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

[biketec]

The grooves you see are due to a warn bushing or loose bell there should be almost zero play on the primary drive. The reason for the bushing is so it wears and not your crank like the Hoots, In a perfect world it would be a bearing in there, but again in a perfect world I probably wouldn't be sitting at work in a snow covered arctic circle I seem to have fallen into I would be filthy rich in the sun on a beach somewhere!
Long story longer the primary was loose in there and that's what caused the markings and 99% of all gear failures! and possibly the broken cases. Not pointing fingers but there's always a method behind the madness and it also could have been a combination of all the above including a bad casting hit just right no clue!

MORAL: New gear box was sent out and you should be up and running in no time free of charge!
If you hear the gears chattering remove cover and inspect! A loose bolt could save you time and money LOL 15 minutes could save you 15%

 

[HoughMade]

I also have no visible wear on my bushing. I think people should keep in mind that the bushing will only wear when the engine is running and the bike is sitting still. When the clutch is fully engaged, the crankshaft, clutch shoes, bell and bushing are all turning the same speed so the relationship between the shaft, bushing and bell is as if all are still.

Try not to let the bike idle still. As MM would say, "Ride that THING".

BTW- the only place I used red loctite on my bike (that I can remember) was the bolt holding the bushing/bell on the crankshaft. When I took it off (a few days ago after 2 years assembled) I heated the bolt by placing the flame of a MAPP torch (about 1/2 strength) on the bolt head. It came off with very little heat, that is, not enough heat to affect temper. By sticking a screwdriver through a hole in the bell and between the spaced on the shoes, I could hold back against rotation and loosen the bolt with a large, flat screwdriver. In other words- fear not the red loctite, fear the loosened bolt.

 

[jblossomgame]

Do you use gear lube in your gearbox? If so, what kind?

 

[HoughMade]

The short answer is "yes, always"....but from there it is a long trip.

At first I used regular grease on the gears, not a lot. Everything worked fine, no discrnible wear, but had some gear whine.

I then switched to a 50-50 mix of 80/140 gearlube and "stop smoke" as suggested by a vendor who sells these kits. That seemed to allow for smoother takeoff, but eventually it led to slippage and the gearbox would get hot. However, the gearbox was quiet.

From there, I just drained that mix and threw in some ATF (Dextron III) and that was the same as the mix above (but I did not clean out the gearbox or even open it before making that switch so I don't know that all the mix was out. The gearbox was still quiet.

Then I went to a lot...and I mean a lot of "Green Grease" which is the stickiest, stringiest, waterproof grease I could find. Much less slippage, if any, quiet. However, it felt like that was sapping some power...as you can expect.

Now, I am working on improving the gearbox. All the rotating pieces are being lightened (speed holes baby!), polished, and some sort of strength treatment is being considered (originally cryotempering, but I am looking at other options as well). I would be a shame to run gears with that kind of care lavished on them in thick grease. Therefore, I am looking at my options.

 

[Irish John]

