start a pissing contest of whose bike is faster. But I would be interested to hear from people who legitimately drive that fast and what the bike does at those speeds and if you were actually scared for life at any point.
     
  2. Hammond Egger

    Hammond Egger New Member

    Joined:
    Oct 23, 2010
    Messages:
    270
    Likes Received:
    0
    Well......the faster you ride the less your cost per mile to stay overnight in the hospital is. It costs about $12,700.00 to stay overnight in the hospital here.

    $12,700.00\20mph = $635.00 per mph

    $12,700.00\35mph = $362.85 per mph
     
  3. Allen_Wrench

    Allen_Wrench Resident Mad Scientist

    Joined:
    Feb 6, 2010
    Messages:
    2,787
    Likes Received:
    1
    I do know that, accounting for a degree of speedometer error, my first MB - the Tempus - would do at least 30 mph. But I only had one opportunity, on the flattest and most level street I found myself on, and at the quietest time of day. Nowhere else and no other time would have been safe enough. Indianapolis roads are terrible right now. (We have an "Adopt a Pothole" program. I am NOT kidding. That was NOT a joke) And the car drivers are trying to become as bad as those in Boston.
     
  4. MotorBicycleRacing

    MotorBicycleRacing Active Member

    Joined:
    Jul 28, 2010
    Messages:
    5,684
    Likes Received:
    24
    Hey ferball
    You want to fan the crazy speed claim flames? I love pissing contest's. Just watch which way the wind is blowing! LOL
    See my signature!

    Have you considered that the so called "factory specs" of 5-6 hp may be ever so slightly exaggerated?
    Even the 66 cc Grubee Starfire label that says 2.85 hp may be a bit optimistic.

    We GPS'ed Bairdco at 54 mph a few weeks on his fast bike which runs
    a 28 tooth rear sprocket. It rides and handles just fine at those speeds
    even though his bike has no suspension.
    Baird's bike has quality components though, check out the pics below
    that were taken on the day by yours truly.

    A good standard kit runs about 32mph with a 44 tooth sprocket and if you
    tweak them a little they will go 38 - 39 mph with a 36 tooth.

    IF you really know what you are doing you will have a bike faster than Baird!

    [​IMG]

    [​IMG]

     
    #4 MotorBicycleRacing, Apr 5, 2011
    Last edited: Apr 5, 2011
  5. ruppster

    ruppster New Member

    Joined:
    Mar 3, 2010
    Messages:
    192
    Likes Received:
    0
    For what it's worth my speedo clicked 44mph once last summer running a 40t sprocket and a Grubee 66cc that I cleaned the ports up a little bit on. I can get it to 42mph when I push it but it's vibrating to beat the band. Do I feel safe? To be honest I don't think about it when it's happening and it doesn't feel all that fast until it's time to stop. Is it smart? probably not. Most of the time I cruise at 30 mph or so and I'm happy as could be doing it. I'm most unhappy when I'm trying to wring every bit of speed out it. It's far more fun to just put along back roads and take in all the country side has to offer.
    I'm on board with bimoped, 2.85hp is optimistic and 5-6hp is out of the question. I might be getting the claimed hp after the mods I did but I doubt it. My old 3.5 hp mini bike would smoke my mb except in top end only because the gearing was so low on the mini bike.
     
  6. mapbike

    mapbike Active Member

    Joined:
    Mar 14, 2010
    Messages:
    5,380
    Likes Received:
    1
    I have one bike with 300miles on it now that will hit a severly vibrating 39MPH with a 36T sprocket, it has a ported intake and an exhaust that I made, I built this engine from ground up after cooking it early on, (trashed the ConRod/Crank Bearing) I milled .012 off of the stock slant head and smoothed up the ports a bit and removed all the burs and such, better plug wire and NGK B6HS plug, rejetted the carb and all else is stock, this bike cruises very smooth with almost zero vibrations at 30-32MPH, very nice ride and would be much better on a better bike.

