Re: rebuild vs. new
Fgose.... When you say that "compression was lost", I am assuming that you are refering to only one (1) cylinder, possibly two (2), but not all cylinders.<br /><br />If this loss of compression was due to a VRO failure, oil restriction, air in the oil line, something of that nature, it would have affected the entire engine, not one or two cylinders.<br /><br />The failure of one cylinder (or two etc) would be caused by (usually) fouled carburetors, of which your engine has one carburetor for each cylinder. Carburetors foul, clog, gum up, etc, due to having the interior of the fuel lines deteriorate which seldom happens, or having the engine sit for a month or more. Faulty carburetors cause the engine to run lean on whatever cylinder they are supplying fuel to. The lean mixture causes friction, friction causes excessive heat, eventually the piston and/or rings fail.<br /><br />Also, if ignition was lost to one or two cylinders, this would eventually cause the fuel to overcome the oil which in turn would create a improper fuel mixture. This leads to what most mechanics call a "washout" which really tears a piston to pieces.<br /><br />NOTE... If there was metal flying around on top of the piston, and any of that metal has embedded itself in the cylinder head dome, replace the cylinder head. No mechanic will ever be able to remove all of those tiny steel flakes that are embedded, and with the engine running, those flakes will glow similar to a model airplane engines glow plug. That glow plug effect will cause pre-ignition which will most certainly melt a piston (don't want that).<br /><br />The fuel primer bulb is hard only when primed. As the engine runs, the bulb is usually in a horizontal position and the fuel drops down to the midway point which is normal, but the bulb will remain fully expanded. If it has a tendency to collapse, a fuel restriction exists between the bulb and the fuel supply.<br /><br />The oil primer bulb will be hard all of the time which is normal as oil has a thicker viscosity. Perhaps there are other reasons it retains its firmness that I'm not aware of. If the oil primer bulb loses that firmness, there would have to be a air leak between that bulb and the oil supply.<br /><br />Whether to rebuild or replace is a judgement call you'll need to make. It's more reasonable to rebuild ($$$) if it's done properly by a mechanic that knows exactly what he's doing, and one that you have complete faith in. Keep in mind that there are mechanics.... and there are parts replacers.<br /><br />Usually when I rebuild a powerhead, and the VRO is a year or two old, I replace the VRO on general principles, but there are exceptions. In your case, your engine has two VROs if I'm not mistaken and replacing them would be fairly expensive. If they're four or five years old, I'd still replace them, or you could re-use them and run the following test.<br /><br />After rebuilding, run the engine at a fast idle (not too fast), then clamp the oil line shut that leads to one VRO. The warning horn should sound off (a beep every other second) within a short time. Release the clamp on the oil line... the horn should go silent. Now do the same test on the other VRO. If the VROs check out okay, and the warning horn system is operational, I think re-using the original VROs would be okay.<br /><br />Do replace the oil pickup filter screens that are located within the oil tank.<br /><br />If you decide to do away with the VRO system and mix the oil with the fuel, instructions are listed below.<br /><br />(VRO Pump Conversion To Straight Fuel Pump)<br /><br />You can convert the VRO pump into a straight fuel pump, eliminating the oil tank and VRO pump warning system, but retain the overheat warning setup by doing the following:<br /><br />1 - Cut and plug the oil line at the engine so that the oil side of the VRO pump will not draw air into its system. Trace the wires from the back of the VRO to its rubber plug (electrical plug) and disconnect it.<br /><br />2 - Trace the two wires from the oil tank to the engine, disconnect those two wires, then remove them and the oil tank.<br /><br />3 - Mix the 50/1 oil in the proper amount with whatever quanity fuel you have. Disconnect the fuel line at the engine. Pump the fuel primer bulb until fuel exits that hose with the tint of whatever oil you used. Reconnect the fuel hose.<br /><br />That's it. If you want to test the heat warning system to ease your mind, have the key in the on position, then ground out the tan heat sensor wire that you'll find protruding from the cylinder head. The warning horn should sound off.
<br /><br />My experience with the VRO primer bulb is that they always remain hard (when they are working properly). This does not mean that there might not be water in the VRO tank. Draining the tank and replacing the pick up sock-annually is a good idea, as Joe says.