[CharleyL]

Make sure you replace the float and the needle inlet valve that it's hitched to, along with the usual rebuild kit. Over time, plastic floats absorb some of the thinner solvents in the fuel and no longer float at the correct level. This takes a long time, but with the age of these engines, they are likely all bad by now. This change in fuel level affects how well the carburetor performs, so even if the carburetor has been completely cleaned and rebuilt using the usual rebuild kits, the engine won't run correctly. Carter makes good carburetors and you might consider just replacing it with a new one, but I have no idea what this will cost. Cushman used Carter, Rochester, and Keihin carburetors on these engines, probably based on which they could get cheaper or in quantity.

I never cared for Rochester carbs after fighting with them on an old Ford 60 Series V-8 in a race car. After switching to the Carters it could actually win races.

Usually, when the rubber parts in the fuel pump fail, it adds gas to the engine crankcase, thinning the oil. This can happen quickly. Watch the oil level closely (check it every day before running the engine). If the oil level starts rising, it's time for a new fuel pump. Of course, it can also fail to pump the fuel too, usually because of a bad check valve in the pump.

The diaphram in the kit is likely the accelerator pump. Yes, change it too. You should be able to buy every part for the carburetor separately or the kit containing the most often needed parts. At the age of these motors and carburetors, a complete replacement of the gaskets, diaphrams, float needle valve and float in the carburetor is the only way to achieve success. Been There Done That, and learned from many hours of frustration.

Yes, you have an 18 hp OMC engine (spark plugs below center of the cylinders. You can gain 4 hp and make it a 22 hp engine by just replacing the cylinders, but at last check, they were $150 each with the valves and valve springs already installed, and you shouldn't replace just one when changing sizes. The cylinders for these OMC engines are the same part number for both sides of the engine. Both valves are identical, so it doesn't matter which is exhaust or intake. You should replace the piston rings if you replace the cylinder too, and make certain that the gap in each ring is oriented 180 deg from the adjacent ring as you insert the piston. On a used cylinder, check for scoring and glazing of the inside, and always hone the inside walls before using them again, even if it's just enough to break the glaze. Very fine honing scratches that spiral up and down should be the finish that you want before assembly.

You will need a ring compressor tool and it needs to be one that's just a collar of the correct diameter and a pair of special locking pliers that squeezes the collar together. Most ring compressors will not work because with OMC engines the cylinder head does not come off the top of the cylinder, so the ring compressor must be used when inserting the piston into the cylinder from the bottom and then be removeable once the job is complete, so the band must open to slide it off the connecting rod sideways once the rings and piston are in the cylinder. This type of ring compressor is available as a kit with many sizes of bands and the special locking pliers. You will likely never need any of the other bands except for the 3.5" band, but this type of ring compressor will work when inserting a piston from either the top or bottom of the cylinder, while those normally available can only be used from the top of a cylinder with removeable head and will not work for these OMC engines unless the piston is completely removed from the engine before it is used.

I'm in Central North Carolina, so not just around the corner from you, so my help is going to be limited to helping you this way.

Charley