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-   -   XT600 Engine rebuild questions (crank, bearings, valveseals etc) (https://www.horizonsunlimited.com/hubb/yamaha-tech/xt600-engine-rebuild-questions-crank-91963)

Doubleyoupee 27 Jan 2019 21:18

Quote:

Originally Posted by jjrider (Post 595122)
That's .002" less but still .0118" clearance (SAE since I'm used to it) , it'll be ok .




.

Thanks. 10W40 fine with the above in mind?

jjrider 28 Jan 2019 15:20

Yup .



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Doubleyoupee 28 Jan 2019 15:27

I just found out that in a XT600Z service information it clearly states 0.25-0.75mm big-end clearance, while in the XT600 EAC 1990 service manual it states 0.35-0.65mm. I thought the 600 engine core (crank, piston etc.) was pretty much identical for all models. Does someone have any idea?

turboguzzi 28 Jan 2019 18:20

Quote:

Originally Posted by jjrider (Post 595122)
That's .002" less but still .0118" clearance (SAE since I'm used to it) , it'll be ok .




.

+1, you should be fine
do a dry mount of the crank in cases, button them up and see if it turns freely to be sure

Doubleyoupee 28 Jan 2019 19:01

Quote:

Originally Posted by turboguzzi (Post 595186)
+1, you should be fine
do a dry mount of the crank in cases, button them up and see if it turns freely to be sure

Wel unfortunately it's not.
I just found out the big-end pin is now touching the bearing:

https://i.imgur.com/025zrDM.jpg

My understanding is that the bearing should be placed all the way against the crankshaft, although there will be some clearance because of a small shoulder that prevents the inner race of the bearing from going any further. Correct?

Either way, it's now rubbing against the pin as you can see in the picture... so I brought it back to be adjusted.. if possible:rolleyes2: (i've already removed the timing gear).

turboguzzi 28 Jan 2019 19:28

1 Attachment(s)
havent changed a left bearing in a while and too many other motors open to remeber, but a crank that i have here has a good 2.4 distance between pin and bearing
im afraid there should be a washer between bearing and crank, the parts list wil not show it because its one assy
no way a few tenths mistake would cancel a 2.4mm gap..

turboguzzi 28 Jan 2019 19:53

had a look in better light, not sure it's a washer. it might be that the bearing should have no radius so it stops at the shoulder sharp. maybe you mounted a non original bearing that has a radius? then it would sit more inwards...

Doubleyoupee 28 Jan 2019 20:31

Quote:

Originally Posted by turboguzzi (Post 595195)
had a look in better light, not sure it's a washer. it might be that the bearing should have no radius so it stops at the shoulder sharp. maybe you mounted a non original bearing that has a radius? then it would sit more inwards...

I already removed the bearing and there is no washer. There is a small shoulder that the inner race of the bearing sits against. That's why there's a gap between the crank and bearing.
There's still a gap for me, but not at the pin. The pin touches the bearing directly. I think it's the original bearing (it's a Koyo).

Either way, it wasn't touching the bearing before. It's because the crank was pressed 0.6mm inwards, so the pin protrudes more and touches the bearing now.

xtrock 28 Jan 2019 20:39

If service manual states 0.35-0.65mm i would for sure use it in the correct value and not hope its ok outside.. But what i find strange here is the shop you had to do this, they must have seen that the bearing touched?They maybe didnt have all parts?

Doubleyoupee 28 Jan 2019 21:13

Quote:

Originally Posted by xtrock (Post 595198)
If service manual states 0.35-0.65mm i would for sure use it in the correct value and not hope its ok outside.. But what i find strange here is the shop you had to do this, they must have seen that the bearing touched?They maybe didnt have all parts?

Well actually, the XT600Z 3AJ "service information" says 0.25-0.75mm. That's what confuses me. I've never seen that mentioned anywhere else.

https://i.imgur.com/hBbpQNT.jpg

https://i.imgur.com/G2tNjpM.jpg

xtrock 28 Jan 2019 21:58

88. Crank 1
34K-W1141-00-00


93. Crank 1
1VJ-W1141-00-00


I dont know it they had some difference spec. Anyway the bearing is not possible to move now and use again, start all over and get the gap you had before dismantle.

turboguzzi 28 Jan 2019 23:03

even if it's 0.6 off, with a 2.4mm measured gap between pin and bearing race they shouldnt touch... it might well be that what defines the bearing position is the gear wheel and you should press the last few mm using the gear wheel as a driver so it stops at the step in diameters in the shaft. what im triyng to say is in other words that the bearing should not go all the way till the shoulder.

was there a gap between the gear wheel and bearing before you took them off?

Doubleyoupee 28 Jan 2019 23:17

Quote:

Originally Posted by turboguzzi (Post 595217)
even if it's 0.6 off, with a 2.4mm measured gap between pin and bearing race they shouldnt touch... it might well be that what defines the bearing position is the gear wheel and you should press the last few mm using the gear wheel as a driver so it stops at the step in diameters in the shaft. what im triyng to say is in other words that the bearing should not go all the way till the shoulder.

was there a gap between the gear wheel and bearing before you took them off?

What are you basing this on? Where did you get 2.4mm from? There was definitely no 2.4mm gap before. More like 0.5-1mm.

I can move the bearing axially with two screwdrivers- it's very loose on the axle. I don't know what position the bearing could be other than all the way seated on the shoulder - otherwise it will just move anyway.

Before I took them off, there was no gap between the timing gear and bearing, and around 0.5-1mm beween crank and bearing:

https://i.imgur.com/wFHVgeI.jpg

You can see the shoulder here:

https://i.imgur.com/as6rFc3.jpg

This was before. Now it's touching the pin every so slightly because it moved 0.6mm

xtrock 28 Jan 2019 23:22

Ok i maybe missunderstood what you wrote, but when its pressed on i would think it couldnt be moved by hand.

Doubleyoupee 28 Jan 2019 23:31

Quote:

Originally Posted by xtrock (Post 595219)
Ok i maybe missunderstood what you wrote, but when its pressed on i would think it couldnt be moved by hand.

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. Unfortunately now, the big end pin hits the bearing first. Just.


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