I Want To Reach And Maintain 40MPH..I Am So Close!

Discussion in 'General Questions' started by 5-7HEAVEN, Mar 14, 2009.

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  1. 5-7HEAVEN

    5-7HEAVEN Guest

    Using "The Dragon Lady", a dual-engined girlie cruiser to commute 12-mile roundtrip to work. Mostly flat ground with two medium hills I can easily handle.

    Bike and fully loaded rider weigh 300 lbs.Aerodynamics is challenged by full front basket and rider with raincoat always on. Raincoat needs to be worn.

    Twin 2.2hp Mitsubishi engines on friction drive. Front has 1.375" roller; engine screams at 10,500rpm @ 38mph. Stock exhaust, flame arrestor removed.

    Rear engine has 1.5" roller; engine buzzing at 9600rpm with ADA S1 expansion pipe.

    Redline/peak hp rpm is probably 8900rpm.

    Extreme rpm at WOT(wide-open-throttle) at intervals only on a 2-mile stretch of highway. Riding in commuter traffic. Claiming the curb lane.

    I can keep up with traffic. I just want to be able to maintain 40mph for a safety margin.

    When not buzzing at insane rpms, engines and I are cheerfully humming along between 20-25mph. That's at 6900rpm-front engine and 6300rpm-rear engine.

    Engines have never protested but I'm pushing my luck. I need to change something so I don't kill them or wear them out prematurely.

    The simplest and zero-cost solution is to switch the rollers front to rear. Rear engine location is the quietest and the screaming engine can suck on the expansion pipe as a pacifier.:jester:

    Next option is to buy a second expansion pipe for the screaming front engine. However, exhaust must be rerouted; if not the fumes blow constantly in my face.

    Another choice is to buy another 1.5" roller to drop engine rpm. Cost of roller and, drum and spacer w/shipping is $120. Local machinist charges $80 to loosen the drum.

    Staton charges me $14.39 for a pair of bearings w/shipping. I bought TEN on ebay for $30, including shipping.

    How about carburetors, tuning or air filters?

    Maybe offset timing keys to shift power to higher rpms.

    I realize the powerband would shift and I'd lose HP and TQ at the low end ...

    but I have TWO engines so power loss is not an issue.

    An EXPENSIVE and labor-intensive option is buying a 4.25hp GP 460 engine..or two. Clutch issues can be solved with 3000 rpm springs. However, I'm doing research on them to see if they're dependable and reliable.

    Any ideas, fellas?

    I am SO close to 40 mph. That's as fast as I wish to go.
    Last edited by a moderator: Mar 14, 2009

  2. seanhan

    seanhan Member

    Does Mitsu. have a power pack with new carbs and Velocity stack like Tanaka does.
    I have read that It can give you 5 MPH boost.

    Maybe you can see if any go carters are using the Mitsu TLE 43 and find some hot rod carbs!!! or buy some NITRO !!!!
  3. 5-7HEAVEN

    5-7HEAVEN Guest

    Well, I've been using 87octane gas. I'll try 91octane.

    No nitro for me, not even race gas at $15/gallon or whatever it is.

    Notwithstanding the two engines, I'm trying to keep it simple.

    The ADA pipe should push the bike to 40mph.

    I'll go check the go kart forums. Been lurking at gopednations for research.
  4. seanhan

    seanhan Member

  5. DetonatorTuning

    DetonatorTuning Active Member


    you are kind of in a either or situation.

    from the research i did 2.2HP is about the max fully usable on friction due to extra power requiring added down force on spindle to hook up to the point of causing tire deflextion that just eats up the extra power again, thus no gain.

    i have about 3000 mls. on my 460, clutch springs are a MUST. these are the engines that most all the gopeds come with stock. many of the guys over at gopednation have many times more miles on them than i do, and there are quite a few that are running them daily with 15:1 cylinders, custom reed cages and chambers.

    early units were known to have poor cylinder plating, this is being reported less and less all the time now. the pull start is weak and i fit goes CAN take out the flywheel and coil. there are conversion parts available to fix this as well.

    if you look around the 460 is THE bang for buck engine out there at this time. you've been here since before i came on forum and may have followed my build history using this engine. you are not going to have ANY problem with the 460 itself that will equal trying to find a reliable way to harness the power on tap.

    a single 460 with either GEBE or chain will give you a maintainable 40mph WITH reserve speed above that.

    PM me if you want to go into this at more length and detail.

  6. duivendyk

    duivendyk Guest

    GP 460 +Mitsu?.Power reqd. vs. speed curve goes up steeply at 40mph.For each mile increase, close to 8% more power is required.To go from 38 to 43 mph takes about 40%. more power!.You could try a streamlined bike helmet,the kind used in time trials,reducing air resistance is more productive than increasing power.
    Last edited by a moderator: Mar 14, 2009
  7. 5-7HEAVEN

    5-7HEAVEN Guest

    dui, I need to keep my motorcycle helmet.

