Crank collar makes crank hard to spin

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11/7/2017 9:41 AM

Rebuilding my cr125. The crank spins freely, however when I put the collar and gear onto the crankshaft it makes it hard to spin. Anyone know why?Photo

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11/7/2017 9:48 AM

The collar also spins with the crank. I'm not sure if it's supposed to or not. All the parts are there and in order. Nothing is missing.

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11/7/2017 10:40 AM

Update: I ended up splitting the cases and checked everything out. It all looks good. The case that the crank is in is the same case with the collar that's causing it not to spin. I spun the crank in that side only and it spun so easily and free without any problems. However I put that gear and collar on while it was just in one crank case and hand tightened it and all the problems came right back. It was hard to spin. With hand tightening and in only one crankcase half!!! What's the deal???

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11/7/2017 10:43 AM

I had this problem once (RM125) and I must have put the cases together and split them again half a dozen times before I worked it out.

In my case, the guy that fitted my rod kit and trued the crank had pressed it together too much and the web to web measurement was 0.8mm less than it should have been. It meant that when I put the crank in the cases, it was fine, but when I fitted the primary gear it pulled the crank out of center and towards the side of the primary gear and it bound up.

Btw - make sure you use loctite and torque that primary gear properly!

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11/7/2017 10:48 AM

What brand crank?

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11/7/2017 10:49 AM



Photo

Photo

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11/7/2017 10:57 AM

Did you overtighten the nut?

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2009 Kawasaki KX450F
2009 Kawasaki KX250F
2002 Suzuki GSXR 600

11/7/2017 11:03 AM

Ok another update. I have the cases back together and everything is tightened to spec including the primary gear and collar. There is only one thing that's not on right now and that would be the crank seal that sits where the collar is. The crank spins very freely and nothing looks wrong so the cause of the problem must be the seal. I'm not quite sure what to do now.

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11/7/2017 4:45 PM

Anyone?

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11/8/2017 5:41 AM

z71will wrote:

Anyone?

Did you first install the crank on the clutch or flywheel-side case?

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11/8/2017 6:05 AM

z71will wrote:

Ok another update. I have the cases back together and everything is tightened to spec including the primary gear and collar. There is only one thing that's not on right now and that would be the crank seal that sits where the collar is. The crank spins very freely and nothing looks wrong so the cause of the problem must be the seal. I'm not quite sure what to do now.

I had the same issue on a yz250 i built. The seal caused some resistence. I was told by others that its just because its all new and needs to break in. Since then that yz has ran great with no issues in the bottom end. As long as it rotates smoothly it should be fine. Maybe put some oil on the face of the seal where it meets the crank and see how that works.

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2009 Kawasaki KX450F
2009 Kawasaki KX250F
2002 Suzuki GSXR 600

11/8/2017 6:42 AM

z71will wrote:

Ok another update. I have the cases back together and everything is tightened to spec including the primary gear and collar. There is only one thing that's not on right now and that would be the crank seal that sits where the collar is. The crank spins very freely and nothing looks wrong so the cause of the problem must be the seal. I'm not quite sure what to do now.

Acidreamer wrote:

I had the same issue on a yz250 i built. The seal caused some resistence. I was told by others that its just because its all new and needs to break in. Since then that yz has ran great with no issues in the bottom end. As long as it rotates smoothly it should be fine. Maybe put some oil on the face of the seal where it meets the crank and see how that works.

I think the problem is that I put the seal in first and then I put in the collar, where as on the instructions it said to put on the collar first. I believe the seals inner area got pushed in a little making the inner diameter slightly tighter in some areas making the crank stiff. I tested this by removing the seal and the collar and sticking the collar onto the seal and twisting it, and then taking it off and instead putting the seal on the collar and the collar was much easier to twist in the seal that way. I ordered a new seal so hopefully when it gets here that fixes my problem.

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11/8/2017 7:24 AM

z71will wrote:

Ok another update. I have the cases back together and everything is tightened to spec including the primary gear and collar. There is only one thing that's not on right now and that would be the crank seal that sits where the collar is. The crank spins very freely and nothing looks wrong so the cause of the problem must be the seal. I'm not quite sure what to do now.

Acidreamer wrote:

I had the same issue on a yz250 i built. The seal caused some resistence. I was told by others that its just because its all new and needs to break in. Since then that yz has ran great with no issues in the bottom end. As long as it rotates smoothly it should be fine. Maybe put some oil on the face of the seal where it meets the crank and see how that works.

z71will wrote:

I think the problem is that I put the seal in first and then I put in the collar, where as on the instructions it said to put on the collar first. I believe the seals inner area got pushed in a little making the inner diameter slightly tighter in some areas making the crank stiff. I tested this by removing the seal and the collar and sticking the collar onto the seal and twisting it, and then taking it off and instead putting the seal on the collar and the collar was much easier to twist in the seal that way. I ordered a new seal so hopefully when it gets here that fixes my problem.

Definitely post the fix so i know for future engine rebuilds.

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2009 Kawasaki KX450F
2009 Kawasaki KX250F
2002 Suzuki GSXR 600

11/8/2017 7:24 AM

Also i was told by paw paw to smack the end of the crank with a deadblow to “set” the crank in the bearings. This did help a lot

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2009 Kawasaki KX450F
2009 Kawasaki KX250F
2002 Suzuki GSXR 600

11/8/2017 9:19 AM

Acidreamer wrote:

Also i was told by paw paw to smack the end of the crank with a deadblow to “set” the crank in the bearings. This did help a lot

^^this. It's pretty common on the CR125's for the collar/seal to be a bit tight when new. Lube well, install carefully and makes sure it rotates smoothly. Better to be tight when new and break in then too loose...........

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