Sketch, I reckon Jeremy is right. To have made those marks on the bell and to have ground through the teeth the bushing must have been too loose. I think that if you assembled it correctly (and many first timers, including myself, don't get it all assembled perfectly) then the damage to the bell bushing may have been caused by two ill-fitting halfs of the gearbox casing. I've noticed lately that some (actually most) of the Grubee gearbox casings can be badly machined so that when you bolt the outer casing on you can see that it doesn't really want to fit tightly at both ends. I have to grind the casings to get a snug fit using dental paper to tell me where the grinding needs to be.
I resent doing this because it shouldn't be like this - playing the unpaid dentist with a blasted dremmel. I feel Grubee owe me months of wages for fixing their negligence. When you bolted the outer casing onto the gearbox with the gasket in place did you notice it see-sawing like if you tightened one end the other end popped out and didn't want to go in? If you forced it in by tightening the bolts it will cause stresses on the two gearwheel shafts and that could lead to rapid wear and distortion inside the gearbox. The bit that broke off may have been blown out by a piece of gear metal or was more likely severely stressed by being one of the many badly fitting gearbox cases that had been bolted tight just like it was supposed to be. I am pretty certain it is a case of a badly machined gearbox case that after being tightly closed exerted a distortion on one of the shafts and caused the bushing and maybe bearings to wear rapidly leading to major damage inside.
This is another quality problem and I have often had to mix and match several gearbox covers to get the best fit and then do a bit of grinding to improve the fit. Sometimes its hard to get the two shafts to go into the bearings on the outer cover and I have to tap a lot with a rubber mallet to get them to go in so the cover can be bolted tight. Houghmade's GB is a beauty and I have one like it that I got from B-E. Com about the same time.
That gearbox (Mark2) is the quietest Grubee gearbox I've ever had and I've had nearly 20 of them. I let it go to a customer last December who was demanding his money back because of his noisy gearbox and now I never hear my Honda because of gearbox whine. I think that there was a batch of GBs that Birddog got where the two shaft bearings on the outer casing were just positioned right and I strongly suspect that on all subsequent castings the position of those two shaft bearings has been out by a few microns and that is where the noise eminates from - not from the gearteeth but from shafts that are not aligned perfectly and cause the gears to whine like crazy. It's just a theory but there must be reason for the excessive whine on posr March 2008 gearboxes. Machining is everything and I keep about a dozen shaft bushings because those actually vary by a few microns too so that I can obtain a good fit by mixing and matching. It's not easy working with Grubee products believe me - especially if you're selling the finished product. Do Grubee supply a dremmel and dental tape? Not yet is the answer.

 

[HoughMade]

I was not impressed with the clutch "finishing". The shoes were OK, but when you remove the shoes, the iron center was rough....was. It's smooth now. Speed holes are planned for the shoes. On the bell, I enlarged the present holes and added 7 more. When I get these polished up (initial smoothing is done) I will post pics.

 

[Irish John]

I was not impressed with the clutch "finishing". The shoes were OK, but when you remove the shoes, the iron center was rough....was. It's smooth now. Speed holes are planned for the shoes. On the bell, I enlarged the present holes and added 7 more. When I get these polished up (initial smoothing is done) I will post pics.

Good on you HoughMade - a true pathfinder - I am interested in the performance report when you've done the improvements. I thought you used just lithium grease in your GB nowadays. I am amazed that your bushing hasn't worn out and put it down to having your gear engaged all the time. Have you worn out the 11T freewheel yet and if not how many miles has it done? My oldest GB you helped me with during first assembly also looks brand new but it's had 2 bushings replaced and 3 freewheels. I reckon we got a good batch.

 

[Sketch]

On both the original and replacement gearbox, the only manufacturing problem was an irregularly shaped key slot on the clutch. There was absolutely no way the key would go in it. I was fortunate to have a nice set of metal files available and extremely carefully. I put the clutch in a vise, using the base of the vice as a stop to ensure that I would not add depth, then filed it to a right angle and took out just enough along the side so that the key went in snug.

I thought about taking a pic but was too busy working on it to stop and go get the camera. Since two of them were that way, I'm sure I'm probably not the only person who had to fix the slot.

 

[Sketch]

Irish John, just notice your question about see-sawing. Nope, didn't see that with either old or new gearbox. The first one's cover went on real nice with just finger pressure. The new one required tapping - which makes me a little nervous given what you've said above. However, it did not want to see-saw. It just seemed snug. Also, right after I put it on I was able to turn the chain sprocket (chain not attached) easily and it *seemed* that everything inside was turning smoothly.

 

[Irish John]

Sounds like you are becoming a dab hand at it Sketch. The clutch keyways often require filing. I'm told the cluches are made in Govy owned factories and that is why the quality varies. The gearboxes aren't made in Govt owned factories though.