05 YZ 250, bent shift fork replacement?

[Cannon00]

05 YZ 250, bent shift fork replacement(now with pictures)?

Hi, I've got an 05 yz that had tranny troubles. Found out two shift forks were worn so I'm replacing them as a set, but in the manual it says if you replace a shift fork to replace the two gears each adjacent to the shift fork. What do they mean by this? Do I need to replace all gears contacting a shift fork and all mating gears associated with them?

Also, is there a way to make sure I didn't bend one of my shift shafts(3rd gear snapped a tooth off) or does everyone just eyeball them with a straightedge?

Thanks for any answers, I'm really lost on what I need to replace when replacing a shift fork, any help is really appreciated.

Jeff

 

[Ol'89r]

You do not have to automatically replace the gears too. Just inspect them. Check the shift dogs. They are the little square looking dogs that come off of the side of the gears and engage with the other gears. If the edges of the dogs are worn at an angle or rounded off on the ends, then you should replace them. If they are still square and sharp, you shouldn't have to replace them.

Worn dogs can force the gears apart. This is what wears and bends shift forks.

You can check your shift fork shaft by rolling it on a piece of glass. If it is bent it will be obvious.

Also, if you broke a gear, you should carefully inspect every tooth on every gear for damage. Make sure there are no nicks in the tooth surface and no cracks at the base of the teeth. Sometimes the broken tooth can get inbetween other gears and damage them too. Use a magnifying glass to check for cracks in the gears.

If you are unsure about the condition of your gears and related parts, take them into a shop and have them inspected.

Good luck.

 

[Cannon00]

Well, I checked every other gear for damage. I had one with pitting on the faces of a couple gear teeth, that was the gear that mated to the damaged gear. The pitting doesn't look serious, but I'm still replacing it for piece of mind.

I have a few gears with wear on the dogs though, but it's very slight,not rounded off but you can see the point where the mating gear engaged. Should I change a gear that shows ANY sign of wear, or only if the wear seems like it would cause mating problems?

 

[whenfoxforks-ruled]

Any sign of wear on the dogs, junk. Nice and shiny, junk. The slot where the fork rides, measure and inspect. Usually its the dogs forcing the gears apart under load. The steel gear can get aluminum flashing rubbed into it from the fork? The forks get measured with a micrometer for thickness, bent is beyond that! Really not good, and expensive. If you see a new one, you will see the difference. There is a slight under cut on both mating surfaces, just a degree or so. Well it used to be there! Pitting? Got some pics of that one? Vintage Bob

 

[Cannon00]

Every dog in the transmission has *some* wear. Also, lots of parts have shiny spots, if I replaced everything with a shiny spot I'd be replacing the whole transmission.

 

[whenfoxforks-ruled]

That is darn near the picture of a used mx race bike tranny. Wait till you see the new gears dogs. It is obvious which ones are disengaging? How much better are the rest? Have you ever seen the thread on speed shifting with no clutch? Sometimes falling on the shifter can mess some stuff up?

 

[Cannon00]

I can't seem to get a decent picture of mine. But the wear is nearly identical to the amount of wear in this pic below, except: There is 0 wear on my shift drum. There is no wear on my gear teeth. The faces are shiny, but the teeth themselves are all in good shape.

http://www.dirtrider.net/forums3/showthread.php?t=163987&highlight=worn+gear

There is a shiny spot on one part of my idler gear that rides on top of another gear, but the shiny ring is perfectly uniform and smooth, and still spins effortlessly on top of the other gear with no strange imperfections.

Only 1 gear was disengaging. I'm replacing the gear and pinion gear for that one. Also had 1 with a chipped tooth that the gear interlocked with, replacing that one. I've found one more gear I'm replacing. I tried to determine the quality of all remaining gears using the following process:

Remove 2 gears whose dogs mate together from the shaft. Interlock their dogs in the way they turn on the shaft. Twist forcefully while slowly pulling the two gears away from each. Then I'd take careful notice of how much of the dogs were still in contact when the two gears slipped apart from the pulling and twisting force. If the gear slipped apart at a point where it would not slip turning in the opposite direction(the faces of the dogs that have absolutely no wear) then I would replace the worn gear. Luckily only 1 gear other than the 2 with severely worn dogs, and the one with a chipped tooth that they interlocked with, needs to be replaced.

http://www.dirtrider.net/forums3/showthread.php?t=163987&highlight=worn+gear

I have not read the thread on speed shifting, just looked for it, but only found one and it had nothing to do with tranny wear?