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XT600 Engine rebuild questions (crank, bearings, valveseals etc) XT600 Engine rebuild questions (crank, bearings, valveseals etc)
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Yamaha Tech Originally the Yamaha XT600 Tech Forum, due to demand it now includes all Yamaha's technical / mechanical / repair / preparation questions.
Photo by George Guille, It's going to be a long 300km... Bolivian Amazon

I haven't been everywhere...
but it's on my list!


Photo by George Guille
It's going to be a long 300km...
Bolivian Amazon



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  #46  
Old 28 Jan 2019
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Quote:
Originally Posted by Doubleyoupee View Post
The timing gear is pressed on. The bearing I can simply tap all the way down using no effort, just some light taps. But as you can see on the last picture - it can't go any further because there's a tapered shoulder that hits the bearing's inner race.
Ok so it seatet with expansion heat, then if you use the 0,5 gap its ok?
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  #47  
Old 29 Jan 2019
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Quote:
Originally Posted by xtrock View Post
Ok so it seatet with expansion heat, then if you use the 0,5 gap its ok?
No, the bearing was cold. There is hardly any interference fit.
I'm just trying to explain why I returned the crank. Unless someone has some official info about clearances/timing gear position I'm quite sure the bearing must sit all the way on the shoulder with its inner race.
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  #48  
Old 29 Jan 2019
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Quote:
Originally Posted by Doubleyoupee View Post
No, the bearing was cold. There is hardly any interference fit.
I'm just trying to explain why I returned the crank. Unless someone has some official info about clearances/timing gear position I'm quite sure the bearing must sit all the way on the shoulder with its inner race.
I understand bearing is cold, if these are floating bearings wouldnt they be seatet when engine heats up rather than floating when heat like you write before?Just thinking both metal expands wouldnt give more float than what you have. But anyway get the specs correct and good luck
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  #49  
Old 29 Jan 2019
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the 2.4mm is the reading i get when i measure the gap in the crank i have.
look at the pic i posted again, these are feeler gauges of a total 2.4mm sliding between pin and bearing.

Hope i am not upsetting you when i'm trying to help....
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  #50  
Old 29 Jan 2019
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Originally Posted by turboguzzi View Post
the 2.4mm is the reading i get when i measure the gap in the crank i have.
look at the pic i posted again, these are feeler gauges of a total 2.4mm sliding between pin and bearing.

Hope i am not upsetting you when i'm trying to help....
Ah okay, I couldn't see it was 2.4mm on the picture.
Definitely not upsetting me. I'm just confused. Looks like your timing gear is way higher than mine (or your bearing is way thinner), because I don't have any clearance between the bearing & timing gear either, but almost 1.5mm-2mm less clearance between crank & bearing.

Do you still have the crank?

Could you take a measurement like this?


It's from the back of the teeth to the start of the cutout. A bit weird I know but it's easy to measure and should be constant. Thanks
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  #51  
Old 29 Jan 2019
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first thing wrong is that bearing should be an interference fit on shaft, not sliding fit
2nd, now that i see, im confident that the bearing should go against the gear, not the shoulder. see pic and pretty big gap.

so measure your shaft, with micrometer, it should be above 35.00,



here are some more dims with a solid reference of the step in shaft
Attached Thumbnails
XT600 Engine rebuild questions (crank, bearings, valveseals etc)-img_20190129_210449-1-.jpg  

XT600 Engine rebuild questions (crank, bearings, valveseals etc)-img_20190129_210220-1-.jpg  

XT600 Engine rebuild questions (crank, bearings, valveseals etc)-img_20190129_210310-1-.jpg  

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  #52  
Old 29 Jan 2019
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Looks to me like this is pressed back with not same distance, what did you measure before dismantle?Its for shure not the 0,05 that makes the problem here.
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  #53  
Old 29 Jan 2019
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Originally Posted by xtrock View Post
Looks to me like this is pressed back with not same distance, what did you measure before dismantle?Its for shure not the 0,05 that makes the problem here.
Those are not my pictures but turboguzzi's.. Mine is not yet pressed back.

Quote:
Originally Posted by turboguzzi View Post
first thing wrong is that bearing should be an interference fit on shaft, not sliding fit
2nd, now that i see, im confident that the bearing should go against the gear, not the shoulder. see pic and pretty big gap.

so measure your shaft, with micrometer, it should be above 35.00,



here are some more dims with a solid reference of the step in shaft
Hm.. I think once the engine gets to operating temperature the interference fit disappears. This is probably why the bearing ends up in a slightly different spot every time. This is why I'm worried the bearing could touch my big-end pin since it can physically move there and touch it.

Unfortunately I've already removed the timing gear now so cannot check those measurements. This is the only one I have. If you could try the same measurement as me that would be grand
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  #54  
Old 29 Jan 2019
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The old bearing, was it the same way with possible to move with fingers?
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  #55  
Old 29 Jan 2019
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Originally Posted by xtrock View Post
The old bearing, was it the same way with possible to move with fingers?
Well, to clarify I used two screwdrivers to lift it from the crankshaft axle, it wasn't loose but not very stuck either. Nu puller required. There is an interference fit (as in it won't fall off by itself) but not much. I could press it back very easily with light taps with a screwdriver + small hammer.

I haven't put the new one on yet, crank is at the shop.
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  #56  
Old 30 Jan 2019
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IMHO bearing should be a interference (read tight) fit, otherwise even when you are dropping the crank back in the cases it will get pushed against the shoulder and touch the pin again.
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  #57  
Old 30 Jan 2019
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Well, I just picked up the crank. Now the big-end clearance is +-0.50mm and the width is +- 74.90mm. Sounds spot on to me.

Unfortunately, the pin still protrudes a little bit. It's 0.2mm less than before but the crank still touches the bearing if I push the bearing all the way down onto the shoulder.

I decided to make a quick video so you can see how easy the bearing comes off the axle:

Video/GIF

Surely setting the bearing to any position on the axle will not matter since with so little interference fit it will just move anyway. Especially with warm engine.

Not sure what to do now.
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  #58  
Old 30 Jan 2019
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What happend to the bearing in the end of video, strange angle suddenly? I still dont understand what you mean happens when engine is hot, why do you think bearing is moving more then? Did you pull timing gear or shop?
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  #59  
Old 30 Jan 2019
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Quote:
Originally Posted by xtrock View Post
What happend to the bearing in the end of video, strange angle suddenly? I still dont understand what you mean happens when engine is hot, why do you think bearing is moving more then? Did you pull timing gear or shop?
The axle is thinner there.. so the bearing can tilt. I think it can move because at higher temperature the interference fit will be even less.
No I pulled it myself.

Anyway you can see here both bearing and axle have a chamfer, and therefore the bearing can go all the way down until the inner race meets the shoulder:





I'm quite sure the bearing should be all the way on the shoulder, or at least be able to go all the way
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  #60  
Old 30 Jan 2019
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Did you only use a normal 2 or 3 arm puller, was it hard pulling out? Iam thinking if its easy to damage gear. The original bearing was 100% like the new one? Iam still thinking bearing will get more stuck when heating up due to the expansion of metal.
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