Repeat failures of water pump seals

[grayracer513]

The '07 bearings are far cheaper. Don't know why. If you can give me ID, OD, and width as precisely as possible, I'd appreciate it.

The flat is not visible. If you have the new shaft, you can see how the flat is oriented relative to the ends. You have to kind of feel for the interference between each consecutive tap on the shaft as you drift it out. I went toward the water pump side first. Once the right bearing is disengaged, you will have to push the shaft back the other way and get the second bearing out to remove the shaft.

When reinstalling, place the shaft in the case first, then put each bearing part way in, then drive them in place.

[tribalbc]

The '07 bearings are far cheaper. Don't know why. If you can give me ID, OD, and width as precisely as possible, I'd appreciate it.

The flat is not visible. If you have the new shaft, you can see how the flat is oriented relative to the ends. You have to kind of feel for the interference between each consecutive tap on the shaft as you drift it out. I went toward the water pump side first. Once the right bearing is disengaged, you will have to push the shaft back the other way and get the second bearing out to remove the shaft.

When reinstalling, place the shaft in the case first, then put each bearing part way in, then drive them in place.

Thanks for that ?

It will be at least a couple weeks before I have the parts and pull it all apart, but I will be sure to post up the bearing sizes when I have them here on this thread.

[tribalbc]

So I finally got the time and all the parts together to do this project as well as a motor rebuild.

Bearing sizes on the 07 are

40mm OD

16.95mm ID

16.45mm width

But in the process of doing this I made a major FU.

I tried first driving the bearing to the waterpump side as you suggested but it was being a bitch to move so I started on thother side, major mistake

It was coming out nice but then wouldn't quite exit. I thought I had more clearance before I hit the crank there. So I got the bearing out the water pump side, removed the balancer shaft and found I had marred the crank a bit. Smoothed it out with sandpaper, it's fine clearance wise, but will it throw my crank out of balance? Do I now need a new crank?

[davidl9999]

Yes, it will throw the crank out of balance. Aside from fixing that, I'm concerned about if you smacked the crank enough to bend it. You may be able to get a *quality* engine shop to re-weight and rebalance the crank, but (imo) your best bet is to replace the crank before you fire it up.

[grayracer513]

The crank plate has only been dented; no metal was removed, so it should have no effect on balance. It could have knocked it out of alignment, but that's really fairly doubtful. Have you run the engine since?

The correct procedure, once you felt the balancer shaft contact the crank, would have been to run the shaft back to the right again. It would most likely have come free of the left bearing before it touched the crank, and then you could have tilted it out of position, removed it, and finished pulling the bearing with a drift from the right, or a blind puller.

[tribalbc]

The crank plate has only been dented; no metal was removed, so it should have no effect on balance. It could have knocked it out of alignment, but that's really fairly doubtful. Have you run the engine since?

The correct procedure, once you felt the balancer shaft contact the crank, would have been to run the shaft back to the right again. It would most likely have come free of the left bearing before it touched the crank, and then you could have tilted it out of position, removed it, and finished pulling the bearing with a drift from the right, or a blind puller.

Thanks for the words of wisdom.

The bearings were a slow process coming out, and I kept checking the balncer shaft that it moved freely, which it did. It was the last fraction of the bearing leaving were I made contact with the crank. Realizing my mistake I then drove the waterpump bearing out, came easier now after the banging the other way, and then finished the other bearing with a long punch on the inner race.

This was my feeling, that no material has left the crank so it should be good to go....

It just happened today, so no I haven't run the engine, I've been contemplating spending the money on a crank and bearings, and splitting the cases

The crank feels so buttery smooth and the lower rod clearance is still the low end of spec so I think I'll try it......

[davidl9999]

The crank plate has only been dented; no metal was removed, so it should have no effect on balance...

That looked like a chip to me, Gray. Thanks for clarifying. Must be old contacts... (well I gotta blame it on something besides old eyes!)

[Mike Martel]

I have a yz450f 2006 that started leaking out the weep hole. taking it apart the impeller shaft was grooved and the seal seemed to have a hole wore in it and was worn. I just ordered all the parts minus the balancer barrings you guys speak of. I don't have any kind of meter to check the barring. Should I be able to feel some slop if I insert the impeller shaft in the balancer. It sounds like that is the part that goes bad and causes all the other parts to fail. My bike only leaks when ridden hard but it would drain the radiators in about 30 minutes. What are the chances it is not the barrings.

Thanks for any advise.

[tribalbc]

Another question for you Grey. Did your balancer drive and driven gear have a little C scratched on the surface? On the drive gear the C is by the punch mark to be aligned. On the driven gear the C is at 12:00 when the punch marks are aligned at the 9:00. I'm surmising I could use this as another way to find TDC when installing the new camchain with the flywheel off? I'm thinking this since the crank is at TDC at this position with the counterbalancer at the bottom. Makes sense I think.....

I'll verify with a rod on the piston on assembly.

Edited December 21, 2010 by tribalbc

[grayracer513]

I don't remember seeing one. Probably a "match mark".

[tribalbc]

I have a yz450f 2006 that started leaking out the weep hole. taking it apart the impeller shaft was grooved and the seal seemed to have a hole wore in it and was worn. I just ordered all the parts minus the balancer barrings you guys speak of. I don't have any kind of meter to check the barring. Should I be able to feel some slop if I insert the impeller shaft in the balancer. It sounds like that is the part that goes bad and causes all the other parts to fail. My bike only leaks when ridden hard but it would drain the radiators in about 30 minutes. What are the chances it is not the barrings.

