Topic: Chewed up (fourth?) gear.

[mysta2]

I've got a '75 750F with a chewed up fourth gear. I'm not actually sure what gear it is, but bike bandit identifies it as fourth.

I purchased a transmission in a box off eBay hoping to scavenge the parts that I needed. But they had almost the exact same wear patterns. Is this something everyone has seen before? What's the fix (to not ruin the good ones if I do manage to finally track some down) Does the shift drum look beat? I'll for sure have to find a new fork and gear, but I'm not sure about acceptable wear for the drum.

And of course finally, anyone got some trans parts laying around that they don't need?

[chewbacca5000]

Wow!  Don't think I have seen a gear that rounded off.  I am not sure about the F model transmissions so I can't say what would interchange. 

That shift fork looks like it was starving for oil or something.  I would be sure to replace that counter shaft o ring while you are in there.

Hopefully the replacement gear is not the one pictured.  If so I would ask for a refund.

[mysta2]

That's the original gear, but the pile of parts gear looked exactly the same, so did the fork and drum.

I still haven't been able to track down any good used parts.

[lucky]

Those shifting dogs look fine.
Notice how they are all exactly the same.
When shifting dogs are damaged the edges get broken off
And you can see the grain of the casting that is rough.

Those angles on those dogs on that gear look like they would
 go into the holes much easier and smoother.
The teeth look perfect.
That wear on the shifting fork is common. As long as it goes into gear.
You can smooth it off with some black carborundom paper.
You can turn the trans by hand and make sure it goes into each gear.
If it does not work when turning it by hand, it will not work when the engine is running.

[iron_worker]

Lucky,

Are you really saying that these parts are ok for re-use?! 

The angle on the drive dog may make it easier for it to slip into gear but it also makes it easy to pop out ... which is likely the problem.

You can have your transmission "back cut" which basically means to cut the drive dogs at an angle such that the pressure driving the drive dog (and thus the gear) actually holds them together. Cycle X does this and some other places as well. I'm not sure if they handle F transmissions though. You could ask.

I'm not sure if that shift fork can be salvaged. It really looks like it probably should just be replaced but that could be a tough part to track down. You could possibly have it hard welded and re-machined but I think these are a cast part so that may not be possible either.

IW

[lwahples]

Is there any way to tell for sure what models are the same? I brought home a truck load of parts with a bunch of gears and such.Not sure if I have what you need,but can look.

http://www.nooffswitch.net/allpics2013/truckload1.JPG

[acollin]

I 'd like a bit of schooling here guys as I have never rebuilt a transmission. The language "dogs" is also,tough for me.

While I can clearly see the wear on the shifting fork, I simply do not see anything other than those worn vertical buttons that would get me worried about the gears. It is clear than wearing has occurred on those buttons. I just don't see the wear anywhere else.

Could someone include a pictures of perfect gears or create a pointer so I will be able to identify things better in the future.

Thanks for the pictures,the lesson and explanation to come.

[lwahples]

This is just one,it has factory flat spots on the pins which the others don't have. And had tiny holes where the forks slide in,oil holes? Some don't have the holes.The pins look real good.
Of course,I'm only guessing this is what you need.

http://www.nooffswitch.net/allpics2013/061013b.JPG

[lucky]

Lucky,

Are you really saying that these parts are ok for re-use?! 

The angle on the drive dog may make it easier for it to slip into gear but it also makes it easy to pop out ... which is likely the problem.

You can have your transmission "back cut" which basically means to cut the drive dogs at an angle such that the pressure driving the drive dog (and thus the gear) actually holds them together. Cycle X does this and some other places as well. I'm not sure if they handle F transmissions though. You could ask.

I'm not sure if that shift fork can be salvaged. It really looks like it probably should just be replaced but that could be a tough part to track down. You could possibly have it hard welded and re-machined but I think these are a cast part so that may not be possible either.

IW

Are these parts out of a transmission that was working?
When shiftng forks are bad or bent they are colored by the heat and actually turn blue. The tips get ground down on the sides.
When people keep their foot pressed against the lever it can heat the shifting fork up, and when they force the bike into gear because the bike is not rolling and they just keep kicking the lever the forks can get bent.

Shifting forks just have to nudge the gear sideways.
What really matters is the tips of the fork.
Also the fork can get bent by idiots with big boots and no brains.

The tip is what actually pushes against the gear.
In the photo above the tip portion is not even shown.

[mysta2]

Thank you for looking Iwahples it's a 34 tooth, and the only gear with dogs on both sides. I can post some more detailed pic of the parts in a little bit.

I'm posting a few info pics here.

[lucky]

Thank you for looking Iwahples it's a 34 tooth, and the only gear with dogs on both sides. I can post some more detailed pic of the parts in a little bit.

