GT50R with Friction Drive or....

Discussion in 'Friction Drive' started by flashstar, Sep 29, 2012.

  1. flashstar

    flashstar Member

    For the last year and a half, I have been dealing with seemingly constant problems with my thatsdax GT50R bicycle engine kit with thatsdax friction drive. I am not bashing thatsdax or Duane since he has been nothing but helpful, but I wonder if I am going down the wrong route.

    I purchased this kit a year and a half ago and purchased a decent Schwinn hybrid bike to mount it on. I got the engine mounted without many problems, but immediately the engine lost compression and shut down on me. After returning the engine to Duane, he broke in another one for me and returned it. The problem was that I used a cheaper "stock" carburetor on this one. Not only did it have trouble running, the university administrators didn't like fact that it was leaking copious amounts of gas and put my bike in the tool room...

    After retrieving my bike and storing it over the summer, I took the engine kit back with me to my home (I attend college in Georgia) and attempted to install it on another bike. Unfortunately, the clutch wasn't assembled correctly, so it would expand prematurely and drag on the clutch bell.. I got a new clutch, but while installing that I damaged my pull starter.

    A new pull starter later, the engine still wasn't running correctly. I ran out of time though, so I returned to school and got my bike back in running condition (it needed a tune-up by now). Then, i spent a weekend installing the engine carefully. The carburetor was still giving me fits, so I installed a thatsdax RT carburetor. Voila! The engine seemed to be running well, I thought to myself. This was after installing a new magneto and spark plug just to be sure.

    The engine cut out on me due to an idle speed issue at one point. When I tried to start it again, the pull starter broke again though! I almost threw it against the wall I was so frustrated! So... I ditched that pull starter and purchased a new "easy pull" pull starter on Ebay (my 3rd so far). Now, the engine was starting properly.

    Thinking that my problems were behind me, I took my bike out for its maiden voyage. I only got a couple thousand feet though before the engine quit on me. It turns out that it probably quit due to its high compression and the fact that I wasn't running enough fuel to cool it off.

    I installed a size 80 jet and ran the engine for a while. Fortunately, it only hit 300 degrees F at idle. I once again tried to ride my bike a couple miles to test it out. This time, I only got about 300 feet before I blew the one-way bearing in my friction drive roller!!! Now, when the engine applies pressure to the clutch bell and the roller grabs the tire, the engine revs freely.

    I checked and while the roller is spinning with the engine, the diamond-pattern drive part is stationary. Apparently, the one way component has failed....

    I'm getting incredibly frustrated with this engine. Duane has been more than helpful but I'm starting to wonder if I am going down the wrong path on this build. Should I go for a rear mounted chain drive system? God forbid, should I ditch this CAG engine and go with something else?

    The engine itself has been great since I got it back from Duane. I just have never had so many problems with a build! The power on this engine is incredible, but what good is it if I can't get more than a couple thousand feet without something breaking?

    What are your guys' opinions?


  2. lowracer

    lowracer Member

    Ditch the cag, I got 3 in a storage box due to problems with all of them.
    I'd keep the friction drive & either get a new 1.25" roller or put the 1" non-bearing roller that came with the kit on there.
    It wont get you as much top speed, but will pull like mad from stopped to top speed.
    The 1" roller is great for hills or a higher revving engine.
    I got 2 Tanaka engines now & they are super reliable.
    Also had a Subaru Robin also with great reliability.
  3. flashstar

    flashstar Member


    I spoke with Duane and learned the importance of keeping the drive roller bearing clean. After flushing half a can of brake cleaner through it, the roller has been catching more like it did when I first tried to ride this bike a couple years ago.

    The CAG is incredible power-wise. It would still benefit from a tuned pipe and my roller is geared more for speed than climbing ability, but it gets me up to 30 mph on a flat much more quickly than my 4-stroke 50cc!

    Thanks for your opinion.

    Can you just smell the premix? :D