Honda GXH50 QXA engine swap, fuel pump, throttle linkage

Discussion in 'Off Topic' started by bikeguy53, Aug 20, 2010.

  1. bikeguy53

    bikeguy53 New Member

    I have installed a Honda 50 engine on my Goped scooter. I came to this site by Google looking for the answers to some questions I had while doing this swap. I got some good ideas, but I have something to add to what has already been posted.

    My first problem was the clutch mounting bolt pattern. After looking at several engines online and failing to find specific information, I finally just bought an Engine from someone on Ebay who was closing them out cheap. When the box got here I ripped it open, got out my ruler and started measuring. Then I called Bicycle-Engines. Now I know why I was confused. The Honda clone comes in two versions, the standard 78mm clutch version and the exact copy with a different bolt pattern. This was actually a good thing, though at first I was peeved.

    I ordered the staton-inc. clutch adaper package. What a joy to install. It practically installed itself. The clutch has the perfect engagement point, (3,300rpm) and really nice engage/disengaging action. A pleasure to use.

    I tried two different fuel pumps, a chinese 4 stroke scooter pump, (very small) and a Mikuni pump. Neither would pump fuel reliably. So, again I turned to the expensive solution and bought the official Honda part. When it arrived I saw what was missing on my other pumps. The Honda pump has a vent that allows the crankcase to breath through the pump. Since there are no instructions anywhere online, I tried the direct approach and attached the pump directly to the crankcase vent. Perfect, gas jumped out of the pump outlet. I turned the fuel inlet elbow 180 degrees so the tubing would attach without kinking.

    Finally, the throttle linkage. After reviewing the pictures here, I designed what I think is the final and best design. Since I wasn't using the stock tank, I used the bracket and cut off one of the mounting tabs. After a bit of judicious carving, I came up with a bracket for the cable adjuster. The nut on the bracket is the same thread size. Then, I got a cable blank from the gokart shop, and added a bicycle brake cable "noodle" to the stock Goped cable housing, and soldered on my cable end. I left a little tail on there, and it makes connecting and disconnecting the cable a breeze. The final trick here is the Zenoah throttle pivot and throttle spring, both from Dave's Discount Motors. I made a little aluminum arm that attaches to the two existing holes in the carburator's butterfly control.

    Ok, I think that's it, if I have left anything out let me know. Now I see that I have posted to the wrong area, help.

    Attached Files:

    Last edited: Aug 20, 2010

  2. 5-7HEAVEN

    5-7HEAVEN Guest

    Something's Missing!

    Yes, you left something out. Where are the bike pedals?

    This is a motorized bicycle forum, sir.

    :jester:LOL! Naaah, just kidding. Welcome, bikeguy53, and thanks for sharing what you've done.

    I've surfed the goped site, bought a rare Tanaka 47R engine there, and gained useful information from some of its members. A different bunch, but hey, whatever turns them on.:jester:

    Welcome again.
  3. bikeguy53

    bikeguy53 New Member


    Thanks for reading my post. I have gotten several tips here and I thought I would give my final results. The throttle linkage thread was a few years old, but I thought I had a more elegant solution, and the Honda clutch thing has been in confusion for a while. I was never able to figure it out by reading online, so I tried to clarify that as well. Oh, and the fuel pump threads didn't really have a deffinitive solution, so I tried to show that as well. Since it is not a bicycle, I got moved to the white Zone, which is appropriate. There is a lot of technology transfer from the gopeds to the motorized bikes, since most of the engines are the same and they have many of the same issues.

    My last issue is with the fuel tank. Now that I have this enormous engine on here, I need a bigger tank to balance it out. I think it would look trick with an old syle metal tank with the soup can edges, like an old Salsbury.
  4. rawly old

    rawly old Member

    glad it worked out for you. I wasn't all that thrilled to discover the
    engine I got from wasn't what I thot I was getting,
    but having spent the extra $122+shpg on that Staton adapter, I have
    made lemonade & put it to use. It hangs further outboard on my bike
    than I would have liked,not really an issue with your scooter, but my
    bike has a much higher center of gravity.
    I solved the fuel issue by making my own siphon-type carb adapter
    which has worked well so far. luckily I had just the right tubing on hand
    for the blow back.