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Hey Dawgs,

I have had a few problems with my 2008 275cc Aeolus (3750 miles) that I seemingly fix, but then pop back up again. I've had on-and-off trouble with the scooter losing power/dying on me, so I recently replaced the stock vacuum pump with a Mikuni high-flow pump. That cleared up all problems for about 600 miles, but it's beginning to act up again.

Before I replaced the fuel pump, the scooter seemed to be consistently losing power over a matter of weeks; every time I rode it, it seemed to need a teeny bit more throttle for the same amount of acceleration and top speed. It would occasionally die and would only run if I kept the throttle slightly twisted at all times. I would adjust the idle speed to bring it up, then a few days later it would "snap" back, and I'd have to adjust it back down again. I also had the scooter die twice and not start for a while; the first time I walked it home (1/2 mile away, thankfully,), took the fuel pump off, put it back on, and VOILA it worked again. I noticed the aforementioned power decrease over the next month or so, until finally it died again; upon taking the side panel off I saw that the stock fuel pump was covered in fuel, so I took it home and replaced the pump with a Mikuni. The next month was a glorious time of smooth riding, great acceleration, and lots of power.

Aaaaaaand...then the power decrease started back up again. It wasn't super sudden, but over the course of a week there was a noticeable decrease in power. It never got to the point of dying, but I would occasionally have to WOT the scooter to pass someone in a 40 zone...when it was running well, 1/2 throttle was plenty for that job.

The only auditory indication that something is wrong is that while running, there is a faint "raspberry" noise from the exhaust; it kinda sounds like someone blowing raspberries from the pipe. It got more noticeable as the power decrease got more accentuated, so I'm guessing they're related; could it be minor, constant backfiring from a lean mixture? Besides that, there is nothing weird.

My dad suggested that I take a stick lighter or flammable aerosol, fire up the engine on the center stand, and spray the butane/propellant along the vacuum line and around the carb; when the engine revved up, there's a leak. I tried that today with a stick lighter; I even took the lighter apart, increased the flow of butane, and waved thing around the carb, hoses, and everything else I could reach. Nothing happened.

So...I'm kinda at a loss. My dad thinks it could be a carb or vacuum issue, but I have no idea where to start. I've looked around forums, including this one, but nobody seems to share my problem. I thought that the fuel pump was the problem, but apparently it isn't; the hoses seem to be in good shape with no leaks. The scooter runs great with no trouble starting; it just requires waaay more throttle than it used to.

Thanks a bunch for helping guys like me with our problems; I probably would have junked the scooter by now...

Well, after putting it all off, I bought a Mikuni high-flow vacuum pump and installed it yesterday...rode about 35 miles today and noticed that the throttle was much more responsive, even when I rode 2-up with my sister. Hopefully it keeps going strong!

Minor question: the Mikuni pump has two fuel outlets; since I only needed one, I plugged the other by melting one end of a 2" piece of fuel line and using a hose clamp to secure it to the outlet. It seems to be holding up okay, but is there a better way to plug that hole?

Thanks a bunch! Is there any way of easily telling what the problem is without doing a full inspection? I really don't want to take the bodywork off in the owner's driveway, but on the other hand I don't want to get it home and find out it needs major repairs that I don't have the time/money to fix. He says it's free of other mechanical problems...