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Clutch/gearbox problem.


Variomatic
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Another week another problem on the YBR front. When pulling away it's almost impossible to do it smoothly, you can get the cluch so far out before a loud clunk radiates through the entire bike and the clutch engages all at once. Weirdly though, it only happens once it's warm, and gets worse the hotter the engine is. 

Been wracking my brains and I can't pinpoint it, the chain is adjusted and lubed perfectly, the clutch cable and lever where both replaced 2 months ago. Can't figure it out, worn out clutch plates, broken gear tooth, bent clutch rod, worn clutch/drive-train? Anyone got any ideas? Don't know what's caused it, I've been changing the oil every 1000 miles religiously yet something seems to have let go

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Only real way to tell is to have it apart and have a look see, measure the plates and see if they are in tolerance and check the steel plates for warping. My best guess anyway.

Read this and it seems to match your problem a little https://www.a7a10.net/forum/index.php?topic=9752.0 I know it's on a BSA but worth as look I should think.

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17 hours ago, slice said:

Only real way to tell is to have it apart and have a look see, measure the plates and see if they are in tolerance and check the steel plates for warping. My best guess anyway.

Read this and it seems to match your problem a little https://www.a7a10.net/forum/index.php?topic=9752.0 I know it's on a BSA but worth as look I should think.

Problem is the foot peg hanger is totally seized (Yamaha was too cheap to use a stainless fastener) so I'll have to have that drilled out, probably gonna be £60 to have that drilled out since it's a 7 inch steel bolt, can't ignore it though. 

18 hours ago, finnerz89 said:

Notched or damaged clutch basket? How many miles on it?

Thats what I was thinking, the fact it seems to give all at once does indicate this, the bike has 31k so I can see this kind of wear happening in that time given how much you need to work the gearbox on a 125.  I hope it's that simple, then again as I said above it's gonna cost be to have that damn bolt drilled. Clutch plates could do with being replaced anyway so may as well not put off the inevitable I suppose 

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9 hours ago, finnerz89 said:

It's not been thread locked has it? Try some heat?

I can lock this thread if you like? B)

  • Haha 2
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22 hours ago, finnerz89 said:

It's not been thread locked has it? Try some heat?

Nope, it's just a common problem on YBRs, happens often on them (wish I'd known that a few years ago so I could have covered it in anti seize whilst I had the chance)

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3 hours ago, Variomatic said:

Nope, it's just a common problem on YBRs, happens often on them (wish I'd known that a few years ago so I could have covered it in anti seize whilst I had the chance)

Ah ok. Just drill the head off and then mole grips are your friend

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I'm a complete idiot. I've found the problem. The sprocket carrier bearing is completely fucked, I the sprocket has about 1/4 inch play left and right. I noticed a very slight clunk when coasting down a hill with the clutch out, meaning it couldn't be a clutch issue and must have been drive train. I have a feeling that the seal has failed and the bearings ended up full of water. 

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1 hour ago, Tommy xs said:

Cushdrive rubbers ?

The rubbers are good, it's not forward/backward rotary play, it's side to side play because the bearing has play in it, simple fix,

New carrier, bearing and seal was only £26. (had to replace the carrier as well because the bearing wasn't a press fit anymore and basically fell out) 

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So you can change it from the outside, without splitting the cases?

You have to strip out the gearbox on the 2 smokes.

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23 hours ago, Cynic said:

So you can change it from the outside, without splitting the cases?

You have to strip out the gearbox on the 2 smokes.

I think so Cynic, you can do the seal without stripping but not bearing,,,,,, night as well check entire gearbox

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I think hes on about the rear wheel  [ sprocket carrier] bearing boys,,:rolleyes:

 

Hi pat,,, good to hear from you :welcome:

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5 hours ago, blackhat250 said:

I think hes on about the rear wheel  [ sprocket carrier] bearing boys,,:rolleyes:

 

Hi pat,,, good to hear from you :welcome:

Yep, rear sprocket carrier, not gearbox. So as I pull away the rear sprocket ends up cocked to the right and the chain hangs up on it, causing that weird clunk I mistook for the gearbox. Not surprised that the bearing died, considering I regularly ford small streams and take "Unsuitable for motor vehicle" signs as a challenge. 

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Did you replace it with a sealed bearing?

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16 hours ago, Cynic said:

Did you replace it with a sealed bearing?

Yep, it's been replaced with a rubber sealed bearing. I've also had to replace the entire sprocket carrier, the old bearing literally fell out just by me pulling it, somehow the bearing race had ended up all wallered out and it was too big to press the new bearing in, thankfully I found a new carrier the same day so no big issue. Still though, never seen that happen before. Haven't gone for a test ride yet but it should be all sorted.

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