Tight crank after rebuild
- Thread starter Agro2424
- Start date
did it go together this easy ?????................
I had to give some light taps to get the right side on.
I had to give some light taps to get the right side on.
Good question. I did not even think about this while assembling. I'll have to look at the key slots in the morning.
It did not. I was not aware the clutch side was a slip fit. Took some tapping to get them to come together. Could have the whole thing in backwards? Geez, I hope you guys don't make me feel stupid tomorrow.
Edit: After thinking about it a bit, I'm pretty sure I've got it in there the right way. I'm almost positive I put the long key back in the clutch side of the shaft. I'll update tomorrow.
I know I put it in the right way. Please update tomorrow, I am very interested in finding out what the problem is.
Blaner
Your Friendly South African Ambassador
I have experiences just this as well before, once, I used a aftermarket crank bearing kit and the one was 1mm wider than it should have been. So I had to get an original one.
OTHER than that, what happens when you tighten up the cases, is that the crank slides into the bearing as the cases come together. To understand whats happening you must keep the nature of a bearing in mind. It has two seprate cases, with balls in between allowing movement. So if the outter is fixed in the cases, the crank tries to push into the inner race, due to friction (and a tight fit) the inner race tends to stay behind resisting the cranks movement into it. So what happens is the inner stays behind and the outter moves inward as you close the cases, so you end up with the inner and the outter OUT OF LINE with each other, jamming up the balls, this is why the crank wont turn, the balls are "squashed" against the bearing races, its sort of lile a shear force.
Now, you can leave it as such, remember the more mechanical advantage you have, the easier it is to turn the crank, IE, you can turn it by the flywheel. BUT do you think you could turn the bearings by hand on your own? I doubt it.
So you can run it like this but be aware that the bearings will wear MUCH faster than normal because the balls will wear themselves into the tight space and once they do that, they will loosen up and probably move to their correct location, now the balls will be worn and the race will be too big for them, so ultimately, they will be shot by the time that happens, which will be VERY soon!
Advice? split it again, and install using a crank puller/inserter. Knock on the crank ends while closeing the cases as often as possible to get them to seat.
OTHER than that, what happens when you tighten up the cases, is that the crank slides into the bearing as the cases come together. To understand whats happening you must keep the nature of a bearing in mind. It has two seprate cases, with balls in between allowing movement. So if the outter is fixed in the cases, the crank tries to push into the inner race, due to friction (and a tight fit) the inner race tends to stay behind resisting the cranks movement into it. So what happens is the inner stays behind and the outter moves inward as you close the cases, so you end up with the inner and the outter OUT OF LINE with each other, jamming up the balls, this is why the crank wont turn, the balls are "squashed" against the bearing races, its sort of lile a shear force.
Now, you can leave it as such, remember the more mechanical advantage you have, the easier it is to turn the crank, IE, you can turn it by the flywheel. BUT do you think you could turn the bearings by hand on your own? I doubt it.
So you can run it like this but be aware that the bearings will wear MUCH faster than normal because the balls will wear themselves into the tight space and once they do that, they will loosen up and probably move to their correct location, now the balls will be worn and the race will be too big for them, so ultimately, they will be shot by the time that happens, which will be VERY soon!
Advice? split it again, and install using a crank puller/inserter. Knock on the crank ends while closeing the cases as often as possible to get them to seat.
Thanks for the very good information. So the hot rods bearings could have been a little wider. Makes sense. I have never had any issues with them in the past, but sounds like the best thing to do is split it and use oem bearings. Thanks again.
Thanks for the advice! This is what I believe is happening too. I'm about to go smack it around with a hammer, and if that doesn't work, I'm going to take it apart and measure the bearings. I still have the original ones I took out, and they seem to still be perfect. If need be I may just shove them back in there for the time being.
Well I split it back apart today. The "slip in" (clutch side) of the crank pulled the bearing out of the case with it. This sucked. Couple hours later we FINALLY got the bearing off after a lot of heat and some creativity with a jaw gear puller. I measure the width of the Boss Bearing and it was almost .010" wider than the stock one. I believe the inner diameter was about .001" smaller.
