Honda GXH50 Kit - failure of gearbox, with photos, warranty claim in progress

Discussion in 'Frame Mounted Engines' started by Sketch, Jan 3, 2010.

  1. Sketch

    Sketch Member

    (please see attached photos)

    Just before Christmas, I received my Honda frame mount kit from I put it together over a period of about 5 days and spent a couple days test riding it for a few hundred yards at a time, attempting to get the problems with the chain alignment worked out. Finally, I switched the orientation of the rear chain sprocket and started to get something that worked without kinking and the chain coming off. With more work on the chain tension, I finally felt that the whole thing was coming together.

    I checked bolts and screws for tightness after the test rides. I checked my oil level and the gearbox level, making adjustments. I had followed all the instructions, as best as they could be interpreted.

    After my first longer ride, which was about a half hour of travel time, the gear box had developed holes (see photos 1 and 2).

    I am currently making a warranty claim, hoping to get an entire new gear box.

    Photo 3 shows my bike. It's a little beat up because the trip included getting hit with a snow storm on the trip back to the house. I don't think that could have had anything to do with the metal failure of the gearbox housing.

    Right now I am a little frustrated, but I know these things can take time to work out. I suspect that the "flatness" of the two sides of the gearbox weren't manufactured perfectly enough, and that the pressure from joining them created the stress that caused the cracking.

    Given the failure, it makes me also think that it's a little frustrating that nowhere in the assembly instructions, which are meant for a shop technician it appears, are there torque requirements - which I would kind of like to see for this type of project.

    Comments welcome???....

    Attached Files:

  2. HoughMade

    HoughMade Guest

    I have never, never heard of a failure like this. Frankly, I can not imagine how it could happen without a manufacturing problem.

    I have had the previous generation gearbox (Stage II) for over 2 years and have never, ever had a gearbox problem of any kind. In fact, yesterday I took the gearbox apart to check things out and everything literally looks like new.

    I hope you get this straightened out. This looks like an oddball failure and I would not let this put you off the Honda/Grubee system. I love mine.
  3. professor

    professor Active Member

    Did a tooth come off and break out the box?
  4. ibdennyak

    ibdennyak Guest

    That would be my opinion too. It looks like the type of fracture from an internal stress buildup of some some jammed up inside.
  5. Sketch

    Sketch Member

    I haven't finished digging into the gearbox so I will do that tomorrow. I was in a hurry to get the photos because the service guy asked for a photo when I contacted him about a warranty claim. I was busy with family/holiday stuff for a few days which kept me from taking the time... It sure looks like something might have busted through, I agree. Or, my original theory was just that the two parts of the cast where not flush and the tightening of the cover plate, combined with the vibration of running for a while causes a stress fracture.
  6. It looks to me as if the case was busted out from something on the inside hitting or being jammed into the case. It should be covered under the warranty. Let us know how you make out on your claim.
  7. nsideus

    nsideus Guest

    Seeing that both sides of the case broke I would look internally. I have heard of problems with the newer gear boxes such as broken teeth. I have many thousands of miles on the type II's with minimal problems. I personally don't use gear oil, makes the gear box run hot.
  8. Youngbird

    Youngbird Member

    Looks to me like thats where the chain "kinked" and it smashed thru the case.
  9. Sketch

    Sketch Member

    I got an email reply - they are going to replace. He says I can keep the centr. clutch attached to the shaft and just send the gearbox and gears. ...I'm happy - I'll be back on the road soon.
  10. Mountainman

    Mountainman Active Member

    that's cool

    that's cool

    wonder if that THING got dropped somewhere
    causing a hairline crack
    which later developed into what we see now ??

    since it involves both halfs of case -- ?? thinking not ??

  11. Sketch

    Sketch Member

    Here's the good news though: I'm very happy with the bike and I have a bunch of questions unrelated to this gearbox problem. I'll start a different thread for that.
  12. Same Problem

    This same thing just happened to me last week. My gearbox failed previously. The bell housing got chewed up. I called Jeremy at and he supplied me with the correct replacement parts. There are some pictures below.

    As for the gearbox housing mine blew a hole in the same exact spot. I don't know what could cause this. Were all the bolts that attach the gearbox to the the motor still there? I noticed when I opened mine up, I was missing the right bottom bolt. I am going to call Jeremy back to get the housing replaced. I will post pictures of this when I get home from Seatlle.

    I haven't had much luck with the grubee. I ordered a EZ Q- Matic off Neil in Anaheim. It's supposed to be here this week. Hopefully this will be better than the **** grubee I got stuck with.

    <a href="" target="_blank"><img src="" border="0" alt="Photobucket"></a><br /><br />
    <a href="" target="_blank"><img src="" border="0" alt="Photobucket"></a><br /><br />
    <a href="" target="_blank"><img src="" border="0" alt="Photobucket"></a><br /><br />
    <a href="" target="_blank"><img src="" border="0" alt="Photobucket"></a><br /><br />
  13. HoughMade

    HoughMade Guest

    Wow. I've got me Stage 2 gearbox apart right now with 2 years of use. I'll post pics....and you guys will swear that the thing has never been run. That wear is incredible.
  14. Sketch

    Sketch Member


    I originally talked to Jeremy about not sending in the centrifugal clutch (just everything else), but then I double checked and I have some chewed up edges on the gear that's attached to the outer housing. I'm still waiting for a reply about getting the whole thing replaced (including the clutch)
  15. Sketch

    Sketch Member

    Just got some cool news from bicycle-engines (Jeremy) - he's going to send me an entire new gearbox (sent out today) without having me have to send back the old one - since he already saw how it's messed up via pics. I'm stoked! This means I'll be up and running again pretty soon.

    Needless to say, I'm going to take great care with the installation of the new one. Whatever I can do to help prevent a repeat...
  16. Danny3xd

    Danny3xd Member

    Klien and Sketch, just wondering what, if any grease you used? I had that happen 2ce. Used white lithium.

    Jeremy and are great. Really good service.
  17. HoughMade

    HoughMade Guest

    OK, here is my clutch bell and intermediate gear. The brown stuff is old grease I have not cleaned off yet- like I said- brand new. Doesn't even look like anything has touched the bell itself. Those marks on your clutch bell are very odd.

    Attached Files:

  18. Sketch

    Sketch Member

    You run it dry?
  19. Sketch

    Sketch Member

    I greased up before assembly (can't recall the exact was general purpose gear grease). Then I filled with 50 to 80cc's gear oil as instructed. (again, I don't have the stuff in front of me so I can't tell you what exactly it was). I didn't have any synthetic lube to use.
  20. HoughMade

    HoughMade Guest

    I have run my gearbox with grease, with 50-50 gear oil and stop smoke, and auto trans fluid.

    In other words, I doubt lubrication had anything to do with you troubles. As for Kline and that chewed up clutch bell, I really don't understand that. I understand that soft metal will result in the teeth getting chewed up, but I am referring to curved gouges on the bell itself. As you can see from the pics of my bell, nothing has ever touched it. Even with good metal, if there was contact, there would be a mark of some sort. That really looks odd.