    If I move my front basket to the rear, that should streamline some.
  8. ZnsaneRyder

    ZnsaneRyder Member

    40 is a good speed for peaks when you need it. If you can get 40, you will probably beat cars, as many people drive slow, and it's nice to go past them.

    In say a 30mph zone with no bikelane or sidewalk, I find it MUCH safer to go 30-35mph in the lane like a regular vehicle. It sure beats riding at only 20 and nearly getting hit by cars or having to ride in the grass.
  9. macarollo

    macarollo Guest

    I think the easiest way to hit 50 is get a smaller friction drive...

    Reduce the RPM on both engines.... since you have 2 you probably have plenty of power anyways for acceleration.

    If you reduce the RPM you will also help the engines last longer.
  10. 5-7HEAVEN

    5-7HEAVEN Guest

    I hear ya, Znsane.

    I try not to drive below the speed limit, unless of course if the flow of traffic is below the limit. If I claim the lane there's a buffer zone so cars shouldn't have to zip by closely.

    macarollo, I'm shooting for 40mph, not 50. Another 1.5" roller will definitely benefit the engine and might push for higher top end.

    Maybe a combination of oversize roller, relocation of front basket, more tire pressure, less cargo.
  11. Happy Valley

    Happy Valley Active Member

    I'm curious what the moped laws in your state say is the legal top attainable speed?
  12. mabman

    mabman Member

    The 5-0

    To be considered a "bicycle" under Hawaii law, a vehicle is required to be human propelled only.
    A scooter with a motor of any kind must meet the State of Hawaii's safety guidelines as required of mopeds.

    [Sec.291C-127] Coasting prohibited. The driver of any motor vehicle when traveling upon a down grade shall not coast with the
    gears or transmission of the vehicle in neutral or with the clutch disengaged. [L 1971, c 150, pt of Sec.1]
    Sec.291C-202 Moped equipment requirements and inspection. (a) Every moped offered for sale for use upon, sold for use upon, or
    used upon the roadways and highways shall be equipped with:
    (1) A motor having a maximum power output capability, measured at the motor output shaft, in accordance with the Society of
    Automotive Engineers standards, of two horsepower (one thousand four hundred ninety-two watts) or less and, if it is a combustion
    engine, a maximum piston or rotor displacement of 3.05 cubic inches (fifty cubic centimeters) and which will propel the moped,
    unassisted, on a level surface at a maximum speed no greater than thirty miles per hour; provided that those mopeds, including
    those modified pursuant to section 291C-206, registered prior to April 23, 1998 shall continue to be subject to the prior
    thirty-five miles per hour maximum speed limitation; and
    (2) A direct or automatic power drive system which requires no clutch or gear shift operation by the moped driver after the
    drive system is engaged with the power unit.
    (b) The director of transportation by rules and regulations, pursuant to chapter 91, shall establish criteria which shall
    comply with approved federal regulations for the following moped equipment: brake system; fuel system components; exhaust system
    components; steering system; handlebars; wheel rims; fenders; a guard or protective covering for drive belts, chains and rotating
    components; seat or saddle; lamps and reflectors; equipment controls; speedometer; retracting stand; horn; and identification
    (c) The director of transportation by rules and regulations, pursuant to chapter 91, shall establish criteria and procedures
    for the annual safety inspection of every moped. Safety inspection criteria shall include the criteria established by the
    director of transportation under subsection (b). [L 1978, c 175, pt of Sec.15; am L 1979, c 107, Sec.2; am L 1998, c 25, Sec.1]
    [Sec.291C-203] Certification of compliance. A person engaged in the business of selling mopeds shall provide to the director of
    finance of the county in which the mopeds are sold a certificate from the moped manufacturer that each class, type or model of
    moped offered for sale or sold meets the performance and equipment requirements of this part. [L 1978, c 175, pt of Sec.15
    4. HRS_0291C-0191.HTM
    [Sec.291C-191] Definition. As used in this part "FMVSS" means Federal Motor Vehicle Safety Standard as prescribed in Title 49,
    Part 571, Code of Federal Regulations. [L 1978, c 175, pt of Sec.15]
    Last edited by a moderator: Dec 16, 2015
  13. 5-7HEAVEN

    5-7HEAVEN Guest

    I Need To Slow Down.

    Originally Posted by Mountainman
    good point HY

    and I have fallen short a few times myself here
    wasn't the right THING to do or say

    at times it all boils down to what we do or what we do not do
    what we say or what we do not say

    I have pushed the -- ride that THING a little far at times

    some of the high speeds mentioned for MBs are a little crazy
    most do not have the skills to be riding at those speeds

    we wish to share in this thread -- The Safe Top Speed
    not the speed attained by a few daredevil's

    ride that thing

    Guilty as charged.

