Help Please. How to remove YZ426F transmission?


10 replies to this topic
  • Dennish87

Posted May 21, 2013 - 08:57 PM

#1

Fifth gear started slipping on my yz426 so I split the cases to find the cause. I still have yet to find that cause because I cannot figure out how to remove the transmission. I removed the gear on the right side of the transmission and can get the shafts to wiggle to the point that you'd think they would come out but there is still something holding it up. All my Clymer manual says to do is tap the countershaft, other shaft and shift drum and it will come out. The whole removal procedure is two sentences. Can someone please help me to figure out how to remove this transmission?

A little description of what it was doing that made me split the cases. At first it would slip gradually then catch up when in 5th gear. It progressed into several sharp jerks after a couple more rides. I replaced the clutch, chain and sprockets. There were alot of metal shavings in my oil filter so it has to be coming from either 5th gear or maybe a shift fork. Just from inspecting it with it still mounted in the one side of the case, I cannot find anything obviously wrong with the transmission.

Any help would be appreciated!

Thanks,

Dennis H

  • grayracer513

Posted May 21, 2013 - 09:32 PM

#2

Under the output shaft sprocket is a steel spacer/collar that the seal rides on. There's an O-ring between that collar and the shaft to keep oil from escaping between them, and when they get old, they can get stuck to each other.

Grab the collar carefully and twist it off, then remove the O-ring before you try to pull the shafts out.

Remove the neutral switch, spring, and plunger, too.

  • Dennish87

Posted May 22, 2013 - 04:08 AM

#3

I've already done that.

  • Dennish87

Posted May 22, 2013 - 05:14 AM

#4

I've read you need to pull out the shafts the shift forks ride on?


  • marv02

Posted May 22, 2013 - 05:15 AM

#5

Did you remove the bolt on the clutch side of the shifter drum this where the shifter detent lever go's this will hold the shifter drum in.

When I did my trans both trans shafts shifter drum and shifter forks come out at once putting back in the same they go in at one time.

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  • Dennish87

Posted May 22, 2013 - 05:42 AM

#6

No, I tried but it was extremely tight and I had no way of holding the shift drum while I turned it. There is a little lever connected to the shift drum I beleive and that was what I was afraid of breaking if I turned the bolt loose. So the bolt on the shift drum needs to come out?

  • grayracer513

Posted May 22, 2013 - 06:37 AM

#7

So the trans is sitting in the left case half? Or the right?

If it's in the right side case, items #2, and #'s 9-16 must be removed from behind the clutch, or you won't get anything out. The star wheel (segment, #16) retains the shift cam in its right side bearing, and the bearing is retained in the case from the inside. As was posted earlier, all six shafts come out at once as a set, including the shift fork shafts, which are pinned to the forks.

Once you get in there, you will find that the locking lugs, or "dogs", on the sides of the third gear and fifth gear pinions (the gears on the main shaft) are worn and rounded over, and the shift fork that controls the third pinion will be damaged.

  • Dennish87

Posted May 22, 2013 - 06:54 AM

#8

ok thank you. That makes more sense once you refernece the schemata. I have everything off besides #9. Can I hit it with the impact to loosen it. The only reason I haven't taken it off yet is because I'm afraid of damaging the shift drum when I loosen it. There isn' t any good way to hold onto the shift drum. So after I take that bolt out it should come out then huh?

Oh and yes, it's in the right case. The left is off.

  • grayracer513

Posted May 22, 2013 - 07:06 AM

#9

Yes. Pull the center bolt and lift off the shift segment/star wheel. Then give the main shaft a shove.

Note that there is a small pin in the end of the shift drum that the segment indexes into position with. Be careful that you align the segment onto this pin when you assemble the trans. The hole the pin is in is blind, and deeper that the pin is long, and the problem is that if you tighten the segment onto the cam with the pin misaligned, it will be pushed in flush, and you will not be able to extract it easily, if at all.

  • Dennish87

Posted May 22, 2013 - 07:10 AM

#10

Ok, Thank you much. I appreciate the help! I'll go out to the barn once the coffee kicks in and it quits raining to tinker on it.

  • marv02

Posted May 22, 2013 - 09:39 AM

#11

It's lock tight in place either muscle it out or put some heat to it them back it out.


No, I tried but it was extremely tight and I had no way of holding the shift drum while I turned it. There is a little lever connected to the shift drum I beleive and that was what I was afraid of breaking if I turned the bolt loose. So the bolt on the shift drum needs to come out?







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