50cc Yamaha Vino bogs down at 10-20mph

[cuwee]

I was given a 2001 50cc Yamaha Vino recently (two-stroke), and am brand new to owning/working on a scooter (literally a week). When I got it, it had been sitting for a long time and would start with starter fluid, then immediately die. I removed the carburetor and took the whole thing apart to clean it. The entire inside was corroded, and I ended up ordering a brand new replacement on eBay (it was the only matching one I could find).

I installed the new carb today, and put in new oil and gas. It starts up immediately, and idles great. I can even ride it around the block with no issues until I accelerate up to somewhere between 10-20 mph. Then it bogs down. If I let off the throttle right away it keeps running and I can keep going at a lower speed. If I keep the throttle on it dies.

It has a new spark plug, and I've tried fine-tuning the throttle stop screw on the carburetor. The current position is the best one I've found, it starts up immediately, idles nicely, and runs smoothly up to the 10-20mph speed. I've confirmed the fuel hose and vacuum hose are in good condition and not blocked. Nothing I've tried has allowed me to run at full speed.

I have no experience with engines other than what I've taught myself the last week trying to get this to run, so there are probably some obvious solutions I just don't know to try. Any help is appreciated!

[cheapeto]

I do not know your machine, but those 2 strokes can fly man.
You may need to get into the variator and clutch assembly.
I once put sliders in wrong, and the result was I could not get my 250 cc motor past 40 mph.
Also once when I installed a new belt, I had to ride like 10 miles before it seated properly in the variator.
You may want to blow out the clutch bell while your in there and check your final drive oil, as many types of scooters you need to fill it after your remove the variator cover.
Good luck.

[Roscoe]

2 cycle engines are sensitive to exhaust blockage. Since it's injected though that shouldn't be the problem. This one found when the air cleaner assembly was installed it fixed the bogging problem. Be sure it has a good fuel filter, it might need a new one since it sat for so long ...

Here ya go

[cuwee]

Roscoe, that was it! The fuel filter was already off when I got it, and I hadn’t put the whole thing back together yet since I was testing it. That fixed the bogging, so it’s no longer dying when I accelerate. However, it is topping out at 15 at full throttle. Is that a carb adjustment, an exhaust issue, or something else?

[Roscoe]

I'd be checking the carburetor to make sure it's clean and clear on the inside. If there is an after market "bug catcher" air cleaner you'll probably need larger jets.

[sc00ter]

I bet its restricted. There is a cone in the top of the exhaust, were it touches the cylinder. Dremel it out. If it still has issues, then its transmission related. Come to think about it, there may also be a restriction washer in between the variator halves.