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Discussion Starter #1 (Edited)
My 15 year old son and I are doing our first engine tear down together on our 2003 Grizzly 660 after it developed a very pronounced engine knock. We have found the source of the knock... the balancer is striking the connecting rod, but I don't know why or how to correct it. I thought for sure we'd find the balancer gears out of alignment (though I don't know how that would happen), however, they appear to be good from what I can find in the service manual and from the forums. To my knowledge this engine has never been apart. Was running great until it developed the engine knock. Where do we go next?

Thanks for any suggestions/info!

Here's a picture of the connecting rod and balancer contact:
IMG_0777[1].JPG

And here is a picture of the balancer gear alignment:
IMG_0770[1].JPG
 

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Discussion Starter #3
Thanks for the reply!

I took a couple more pictures of the rod and attached them below.

It seems like the balancer is contacting the rod no matter what position the rod is in, laying on the base of the opening, held to the top of the opening, or centered. The contact is right at the base of the rod where it widens to attach to the crank. If it were a bent rod, it seems like moving the rod to different positions in the opening would effect the contact from the balancer, yet no matter what position the rod is in, the level of contact from the balancer seems the same, and is pretty solid (notice the mushrooming of the balancer edge in the initial pictures).

Just trying to make sure I'm going after the correct part before tackling removing the engine completely and splitting the case (already feel like I'm in over my head :) ).

Thanks again for any responses.

IMG_0783.jpg IMG_0784.jpg IMG_0785.jpg IMG_0788.jpg
 

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I guess I'm not familiar with the actual balancer, but is it possible for balancer sprocket to spin on the shaft, or for that matter the crank shaft gear, therefore going out of sync?
 

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@Type10 Welcome to GC from Wisconsin.

Unfortunately it is time to pull the balancing gear set for inspection.
It appears that one or both of the gears has moved.
The balancer driven gear is keyed to the shaft. Never heard of it but it be the key is sheared. Allowing the gear to creep around the shaft. The timing makes will always be proper as they are mechanically sync'd to each other.

Get a factory service manual from GC member oleblue22 site www.501parts.com
 
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Discussion Starter #6
Thanks for the additional suggestions.

I'll get the balancer gears pulled and report back with what I find. Might be a couple days before I can get back to it.
 

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Thanks for the additional suggestions.

I'll get the balancer gears pulled and report back with what I find. Might be a couple days before I can get back to it.
This will require the crankcase to be split...


 
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