Front sprocket play

[Dropsix]

Hey guys, just picked up a 2005 yz250f and am familiarizing myself with it. I noticed it was leaking oil out of the countershaft seal so I decided to replace it. 

First i noticed the previous owner had used that high temp gasket/silicone stuff which I thought was weird since as far as I know you’re only supposed to need a coat of grease usually but ok. I cleaned everything up and installed a new seal. Put everything back together and noticed that the previous owner had two of those lock washers holding the sprocket on. Also found that strange. Reinstalled it with just one and found there was quite a bit of play (front and back not left and right). In any case sure enough the seal leaked again. 

So I’m wondering if it’s supposed to have this much play in it. I know a bit of play was alright since it’s supposed to be sorta self straightening with the chain. If the video below is normal, why would the previous owner have used two washers? I tried two of them and the spocket no longer has any play. 

Also anyone have any tips regarding the leaking seal? 

Heres the video of the spocket play. 

 

[GuyGraham]

Your spacer is worn from it coming loose previously and hence the nut cant clamp down onto the sprocket as the nut bottoms out first. The second washer was to take this out slack (bodge)

Replace the spacer as you risk oil starvation if the half moon cut outs disappear from the inside edge of the spacer

Sprocket is supposed to be clamped thight by the nut. Loose, as in your vid is not good. With a new spacer an another new seal you should cure your oil leak

Edited May 6, 2018 by GuyGraham

[Dropsix]

By spacer do you mean this thing?

 

Edited May 6, 2018 by Dropsix

[GuyGraham]

No, number 24 in the diagram below

 

[Dropsix]

2 minutes ago, GuyGraham said:

No, number 24 in the diagram below

 

Ahhhhh, I see the problem right away. 

I got an all balls countershaft seal kit so I have the part you’re talking about. The problem is actually the nut holding the sprocket on. The diagram you posted shows a bigger nut than what’s on mine right now. The previous owner must have lost it and used a different one hence doubling up on the washers. 

Thanks man, I appreciate the help on this!

[GuyGraham]

3 minutes ago, Dropsix said:

Ahhhhh, I see the problem right away. 

I got an all balls countershaft seal kit so I have the part you’re talking about. The problem is actually the nut holding the sprocket on. The diagram you posted shows a bigger nut than what’s on mine right now. The previous owner must have lost it and used a different one hence doubling up on the washers. 

Thanks man, I appreciate the help on this!

whilst its apart, check the half moons on the inside face of that spacer are still present, as these can wear down if the sprocket has come loose

without the half moons, no oil can get to the output transmission and thats not good

if the allballs kit has a new one, you can compare the size of them to see if the spacer is worn

 

Just because the nut looks quite big in the drg, doesn't mean you have the wrong one, although it does look incorrect in your vid as the Yam ones normally have two diff size hexagons (as drawn) and yours in the vid doesn't

[YZEtc]

It's obviously the wrong nut, and looks like a run-of-the-mill nut that's flat on both sides.

The result is the nut is merely bottoming out against the splined shoulder of the shaft and not touching the sprocket.

The correct nut will make the problem so obvious.

[Dropsix]

42 minutes ago, YZEtc said:

It's obviously the wrong nut, and looks like a run-of-the-mill nut that's flat on both sides.

The result is the nut is merely bottoming out against the splined shoulder of the shaft and not touching the sprocket.

The correct nut will make the problem so obvious.

Yeah definitely. I actually have a spare bottom end and looked at the nut and noticed it was different too. Only problem is I can’t get it off as I have no way to stop the sprocket/shaft from spinning 

[hillclimb426]

Yeah definitely. I actually have a spare bottom end and looked at the nut and noticed it was different too. Only problem is I can’t get it off as I have no way to stop the sprocket/shaft from spinning 

I think you could put it in 5th gear remove clutch. Then have someone hold that side with a large breaker bar and socket on the nut for the clutch basket. then try to remove the sprocket nut with an impact .

[Dropsix]

1 hour ago, hillclimb426 said:

I think you could put it in 5th gear remove clutch. Then have someone hold that side with a large breaker bar and socket on the nut for the clutch basket. then try to remove the sprocket nut with an impact .

I wound up getting it off and installing it on the bike. Just went for a half hour ride and all is well. 

Thanks all! 

[DOMINICWR450]

Quote

I think you could put it in 5th gear remove clutch. Then have someone hold that side with a large breaker bar and socket on the nut for the clutch basket. then try to remove the sprocket nut with an impact .

I try to not use this method...i prefer someone hold the rear brake and then i remove the nut with an impact , IMO less stress on the transmission. 

[Dropsix]

45 minutes ago, DOMINICWR450 said:

I try to not use this method...i prefer someone hold the rear brake and then i remove the nut with an impact , IMO less stress on the transmission. 

The issue here being that the spare motor I was taking the nut off of was out of the bike.