Gearbox Teardown with plenty of pictures
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RennieK said:
So should I get it re-hardened or replace it, if it's bad?
I'd look for a used one or take a chance on buying a whole new used trans on ebay or just buy a new one. On the assembly line when they make them they can use a specific blend of steel and temper it with a particular method and then harden to a specific depth under very controlled conditions. Even sending it back to the manufacturer could cost as much or more than buying a new one as they may not want to deal with it. I could be wrong about that though and there may be places that would do it according to modern standards for a reasonable price.
I generally stay away from metallurgy but.....to get a soft piece of steel through hardened it must be quenched with involves heating to a high temperature and dropping it in a bucket of oil or water. The metal is not the same shape after this process so it must be machined. Costly for a repair guy.
There are some low temperature surface hardening techniques be they're probably not cost effective, either. If you really got the piece hot enough for it to soften it's probably not straight any more.
There are some low temperature surface hardening techniques be they're probably not cost effective, either. If you really got the piece hot enough for it to soften it's probably not straight any more.
If the bluing is from heat it's structurally weakened/ more brittle. I'd replace it.
I was an indution hardening tech and a spline roller tech, grinding tech, among other things. It's a little more complicated than just quenching as the quench has to be timed. Too much or too little can create cracks and change the hardness. heat placement is important to size distortion and heat pattern. after quench the part must be tempered. The heat must not distort the shape too much, or the id of the roller will be out of spec. The hardness is important not just structurally, but also for the finish-grinder.
I was an indution hardening tech and a spline roller tech, grinding tech, among other things. It's a little more complicated than just quenching as the quench has to be timed. Too much or too little can create cracks and change the hardness. heat placement is important to size distortion and heat pattern. after quench the part must be tempered. The heat must not distort the shape too much, or the id of the roller will be out of spec. The hardness is important not just structurally, but also for the finish-grinder.
pelican said:
Well, a bit grungy but I sure don't think it's blued.
Re: Gearbox Teardown with plenty *more* pictures
Ok, more gearbox pictures.
First, I'm sure I'm not going to get much sympathy for this, but to even get to my work bench I have to push one car out of the garage and roll three bikes out of the way. That's my excuse for not getting out there more often and I'm sticking with it.
First up is removing the mainshaft nut. Stuck it in the vise (not too tightly) and off she came. Few light taps with the rubber mallet and out came the shaft.
Next up was the kickstart shaft. The rebuild kit has a spring so this one is going away.
And the pawl. $20 for a new one? Is it worth it?
Anyone want to guess if I got the gears in the right order?
So parts all cleaned. Cases look ok. Light polish on the outer cover and it should be good.
So, the one thing that has me stumped is how to do you replace all the bushes? I assume the ones in the cases my pop out when I heat the cases? What about the ones inside the gears? Only one fell out during disassembly, the rest look to be in there good. Thoughts?
Ok, more gearbox pictures.
First, I'm sure I'm not going to get much sympathy for this, but to even get to my work bench I have to push one car out of the garage and roll three bikes out of the way. That's my excuse for not getting out there more often and I'm sticking with it.
First up is removing the mainshaft nut. Stuck it in the vise (not too tightly) and off she came. Few light taps with the rubber mallet and out came the shaft.
Next up was the kickstart shaft. The rebuild kit has a spring so this one is going away.
And the pawl. $20 for a new one? Is it worth it?
Anyone want to guess if I got the gears in the right order?
So parts all cleaned. Cases look ok. Light polish on the outer cover and it should be good.
So, the one thing that has me stumped is how to do you replace all the bushes? I assume the ones in the cases my pop out when I heat the cases? What about the ones inside the gears? Only one fell out during disassembly, the rest look to be in there good. Thoughts?
Warm up the gear (oven at 200) put ice on the bushing and quickly tap out the bushing using a socket or what ever you can find that has a smaller diameter as a drift while supporting the gear on something solid.
You can press it out in a vice using a socket that is slightly smaller in diameter so it passes through the gear while supporting the back side of the gear with a bigger socket that can "swallow" the bushing. Hot and cold is good this way too.
You can press it out in a vice using a socket that is slightly smaller in diameter so it passes through the gear while supporting the back side of the gear with a bigger socket that can "swallow" the bushing. Hot and cold is good this way too.
For bush removal, I like to thread in an appropriate tap, then chuck the tap into a vise and knock the gear/cover/kickstart assembly/etc. away with a hammer/drift/mallet. For covers, a bit of heat helps. I wouldn't heat a gear, for fear of losing some hardening.
I would have replaced that pawl, yes, as it appears the wear is through the hardened surface already. Although it's not hard to do so later, as you can do in situ.
I would have replaced that pawl, yes, as it appears the wear is through the hardened surface already. Although it's not hard to do so later, as you can do in situ.
BrianK said:
I was thinking of putting gears in an oven, thuse relatievely easy to modulate temperature. I don't think 3-500 degrees is going to have any affect on hardening. I think it's not until you get hot enough to turn the metal a colors, such as red that you are in trouble. Am I right?
I'd rather get the gearbox back together than hold off waiting for a pawl. Look for a future post on replacing a pawl... :mrgreen:
I don't see those temperatures having any effect on hardening.
Yeah, like I said, I'd do the pawl now, but I do tend to have a "throw new parts at it" approach that I can't really afford! Still, my bikes are my children. Oh, plus my real children, of course!
Pawl replacement is real easy. Knock the pin out. Put the pawl and spring back into position. Knock the pin back in.
Good luck!
Yeah, like I said, I'd do the pawl now, but I do tend to have a "throw new parts at it" approach that I can't really afford! Still, my bikes are my children. Oh, plus my real children, of course!
Pawl replacement is real easy. Knock the pin out. Put the pawl and spring back into position. Knock the pin back in.
Good luck!
BrianK said:
I was surprised at how easily the pin came out. There is a small spring in the rebuild kit, I think it's for the pawl.
So I kinda forgot about this set of bushing/bearing drivers. I can't remember what I bought them for but this sure seemed like a good time to break them out. Of course I got it from Harbor Freight.
Driving in the sleeve gear bushing.
Driving the First gear layshaft gear bushing out.
Driving the new bushing in.
All the other bushings went in fine and fit back on their respective shafts... except this one. Bushing ID is too big by a couple thou. My choices are to remove the new bushing and put the old one back in or try to get this one reamed to fit. Assuming I can find someone I know who has a reamer...
BrianK said:
Yes, ID too small. Can't even get the shaft on it to grind it down.
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