GEBE Dooz and Not Dooz - Reveal Your Trix Bike-Wyz!!!!




Basics (and see also the "sticky" on How GEBE systems work.)

Let's keep it simple suggestions as starters - tell it here!.

GEBE kits allow 100% free wheel pedaling.

Bike having wheel with internal transmission shifter cable entering axle from end will not work. Will have to switch trans or go to coaster only.

Be sure to measure bike correctly - best not to buy bike with incorrect measurements; You need 1.25 inches from closest spoke at point 7.25 inches forward of rear axle - see GEBE site. Guessing seldom works. Ask first.

Thin (700) wheels and road bikes are not really safe or comfortable, though they may be ones you have. You are better off finding a used cruiser or MTB and going from there. Used MTB are all over the place and cheap.

Engines, yours or GEBE are all better off vertical or very close to vertical to max fuel fill.

High horsepower is not a big deal. You do not really want to move a cruiser or MTB faster than 15 - 20 mph; bad for bike, dangerous for you. Engine weight and noise are factors. Need speed, get a different rig.

Be sure Fuel Tube extends all the way to bottom of tank. It is not good for 2-cycles to run dry and you want to use all available fuel. You can find fuel tubes at local mower dealers. Not difficult to remove tank and R & R the tube.

Only start and run engine with drive belt in place, per GEBE.

Run 2-cycles as recommended. Rich break-in formulas are urban myths. Engines are chrome-lined and built to last.

Break-in is 1,500 to 2,000 hours.

Two brakes. Coaster plus or any other sets.

Larger tires , say 2.25 size can cause problem, BUT, you can place SS washers between drive gear and spindle to move belt outward; and move engine around on mount per GEBE site, so belt is not rubbing on drive ring or tire. I ran engine with big Bontragers and no problem, but I guess the rule should be only as wide as practical and that may be limited to 2.00 inches, so extra tweaking is not needed or will downgrade performance. Am using 1.95 Armadillo now and it is perfect. Comfy ride and no adjustments needed. It is also bulletproof.

36-spoke rear wheel is best option and these are available from GEBE, prevents slippage of drive ring more likely with 34 spokes.

High rev starts without pedal assist will also cause spoke problems and slippage, I understand.

Longer axle - 8.5" minimum is recommended, so you may use SS washers between nuts and lock mount to axle mount nut, etc. If you use a 9 incher, maybe ss acorn end nuts will protect the threads best. My 8.5 is nutted to ends.

The main engine axle support can be easily spread and drilled for additional support bars, lights, etc.

The single engine support bar can be any material and can be bent as needed and mounted to seat post, cross bar supports, seat bolts, etc. Normally, the two strips that they supply will cover most applications.

Bolts supplied by GEBE can be replaced with SS.

Rear fender may not have enough clearance under engine with fat tires, and this can sometimes be fixed by drilling hole in fender where nut is located - rare.

Drive ring is self-centering, if you get the spokes lined up correctly. I used WD-40 (not the spray) to install drive ring and wiped off, but soap needs to be washed off to prevent rust and problems with painted spokes. Need to reduce potential slippage of ring.

Replace throttle and stop button clips with SS hose clamps.

There is site on install on CF bike here: and another by Lee here: First shows problem solving and logic to compare to your situation and how you might do differently. Second site has loads of links and info. Good stuff to review.

Pedaling bike under power is what lots of people do. Steep hills will often require pedal assist.

Look for separate thread on making throttle cables.


Active Member
Sep 30, 2006
You learn something new EVERY day, and this is a DON'T.

Don't by a 3 speed/coaster brake type cruiser AND expect you can changed to heavier 12 gauge spokes.

I ordered the bike, picked it up today, and just found out it has an expensive internal hub, could cost $100 to change out to heavier spokes, can't be drilled for re-lacing. :???:

Learn as you go, this will be the first and last 3 speed I build for someone.

I'll sell the kit to them, show them how, but I want to stand behind the builds, and 16 gauge has proven too weak to handle the torque.

AND, I read the discussion about 3 speeds BEFORE I ordered, I thought the issue was mainly usage, not axle length.

Consensus seems to point to either single speeds or seven speeds.

Luckily, its for a lady who won't be going fast, with the mountain gear installed, and I'll take extra care on the spoke ring installation.


Here's my GEBE

Here's my experience blog.

My bike is a Trek 850 about 9 years old.
Other than a gear hub issue everything is fine.

Oh yes, also my brake cable is center set and so is the seat brace bar so I had to bend a little.

