I have a craftsman self- propelled lawn mower, model 917.377791 that won't self-propel. The drive belt is cracked but intact and the idler pulley does not tighten the belt. I would like to replace belt but have not been able to determine how to get it off the engine. Its easy to get off the idler system and transmission pulley. How do I do this and second what is the correct configuration of the belt on the idler pulley?

Thanks

Hi,
Your machine has a BBC(blade brake clutch) on it that must be removed to access the belt under the engine. The parts breakdown is not clear, often if the retaining bolt is removed, then there is a threaded area to push this off the crank with the correct bolt.
Another thing is that the gears on the inside of the wheels can strip, especially if the dustcovers have been damaged.
Peace,
Clarke

Could be due to several causes... (1) transmission, (2) internal wheel gearing is worn, (3) torsion springs in wheel drive pinion is broken (4) drive belt is too loose. I would do the following to trouble shoot. With the belt cover removed and the drive engaged does the transmission shaft move? If it does, the problem probably resides in the pinion assembly or the gearing in the wheels. Remove wheels and check to see if gear teeth are worn off. If so, replace the wheels. If wheel gear teeth are OK... check the pinion assembly. It could be the torsion spring or the small lug within the pinion. You easily rebuild the pinion or simply replace the assembly. If the transmission shaft is not moving, its either the belt is too loose and needs to be replace or the transmission gearing is shot. First try to tighten the drive cable by pushing the button behind the ez walk handle and using the grip. Instructions are in the manual. If the drive belt needs to be replaced the BBC DOSE NOT have to be removed. To remove the drive belt... remove the blade, remove the plastic grass cover(4 bolts), take pictures of the entire assembly. Find the manual and the diagram of parts of the assembly. Remove spring 80, remove U retainer 81 by knocking in through the retaining bracket holes. The clutch is spring loaded and will snap back to its untensioned position. Rotate part of the clutch to loosen tension of spring 83. Unhook spring 83 from bottom. At this point the belt can be removed from the bottom of the mower. From the top of the mower, remover top cover, take pictures of belt area, loosen pulley tension bolt,61, to the point where you can work the belt off. You do not have to remove. Detach the drive cable spring from the pulley tension and remove belt. If there is not enough slack in cable to remove the spring from the pulley assembly simply press the button behind the ez drive assembly on the handle and work the grip to loosen. To install just reverse the procedure. Once the drive belt is replaced the next challenge will be reinstalling part 81. First reattach spring 83. Then using a lever push the clutch plate to the proper position until you can re insert part 81. Then install spring 80. With the lawnmower position with the carb up there is a slot in the engine where you can insert the lever to position it correctly. It will take a bit of fussing. Reinstall the cover shroud and blade.The drive belt replacement is actually quite simple once you have done it... maybe 30-45 min. The final operation is to retension the drive cable using the EZ grip handle. Other suggestions... remove oil, position the lawnmower with the carburetor in the up position, take pictures to aid in reassembly. If the transmission is shot and needs to be replaced... don't know... have not done that yet. Home this helps someone.