GEBE Tension Arm/Belt Junp Issues Solved

Discussion in 'Rack Mounted Engines' started by AndyT, Jul 31, 2009.

  1. AndyT

    AndyT Member

    I have had my GEBE Tanaka 32 kit for a few months. I have really enjoyed it, and have no regrets. I have it mounted on a Novara Metro (from REI) and have run about 2 gallons of fuel through it, and only noticed some problems after the 1st gallon.

    I was having trouble with the tension arm jumping when I accelerate or climb a hill. I also noticed that my drive ring was moving around on the 14ga spokes. After calling Julia at GEBE, I super glued the spoke ring after truing it up, and this helped, but the tension arm was still hopping like mad under power. I added a smaller 18# spring along with the stock one and this helped get the arm under control, but I still felt it "hop" occasionally under power.

    I also noticed that when starting the engine, the whole rack mount was moving around. Everything was tight, so I just thought that was how it should be. Also when revving the engine while holding the wheel off the ground, I could see the belt moving around on the gear. I thought that this was due to the mount flexing, and decided to look into the issue.

    I took the engine off today to get a better idea of what was happening. I pushed around on the lower mount strap, and found it pretty easy to move side to side. When I installed the kit, I added some steel spacer washers to keep the strap away from the paint on my new bike. This kept the strap from seating against the dropout (where the rear axle goes). I found that removing the washers and having the strap tight against the dropout makes a big difference in the stiffness of the mount strap. I do not recommend using any spacers washers at all, not even to help with gear alignment. Use the "tweaking" method on the GEBE site for alignment instead.

    Next, I took a hard look at the tension arm. In my mind there is one flaw that is easily fixed. My arm never seemed to operate smoothly. I made sure that the retaining nut was loose so it wouldn't bind, but it always felt somewhat sticky. I tried using dry lubricant spray and synthetic grease to lubricate it, and while it helped, it still wasn't smooth. In this application, you have two plated steel surfaces acting as a bearing. This is not ideal, and contributes to the stickiness that was causes the tension arm to hang up, instead of tracking right along and following the the belt.

    I removed the tension spring and the arm, carefully put the arm in a vise and got it as flat as possible. I then cleaned off all of the grease from the surfaces. When reassembling, I added a 1/16" thick nylon washer (found it at my local hardware store), with a 1-1/4" outer diameter and a 1/4" diameter through hole. I put the nylon washer on the the tension arm bolt before putting the arm in place. I then added a steel fender washer with the same dimensions, then threaded the 1/4" locking nut in place. I left it just loose enough to move freely. The large washers stabilize the arm, but allow it to move very easily. I then sprayed it with dry lube. Do not use grease or oil! The dry lube will not attract dirt and won't get sticky. The nylon washer acts as a new bearing surface, and makes a big difference. I installed just the original tension spring and left the extra spring I was using off.

    Making the above mod will move your arm 1/16" away from the engine mount. This puts the arm closer to the belt when engaged, but it doesn't touch the belt at all on my setup, so it will not cause any damage. The bearings on the arm work just fine as well, and they will track the belt perfectly. If you try this, make sure you check belt clearance after assembly. Having your tension arm rubbing on the belt is very bad!

    I did a test run, and my tension arm/belt jump problem is solved. The arm tracks right along with the belt, and I don't feel a hint of jumping or skipping.

    When starting and revving the engine, the mount is definitely more solid and flexes less. Having the strap rest against the dropouts instead of resting on steel washers, makes a noticeable difference. It feels more solid when riding as well, and helps the belt track better.

    One pic is worth a thousand words! See attached pics:

    Attached Files:

  2. Happy Valley

    Happy Valley Active Member

    Good post, nice explanation. Timely for me, I'm rehabbing an older GEBE drive assembly getting the kinks out. Gonna hit the hardware store tomorrow, thanks.
  3. AndyT

    AndyT Member

    I'm glad this was helpful. I spent many hours reading and trying different things to get my bike running properly. I also spent time on the phone with Julia and Dennis at GEBE. They were very helpful. I the end it had to do a little re-engineering. I enjoy tinkering, so I had some fun along the way.
  4. BigPotato

    BigPotato New Member

    I have a similar problem with my 40 cc Tanaka GEBE setup. I've only encountered it on very warm days after a long uphill pull. I'll feel a jump/hesitation about once every wheel or belt revolution. If I take a look back at the arm when this is happening I can see it making an extreme and rapid movement at the same time as I feel the jump. I too ascribed the problem to the arm binding and not moving smoothly. I tried grease and other lubes but at best they provided only temporary relief.

    Since it only happens under extreme conditions it hasn't been a huge issue for me but I'll definitely try your fix.

  5. AndyT

    AndyT Member

    Hi BigPotato, your problem sounds very similar to mine. The arm seems to stick and hang up when it tries to follow the belt. The tension arm is supposed to move around some. GEBE says 1/4" of movement is typical. This allows the drive train to deal with the torque of the engine twisting the mount slightly, and with the flexing of the wheel and spokes.

    Let me know if you have trouble finding the nylon washer. I believe it was called a fender washer, and as I remember I found it at True Value Hardware.
  6. mechcd

    mechcd Member

    I had the same problem with my EH035. I used a thin brass washer with graphite rubbed on it instead of a nylon washer though. It seems to be working much better now. Plus it keeps my paint from getting scraped off!

