Chainsaw Clutch & Idle Mystery

[Larry Leveen]

I have a used Craftsman 358351702 chainsaw. I opened up the clutch assembly and can see what looks like dark discoloration on the drum and clutch, plus some melted plastic on the chassis ("~12-1 o'clock" as viewed from the saw's right side) and on the chainsaw brake.


I removed the excess melted plastic with a blade. The brake drags on the drum, however; it does not retract concentrically/evenly all the way around the drum.



When the brake is off, it "sits" on small plastic "seats" molded into the chassis. These were deformed by melting -- see where the tool is pointing -- and my shaving didn't help.



I could make the band take proper, concentric shape by pushing on it gently (where the tool is pointing) and the drum will rotate freely, but the loss of brake seat material was a real problem. There were not seats all-the-way-around the band to allow me to shave them all down equally, so I built up the shaved seats and now the drum rotates freely. But, I want to know why the plastic melted in the first place. I have not operated the saw, though it was used recently. I noticed the chain movement under idle immediately when it was started up. Since it is a few years old, I have incomplete info on how it was (ab)used. Any thoughts?

Also, I'd like to solve the underlying problem for the chain moving while the motor idles. I tried some minor adjustment of the idle screw (not the L and H carb screws), but did not get a solid result before opening things up and revealing the clutch-area issues. Could the carb that needs to be cleaned cause excessive high-idling regardless of the idle screw adjustment? Maybe if the butterfly valve was jammed?

Is the clutch destroyed, or could that just be burned oil coating it and the drum? It appears to be fully retracted at rest, and as I mentioned above, the drum can rotate freely now that the brake band is relaxed in a concentric position. The drum's teeth looked OK, also -- very minor wear, that I can attribute to normal use/contact with the chain. If the discoloration is due to the clutch slipping, could that heat have changed the springs' temper such that the clutch shoes move out at lower-than-normal RPM?

Other constructive thoughts and advice are appreciated. Thanks.

 

[scottr]

I recently bought a PP295 in like condition. My guess is that the saw got pinched and ran slipping the clutch to overheat and blue the clutch. Remove the clutch and drum clean and relube the bearing if it's still ok.

 

[Old2stroke]

Do a search for my thread, "Clutch abuse" Jun 6, 2017. How this happens will be explained.

 

[cus_deluxe]

try turning the L screw counterclock a little bit, you may hit carb limiters, which is another subject. I would bet that any loss of temper on the clutch springs would cause them to be stiff, not more flexible but i could be wrong. 99% sure you have a tuning issue. Could be a little lube in the right spot could help ur chain brake retraction issue.

 

[Bwildered]

I'd be just getting some liquid metal rolled into a ball & stick it over the melted bit, the get a burr & remove the excess until the band sits in its intended position & the drum spins freely.
Thanski

 

[Old2stroke]

try turning the L screw counterclock a little bit, you may hit carb limiters, which is another subject. I would bet that any loss of temper on the clutch springs would cause them to be stiff, not more flexible but i could be wrong. 99% sure you have a tuning issue. Could be a little lube in the right spot could help ur chain brake retraction issue.

You are wrong. Spring steel is very hard, taking the temper out of it will make it softer (more flexible) not harder.

 

[67L36Driver]

Most times clutch springs take a permanent set (too long) when overheated. Loose the necessary preload.