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Motomike1

Transmission Problems - WR 450

12 posts in this topic

Get the bike on a stand, and with a dead engine and spinning the back wheel , find out what it can and cant' do, shifting wise.

 

Pulling the clutch cover off will reveal nothing about the transmission.

 

It sounds like you fractured a gear, and it is stuck in between cogs in the transmission.

 

Hopefully Grayracer will chime in, as he is an expert on the transmissions.

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Just contacted grayracer513.

I think the bike is stuck or semi stuck in all gears. If i spin the back wheel on the stand, Idk why it would spin in any gear other than neutral.

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Sounds like you knocked a tooth or more off 4th or 5th alright.   The transmission is, like virtually every other remotely modern manual trans, of a "constant mesh" design.  That is, the actual driving teeth of each of the gear pairs are always in mesh with each other so that the teeth themselves never have to bear the clash of engaging as the gearbox is shifted.  One gear of each pair is splined to one shaft or other, and the second gear of the pair turns free on the opposing shaft. 

 

In the WR/YZ, 4th and 5th are keyed to the output shaft.  In neutral with the engine off, the clutch holds the main shaft still by locking it to the engine, so gear pairs 1, 2, and 3 don't turn if the output shaft moves. 4th and 5th do, so it's likely that if you are encountering something other than smooth rotation as you turn the wheel that the problem is either a broken gear, or something jammed between the teeth of one. 

 

If there is no damage to 1st, 2nd, or 3rd, the engine should start and run at idle in neutral completely normally, or if you pull the clutch plates out, you should find the clutch boss and main shaft rotate smoothly.

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WTF 

 

Instead of telling us what went wrong and what the fix was, you just delete the thread?  That's sure to help future answer seekers a LOT!!

 

:rant:  :smashpc:  :banghead:  :foul:

 

Thanks!!

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Can the moderators delete this thread?

 

It's not our practice to do that, no.  In cases where there is some clear reason, like you posted your SSN or something, or thought better of what you said about someone, or your post breaks a rule, then we might, but the forum isn't useful as a searchable source of information unless information stays in it.

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&%$#@! 

 

Instead of telling us what went wrong and what the fix was, you just delete the thread?  That's sure to help future answer seekers a LOT!!

 

:rant:  :smashpc:  :banghead:  :foul:

 

Thanks!!

no real information learned so i haven't updated, but sorry to keep you guys on a cliffhanger. the 5th gear pinion cracked. that was all, my mechanic said everything else looked really good.

fix: replace 5th gear pinon ($26 OEM ), and $122 gasket kit... 

 

kinda boring and uneventful, i know...

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Hi

I'm new on here and hope this is the appropriate forum for this.

I just picked up a 2005 WR450 with the same transmission problems written about here with fifth gear.

Having been a M/C mechanic previously I wasn't too daunted with the tear down prospect and since getting a great deal on the bike wasn't too worried about the parts cost.

After tearing down the engine and making my parts list I kept examining the third and fifth gears where the dogs were rounded as expected.

What I found wasn't so expected. As you can see from the photos where I'm pointing to there are reliefs machined into the (for the lack of a better term) channel that the third gear dog goes into to engage fifth gear.

When the gear drops into here and spins to lock in this machined area actually lifts the third gear out and away from the fifth gear (this happens when the washer between the gears is in place).

This seems like an incorrect way for the gears to connect and would actually cause premature wear to occur.

My questions are: has anyone else encountered and pondered this one?

Has anyone gone to the trouble of removing this ramp up?

And what success or problems has this been to do.

I'm waiting for my new parts and am contemplating removing these if Yamaha hasn't modified them in later production.

I don't want to have the same problems several months down the trail.

Any ideas from members?

Thanks for your input

image.jpg

image.jpg

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The area you point to is never in contact with the lugs on the third pinion, and it is in fact a revision made for the purpose of elongating the engagement slot in the 5th pinion, which acts to reduce the clashing sort of damage the lugs suffer from impacting each other while partially engaged.  The longer slots allow more time during the shift so the lugs can be meshed deeper before the load applies. 

 

When the shafts are fully assembled with the forks in the right side crankcase, you can shift into fifth and see that the leading ends of the lugs on the third pinion never reach deeply enough into the 5th pinion to come into contact with the bottom of the slots in 5th.  The entire problem results from the deformation of the locking lug drive side surfaces to the point where they are no longer square with the shaft axis, and have become "cams", if you will, that force the gears away from each other under pressure.  From the pictures, yours are very definitely worn.

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Hi

Thanks for the quick and concise response!

That all makes perfect sense

I attached a little closer up (unfortunatly not the clearest ) picture where you can see actual wear down in there.

I also am attaching a video that shows the action. Unfortunatly I don't think there is sound but in it I'm showing the gears on the shaft with washer and circlip and how they engage and as I turn the gears to where the dogs make contact, just before there is a click from contacting the area in question and as I continue to turn till the dogs engage it moves the third gear back out almost 1/8".

My thought is that the intention of Yamaha may have been to make that bottom channel not quite as wide so when the gear moves over it contacts 5th gear with only very small supporting shoulders to help it glide to contact the dog face.

My theory may still be incorrect but the other gears with the oval type engagement dogs do not do this riding up.

What do you think?

Thanks. It's not permitting me to upload the video how can I do that so you can watch the action?

image.jpg

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