    I also stuck some washers between the U shaped mount and engine bracket to raise the engine a bit for some more tension.
  7. AndyT

    AndyT Member

    New Spring Mod - Resolves Tension Arm Sticking Issues

    I have another fix that I added to this mod. I added a fairly light, 7/16" Dia. x 2 1/2" long x .047" wire, 11.5 pound spring, so that the belt tension isn't altered all that much. I attached it to a washer with a 1/16" hole drilled in it, mounted on the threaded handle shaft that the black knob screws on to. Then I put a large wire tie fairly tight around the stabilizer bar, to create a mounting point for the other end of spring. You can adjust the position of the spring by rotating the washer, so that the arm still disengages (see pic). You have do a balancing act to get the arm to stay put. Changing the mounting point of the helper spring alters the geometry and helps keep the arm/belt under enough tension when in the running position. I found that the original main spring works better when it's moved to where I have the helper spring mounted, but then you lose the ability to disengage the arm, making things difficult. This also gives you some safety factor in case the wire tie fails (not likely).

    The springs came from Lowe's Home Center, in a pack of 4; 2 long and 2 short.

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    Last edited: Aug 19, 2009
  8. Happy Valley

    Happy Valley Active Member

    Good tip on making things better. BTW, thanks for including a source for the springs, I've been looking for some general use springs of that size for other applications and come up empty at my local Indy hardware.
  9. AndyT

    AndyT Member

    The brass washer sounds like a good idea.

    I would consider adding a spring like above instead of raising the engine. Washers can't provide as solid a mount.
  10. AndyT

    AndyT Member

    I usually end up at every hardware store within 15 miles looking for parts. Might as well share a good find.

    If anyone tries these mods, let me know how it goes.
  11. augidog

    augidog New Member

    i've refined tweaking the stock tensioner as far as i can...getting everything flat & true is the key...some great input in this topic...i always carry a spare spring now. my ring is not completely true, so tensioner theory is crucial to me.

    recently, i made a climb to mt st helens that taxed the system pretty hard, long 6% climbs mixed with 40mph+ downhill runs...pretty grueling on the stock the second day, i had added a "tuned" bungee-cord helper that made all the difference.
  12. AndyT

    AndyT Member

    Thought I would bump this for anyone that night need to see it.
  13. augidog

    augidog New Member

  14. fm2200

    fm2200 Member

    It's too bad you had to modify your stock set up, I would think that the GEBE folks would put these items in their kit. This is not the best thing when you only get a little use and then encounter this adjuster malfunction. I think it would be in there best interests, if they made these items you mention available in their stock kit as a standard set up.
    Last edited: Oct 27, 2009
  15. AndyT

    AndyT Member

    Just to clarify, most GEBE owners never have any problems. I tend to be a perfectionist, and always "improve" everything I own. The only thing that I really had to do for my build is add the extra spring. The other mods improved things a bit, but unless you are having problems, or are looking for a project you shouldn't bother.

    Overall, the GEBE kits are well thought out and nicely made.
  16. I had read this before I got my GEBE kit, so I used your ideas from the start. I couldn't find nylon washers thin enough locally so I cut some from a polyethelene bottle in the recycling bin. The bottle was marked HDPE (high density polyethelene). I lubed it with a thin layer of some water proof plumbers silicone grease I had on hand. I haven't needed the auxillary spring as the tensioner has not been jumping at all. So far it is working fine.
  17. AndyT

    AndyT Member

    That's good to hear. The spring mod is only for those having problems with the tension arm. The nylon washer (brass would work as well) is more to prevent any sticking issues that could develop.

    Since not every bike is the same, most come with cheap wheels, and not every kit is exactly the same (all parts have tolerances), some may have minor issues and some don't. There are many variables. The old "If it ain't broke, don't fix it!" applies here.

    GEBE quality is terrific, and they are one of the best companies I have ever dealt with. I will definitely buy more kits in the future.

    I recommend that serious riders purchase at least the Eagle/Velocity rear wheel with the high quality 105ga stainless spokes. I had GEBE install a new drive ring for me on their wheel, and it has worked out great. You won't worry about spoke breakage, and the drive ring runs perfectly true. I wish I had done this when I first purchased my kit.
  18. cpuaid

    cpuaid Member

    does anyone know where i can get a replacement ball which screws onto the tension arm lever? i don't see that part listed on the GEBE site. i've had problems with my tension arm moving back and forth due to the drive ring not being perfectly centered and after a 25 mile ride, i noticed i had lost mine somewhere along the way. right now I have a nylon acorn nut in it's place but it just looks weird.
  19. AndyT

    AndyT Member

    Give GEBE a call. Julia should be able to hook you up with a ball.

    The McMaster Carr catalog does list them, but you will need to figure out the diameter and thread size.

    McMaster-Carr Catalog
  20. cpuaid

    cpuaid Member

    Thanks for the tips guys. I now have a spare belt and spare spring in my back pack. Augidog, it's nice to know that even YOU don't have a trued wheel ring! That tension arm going back and forth drives me crazy.