McCulloch Timber Bear Issue

[wood_cutter]

Hi Folks...

I have a Timber Bear that I had an issue with last time I went wood cutting. I was felling a tree, so saw was 90 deg with the drive sprocket upwards. The chain apparently rain into the cylinder plate/jacket and tore it up and got jammed/ripped up. I was out in the forest and didn't want to come home empty handed, so I ripped the rest of the metal off and got by for the rest of the day though the chain hit at least one other time. (and later that day once home learned how to actually get the sprocket off)

Question: What could have caused this issue? Why would the chain hit the cylinder plate/jacket AND dig into it? I figured, okay, maybe a loose chain is the main culprit, but wouldn't the jacket deflect the chain (its purpose)? Any thoughts? Some pics...

Thanks!

 

[Chris J.]

I'm curious to read the rsponses. Just about everyone of my Jonsered 49SPs have serious chain gouges.

 

[heimannm]

Do you have a floating rim sprocket? Is there a washer next to the inside bar plate? Loose chain may exaggerate other problems but there is something more basic at the root here.

Mark

 

[wood_cutter]

Do you have a floating rim sprocket? Is there a washer next to the inside bar plate?

I don't know exactly what a 'floating rim sprocket' is Mark. I'm attaching a picture of the sprocket.

It basically goes in this order; cylinder jacket plate, washer, bearing/sprocket and nut. ETA: attached a parts list that shows the plate (that got mangled) and the other components.

 

[Biker Dude]

About half of the PM 610s I have seen have some damage to the tin shield in the spot where the nick on yours is. If that shield isn't held flat against the engine very well the edge can get peeled up by a wood chip, bark, etc. and once that plate bends a little the chain grabs it. Having a loose chain doesn't help either. It's just a design flaw in the 600 series saws but luckily that plate can still be had on feebay.

 

[Roanoker494]

I have a 650 with very low hours and the same problem, I stole the plate off a old 610 for it. In my case a piece of wood caught the edge and started it to bending, which caused the chain to catch it. It "peeled" a nice semi circle swipe out of the plate, like a old can opener would have done. I just seen a couple of those plates on Ebay, not sure it they are still listed though. I believe the plate from a timber bear, 605, 610 or 650 will fit it. The was also a Eager Beaver 3.4, or 3.7, that make have the same part.

 

[wood_cutter]

...It "peeled" a nice semi circle swipe out of the plate, like a old can opener would have done...

It was just like you said Roanoker494, mine did the an arc at the top and bottom. I was in the field and didn't know (at the time) how to pull the sprocket off, so I used my Leatherman tool to peel the plate out (not fun). I ordered one (used) for 7.50 + 6.99 shipping off chainsawr.com. Waiting for it to arrive. Last I looked on ebay there was only one for 19.99.

I guess it was just one of those things. Something must have gotten in there and bent it up, then the chain caught it. I'll keep my eye on it...

Thanks for the replies folks!

 

[heimannm]

The sprocket you show is what is commonly referred to as a spur type sprocket and it not replaceable, you must replace the entire clutch drum and sprocket. That type of sprocket can allow the chain to flop a bit more, particularly if the chain is too loose.

Do a little searching if you are interested in rim type sprockets, looks at Bailey's site for example and you will see photo's of clutch drums with a spline and rim type sprockets that are replaceable. The rim type sprocket supports the tie straps as the chain goes around and helps provide better support.

Mark

 

[lawnmowertech37]

i found a sprocket in my vehicle i did not know i had it fits the 600 series saws and is the rim type sprocket

 

[wood_cutter]

The rim type sprocket supports the tie straps as the chain goes around and helps provide better support.

Thanks Mark, those rim & drum systems look pretty slick. Looks like they've got a channel the chain rides fully in - that would be a nice improvement I would think. I'll try and pick one of those up locally, or at some point. Seems like that would certainly add a layer of preventive medicine.

i found a sprocket in my vehicle i did not know i had it fits the 600 series saws and is the rim type sprocket

Good to know.

Can I just swap that out and run the same chains?