Chain locks up, smoke from clutch, chain and bar suddenly super-tight

[Pilgrim1]

Well, despite how little as I know about chainsaws, I think I found the problem. The drive sprocket has a deep groove worn in each tooth. (See photo.) Is this normal wear or perhaps a sign that I'm over-tightening the chain?

I surmise that when the chain would jump down in the groove, the chain would be loose, and I would tighten it. Then when it jumped back out onto the high (normal) part of the teeth, the chain would be super tight.

Now I need to figure out to replace the wear parts that Philbert mentioned.

Addressing some of the suggestions:

• oil comes out the port
• the bar groove was pretty clean
• the sprocket doesn't spin freely, but it turns easily with slight pressure
• the brake band does not appear to be colored by heat
• I'm pretty sure the chain and bar are the right sizes

Thanks everyone,


Luke

 

[Philbert]

Yep. That’s past due. Replace the small cage bearing at the same time. Clutch itself is probably OK. (I save worn parts like that for training purposes!).



It’s not hard to do, but not necessarily obvious. You need to stop the piston (usually using a short piece of rope) and strike / turn the clutch *clockwise* to remove.

When installing the new spur sprocket, it has to mesh with the oil pump drive gear.

Probably some YouTube videos. Or pay a shop to do it.

Philbert

 

[PV Hiker]

Perhaps new bar and chains to go along with a new spur sprocket. Your existing chain drive links might be compromised. Have any pictures? Any pictures of bar rails and end sprocket? Your on the right track

 

[Philbert]

Here’s a good YouTube video.

Usually does not take that many hits. Clean and inspect behind while it is off. Work a small dab of grease into the bearing.



Philbert

 

[sean donato]

You win the most shot spur gear I've seen in a long time award! Good advice given on replacing the needle bearing and checking out the chain drivers. They can't be in good shape running in a spur gear like that.

 

[Pilgrim1]

Here’s a good YouTube video.

Usually does not take that many hits. Clean and inspect behind while it is off. Work a small dab of grease into the bearing.



Philbert

Thanks. The video is very helpful. So replace the clutch, sprocket, and bearing whether I can tell if they're worn or not? Or how do I tell if they need to be replaced?


Luke

 

[trains]

Thanks. The video is very helpful. So replace the clutch, sprocket, and bearing whether I can tell if they're worn or not? Or how do I tell if they need to be replaced?


Luke

If its as badly worn as the photos show, then chances are you have put some high load on the clutch drum bearing, so just replace it and be done with it.

 

[Philbert]

Thanks. The video is very helpful. So replace the clutch, sprocket, and bearing whether I can tell if they're worn or not? Or how do I tell if they need to be replaced?

I would not replace the clutch. Yet.

Your sprocket (‘spur sprocket’: a combination of the sprocket and clutch drum) is clearly done. It looks like a chariot wheel from ‘Ben Hur’ or ‘Sparticus’. $20 (?)

The bearing I would replace as cheap insurance, due to the condition of the sprocket. $10 (?)

Reassemble and run the saw. You can always replace the clutch later, but it’s a more expensive part, if not needed.

Philbert

 

[cookies]

When you remove the clutch look at the shoes and spring, if the shoes are purple replace the clutch. I will say you should also replace the clutch springs at a minimum since you smoked it repeatedly + the spur+ the bearing

 

[Jasonrkba]

That sprocket is as worn as I have seen them. Replace the sprocket, bearing and inspect the crank seal. May as well go to a rim sprocket. I bet the chain is toast also.

 

[Pilgrim1]

That sprocket is as worn as I have seen them. Replace the sprocket, bearing and inspect the crank seal. May as well go to a rim sprocket. I bet the chain is toast also.

Thanks everyone. I've ordered an OEM clutch drum/sprocket. Amazon had the best price.

I measured the clutch outer diameter, and it was 66.5 mm, so I'm not replacing it yet. The manual says it should be at least 65 mm.

I've replaced the bar once already and gone through many chains. I'll look at the drive teeth for damage.

How would I inspect the crank seal?

I hope to be able to post more photos soon, but it may be a few days.


Luke

 

[cookies]

Thanks everyone. I've ordered an OEM clutch drum/sprocket. Amazon had the best price.

I measured the clutch outer diameter, and it was 66.5 mm, so I'm not replacing it yet. The manual says it should be at least 65 mm.

I've replaced the bar once already and gone through many chains. I'll look at the drive teeth for damage.

How would I inspect the crank seal?

I hope to be able to post more photos soon, but it may be a few days.


Luke

The reason I suggested to replace things is heat damage not from wearing down, that clutch will get so hot the temper of the steel changes hardening it to the point it will slip under hard load when it should not and the springs will fail or stretch. The crank seal when failed will allow air past it, the saw will run funny and idle funny.

 

[SteveSr]

Thanks everyone. I've ordered an OEM clutch drum/sprocket. Amazon had the best price.

I measured the clutch outer diameter, and it was 66.5 mm, so I'm not replacing it yet. The manual says it should be at least 65 mm.

I've replaced the bar once already and gone through many chains. I'll look at the drive teeth for damage.

How would I inspect the crank seal?

I hope to be able to post more photos soon, but it may be a few days.


Luke

With that much damage to the sprocket you will likely be needing a a bar and a new chain. Bin the existing bar and chain. All of these parts have to wear together. Replacing just the sprocket will result in rapid wear to the new sprocket.

 

[Jasonrkba]

If the chain smoked then it will not hold an edge. For the seal just make sure the heat didn't get to it to the point of burning or melting.