Phils
Platinum Member
That electric pump is in its third and final mounting location: on the inside tub wall just fwd of the battery, under the gas tank, almost to the hyd filter. The hose is routed back under the tub 'lip' and then goes up to the carb at the right rear corner of the Robin engine.
Friday I was able to completely mow my entire yard without once being stopped because of vaporlock. I'm guessing it to be 3 or 4 sometimes steep and hilly acres and I've always been stopped by VL before the job was finished, making it a two or three session project (which hasn't been a problem as this could be considered a 'two-or-three-beverage' job). I'd still have it all done in two or three hours counting a lot of 'cool-down' time. This time I was finished in an hour.
Interestingly enough, I also have no more "run-on" when shutting down. Not even a little. During some other jobs Saturday I found the little "pop" when shutting down has almost disappeared too. If I let the PT engine idle for 1/2 minute or so before turning it off (after full power PTO operation), no "pop". I haven't had enough time to try all the combinations (ie - shutting it off at other throttle settings) yet. Before this fuel modification I got the pop or run-on no matter how I shut down, although I never tried letting it idle for more than a long minute as that really should be enough.
This indicates to me that the Robin-powered PTs suffer hot fuel problems because the fuel hose and pump are in such close proximity to the [very] hot exhaust. The engine runs lean (until it stops altogether from VL) which makes it run hotter, which puts more heat to those fuel components. Which makes the engine run hotter as the fuel mixture gets more lean. A vicious cycle.
But not a problem that would affect a PT powered by an engine with a rear exhaust and fuel hoses and pump away from those hot parts (like MR's Kohler, for instance).
Phil
Friday I was able to completely mow my entire yard without once being stopped because of vaporlock. I'm guessing it to be 3 or 4 sometimes steep and hilly acres and I've always been stopped by VL before the job was finished, making it a two or three session project (which hasn't been a problem as this could be considered a 'two-or-three-beverage' job). I'd still have it all done in two or three hours counting a lot of 'cool-down' time. This time I was finished in an hour.
Interestingly enough, I also have no more "run-on" when shutting down. Not even a little. During some other jobs Saturday I found the little "pop" when shutting down has almost disappeared too. If I let the PT engine idle for 1/2 minute or so before turning it off (after full power PTO operation), no "pop". I haven't had enough time to try all the combinations (ie - shutting it off at other throttle settings) yet. Before this fuel modification I got the pop or run-on no matter how I shut down, although I never tried letting it idle for more than a long minute as that really should be enough.
This indicates to me that the Robin-powered PTs suffer hot fuel problems because the fuel hose and pump are in such close proximity to the [very] hot exhaust. The engine runs lean (until it stops altogether from VL) which makes it run hotter, which puts more heat to those fuel components. Which makes the engine run hotter as the fuel mixture gets more lean. A vicious cycle.
But not a problem that would affect a PT powered by an engine with a rear exhaust and fuel hoses and pump away from those hot parts (like MR's Kohler, for instance).
Phil