I'm posting a few info pics here.

That part that you are concerned about was cut that way to clear the teeth of the gear. Otherwise you would see both parts damaged.

Those dogs can have stellite welded on the tips. It is useable.
Better check with a new gear on the dogs because I think the dogs could be cut that way.
Otherwise the holes where the dogs go would be worn extensively to get that much angle and be all the same. You have not shown those to us at all.


Can you please tell us how many miles are on this engine???
I have seen Honda transmissions with 250,000 miles still working.

[ekpent]

Good Dogs !

[mysta2]

The Odo says 129000 miles. I tore this motor down because the bike came basically from a junk yard and when I got it running enough to ride it around the block. It felt like it had no first and possibly second gear, it was hard to tell on such an unfamiliar bike though.

Pics to follow. All the parts on the right are out of my bike a '75, the parts on the left are out of a '78 transmission I bought off eBay in a box. Obviously the '78 parts are slightly less worn. I've been banging my head against the wall on this so long that I'm about ready to put those in there and call it a day.

[mysta2]

Those Cycle X dogs are what I expect good dogs to look like (except of course for the undercuts)

Mathematically speaking to be equal the pockets would have half the wear of the dogs because there are twice as many of them. That might explain a bit how uneven they look.

I have a very hard time believing that they are anywhere near that slanted from the factory.

I also have a hard time believing that Honda hard anodized the drum before final machining. That seems very counter intuitive.

[chewbacca5000]

Those Cycle X dogs are what I expect good dogs to look like (except of course for the undercuts)

Mathematically speaking to be equal the pockets would have half the wear of the dogs because there are twice as many of them. That might explain a bit how uneven they look.

I have a very hard time believing that they are anywhere near that slanted from the factory.

I also have a hard time believing that Honda hard anodized the drum before final machining. That seems very counter intuitive.

What about the cycle x picture makes you think these gears are undercut?  I don't see the difference and would like a set of undercut gears.

[scottly]

I have a very hard time believing that they are anywhere near that slanted from the factory.

You are not mistaken; the dogs when new looked like the unworn areas all around. My bike with less wear than that on the dogs popped out of gear on a regular basis, and the shift forks were in very good condition compared to yours.

[mysta2]

The shiny fresh machine marks of the dovetail cutter in the bottoms of the pockets. Also on that gear on the upper right you can see the dogs are not straight but slanted inward. It's out of focus so its hard to tell, and it looks like they finished the edges after machining so its less obvious.

[mysta2]

You are not mistaken; the dogs when new looked like the unworn areas all around. My bike with less wear than that on the dogs popped out of gear on a regular basis, and the shift forks were in very good condition compared to yours.
[/quote]

Hey Scottly, welcome to my thread. How are your hand cut dogs holding up after all this time? Reading your posts when I first encountered this problem had me warming up the dremel. Realistically though I don't think my dogs have enough meat left on them to undercut.

[scottly]

Realistically though I don't think my dogs have enough meat left on them to undercut.

I was kind of thinking that, myself. My best guess is the gear was being forced against the fork, causing the wear there. Does the other side of the fork look OK?

[mysta2]

Yep, other side of both forks are shiny new looking.

The way I see the assembly working/failing is that when the dogs started to wear and the gear was being pushed out of its pocket by the slanted surface, that in turn forced the spinning gear against the fork grinding into it which also tried to force the drum to rotate and ground away the corner of that slot.

[scottly]

Is there a flat worn into the fork pin, where it engaged the slot in the drum? The dogs on the gear in the left side of the pic may be salvageable with undercutting. Is this a big-bore hi-po motor?

[HondaMan]

You are not mistaken; the dogs when new looked like the unworn areas all around. My bike with less wear than that on the dogs popped out of gear on a regular basis, and the shift forks were in very good condition compared to yours.

Hey Scottly, welcome to my thread. How are your hand cut dogs holding up after all this time? Reading your posts when I first encountered this problem had me warming up the dremel. Realistically though I don't think my dogs have enough meat left on them to undercut.
[/quote]

You're correct, Mysta: even APE would refuse to attempt to re-cut dogs that bad.

I think I have most of a 1975 F tranny here, it will need to have the C2-C5 set undercut to make it a nice one again. It had about 20k miles on it. I'll go see if I can find it. PM me, so I can find your post again?

[lwahples]

Will look for the parts you are needing.

[mysta2]

Thanks Iwahples.

He may have found the parts I need.

[mysta2]

Scottly, I'm not really going high performance, I just want to ride it more often than I drive my Jeep. It is bored to 65mm (836) but that was just out of necessity to get out the groove carved by a broken ring. Stock air box, stock 4into1