    I need to slow down. My quest for 40mph is probably too dangerous for me.

    Dropping maximum speed down to 30-35mph on the highway.

    I might buy a moped/motorscooter to ride above that speed in traffic.:grin5:
  14. duivendyk

    duivendyk Guest

    Conventional bicycles are not the best vehicles for attaining high speeds,for the following reasons:
    High CG (center of gravity),makes fast stops difficult and hazardous,even with good brakes, especially at high speeds.
    Poor aerodynamics,power requirements increase rapidly with speed (third power law).Because of relatively low rolling resistance,wind drag predominates even at relatively low speeds (above 10-15 mph).So speeds above 25 mph are uneconomical in an absolute sense,although still much better than cars of course
    Limited high speed manoeverability.at high speeds directional changes can only be made by using the gyroscopic effect to 'lean' into a turn (also called counter steering),without this effect it is not possible to lean and consequently to execute a turn,that is to change direction quickly.On a bicycle the gyroscopic moment is limited because of the relatively low weight of the wheels relative to the total mass of rider+vehicle.This reduces high speed agility.Heavier wheels & tires would help,(which is a good idea in any case for safety reasons).If you want to travel above 30 mph,get a good moped or a small motorbike.My first motorcycle a DKW 125 cc,could hit 50 mph (with no head wind) and got over 100mpg and handled pretty well.The drum brakes could have been better it was a decent commuter vehicle (if it didn't rain)
    Last edited by a moderator: Mar 18, 2009
  15. 5-7HEAVEN

    5-7HEAVEN Guest

    :idea:Yep, keep speeds down on "The Dragon Lady".

    Looking to install steel front wheel.
  16. duivendyk

    duivendyk Guest

    Super,the problem with riding around is that everything is A OK then all He** breaks out,and you find out what your ride isn't capable of,which is of course a bit late,as I had occasion to find out a couple of times, and survived more by luck than skill,but it taught me the precautionary principle,check your brakes& be mentally prepaired for trouble& to take action without freezing up.You have no time to mull things over.I once saw someone on the Kurfursten Dam in Berlin on a motorcycle once plow into a truck the came from a side street, which he could easily have steered around ahead of.He froze& hit the brakes.It killed him.
  17. DetonatorTuning

    DetonatorTuning Active Member

    yep, disabling panic and / or the inability to purposely steer into a "possible" injury to avoid "certain" death are MAJOR contributors.

    i was once a passenger in a car involved in just this kind of accident. the driver was so busy yelling and waving their arms around about "what the H#!! is that guy doing ?!!?, get out of my lane !! " that we went straight on in to the collision.

  18. Revorunner

    Revorunner Member

    SPEED KILLS it's a proven FACT.Like the old saying goes,don't do the crime if you can't do the time.Same with riding MB's,don't go fast if you can't handle the Consequences.

    Pretty Simple IMO.:grin5::grin5:
  19. SimpleSimon

    SimpleSimon Active Member


    Speed never killed anybody.

    What kills is the sudden impact. Calculate the G forces involved in stopping a vehicle from X mph to zero in one foot. It can be transients of hundreds to thousands of G's. The human body is remarkably resilient, but exceed its limits of material strengths and the results are catastrophic.

    I watched a Cessna 150 crash years ago, and was the first person to reach it. The pilot and copilot were dead, chests utterly crushed by the impact with the yokes. The young lady in the back seat died as I reached her - securely belted in, no head damage - but both of her feet were torn off at the ankles by the transient G forces, and her neck was snapped forward.

    Speed is great - control is much, much, MUCH greater.
  20. lordoflightaz

    lordoflightaz Member

    Ode to going 40

    I guess it would be nice to go 40. I was on the sidewalk yesterday and 15 was too much, but even if I could go 40 on Bell Rd, I would be nuts to try it I would get killed, They don't see Motorcyles or people walking and if they do they don't care, so me I would just be a light thud sound in passing.

    It would be nice to go 40 on a nice flat road with that kind of limit. Now where would I find one of those? My street has a posted limit of 25, I think I will NOT break the law. If I lived in Glendale, AZ I would be hard pressed to find any street, that was not a freeway, where even cars can go over 40. You leave Phoenix and the limit drops to 40 from 50 or 45.

    It would be nice to go 40 this summer, the breeze created will make 110F feel like 85F. It would not be bad at night when the temp drops to 90F. I have my dual flashlight headlights so folks will see me, but those coming up from behind will still ignore me.

    It would be nice to go 40, the sound from the bike will totally overcome the ringing in my ears, but I can do that at home watching the Speed channel and cranking the volume.

    It would be nice to go 40 and I will I just will get with the rest of the world and use the metric system just like the 48cc bike I am riding does.

    It would be nice to go 50 ...


    Like SimpleSimon said though speed is not what kills it it the abrupt changes in motion that do all the damage.