IF YOU CAN, order the steel spoke rear wheel rim. GEBE will install the proper bolt and drive ring for you.

Also, recommend a seat post shock absorber. I still have not got one yet but will.



Active Member
Sep 30, 2006
If you are going to build bikes for others as a hobby, there are 4 main pieces of equipment which will enable you to save a LOT of frustration.

I got my basic bike stand for about $120 through my bike shop, including shipping. The only thing it lacks is one of those trays to put parts and tools in a handy spot, but it flips the bike over for easier wheel installations and brake adjusting...


Before I got into serious advertising for business, I had a "broken" garden fork (one prong always survives), attached at counter height, to keep a wheel off the ground while I adjusted things...

But now that the newest 25cc's have the motor attached with 4 small Allen's bolts, instead of the single mounting bolt on the old drive shaft models, the bike stand comes in REALLY HANDY when attaching the entire motor and axle mount on a bike in one fell swoop...


Second thing to have is a table vise, mine's antique. Before GEBE added the 90 degree angles AND increased the gauge of the straps, there was a lot of bending to make a good attachment, especially to the fender brace, but the angles make that type installation easier nowadays....



BTW: this pic is for demo purposes, it is best to heat the newer heavy gauge strap if a bend is necessary...

I picked up a simple bench grinder for $35 at a flea market. Sometimes a quarter inch of the strap has to be removed to reattach a fender properly, and when using radiator hose clamps to attach the throttle, the end has to be narrowed to slip into the throttle's "slot". You can just take the hose clamp to the grinder and take a bit off both sides, thread it into that slot, then pull all the way thru with needlenose....


My last purchase was a small air compressor from Northern Hydrolics, about $70. I got so frustrated one day seating the tires into the rim, especially inflating/deflating/inflating/deflating those slime tubes three times or more, using a hand pump, that I broke down and got this small compressor.

It also will be necessary handy if you need to blow out carbon buildup in an engine after a few thousand miles ...



Active Member
Sep 30, 2006
If you take a pencil and push it into the exhaust, you will find there is a screen.

Things are running smoothly until one day, after maybe 700 miles, you start losing horsepower, hiccuping or having coughing type performance.

The screen is clogged, theoretically you are supposed to remove the screen, brush it clean and replace it.

I toss them out right off the bat.


They are attached via a "collar". Take your needlenose and grab the very end of the exhaust, then pull a bit at the 6'clock, 3o'clock and 9 o'clock, the collar should pull free with little effort.

The collar is VERY narrow, maybe 2-3 millimeters, so barely bite in with the pliers.


Active Member
Sep 30, 2006
There are basically 3 places to attach the front strap.

1. to the fender brace, which is where I do my bike of choice, the Sun 7 speeds.

2. tap a hole into the bike frame, secure with a very small bolt and loctite the newly threaded hole.


THERE IS NO WORSE FEELING, than to be cruising down the road, and something snap or give or pull away, have that strap "come loose" and the engine slip backwards, pulling the throttle to full blast.

For insurance, add a zip tie somehow, somewhere, to be a backup for the strap.


Oh, the third way to attach the strap probably is the one where no zip tie is necessary. You ream out the hole at one end of the strap, twist it 90 degrees, and attach it to the seat post, where that bolt is a bit larger than the hole.



When I got the drive ring on the Worksman wheel I found that there were several high and low spots of the drive ring visible as the wheel rotated. I didn't want to take off the ring and try again because I didn't know how well the self-cut notches would take it.

What I found was that it's possible to smooth out the high and low spots by moving the ring around on the spokes. You put your hands together and push down with your thumbs, while pulling outwards with the outside of your hands, and you can get the ring to move a bit on the rim. A couple minutes of fine-tuning and it was possible to get the ring so well centered that I couldn't see any more definite high or low spots at all.



Active Member
Sep 30, 2006
A customer just called, saying one of his engines was having a time cranking, and I e-mailed him this response about a "fluke/fix" on the kill button.

This happened once, I've never been a fan of the "kill" button that comes with the kit.

If an engine fails to start, disconnect that wire at the engine and see what happens.

If it cranks, that means the wire, right beneath the button on the handlebar, may have cut through the plastic coating due to vibration.

To fix it, take a plastic straw, cut a small piece off the end, then cut a small "shim". Loosen the screw a tad and slip that shim between the wire and metal and retighten the screw.

That fixed my "kill" button permanently, but when I carry my tent I can't get to the button, so I just got into the practice of reaching back and flooding out the motor.