Fat man needs advice

Discussion in 'Friction Drive' started by AquaManAndy, Jul 18, 2016.

  1. AquaManAndy

    AquaManAndy Member

    Ok guys im new here I have a little bit of motor experience I had a 2 stroke 80 cc inframe motor with a shift kit my much more mechanically inclined friend put together for me, and right now I have a GEBE honda gx35 setup on my current bike. I like it alot it was simple enough i put it on myself and it seems very reliable. Here's my question: Im 260 lbs before gear and i live in an area with lots of hills, i love my engine but its under powered when I try to ride up hills, I pedal and everything but it feels like the motor is barely helping me. I know its because I need to lose weight, Im wondeting would it be smart for me to get a second motor to power the front wheel? Such as a staton friction drive or even another gebe kit over my front tire? I need more torque and power for these hills.
     

  2. David Bogle

    David Bogle Member

    Why do you prefer friction drive?
     
  3. jaguar

    jaguar Well-Known Member

    35cc 4 stroke engine theoretically has 1/4th the peak power that a 66cc Grubee 2 stroke has.
    ?Why not one of those and if it's still under-powered then do some simple mods to it.
     
  4. Frankfort MB's

    Frankfort MB's Well-Known Member

    He said he's mechanically inclined.
    I don't think the grubee motors are that hard to work on. Simple parts to learn
     
  5. jaguar

    jaguar Well-Known Member

    cool. chunk that 35cc engine. it's power is for lightweight kids on flat roads.
     
    Frankfort MB's likes this.
  6. AquaManAndy

    AquaManAndy Member

    It looked simple to put on
    i cant say i prefer it i was looking for another set up to similar to my gebe engine but cheaper. I figured a friction drive motor could sit over my front wheel and power it
     
  7. AquaManAndy

    AquaManAndy Member

    I didnt like all the problems that came with my ht, it was powerful but power is no use when it breaks down far from home.
     
  8. jaguar

    jaguar Well-Known Member

    good point. you have to get a nut/bolt kit from SBP to replace the buttery original ones.
    also you need to drill a couple holes into the crank wheels to get rid of engine vibration.
    and a good aftermarket CDI can replace the crummy original one which fails easily.
     
  9. Frankfort MB's

    Frankfort MB's Well-Known Member

    In a few years, jag will have the most reliable HT engine anywhere (and might already have it)
    He knows his stuff if you use his products or take his suggestions you'll have something more reliable with more power.

    I've had good luck with minor things upgrades but I havent had problems that could be prevented (maybe prolonged) so I don't have a reason for CDI boxes or upgraded parts.... I've just got lucky:)
     
  10. AquaManAndy

    AquaManAndy Member

    Any other suggestions you have for ht engine? I have one from bikeberry that is brand new
    Any other suggestions for a ht?
     
  11. jaguar

    jaguar Well-Known Member

    click on my signature link if you want more suggestions than you'll know what to do with
     
  12. JunkyardDog

    JunkyardDog Active Member

    I am on the heavy side myself. I went to a friction drive because I was almost killed by one of those Chinese chain tensioners getting pulled into the rear wheel. I have a Honda GX35 4 stroke. I do have to pedal to get it started, but once up to speed it will pull me along nicely at around 20 mph on flat ground. I'm in AZ, and the MB speed limit here is 20 mph. It needs a little help on steep hills. A smaller roller would help there, and I may change to one. I don't really need to go over 10 mph, which is about the speed of a pedal bike around here.

    However, I may be doing another Chinese engine build in the not to distant future, as a couple of products have come out since my crash that solve the two main problems with the Chinese kits. An engine mounted chain tensioner, and a clamshell rear sprocket mount. Yes they are expensive by the standards of this forum, they would add almost $60 to the build. But I expect the total to be close to $800 by the time it's all done, including the cost of a high quality used bike from Craigslist. Older name brand steel framed mountain bikes with small diameter frame tubes work well, and already have good front brakes. I convert them to very low geared single speeds.
     
  13. Tibilt

    Tibilt New Member

    I been doing some reading and YouTube viewing. Plus through life experience I know two cycle engines just have especially more bottom end torque. There RPM's are way higher like 8000 to 12000 in comparison.

    Stanton has a .93 friction roller where they seem to run one to one and a half inches most other sources. I know the size don't seem like much, but an old trick is to take 3 teeth away from the front sprocket instead of adding twice that many on the back sprocket.

    I weigh 360 lbs. I'm getting the Stanton kit with the .93 roller and a Tenaka or Zenoah @ 40 cc two stroke motor. See we need a mule rather than a stallion in terms of roller size. At full throttle a 4 stroke is turning 133 revolution per second where a two stroke is turning 200 revolutions per second. That an two cycle low end torque is the solution. Oh course some of that gets lost in slippage on the tire, but more is transferred to the rubber on the road.

    You might try seeing if the .93 roller will fit before replacing the motor. Call Stanton, he WILL call you back.

    I'm in save up stage. This is pricer,but like you I need to use my bike for exercise, but need to get my ya ya's out too.

    I will report back my results on this idear/therom.

    Somewhere there is a kid with a Tanaka 2 cycle friction drive on YouTube that is having noooo trouble at all with power/speed.

    Tibilt
     
  14. Tibilt

    Tibilt New Member

    Oh, play with more and less roller pressure on the tire. The Bikeberry friction drive video says there is a sweet spot.

    All the best!
     
  15. jaguar

    jaguar Well-Known Member

    If you look at horsepower graphs of 2 strokes (with expansion chambers) and 4 strokes you will see that 4 strokes have more low RPM power (as a percentage of their peak power).
    Maybe without the expansion chamber the 2 strokes would be even. I don't know but I doubt they would.
    But since the law requires the same engine size limit for 2 strokes and 4 strokes then the 2 strokes have the advantage in power because they have twice as many power strokes for the same RPM.
     
  16. JunkyardDog

    JunkyardDog Active Member

    The more I think about it, the more i think you need a 4 stroke shifter bike. While My GX35 friction drive works fine in the desert, it would not be suitable for mountains, and we do have mountains here. I was unable to climb those mountains with a 125cc CVT type scooter, because it did not have a low enough gear range to pull me up the mountains. It lugged the engine badly. But a 125cc manual transmission motorcycle had no trouble climbing anything I could find. Yes it was slow, but the manual transmission kept the engine rpms up and it just kept going. Gears are everything. With the right gearing, a 50cc motor will climb almost anything. Shifter bikes are not cheap, but you could have someone build it or buy it from someone. Being close to your weight myself, I have never been able to climb much of anything with a small engine without a super low gear ratio. A low enough gear ratio for climbing is going to be too low for flat roads. That's why pretty much all motor vehicles have several gears, either manual or automatic. Same thing applies to pedal bicycles. Internal combustion engines simply do not have the ability to operate over the wide range of speed and load conditions you need.
     
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