Balancer Shaft Damage from Impellers seals failing

I just found where my balance shaft needs to be replaced as it no longer has the mating material to turn my impeller shaft. Do i need to split my cases to get the shaft out to replace it? It is a 2007 wr 450. Looks like they changed the balancer shaft from earlier models to this style.WP_000880.jpg

Edited by chambo3232

I am sorry, but yes you do need to split the crank case the shaft has a lip on both sides. once the case is starting to split lay it on it's left side and slowly lift the right side up off but don't twist it (straight up) once off you can lift out the shaft. Perhaps someone out there knows some good shortcuts but I have not found any. good luck.

Allterra, Are you sure the cases have to be split? On my previous Yamaha's, you could remove the balancer shaft without splitting the cases. It's all in the manual.

Maniac

Allterra, Are you sure the cases have to be split? On my previous Yamaha's, you could remove the balancer shaft without splitting the cases. It's all in the manual.

Maniac

I could be wrong but I am pretty sure there is a lip on the inside of the 07's shaft that rides next to the bearing I just looked at the book just to make sure it did say to split the case. I didn't have to on my 05 WR

. I had to split mine (07 WR) to retreve a missing screw that I found in a rag later :devil: .

Edited by allterra

looking back at the 05 manual. no you did not have to split the cases.

I will agree with you on the fact that '06 on back, you don't have to split the cases to remove the balancer shaft. I don't know for sure on '07 on up. Chambo, do you have the manual?

Maniac

I will agree with you on the fact that '06 on back, you don't have to split the cases to remove the balancer shaft. I don't know for sure on '07 on up. Chambo, do you have the manual?

Maniac

If you need one in a pinch check out this site. http://www.yamahaownershandbook.com.au/?r=0 it is in 4 languages so it can be a pain in the but. also it is on the international bikes so some things may differ but the motor should be the same.

Edited by allterra

Thanks for your help i am going to split the cases tomorrow night.

It's a bit of a tricky thing to do, but yes, you can replace the balancer shaft on the '07 and up ('06-'09 on YZ450) WITHOUT splitting the case.

The shaft "floats" in the bearings, which are pressed into the cases. Start by removing the gears and counterweights from both sides, and the bearing retainer plates. Replace the nut on the left (flywheel) end and apply some heat carefully to the crankcase around the right side bearing. Rap the left end sharply with a steel hammer and punch. Use a large pointed or flat point punch that will sit in the center drilling at the end of the shaft.

Once the right side bearing has "broken free" and is moving, proceed cautiously. The shaft has a cutout in the middle of it to clear the crank flyweights. Position the crank with the rod at around 30 degrees forward and listen/feel for the end of this cut out to strike the crank. If this happens, STOP. Usually, the right side bearing will have cleared the case by that time, but it may not have. If it has, remove it, and then drive the shaft in the opposite direction to free the left bearing. Once the bearings are both out, the shaft can be moved forward in its bore far enough to clear the crank.

If the right side bearing has not come free of its bore when the shaft stops on the crank, you can either see if it can be wiggled out of place with pliers, or drive the shaft back the other way to free the left bearing, after which the right can be knocked out from the opposite side.

I figured someone would have found a short cut.

Hi Gray,

I too have been going through water pump seals. (06 YZ450) Moving fwd with replacing the balancer shaft bearings. (have gears, counterweights, and retainer clips removed as of right now) Chambo indicated, he found the balancer shaft to no longer have the 'mating material' to turn the impeller shaft. As this pertains to to my impeller and balancer shaft - it does have some slop; can rotate the impeller shaft back and forth approximately 1/8"-3/16", as I seat the end of the impeller shaft into the balancer end and, some significant rust is apparent. Looks ugly in there IMO... Thoughts?

Image.jpg

Edited by probracing1

It's not unusual for the impeller to rotate 30 degrees or more. If you're concerned that is getting to the point of not driving the pump, look at where the wear is. Wear to the shaft tab itself will cause it to fail long before wear in the drive pocket itself. The rust is due to the extremely fine debris that gets created by the tab rattling around over time. If more oil got in there to wash it away, it wouldn't sit there and oxidize while the engine was off.

So far, I don't see anything particularly wrong with yours.

Thanks Gray. After removing the balancer shaft, uneventfully I might add thanks to your instructions on positioning of the crank correctly, I decided to simply replace the shaft along with the bearings. Visible wear can be seen in the balancer shaft recess. My best guess is that the corrosion/rust present could have weakened the metal and further allowed the impeller shaft end to maul the recess. Felt it was best to simply replace the part.

With '06 and earlier WR's ('05 and earlier YZ450's) The shaft cab be easily removed, but what you can't do is replace either bearing without splitting the cases. That's simply because the bearing retainers are on the inside.

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