It's not elctro-mechanical, it's a diaphragm pump driven by a hose that connects to the crankcase vent so it gets a pressure pulse from the crankcase. It doubles as the crankcase vent and filter. Without it, like mine, the crankcase vent hose is probably connected to the airbox to use that filter. There are filters you can just stick on the end of the hose, too. Without the pump, that hose has to go somewhere. The crankcase vent hole should have a hose stuck in it, it's just below the carb. The fuel pump would be bolted to the case just below the vent hole, near the bottom of the case. In the picture, I have my stupid ****ty (that died, and is not replaceable so I have to buy another engine because of it- I have the Huasheng 144F 53cc engine with the 14v, 7A stator, the only one with a CDI box, instead of a magneto type coil) CDI box is attached where the fuel pump would have been, so you can't see it. I had a bad feeling that CDI box wss going to be trouble.
And again, your other option to mount a tank elsewhere (you can buy that pump from Honda) would be to adapt one of those rotary valve diaphragm Walbro (or a clone thereof- use the 15mm, the 10 and 12 are too small) "squishy bulb" carbs, like I did. I got mine from another engine, so I had the manifold, too. Those are either plastic or aluminum. This is what mine looked like before I put the velocity stack and it's airbox on.
It shows that crankcase ventilation hose, that I had to do something creative with. I drilled a hole into the airbox, past the air filter, and put in a hose fitting that I could stick the hose on. It just has to be open to a clean air source, with some kind of filter to keep grit out of the crankcase. On original GXH50's, that is done by the fuel pump. That pump, btw will have 3 hose connections, inlet, outlet, and crankcase pulse to drive the diaphragm.
maybe if I get bored (it's not there is anything worth watching on tv anymore these days) I'll elaborate on the story of this engine, and it's charging system, since I am the only person who ever got it to work, which was an ordeal of it's own, which has me hopelessly locked into this engine, now. What a huge pain in the ass.
The so called charging system on this engine, which is the only feature that makes this engine unique (as well as $100 more expensive) is extremely unusual. It's a 14vac, 7A stator (or "half a stator", as I refer to it), as opposed to a conventional stator which produces 28vac, and uses a half wave, single diode rectifier circuit like a voltage divider, to create pulsed 14vdc at 50% duty cycle. That means that it needs a very special full wave regulator-rectifier (that it didn't come with for reasons that are obvious, now, in hindsight, they didn't know where to get one, either, I think) that was very hard to find. There are only 2 different kinds of them made, anywhere, and only one of them will work on this engine. And wouldn't you know it, it had to be the $50, 150 watt one, I burned up 2 of the $8, 100 watt ones, and even tried to use a separate charge controller and full wave bridge rectifier, before I gave in and bought the $50 one, which worked wonderfully until my CDI box took a **** on me one morning for no diagnosable reason. But I really liked that charging system, that didn't need a battery to run the lights. And it was soooo much ******** to get working, I just can't bring myself to take that many steps backwards, you know? And thank goodness I got me degree in automechanics, so I actually have the book knowledge that to took to figure out wtf was up with this engine in the first place. Like I said, as far as I know, nobody else ever got it to work, at least not before I did, and posted the way to do it so that hopefully, nobody else would have to go through what I had to to do it. A wise friend of mine once told me "to go only 9 10ths of all the way, is to suffer at each of those 9 steps, utter madness", so true. And here is what I say:
"If you set a man a fire, you'll keep him warm for a night, but if you set a man ON fire, you'll keep him warm for the rest of his life!" and that is also very true. But then again, I'm as crazy as they come, so what do I know, anyway?
