I have a McCulloch Mac 310. The chain seizes up after a few minutes use. When it cools down the chain will move. I replaced the sprocket. I removed the brake. Same problem.

I had a saw that did that and found my blade the chain runs in was bent. Another problem was the groove the chain goes in had a gouge that did not look like much but was just enough to throw the chain. Also check the drive sprocket and make sure it lines up with the groove in the blade the chain runs in.I replaced the blade and its ok now.

Loosen and remove bar lock nuts and cover. screw tensioning screw to loosest point. wrap chain onto teeth of drive sprocket, then within grooves on bar. Be certain cutting edges are facing forward. Look at chain before removing. set bar with new chain to ensure the tension pin aligns with bar tensioning hole. Replace cover set nuts loosely. Tighten chain to about 1/4" out of groove when pulled on (wear gloves). Tighten nuts, spin chain to see it moves freely but does not hang free og bar groove. re-tension as necessary. Happy cutting!

With the cove off you should be able to turn the sprocket easily, if not the brake is on, grab the hand guard and pull it fully back toward the rear of the saw until the brake clicks and the drum can be turned.

You'll need to take that to your local authorized service center.

You may contact the manufacturer, download manuals, check fuel/oil ratios, order parts, find your local service center, and view other resources using these links:

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What is the correct fuel mixture for McCulloch products Chainsaw Trimmer...
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did u take the cover off ? the sprocket or chain could be packed. did u check the brake?

Refer to your service manual or I recommend contacting your local authorized service center for assistance.

You may contact the manufacturer, download manuals, check fuel/oil ratios, order parts, find your local service center, and view other resources using these links:

Contact us
User manuals
What is the correct fuel mixture for McCulloch products Chainsaw Trimmer...
McCulloch Service
McCULLOCH PARTS ACCESSORIES

I trust this information has proven beneficial.

User manuals may be downloaded using the provided links:

You may contact the manufacturer, download manuals, check fuel/oil ratios, order parts, find your local service center, and view other resources using these links:

Contact us
User manuals
What is the correct fuel mixture for McCulloch products Chainsaw Trimmer...
McCulloch Service
McCULLOCH PARTS ACCESSORIES

I trust this information has proven beneficial.

The chain may have come off the sprocket.
There are 2 nuts about an inch apart down just past the bar which hold it in place.
Remove the 2 nuts, take off the cover which they hold in place and the bar and chain will loosen.
Check that the teeth on the inside of the chain are on the sprocket. Pull the chain tight against the sprocket and move it. Check that the sprocket turns. With the chain set in the sprocket replace the bar, chain and cover and try turning it again by hand. If it doesn't turn don't try to start the saw as you'll do damage.

If the chain was on properly and it still won't turn the clutch may be burned out. However the fact that you couldn't turn it by hand suggests that the chain was off the sprocket.

A parts book can be found at the following URL.
http://mcculloch.motoruf.de/spell/get_file.php?filepath=/Mipl/pspm310.pdf
That's all i could find?

Remove the bar and chain. Does the motor run and not quit? If not, inspect the motor for sawdust plugging the vents and check the brushes for condition and length. If runs ok, check the side port for oil coming out. If ok, clean all of the holes in the drive end of the bar including the two small holes that pass oil to the chain slot. Use compressed air if available. Also, clean the chain slot all around. Oil the sprocket tip if the bar has one. Adjust the chain so that it moves freely, but doesn't droop from the bar.