Here's the story as I know it and then I'll speculate.....
I cranked my 3.5HP Mini Petter pump today to take videos for Emerald. I took one at about thirty seconds and several more for grins with a dark background and the exhaust plume in the sun. No smoke after the muffler burnt off a little oil. It was holding 32 psi and pumping water into two one inch poly pipes and then to nearly an acre of sprinklers. No problems so I went up to the shop to break into a spanking new PS-Jkson short block for my tired ol' Listeroid, but I degress.
The Petter ran great for about 25 minutes...full of fuel and oil and everything ready to go all day, then I heard the tone change into 'dragster' mode. I ran that way for about nine leaps and decided since IT was on the OTHER side of a poured concrete building full of hot water and *I* was on the safe side....I'd just stay there and try to figure out what happened once the smoke/dust/parts cleared some.
There WAS smoke! Black, unburned fuel smoke and puffs of white. The RPMs finally leveled off but the smoke kept rolling. The engine sounded rough...much like the video posted elsewhere, and popped and missed a bunch but kept right on running. I considered going down and pushing on the throttle bar with a rake handle, but not for long.
IT took six minutes by the watch for the engine to start missing more often and finally staggered to a stop. I'd already gathered a fire extingisher and my IR gun to see what a molten puddle of Petter actually measured.
I peeked around the corner and it was sitting there slightly smoldering around the pepper can muffler but otherwise plumb normal. The head was a little warm at 199 but not bad.
The mystery became 'why did it quit'? I checked the oil---down to the 'add' line. I 'shot' every part of it with the IR gun and saw nothing out of ordinary hot except the muffler. IT was toasty!! The flywheel was perfectly free and it had plenty of compression, too! I couldn't help but try to crank it back up. No squeek from the injector. OUT of fuel!!
It had sucked down a whole tank in 31 minutes! NO wonder it blew a lot of smoke!
I re-filled the fuel tank and purged the line and tried it. FIRST time it fired and off it went. BLACK smoke, white smoke, billows of it. I noticed the governor lever was bouncing back and forth when I shoved it over to shut it down.
The governor weights are NOT controlling the throttle bar. I thought about that for a while.
The pumpsets are crankshaft started on the 'other' side. The pump is mounted on the ordinary crankshaft extension. That means the governor end of the camshaft is behind the flywheel and tough to get to. I decided, in the interest of science and just because I'm not too bright, to get out my fancy new laser guided tachometer and find out what the engine was really doing and where was it *supposed* to run. (1500 on this one).
I cleaned of an area of the flywheel across the face and then on the back towards the throttle bar for the tape. I wanted to be able to see the reflective tape from somewhere other than in line with the shrapnel, but I put enough on the face that I could compare readings.
The first run I took video with one hand and controlled the throttle bar with the other, then I switched to the tachometer and re-started the engine.
WOW!! This engine will climb to 2500 rpm so fast you don't know it's gone! Past that the black smoke starts (along with squirts from my adrenal gland) until the valves float(?) and the popping starts with puffs of white smoke. I pushed the 'record' button on the tach and, after several partial shutdowns to rearrange my escape path, let it climb to 3855 rpm.! It *might* have gone a little higher if I'd let it try, but I'd seen (all too close) what I wanted to see and there's no use doing it just for grins.
I monkeyed with the governor bar. It takes about six pounds of pressure by hand on the yellow knob to make it slow to 1500 rpm. If released it immediately goes into boogety boogity mode. The governor bar just hangs out and rattles back and forth when the engine is in full runaway. The six pounds is the spring inside the rubber sleeve on the throttle bar. The governor is somehow 'disconnected'.
Here's the innards of a MP governor--
http://community.webshots.com/photo/2817818680028237237LaeogPI don't yet know HOW it can DO this!!
Comments welcome.