    My other is a MT Bike that has the Straight Plug 6mm stud jug and it has the stock Alum. intake, a home built exhaust, all internals completely stock and only mod so far was just rejetting carb. it has 945miles on it now and has a 41T Spr., it will hit 34-35MPH but is not a comfortable ride past 27-28MPH with the 41T Spr. to many R's and the vibration is murder on the ole "duffle bag/marble sack" and anything else that is on the seat or bike in general, it is a very strong running engine and I plan to put a better intake and and raise the compression a bit by making a new head gasket out of some .016 Alum. I have, the stock gasket is .027 so by reducing the combustion chamber by .011 should up my torque a tad and then I plan to put a 36-38T Spr. on that bike as well.

    Here is a link that will explain my upcoming pusher project, and this will get me in the 40-45MPH cruising speed I'm looking for, and yes I will be using a very high quality MT Bike with disk brakes and all the good stuff.... and No I will not be cruising at the speeds this guy is, that is just wicked fast on a bike and more than I desire...

    Enjoy this one guys
    YouTube - BICICLETA CON MOTOR 95 KM/H 60 MP/H PUSHER BIKE


    Peace
     
  7. bairdco

    bairdco a guy who makes cool bikes

    Joined:
    Aug 18, 2009
    Messages:
    6,334
    Likes Received:
    19
    the bike BiMoPed pictured is the smoothest thing ever at top speed. as he said, we GPS'd it at 54, but i ran outta road and still coulda gone a little faster. i've drafted trucks down PCH and had a guy yell out "59!" at me once.

    the bike itself is more like a small motorcycle than a bicycle, now. evrything's heavy duty, nothing rattles, and it's a thrill to ride.

    there really is almost no vibration to it at all.

    i've been riding the bike i built for the Death Race around lately, and it'll get up to 45 in a hurry, but it's a little more twitchy.

    my very first bike, stock, with a 35t sprocket could cruise 35 all day, and after porting the intake and exhaust would hit 40 on a good day.

    a bone stock engine kit with a 44 sprocket and some minor porting, head-decking, and tuning can reach 35 easy, ya just gotta know what you're doing.

    as far as the safety aspect, i feel totally safe riding at 50+, even passing cars and drafting trucks.

    it's always in the back of my mind that if anything goes wrong i'll be sliding (or bouncing) down the street.

    all the bikes i've sold, though, don't really go over 35. i know how i can ride, but who knows what the guy i'm selling it to is capable of.
     
  8. The_Aleman

    The_Aleman New Member

    Joined:
    Jul 31, 2008
    Messages:
    2,658
    Likes Received:
    1
    The red Schwinn on my profile had 5 stock 66cc engines in it's lifetime (3x Dax, 2x GT5). I blew my first Dax engine at 300 miles trying to hit 30MPH with the 44T rear sprocket. Con rod gave out. I put a GT5 in there and laser-cut an adapter to take 130mm BCD 5-bolt BMX chainrings, then slapped a 39T on the adapter. 30MPH was then cruiseable, but still revved too high for my taste - indeed, that GT5 failed after 1200 miles (con rod), and I replaced it with another and switched to smallest sprocket my adapter would take - 34T.

    With the 34T, 30MPH was a pleasant cruise and topped out ~42MPH (load limit). By my estimation, that's 3HP or slightly less, and the tag on the engine said 2.85HP. Some sites do claim 5-6HP, and maybe these engines can make near that with porting, tuning, and an expansion chamber. I watched Baird do over 50 a couple times, and his engine had to be making at least 4HP to hit that.

    Of course it seems no 2 Chinagirls are truly the same, not to mention the builds themselves, so mileage is going to vary. Yet it's easy to call BS on a lot of these speed claims with 44T sprockets.
     
  9. Nashville Kat

    Nashville Kat Active Member

    Joined:
    Apr 20, 2009
    Messages:
    1,427
    Likes Received:
    1
    I'm sure I can get over 30- only by how much is in question- someday I'm gong to put that cheap electric speedo on and see what it says- got no one to drive behind to check my speed

    I have "dual" suspension- a front mountain bike style front fork and a shock seatpost on the Micargi cruiser

    a 66 with a 66 carb and a billet intake give me enough power with a 36 sprocket- I don't like to open it up but I would for a bit to see what it will do- I can keep up with traffic in a 30 zone if I want so that's probably close to 35

    also got a narrow 27 x 1 1/4 on the front for the roll- still thinking about putting the 27 x 1 3/8 on the back mostly for the weight and roll and then I can carry the same spare tube for both-

    and it would give me at least another mph or two or more top end- a better roll and a slight mechanical advantage with a bigger wheel-
    but it's running well with a 1.75 26 inch tire so I'm waiting

