murp
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Posts: 239
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Post by murp on Jan 27, 2021 20:46:16 GMT 1
Stupid question alert.... I know the outer bearings are an interference fit on the crank, but should the inner 2 bearings and lab seal have a little lateral play ...or move side to side on the shaft.... I hope this question makes sense and the answer is yes....
Cheers 👍
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Post by Tobyjugs on Jan 27, 2021 21:12:30 GMT 1
They should not be sliding around.
If your thinking about changing the outer main bearings then change the inner main bearings as the mainbearings in the center of a crankshaft bear more load than the rest. Generally speaking.
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murp
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Posts: 239
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Post by murp on Jan 27, 2021 22:53:15 GMT 1
I can change the outer bearings without having the crank rebuilt, I removed them quite easily, but I don't want to have the crank rebuilt if it doesn't need it....surely there needs to be a tad of lateral movement on the inner bearings and lab seal, so that they can all spin independantly
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Post by bare on Jan 28, 2021 4:26:18 GMT 1
They should not be sliding around. If your thinking about changing the outer main bearings then change the inner main bearings as the mainbearings in the center of a crankshaft bear more load than the rest. Generally speaking. Don't believe that's the case in our Yamas. Inners often outlive the outer bearings |
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Post by dougw on Jan 28, 2021 9:32:19 GMT 1
The few I have had apart the centre mains are not a sliding fit on the shaft.
In the search for ultimate HP the recommendation is that the main bearings are a very close sliding fit on the cranks. Supposed to allow for the slight amount crank flexes and good for that last fraction of a HP.On engines that spend more time apart than together.
How that ties up with a relatively high mileage road engine I wouldn`t like to comment.
That fine line between "Worn" and "Worn Out" ?
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Post by dougw on Jan 28, 2021 9:35:16 GMT 1
They should not be sliding around. If your thinking about changing the outer main bearings then change the inner main bearings as the mainbearings in the center of a crankshaft bear more load than the rest. Generally speaking. Don't believe that's the case in our Yamas. Inners often outlive the outer bearings The old outers on my recent crank rebuild where worse than the inners. |
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Post by Norbo on Jan 28, 2021 9:39:35 GMT 1
inners should not move on the shaft by sliding the outer cage may have very little movent they are a bearing that moves and spins after all but the bearing its self should not slide t all, the outer bearing take the most load . but con rods stretch over time so if its an old crank id replace everything
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Post by midlifecrisisrd on Jan 28, 2021 10:13:40 GMT 1
Those bearings are only fit for the bin
It may not be sliding on the shaft but just slop in the bearings
Outer shell will be moving, inner won't
If you spin the bearing it should be silent. Any noise and it's shagged
There is over £100 of gaskets and seals swapping a crank and a good fee hours labour pulling an engine out and stripping
Do it properly and the engine won't need to come out ever again
Also have you seen cases after a bearing has broken up and jammed?
Steve
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murp
Drag-strip hero
Posts: 239
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Post by murp on Jan 28, 2021 10:49:47 GMT 1
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Post by reedpete on Jan 28, 2021 11:10:32 GMT 1
That vid shows that it’s totally shagged.
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Post by arrow on Jan 28, 2021 11:14:00 GMT 1
That vid shows that it’s totally shagged. Agree. |
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Post by tony2stroke on Jan 28, 2021 11:20:50 GMT 1
The vid shows the interference fit is no longer tight, crank will need re-build and most likely new centre webs too, its a risk not worth taking IMO.
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murp
Drag-strip hero
Posts: 239
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Post by murp on Jan 28, 2021 11:21:59 GMT 1
Cheers guys.... New crank it is then👍
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Post by Tobyjugs on Jan 28, 2021 11:42:17 GMT 1
They should not be sliding around. If your thinking about changing the outer main bearings then change the inner main bearings as the mainbearings in the center of a crankshaft bear more load than the rest. Generally speaking. Don't believe that's the case in our Yamas. Inners often outlive the outer bearings Yeah I keep forgetting there's two bearings in the centre. |
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Post by steve63 on Jan 28, 2021 14:02:02 GMT 1
The alternator side tends to go first.
On an X7 the inner (1 bearing) runs in gearbox oil. It sounds like a good idea, save weight, friction size (1 bearing), plentiful oil, running in gearbox oil but the (rubber not lab) seals just give up pretty quickly and they suck all the gearbox oil in.
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Post by steve63 on Jan 28, 2021 14:05:23 GMT 1
Cheers guys.... New crank it is then👍 Seems an odd way for it to go, becoming lose on the shaft. I wonder if it has seized at some point and they have spun on the shaft but usually it would be the outside that spins in the case? I wonder if they have ever been tight? |
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Post by Tobyjugs on Jan 28, 2021 14:33:47 GMT 1
I had a crankshaft the same. When i went to to pull the outer bearings off they just fell off. Once the crank was pressed apart the middle bearings fell off as well.
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Post by paulsx on Jan 28, 2021 15:57:01 GMT 1
They can lose the interference fit if the cranks been built a few times or poor quality bearings are used
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Post by midlifecrisisrd on Jan 28, 2021 16:00:35 GMT 1
I've had it on a LH outer bearing.
Freely slid on and off. Sent it to Grampians and it needed a new web as the new bearing wasn't tight enough on it so both bearing and shaft were goosed
Steve
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Post by chippy348 on Jan 28, 2021 17:47:33 GMT 1
That is not a normal LC center bearings, they look like TZ roller bearings rather than ball race type, hence why they are sliding. Post a photo of your crank case up please where these bearings fit ? do they have groves in them ? |
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Post by bare on Jan 28, 2021 17:52:11 GMT 1
Yama cranks take a real beating during use. IF actually used for sporty fun.
Always incredulous at those who claim 30k miles OR more on a crank.
If true.. I Suspect it's 3 or 4k rpms max, putting to the shops and back uses.
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Post by midlifecrisisrd on Jan 28, 2021 18:34:26 GMT 1
Deffo not original as they should not have grooves
Also with that much room to move it has maybe spread off the centre pin
Steve
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Post by st66 on Jan 28, 2021 18:40:15 GMT 1
Yep that's fooked pal,,,,, 👍
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murp
Drag-strip hero
Posts: 239
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Post by murp on Jan 28, 2021 19:23:33 GMT 1
That is not a normal LC center bearings, they look like TZ roller bearings rather than ball race type, hence why they are sliding. Post a photo of your crank case up please where these bearings fit ? do they have groves in them ? There you go  |
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Post by chippy348 on Jan 28, 2021 19:59:20 GMT 1
Ok so normal LC cases, so for some reason someone has fitted roller bearings to the crank, wonder if it's a air cooled center section?
Anyway best to get a new LC crank for it.
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murp
Drag-strip hero
Posts: 239
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Post by murp on Jan 28, 2021 20:18:30 GMT 1
Will do..... Thanks for everyone's advice ..👍
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