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Model MC, 3 strand PTO drive belt failure and replacement.

Was mowing last week, with 335 hrs. on the clock, heard a thump and pieces of rubber flying out but still running. The 3 strand PTO drive belt had come apart. Its outer surface, holding the 3 V belts together as one had disintegrated but the belts were still in tact so could finish mowing very carefully before looking into the problem.

Local dealer had several belts in stock @ $59. In no hurry, so research determined that it is a standard 3 strand, 3L section, 40“ V belt. So went on eBay and found 3 generics from $27. To $55, all available from the same industrial supplier in LA. Talked to him and bought the cheapest, of Korean manufacture, a Jason 3-R-3-VX-400 3-Banded 3VX400 V Belt. Looks great!

A bitch to install, but fits perfectly, exactly the right length.
Adding to the Owner´s Manual replacement instructions, pg. 60:
1. Must remove the jack shaft drive belt from its driven pulley for reasonable access.
2. Had to disconnect the clutch linkage from the PTO belt tightener arm to drop the idler pulley far enough.
3. Belt was a very tight fit between the engine pulley hub and frame, had to lube it with liquid soap and pry it carefully thru the tight gap. In hind sight, I should have just removed the engine pulley and had a chamfer machined on its hub, an ⅛ off the sharp corner would have made the job a piece of cake.

Next I did the PTO clutch and brake adjustments and when doing so started to check pulley alignments.
Noticed that the clutch idler pulley was slightly out of line with the engine and PTO drive pulleys, inboard too far. Took the belt tightener arm off its pivot bolt and noticed that its outboard needle bearing was not pressed flush into the arm´s pivot hub, out by maybe 1/16“ Just what I needed to move the pulley out that far for better alignment. Pressed it in flush and reassembled. The pulley alignment now looks better. That misalignment may have been a cause premature belt failure. Not much, but that 1“ wide, 3 strand belt is very stiff latterly and being forced to flex in that plane to accommodate pulley misalignment I think may have fatigued the backing material holding the 3 strands together. Anyway, it´s back on the lawn.
Bet this belt will last 1000 hours.

berniebenz said:

That misalignment may have been a cause premature belt failure. Not much, but that 1 wide, 3 strand belt is very stiff latterly and being forced to flex in that plane to accommodate pulley misalignment I think may have fatigued the backing material holding the 3 strands together. Anyway, itｴs back on the lawn.
Bet this belt will last 1000 hours.

Click to expand...

Just a little mis alignment will build a lot of heat in those sleeve belts... heat causes them to break down ... you could get a lot more than 1000 hours with everything set up correct..
:smile:KennyV