    I also have a 32 sprock I could put on just for speed- an advantage of using a freewheel hub I think- a little easier

    but to ride around town there's no need- I think it might do 40 with that but I'd lose low end torque. (that's a word I learned when Andy Granetelli was racing turbine cars back in the '60's)
     
    #9 Nashville Kat, Apr 6, 2011
    Last edited: Apr 6, 2011
  10. ToxicAz520

    ToxicAz520 New Member

    Joined:
    Mar 11, 2011
    Messages:
    288
    Likes Received:
    0
    I can only do 30mph havent done much but dnt like the vibration. The speed isnt that scary. I worry about someone pulling out on me at that speed. I dnt have a lot of money so I cruise slow about 20-25 cause i wanna save the motor till i can save up to get a spare. I have hit 33mph down hill but that dnt count I is kind of fun to cruise with traffic but not worth some old lady thinking i am a bike not going 30+ and pull out.
     
  11. halfevil333

    halfevil333 New Member

    Joined:
    May 18, 2010
    Messages:
    307
    Likes Received:
    0
    I cruise an easy 35-40 all day, trying never to slow for anything less than certain doom!...
    Take into consideration however; I only weigh about a buck fifty, I've cleanend and port-matched both intake and exhaust, better plug &wire, tuned carb', better airfilter, good grade oil I think is pretty important too!...& of coarse, 36t. sprocket
    I'm hoping to reach Bairds' speeds once I do some more kanoodling!!!

    ...oh, and as far as the suspension issue, I can adjust the spring tension on me home-made monarch-ish forks according to how springy(for beach cruising) or stiff(haulin azz) I want!
     
    #11 halfevil333, Apr 6, 2011
    Last edited: Apr 6, 2011
  12. 5-7HEAVEN

    5-7HEAVEN Well-Known Member

    Joined:
    Aug 2, 2008
    Messages:
    2,364
    Likes Received:
    37
    My friend Hawaii Ed runs crazy speeds over 50 mph on the flats. He's tricked out his HT engine and runs a shift kit.

    I run either a 4.25 hp GP460 engine or a 2.8hp Tanaka 47R on my shift-kit bike.

    My top speed was 45 mph. The engines have power to spare, but the rider backs down. I love the cruising speeds between 25 mph and 35 mph. Over that, and it's a race with Death for me.xct2

    Besides, how am I going to explain to the judge that I was going over 10 mph past the speed limit?:-||
     
  13. ToxicAz520

    ToxicAz520 New Member

    Joined:
    Mar 11, 2011
    Messages:
    288
    Likes Received:
    0
    I have the suicidal coaster brake. I been trying to find a good brake or at least save up for a regular one.Then I can get a hd wheel with a freewheel. Wanna try to figure out how to put disc brakes on
     
  14. djnutz

    djnutz New Member

    Joined:
    May 14, 2010
    Messages:
    22
    Likes Received:
    0
    I have the 66/80 Flying Horse. It is in a 15 yr old Raleigh mountain bike frame. I have also recently upgraded to the CNS racing carb. The old bike frame was 20+ year old heavy steel frame with steel rims. The "new" frame is aluminum with aluminum rims. The old bike would just barely hit 30mph on the flat and there was a lot of vibration. With the new frame and other changes I can easily cruise at 35. This really feels plenty fast enough for me. Everything rolls smooth with no vibrations at all. My top speed on a bicycle was on RAGBRAI last year on my Trek road bike. (yes I am a spandexter) I hit 50mph on a downhill and it was the scariest thing I have done on a bike. If I wanted to go that fast on a MB, I would just buy a motorcycle.
     
