Picked up a beatup YS624W which needed work. It came with a matted mouse nest in the tractor base and a worn through impeller barrel due to tossing rocks. The rusted sections on the right and left of the barrel bottom are pushed out about 1/2 -3/4 of an inch. The main drive gear support post and flange bearings were also worn (pictures below).
The impeller area diameter is only 10.5 inches and has a whole worn through. The worn an pushed out sections are in the forward part of the lower barrel. A sheet of steel was installed with rivets. The machine is an impressive tosser and due to it's high impeller speed and powerful engine that does not sag much under load so able to keep up the RPMs.
A nice feature is a class viewing window to check the oil level. Note the heavy cast iron oil catch whch is part of the bracket for the engine support mount.
The impeller arms are mishapen and the plate also distorted but not as bad as the picture shows. The bent area is due to camera angle distortion. Note that the impeller diameter is 10 inches.
Got the impeller back into reasonable shape and put on some Rustoleum.
The muffler was rusted but the metal solid so taken off, wire brushed and painted with hight temp paint.
Muffler heat shield and air box covers painted. Muffler in much better shape.
The engine sits on motor mounts about 1/2 in above the tractor base. Two big rubber mounts on standoffs support the mounts which are connected to the engine cover by heavy brackets. The left facing bracket has a rusted section at the L bend. It's cracked at the rust area for almost it's entire lengts. I've had about 6 of these machines and two have had broken motor mount brackets. The other was on an 828 base bracket but both 6 and 8 hp machine use the same bracket. 2 out of 6 with broken brackets makes me suspect that the brackets may be a weak point in the design. I did not notice on the other machine if the brackets were broken or cracked but they may have been.
Note the brackets are mounted to the engine front cover which is made of very thick aluminum about twice the thickness of a Tecumseh cover. It's also very nicely machined.
Rear engine mounts.
The engine is raised up off the base about 3/4 of an inch, enough to snake a cable underneath.
Wheel drive gears are enclosed in a case which mounts to the tractor base side. Note the grease is well spread on the gears. There are voids in the case but the paste grease still got around somehow. BUT, notice the center of the primary gear on the left. It's mounted on a post with flange bearings on both sides. The flange bearings were completely worn away. There were no traces of the flange bearings in the case. They had been ground to a powder and mixed into the grease.
The gearcase cleaned up. Note the roller bearings in the case. You can see the primary gear support post is heavily worn out of shape. The post is a tight fit so pops out and only a few dollar part. The post may be a weak point in the design due to not getting any grease. The flange bearings on the primary are very thin and do not have self contained oil so they don't get lub'ed. The gase does have a gasket so fitting a new gasket and adding sealer might be tried in hopes it will hold liquid grease. A screw hold can be added to the top for dumping in liquid grease. The primary gear center section was worn so bad it had to be replaced, $89. The teeth of both gears were fine so the paste grease fine there but did not help much for the center section and post. All in all it lasted about 26 years so not bad but having lub would be better.
Nice engine with lots of power. Note no crankshaft going out of the block. The drive is from the camshaft PTO. The engine runs at 4000 rpmon the 6hp and 3850-3900 on the 8hp. The PTO runs at 2000 RPM. The rakes I think run at 300 and the impeller 1400 or so. These engines are very nice and do not sag much under load compared to a Tecumseh. They are at least equal to a Honda GX and probably better. Note the black rubber mounts on top to dampen gas tank vibration. The tank has 4 posts and set into the tank mounts with hair pins.
Nicely machined head area. The engine is getting rings and a valve job. The engine compression was within spec but at the low end of its range but it had very good spring back. It would be nice to get it peaked so with get some work. The goal is to get it running well and compare it to a Honda 624. The Honda 624 is a great machine and so is the YS624 but I think the Yamaha may have a slight edge.
When the piston is covered with my hand and the flywheel turned through a compression stroke the flywheel will bounce back and the spring back can be done once or twice more before it leaks by the rings.
Liner inserted and painted.
Lower bucket side distortion due to being thinned and pushed out by rocks. The machine will clean up nicely but unfortunatly will have the rivets showing and the bulges.