But the thing is, I can slide my stock bearing on and off the stock crank fairly easily. But the same bearing won't slide on the Vito's crank with the same ease. As far as I can tell, the Vito's crank is roughly .001" bigger around than the stock one.
So, I'm thinking the combination of the wider Boss Bearing with the slightly smaller inner diameter combined with the slightly larger diameter of the Vito's crank is what is screwing me?
It's still apart. I'm afraid to put it back together because if it does the same thing, I may not get it back apart without killing another bearing.
Not sure where to go from here :-/
But the thing is, I can slide my stock bearing on and off the stock crank fairly easily. But the same bearing won't slide on the Vito's crank with the same ease. As far as I can tell, the Vito's crank is roughly .001" bigger around than the stock one.
So, I'm thinking the combination of the wider Boss Bearing with the slightly smaller inner diameter combined with the slightly larger diameter of the Vito's crank is what is screwing me?
It's still apart. I'm afraid to put it back together because if it does the same thing, I may not get it back apart without killing another bearing.
Not sure where to go from here :-/
Blaner
Your Friendly South African Ambassador
well you want and need that crank to fit tightly into the bearing, or else it will turn in the bearing and make a big mess!
As for them being a little wider, Hotrods bearings should be good, but if in doubt, get some genuine KOYO made Yamaha bearings.
Take care when installing, its not as simple as whacking them in and bolting everyhting fast, you need to methodically tap the crank ends (put A Nut on the end of the threads! ) after every set number of turns on the crank case bolts to make sure the bearings settle.
Other reasons for this can be if you have flatted the case halves (Too Much) in which case you will have to make a very thin gasket or if you have used unmatched casings.
as for the tight fitting crank into the bearings, have you tried freezing the crank on ice before you for it? it should drop right in then. I would be wary of heating the bearings though, id rather freeze them, heat up the cases, drop in the bearings, then freeze the crank, allow the bearings to attain room temp then drop in the crank without heating the bearings.
As for them being a little wider, Hotrods bearings should be good, but if in doubt, get some genuine KOYO made Yamaha bearings.
Take care when installing, its not as simple as whacking them in and bolting everyhting fast, you need to methodically tap the crank ends (put A Nut on the end of the threads! ) after every set number of turns on the crank case bolts to make sure the bearings settle.
Other reasons for this can be if you have flatted the case halves (Too Much) in which case you will have to make a very thin gasket or if you have used unmatched casings.
as for the tight fitting crank into the bearings, have you tried freezing the crank on ice before you for it? it should drop right in then. I would be wary of heating the bearings though, id rather freeze them, heat up the cases, drop in the bearings, then freeze the crank, allow the bearings to attain room temp then drop in the crank without heating the bearings.
I know it's supposed to be snug, but the clutch side should be able come back out without the bearing being pulled out with it.
I guess I'm going to have to go for it and do what you say with the heating/freezing and tapping.
And yes, I was wary of heating the bearings too, but I was in a tight spot with nothing else to try. That one will be going in the trash.
Blaner
Your Friendly South African Ambassador
well if it were me, I would take that crank an bearing in to a GOOD machine shop and have it machined down a fraction to get a good fit and while I was at it Id get them to true and balance the crank.
As long as you can assertain the vitos crank is indeed larger than the stock. Those Vitos cranks are good but Vitos in general are not too well know for excellent quality control. It may very well be out of spec
As long as you can assertain the vitos crank is indeed larger than the stock. Those Vitos cranks are good but Vitos in general are not too well know for excellent quality control. It may very well be out of spec
Well, It's back together again. I've still got the Boss Bearing on the flywheel side and I put the OEM bearing back in the clutch side. It's better. I wouldn't call it great, but definitely an improvement. I'm still waiting to get my top end back from Ken. I'll just have to see what it runs like after that. Hoping it works itself in.
Well we took the top end off my buddy's and checked it. It seems to be fine. Just a hair tighter than the stock one. We put about 15 hours ride time on it so far and it runs great. He never got the cylinder ported to match so it wasn't a huge gain. It was noticable though.