  15. DaveC

    DaveC Member

    Joined:
    Jul 14, 2010
    Messages:
    970
    Likes Received:
    0
    I don't think my bike could hit 30 going downhill ;) Then again, I have 28" wheels and the first thing I did was replaced the stock 41 with a 56 tooth gear. Speed here is not inportant, getting up hills is. From what I've read in the bike forums I might have one of the most modified motors as far as bolt on's go. Everything external has been up-graded. When I get a new 49cc I'll be tearing into the 66cc and modding everything possible to make more power and the up-grades needed to handle the output. Right now I've started on that; clutch improvements were needed with what I've done already. It now wants to wheelie when I start it! I have to lean forward to keep weight on the front wheel.

    New motor the first of June, hopefully Spooky Tooth is back online by then :p
     
  16. Shorty

    Shorty New Member

    Joined:
    Apr 2, 2010
    Messages:
    30
    Likes Received:
    0
    My first bike would hit 43 according to the radar sign by my high school. I was running a 66cc Raw motor, well tuned CNS carb, port matched, straight piped, and a 36t sprocket. I only way around 140, and took as much weight of my bike as possible. It also had really low front forks and the handle bars were low so I could lay down on it.

    It was a rush goin that fast, man! Especially with only a coaster break to slow me down. And no, I'm not suicidal. I just really like going fast a lot. And if a wreck, I consider it my homage to the Holy Mother of Internal Combustion. LOL!

    My new bike doesn't go nearly as fast... It hit 26 today according to the same sign. It has a 66cc RAW, not ported yet, stock muffler, 44t, and stock NT carb.
    Im waiting til it broke in to try for a speed record! :D

    Good luck, my fellow speed demons! And be safe out there!
     
  17. James912

    James912 Member

    Joined:
    Apr 12, 2011
    Messages:
    586
    Likes Received:
    0
    I have a 26in Shimano Deore mountain bike with a silver slant 2.67-2.89hp 80cc(technically 66-69)motor slanthead, stock spark plug, 44t, nt carb, stock exhaust and i used an app on my android phone and it said 23mph and it was still trying to catch up to my speed, and i still had like half throttle to go,but i backed off because of all the vibration. My hands were numb in seconds. I went a block in like 5 seconds. lol When i get the sbp expansion chamber and a better carb, airfliter itll go probably atleast 35mph.
    Just my bike alone is worth $200. I got it at a yard sale for $40.00. Its one of those professional top of the line mountain bikes. I use the rim breaks that came on it. They work great. I can stop easily using either one seperately. The back takes a second or 2 longer.
     
    #17 James912, May 5, 2011
    Last edited: May 5, 2011
  18. fall_down_stand_up

    fall_down_stand_up New Member

    Joined:
    Apr 26, 2009
    Messages:
    555
    Likes Received:
    0
    I have a 26in cruiser bike with a 66cc Raw engine on it with a 44 tooth sprocket with stock everything....On flat ground without the wind blowing I have gotten up to 30mph once....
    John
     
  19. mapbike

    mapbike Active Member

    Joined:
    Mar 14, 2010
    Messages:
    5,380
    Likes Received:
    1
    I GPS 39MPH with a 66cc slant HT, head has been seriously shaved, transfer ports polished and matched, intake deburred and cleaned up, exhaust depurred and polished real nice, manic port matched intake, good plug, boot, wire, extremely free flowing exhaust and I'm running a 36T sprocket.

    This thing sounds like it's turning 10,000 RPM's at 39mph, I still dont know how people are getting these approx. 40+mph speeds out of bikes with a 36T sprockets.

    I'd like to know what I'm doing wrong or maybe just failing to do to get over that 40mph hump....because I can't seem to get there with mine and it is a very strong high torque engine that pulls hills like crazy and is just a very good running engine, with a nice cruise speed of 30-32 with very little vibration, I hit 39MPH and it goes flat and she wont turn another rpm period, I would love to have it cruise nice on the flats at 35mph and top out at 40+mph maybe I need to put a 30T or 32T sprocket on it to get those speeds, not sure.

    Peace
     
  20. Greg58

    Greg58 Well-Known Member

    Joined:
    May 1, 2011
    Messages:
    2,849
    Likes Received:
    60
    To be street legal in Ga. i bought a 48cc grubee, after break-in I have got 31 mph on flat roads 35 on downhill. The vibration is what i don't like, 23 to 25 is a nice ride for me.
     

Share This Page