jb-chainsaws
Pinnacle OPE Member
I've had far too many ms261's come to the shop recently with the owner saying that when they put the brake on the saw cuts out. As some will know there is a fault with the early 261's with regard to lubrication of the sprocket bearing from factory and also the heat treating of the cranks. The result is that the bearing wears a groove in the crank, causing too much slop in the sprocket, and can even start letting it cut into the oil pump.
Previously I'd either told the customer it needs a new crank if it was really bad, or torn it down or parts. However I've gotten sick of tearing down perfectly good saws, so a fix was in order.
I was doing some reading and found that McCulloch used an oil filled bronze bushing on some of their saws in place of a sprocket bearing, so I set about finding myself the right product. I ended up with an oilite sintered bronze bushing, cost 1.50 each.
Mac sprocket with bushing installed
They're designed to be a tight running fit, so they immediately take up the slop of a needle bearing. Here's some pics, this saw will be getting a month of hard work and will then be torn in bits to see what the bronze is like.
I immediately noticed how little slop there was on the sprocket, and the saw now runs and idles fine. Also the bushing won't be doing anything unless the saw is idling, so I'm not overly concerned as no matter what happens the soft sintered bronze can't damage the crank (any more).
Even if it only lasts a month, It'll be a practice I'll start adopting for some of my customers and my own work 261, as I can deal with 1.50 and 5 minutes work once a month.
Previously I'd either told the customer it needs a new crank if it was really bad, or torn it down or parts. However I've gotten sick of tearing down perfectly good saws, so a fix was in order.
I was doing some reading and found that McCulloch used an oil filled bronze bushing on some of their saws in place of a sprocket bearing, so I set about finding myself the right product. I ended up with an oilite sintered bronze bushing, cost 1.50 each.
Mac sprocket with bushing installed
They're designed to be a tight running fit, so they immediately take up the slop of a needle bearing. Here's some pics, this saw will be getting a month of hard work and will then be torn in bits to see what the bronze is like.
I immediately noticed how little slop there was on the sprocket, and the saw now runs and idles fine. Also the bushing won't be doing anything unless the saw is idling, so I'm not overly concerned as no matter what happens the soft sintered bronze can't damage the crank (any more).
Even if it only lasts a month, It'll be a practice I'll start adopting for some of my customers and my own work 261, as I can deal with 1.50 and 5 minutes work once a month.
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