"Gordon,
When ever considerin
"Gordon,
When ever considering a power head rebuild the very first thing that needs to be done is to disassemble, clean, and inspect. You cannot second guess anything. With the compression numbers you gave it is almost certain that you have some scoring. Viewing the cylinder walls through the exhaust ports doesn’t give you the full picture, however, if extensive damage is seen on the intake side then it may negate wasting further time, but a trained eye would be necessary for that determination. Disassembly will reveal the most obvious and I think it will be in the cylinders. From there a good eye can determine the necessary over bore. Next, unless there is obvious damage to the crankshaft and lower connecting rod bearing surfaces I would start inspection, paying particular attention to pitting, flaking, and discoloration, followed by dimensional inspection. If all is good at this point you probably have something to work with. Next, and very important, is to determine the cause of the damage and correct it so it doesn’t happen again. Fuel restriction or air leak do to, tank, hose, primer bulb, connections, carbs or fuel pump? Water pump? A rebuild of all items is inexpensive and should be done to eliminate those possibilities. One other item that is most often overlooked is the gear case. What kind of shape is it in? Nothing like spending a bunch of money on the power head only to have the gear case go. Considering the age of the motor I would polish all crank and rod bearing surfaces and replace all bearings as this will most likely add to service life. All gaskets and seals? Well we know what to do with them, right? Now that you know what is needed for parts and labor, and you have a good idea of the condition of the rest of the motor, you are in a position to make an educated decision. The plus side here is that if it is done correctly you know what you have and you can expect it to last. This is by no means all there is to it, and I’m sure that others could easily add to what I have failed to mention, but it should at least get you thinking."