Thanks for any advise.

There will be a bit of spinning play in the impeller in the balancer shaft but the balancer shaft itself should have no play.

That's a big leak.

[Mike Martel]

There will be a bit of spinning play in the impeller in the balancer shaft but the balancer shaft itself should have no play.

That's a big leak.

the balancer shaft will not move side to side or in and out at all. It will spin round in the minute space between the teeth of the gears.

It looked like the outside seal had a hole in the bottom of it and was ripped. Looking at how it goes together it makes sense that all the fluid was coming out the weep hole. YOu guys sure seem to know what you are talking about on this forum. Are all you guys machanics or something?

[grayracer513]

the balancer shaft will not move side to side or in and out at all. It will spin round in the minute space between the teeth of the gears.

Then you should be OK. Be sure the seals face the right way:

https://www.thumpertalk.com/forum/showthread.php?t=940018

[tribalbc]

. Are all you guys machanics or something?

Grayracer knows more than any mechanic I know

Myself I race offroad, on a budget. So I do all my own wrenching. This site is a wealth of knowledge. Anytime you get really stumped, one of the big guns on here can sort you out real quick

[Mike Martel]

thanks for the help guys. parts are on the way.

[Mike Martel]

Quote: and since the balancer shaft is deliberately out of balance

You wouldn't be able to feel this or hear it. Seems like if the balancer is out of balance it isn't doing it's job. That being the case what does it exactly balance in the engine and is it really needed? Seems like the only way you noticed was from the water pump issue it created.

[davidl9999]

Quote: and since the balancer shaft is deliberately out of balance

You wouldn't be able to feel this or hear it. Seems like if the balancer is out of balance it isn't doing it's job. That being the case what does it exactly balance in the engine and is it really needed? Seems like the only way you noticed was from the water pump issue it created.

Not sure if I'm reading this right, Mike, but here goes:

The short answer:

The balancer shaft is deliberately unbalanced to oppose the transverse force (vibration) caused by the connecting rod moving front-to-back-to-front in the engine. That force cannot be balanced by the crankshaft, because the crankshaft balances the up-down-up force of the piston.

The long answer:

In any reciprocating engine where there are are asymmetrical loads that aren't completely eliminated by an opposing force, there are vibrations that cannot be eliminated even by perfectly balancing the reciprocating parts. For even-cylinder-count (2,4,6*,8,10,12*...) engines, the first order harmonics (those that vibrate at the same frequency as the engine RPM) can be balanced-out by balancing the reciprocating parts, but the second order harmonics cannot. For odd-cylinder-number engines (1,3,5...), there aren't much in the way of second order harmonics to worry about, but the reciprocating parts cannot be balanced to account for all of the forces generated at the fundamental frequency (the engine's RPM), and a balancer shaft is used for that purpose.

Just an aside: Flat-four engines, for an example have minimal, if any asymmetrical load issues and generally don't need a balancer shaft.

Point 2: odd-cylinder-number engines can get away with one balancer shaft spinning at the engine RPM, even-cylinder-number engines need two, spinning at twice the enginer RPM. That's not because two are needed to cancel out the second-order harmonic, it's because they can spin in opposite directions and cancel unwanted "transverse" (side-to side) forces that each shaft generates, resulting in a better suppression of the second-order harmonic without introducing new vibrations that would occur with a singe, large shaft rotating at 2x engine speed.

So, the balance shaft (or shafts) is/are weighted and tuned to provide the force that opposes the direction that the engine will be vibrating at any given time for the first or second-order harmonic - whichever one is being tuned-out. Higher-order harmonics (3x, 4x engine speed) generally are of low enough amplitude that they're not noxious and don't need to be suppressed.

Why balancer shafts are problematic for engines is because they're deliberately out of balance. Imagine trying to hold a spinning eccentric weight, and then consider that the engine is also trying to move in the direction opposite to the spinning weight with the same amount of force being generated by the weight - so there's twice the force in play at the force amplitude peaks and that puts a serious load on the balance shaft bearings. (and also makes the bike nicer to ride!)

I hope that this isn't too babbly, and is precise enough to be helpful (pretty hard to fit this topic on a forum post).

* Inline 6 and inline 12 cylinder engines are inherently balanced (because the inline 6 is inherently balanced and the inline 12 is simply two inline 6's on the same crank in the same geometry). V-type engines are unbalanced because an end-to-end vibration is created due to the way that the forces are applied to the engine when a cylinder fires.

Here's a really good read:

http://www.autozine.org/technical_school/engine/smooth1.htm

Edited December 22, 2010 by davidl9999

[tribalbc]

I guess I can add my part on this procedure now since I've just gone through it.

The flat spot on the shaft can be located by the key hole on the shaft for the counterbalancer shaft. It only is meant to work one way so drive out the waterpump side bearing FIRST, then use a drift/punch onthe inner race to remove the other bearing.

Here's a shot showing the flat part of the shaft and how it aligns with the keyhole.

[grayracer513]

Seems like if the balancer is out of balance it isn't doing it's job. That being the case what does it exactly balance in the engine and is it really needed?

Read:

https://www.thumpertalk.com/forum/showthread.php?p=9214483#post9214483

[Mike Martel]

wouldn't you be able to feel some added vibration in the bike when riding it? I am assuming your kid didn't mention anything when you replaced the water pump seals.