Rear Mount Engine Kits?

Discussion in 'Rack Mounted Engines' started by Steve, Dec 25, 2006.

  1. Steve

    Steve Guest

    I'd like to hear some reports from those that have the rear mount engine kits on bicycles. Don't know the brands, but the ones that use the toothed belts seem to me to be the best idea? How are they for performance, reliability (this would mostly be the drive/mount system as an engine is pretty much an engine), vibration level, and sound level as compared to one of the Chinese frame mount engine kits.

  2. bamabikeguy

    bamabikeguy Active Member

    Steve: this is the 2004 Popular Mechanics article I found that got me going with GEBE

    Although I haven't tried the 35cc GEBE yet, this guy "Tool Guy" in NM has

    The thing I like is they keep modifying to make it more efficient, for instance late last years the thickness of the belt was increased dramatically, the gears modified, and the depth of the tread made for a small surge in speed.

    I have found the key thing to be properly breaking in the engines, over the first 100-150 miles.
    If you do that right, the engines get stronger, easier to crank.

    The one thing you CANNOT do is let a friend or stranger get on the bike, especially in hilly terrain. The bike/engine gets used to your weight and habits, and bites you in the butt everytime a "newbie" jumps on and doesn't respond when the engine says "hey, either let off the throttle or start peddling to help on this mountain".

    That's why I tell folks "it's like having a horse", and a horse only listens to one owner, everybody else LOOK OUT.

    It is also best to start with a single speed cruiser, which is what my demo bike is, then go to the 3 or 7 speeds.
  3. Steve

    Steve Guest


    Thanks for the links...interesting. I guess what I was looking to hear is, how is the vibration level, and frequency of problems with the rear mounted engines compared to the frame mounted Chinese 2 strokes. I don't have much time on mine (about a half gallon of gas) but I can already see where the thing is going to be problematic. It vibrates really bad, the chain seems to need frequent re-adjustment, and the chain tensioner bracket seems imposible to get tight enough.

    The rear mounted engine totally does away with the chain and tentioner problems, so those problems are gone, but I still wonder how the vibration level compares?

    From the information given in the second article, the 25cc four-stroke engine certainly does not have the power of my 70 cc two stroke, which is expected.
  4. bamabikeguy

    bamabikeguy Active Member


    There are 3 aspects to vibration with rear mounts.

    The first one, actual engine vibration, is negligible, the axle mounted brace really absorbs any vibration, and the noise is behind you.


    The second part involves the front strap. In the Ozarks I hit a pothole and the brace snapped at the hole where it curves and attaches to the fender support. GEBE started using a heavier gauge metal for the straps this year, and as "insurance" I put a long, heavy duty zip tie from the engine bracket to the fender support.

    When I started last year, the first bikes I used were those $100 Wal-Mart Avalons, where the front strap attached under the shock. I'd tap a hole, use a little lock-tite, I never had a problem with that set up.


    The third type of vibration involves the belt IF the ring is not "true and centered". Once I switched to 12 gauge Workman wheels, broken and bent spokes were a thing of the past, PLUS when I snapped the ring on, the thing WILL NOT MOVE.

    The trick is put a little liquid soap or vegetable oil in the notches, snap in the 12 o'clock and 6 o'clock positions, MEASURE. Then snap in 3 and 9 o'clock, MEASURE.

    If you have these 4 spots equal (use a caliper, protractor, or I made some plastic gap wedges), THE TENSION ARM WILL BARELY MOVE. That prevents the tension arm from springing open, or seldom anyway. It adds to the belt performance to make sure the ring snaps on true.


    BTW- before this forum, the only place I found talking about rear mounts was here:

    The discussion really deteriorates at the end, it's pretty funny when they talk about the death trap this kid built for $25. :D
  5. DougC

    DougC Guest

    I have a GEBE 35cc 4-cycle kit. I had it on a RANS Fusion for a bit, but took it off because I wanted to use that bike normally, and I wanted a rack on the back. Also cruising at 27 mph tends to pound the bike a lot, and the Fusion is not a bike intended for much pounding.

    I will likely obtain another bicycle later on just for permanent motorization.

