Vino performance issues

[dirtrider]

Hi, new to this forum. I have a 2003 vino 49cc 2500 miles. Previous owner did a lot of mods, to exhaust, airbox, suspension, etc. I had to replace the exhaust pipe, airbox, install new filter, new plug, manifold, etc. The issues are; 1) scoot stalls at stop after riding aways, 2) motor stutters at about 1/4 or 1/2 throttle to full, 3) the main and pilot jets in the carb are a number higher than shop manual calls for-#64 main, is #65, #46 pilot jet, is #48, 4) pilot air screw on outside of the carb, is turned all the way in. 5) After filling the tank up with almost 1.5 gallons, its almost empty after 40 miles. I live in Colorado Springs at about 6500 feet. I removed the retrictor on the new exhaust, the scoot has pretty good power top speed around 45 mph. the scoot does not leak any fuel on the ground, though it did until I had to fix a hole in the carb caused by 2-up riding and rubbing on the swing arm. Fixed with JB cold weld.

Does anyone have a theory on the bad mileage and other performance issues?

[mpathus]

Reverting to original parts (airbox etc.) will most likely require close to original jetting as well, albeit on the side of leaner than original due to your altitude.

That #48 pilot jet seems too large for your altitude and could need to be down jetted to lean out a very rich idle. That over richness at idle could be your stalling issue. (I purposely over-leaned my idle some so it wouldn't almost stall after riding. My mid throttle is intentionally rich. I'm near sea level.)

Your high altitude has less dense air and all jetting should be proportional. If you decide to down jet the pilot, you MAY need to upjet the main some to compensate for your carb's overall a/f ratio.

Example: I'm at sea level and my Dellorto PHBG pilot jet is #45, a/f mix screw ~1 turn out. If I were tuning for Colorado Springs (I wish!) I'd try a #35-#38 pilot and start from there.

Over richness will decrease fuel economy.

[dirtrider]

Thanks, I now have the slightly leaner main jet installed, pilot was correct, just needed a magnifier. Carb put back in, now, it wont start.

[mpathus]

Starting circuit ok? As long as you put it back together right and you're getting fuel (no air bubbles in the fuel line, bowl full?), you will still need to richen when cold starting. Make sure there are no air leaks to spoil the vacuum through the carb's venturi.

Todays starting circuits may differ one to another technically, but aim to do the same thing: give a shot more fuel when cold.

For example: my Dellorto PHBG carb has a manual "choke" cable that I pull to disengage a stopper that normally closes off an enrichment tube to bypasses the throttle slide. This cable can be adjusted to open the stopper more and allow more enriched air/fuel if needed.

Your Vino's system is probably different but may have some adjustability. Then there is the pilot's A/F mixture screw that can be adjusted to allow overall richening at idle, which may help startup.

In the old days we could just cover the carb mouth with our hand some till she would start - simple and "hands on" reliable.

[dirtrider]

After 3 days and one battery recharge it rose from the dead. I'm thinkin the bowl maybe didn't have gas in it. It started up and runs like a champ! It's run better than past 3 years. Thanks for all the advice, mpathus.

[mpathus]

:) !