Do you have any reccomendations for the jackshaft, cutter head bearings? Im also having trouble setting the right belt tension it seems. The owners manual reccomendations are slightly confusing to me and there are no videos on youtube to use as reference! I will definitely take your advice on the larger oil filter as well! How can i tell if that CH25 is a nikisil lined block? Can you rehone them? Or does the nikisl chip like on chainsaw cylinders?
For the bearings, DO NOT skimp on bearing quality. Get the original style bearings (Dodge if I remember right). Drop the coin and get the best bearings money can buy. Been there, done that. The China, Taiwan, etc bearings do not hold up. Like not even half the life of the Dodge bearings, and it's a lotta damn work to replace them and line everything up again.
Which brings me to the next thing... That toothed belt is REALLY expensive. Pulley alignment is critical to making it last. Get (or make) a good straight-edge to help with this. I used a section of shaft from a commercial trimmer cut down to about three feet long. Use this to lay on the outer edges of the pulleys to reference one to the other. Get the cutter shaft set in place and square with the frame, then torque the bolts down. Then, remove each bearing collar setscrew one at a time, use a drill bit that barely fits the hole, drill a DEEP divot (1/8" ish) in the cutter shaft for the setscrew to seat itself into, and re-install the set screw with BLUE loctite and tighten. NOT RED (learn from my mistakes). Repeat for the other three setscrews on the cutter shaft. All further adjustments are done at the jackshaft. Use your straight edge to line the pulleys up so that both are on the same plane, and the jackshaft is absolutely parallel with the cutter shaft. And I mean dead nuts parallel. Use shims under the jackshaft pillow blocks if need be (this would be unusual, but always a possibility). Leave the jackshaft bearing collar setscrews loose while sorting this out. Once you're happy with how everything is lined up, snug the setscrews down to hold everything in place and repeat the drill each hole one at a time just like with the cutter shaft. If I were starting with all new pulleys, bearings, etc, I would get everything lined up before installing the toothed belt, mark the taper hub location on the shaft, then remove one pulley and install the belt. Then use the jacking screws on either side of the bearing to adjust the tension. Take care to move each bearing the same distance by counting "flats" on the jacking screw. This will maintain your shaft alignment. Your belt should NOT be tight. You should be able to easily deflect it back and forth. You actually want it to run "loose" but not "floppy" if that makes sense. Think of it as a rubber chain. You don't want it tensioned like a normal belt, just barely snug (for a new belt). Once broken in, it will feel kind of loose. Only re-adjust if it's flopping around a lot when running. Even then, adjust it to take the "floppy" out of it and no more. If the teeth are skipping, your pulleys are worn out. Over tight belts trap dirt and wear pulleys out faster. If your pulley teeth have an "edge" then you need new pulleys. Don't put a new $250(probably more today) belt on worn out pulleys. They will eat the belt and you'll be right back in there in less than 100 hours. A well cared for belt should last hundreds of hours. Pull that cover off every day you work the machine and clean the dirt out. Grease the HELL out of the bearings every time you use it. Pump new grease in until you see clean grease coming out. Flush out that dirt. Those bearings ain't cheap. Grease is.
The engine electric PTO to jackshaft belt from Rayco was a double v-belt. It, too, was somewhat pricey and sensitive to alignment issues. Also subject to shredding and grip issues if the PTO clutch pulley was worn down.
Don't use it. Use a pair of regular industrial v-belts. The size should be either an A69 or A70 depending on when it was made. These are fairly cheap and also provide you a "weak link". If you hang/overload the cutter wheel, you're less likely to break stuff if you just smoke $20 worth of cheap belts. Keep an extra pair on the truck just in case. If you have slipping problems (and with that CH750 you might), try using AX70 belts. They are "slab sided" instead of wrapped and grip the pulleys better.
The nikasil lined Kohlers were fairly easy to spot. Use a magnet. If the liner is cast iron, it'll stick hard. Nikasil won't stick. Nikasil engines were easy to rebuild. Run a dingleberry hone thru it a few passes and clean it up. New pistons. Done. The cylinders mostly didn't wear unless there was dirt injestion. With that little dome filter on yours, it's a real possibility. They did a horrible job even when well maintained. That filter setup was fine for mowers, but not stump grinders. I once picked up a used nikasil engine from a guy who repowered his 1625. Had that dome filter on it and it was never changed. Cylinders were trashed. The plating had worn through to the aluminum in a couple spots. Block was scrap.
I don't imagine there's many of them out there now. Once they stopped making them, all replacement engines and shortblocks were cast iron. I worked at the saw shop for about 6 years maintaining those stump grinders and I can tell you that when I went to boot camp in 2007 those nikasil blocks were getting hard to find and I was always on the lookout for them.
Hope this wall-o-text makes sense.