    I like the idea of using a bike with the wide tires (three or four inches) but don't know about the puncture resistance. The Felt Chief has 3 speeds and 3" tires, it is only a coaster brake but when using the motor on the Fusion, I noticed that I did not really need teh brakes too much (the engine has a decent amount of drag when idling anyway). Do they make tire liners/Mr Tuffies wide enough for those tires?....
  6. bamabikeguy

    bamabikeguy Active Member

    You can make your own tire liner if Huffy doesn't have that size, by cutting the sidewall off an old tire.

    My thinking on taking a 2-3 foot peice of duct tape, doubling it on itself, and using that as the first layer is that will deflect nearly anything. About 5 of these doubled up peices laid inside the tire, then the tire liner.

    I guess a liner could also be made of an old tube, minus the stem.

    Then finally the slime tube, only to hold air better, not to prevent leaks.

    That should be enough to ride with assurance that a flat isn't going to ruin your travels.....
  7. DeadBleedRed

    DeadBleedRed Guest

    Rear mounts rock. Mine is a Dimension Edge kit...43cc 2 stroke. Installation is a snap and performance is great...35mph flat out...speeds near 50mph down hill. Doesn't do well in the rain though. Came with an all weather drive wheel (Drive wheels can be easily changed) but don't use it...riding in the rain is a death wish @ speed. Starts on the fly too...

  8. uncle_punk13

    uncle_punk13 Guest

    I like all different kits, as they give different performance and feel, for different riding moods.
    I like the Tanaka 23cc kits for the mellow "sunday afternoon bike ride" without peadaling feel, but I also like the snap and performance of my 80cc Grube. My Island hopper is great for the in -between these two.
    The Whizzer... Forget about it!!! Across America averaging 35 M.P.H., topped out at 43.5 on the flat with no head wind, plenty of torque (some pedal assitance needed in the Sierra Nevada range, and again in the Grand Teton range, due to the atmospheric conditions; fuel too rich)
    The big problem with friction kits is the weather. The drive roller slips in any amount of moisture or dampness. This is why the Dimension Edge kits intrigue me. I don't worry about riding in the wet, I'm in Western Washington, If I only rode on nice days I would ride about 7 days per year!
    How do you like your dimension edge kit? How is the performance on it?
    Rif 8)
  9. DeadBleedRed

    DeadBleedRed Guest

    Performance is great in my opinion. I have never broke 40 flat out....more like 35....but it hauls on down grades. I'm still tweaking my setup & I'm confident I will squeeze out more power. The large drive wheel I use has lousy low end torque, but provides me with the top speed I like. A smaller wheel would increase torque and is suitable for tearing up muddy trails. The off road/ all weather wheel is similar to a grinding stone....provides good traction but increases tire wear. Price is also an kit was about 650 bucks...but I am very pleased with it. Pic in gallery---

  10. Haggard

    Haggard Guest

    Hi all .I designed my own rearmount engine kit using a 49cc 2 stroke.
    i use a chain drive from the engine to a pinion and a v belt from the pinion to the rear wheel. will do 40mph on straight stretch and have topped 50 mph on slight slope. the belt does not slip in the rain and i,ve even ridden in the snow. mind you i do have casts on both arms from the knuckles up. lol
    maybe riding in the snow not a good idea??!!??
  11. Haggard

    Haggard Guest

    a couple more pics
  12. bamabikeguy

    bamabikeguy Active Member

  13. istbenz

    istbenz Guest

    ouch! that doesn't look like it's any fun at all. :cry: :cry:

    can i borrow yor bike while you're down. hahahahaha :D :D :D :D :D
  14. DeadBleedRed

    DeadBleedRed Guest

    You are a lunatic.....but I gotta love it. What kinda hub setup you got there? Just curious...have considered something similar for more "grab". Take it easy & heal up!!!

  15. Haggard

    Haggard Guest

    lol nO u cant borrow my bike . casts or not i'm still riding .
    and as for the hub[​IMG] its just a vpulley that i cut the middle out of and cut grooves for the spokes with a backing piece cut out of an old computer case .lol