Hot chain brake handle MS310

[turnkey4099]

A few weeks ago there was a thread on this. I bit the bullet and put it in John's Saw Service - Lewiston, ID. He spotted a place on the chain brake that had actually started to melt. Couldn't see anything wrong, suggested maybe a blown exhaust gasket. I asked him to pull it and check it out. Next trip he said he replaced the entire muffler as the old one rattled when he took it off, something loose inside, the new one didn't. Had run the saw, it is set up correctly, the limiter caps are still in place so not running lean.

I picked up the saw and decided to post mortem the muffler to see what the story was. Hacksawed it open and folded it out. The rattle was only the interior baffle that would be held tightly in place when the muffler is bolted up. Therefore it can't be that.

I took the cut open muffler back to him as an educational item so he wouldn't bite on the 'rattle' again in the future. He is puzzled as to why the excessive heat but did suggest that the muffler deflector off an MS 390 will fit and if it is still running hot he'll put one on.

Just thought you all might be interested as in the other thread there was at least one other MS of some type doing the same thing.

Harry K

 

[Cut4fun]

Dont them stihls have a heat shield on the chain break area? Seems weird that my PP 330 would have that and the stihls dont.

 

[Fish]

A molten spot in the chain brake area usually means that there is a chip or something
under the brake band, causing the band to rub the drum, or something like that.
If the head was obviously coming from the inside, behind the bar studs, then the muffler would be suspect. Also look and make sure that the oil pump worm lever is
aligned correctly with the notch in the drum, and it is not bent down by someone forcing the drum on, or there is some other problem in the chain brake area.

 

[turnkey4099]

Fish: It isn't the chain brake, only on the handle right above the exhaust about where your knuckles hit the brake. Last time I ran it, that area was too hot to touch bare handed.

Nope, there is no heat sheild. In the other thread someone mentioned a foil cover on the handle. Both me and the dealer checked the new saws on the shelf, none had it.

It is a real puzzle as the saw sounds good, runs good and cuts like a dream. 2 shops have checked and said it is not running lean. If it does it again, I will try going leaner on the idle and richer on high.

Harry K

 

[Cut4fun]

Make one, take your chain brake side off and put a homemade heat shield there, Or buy one from another stihl saw that they were smart enough to put one on and install it.