Strange case  By  omarx646 (Read 750 times)

Omarx646,

Welcome to the site!

Your experience is quite normal. When you run out of gas, for a short time (before running dry) the engine leans out which will speed it up.

When it's cold, the air is more dense, and you get a slight power increase (like a little bit of supercharging). When it's hot, the air is less dense, and you get a slightly "weaker" air/fuel charge into the cylinder, producing a little less power.  Gas engines usually run their very BEST on cool, damp days.

Probably this phenomenon is more pronounced with carbureted engines, while electronic fuel-injection maintains a more even air/fuel mix in a variety of temperatures.

Most all of us have the same experience with our scooters, cars, etc.

Ride safe!

Leo in Texas

Sept 2, 2015 9:25:38 GMT -5 omarx646 said:

oldchopperguy and JR thanks by your response. I supose Iwil have to play wit carburetor jets and see what ocurrs.

Playing with your carb jets can indeed improve performance. I happily rode a Chinese 150 for seven years (a Xingyue, similar to your scooter) and had to use a richer main jet to obtain optimum performance. (My factory idle jet was OK).

In addition, I had to adjust the "needle" in the carb-slide to get it to give snappy acceleration from idle.  The air-filter also made a BIG difference, and when replaced with a UNI "sock" filter, then, the main jet and needle "fine-tuned" it ran really well.

Other mods which produced improved performance were: 1. Replacing the factory CDI with a no-rev-limit performance unit.  2. Replacing the factory coil with a Japanese Bando coil and iridium plug. 3. Experimenting with roller-weights in the CVT variator brought MAJOR improvements in acceleration and cruising speed.  4. Replacing the factory exhaust-header with a full-diameter header and a free-flowing muffler.

The factory headers on most GY6 150's are UNDERSIZED, being SMALLER than the actual exhaust-port in the head.  This "chokes" the exhaust right at the port, where it does the most harm.  A full-diameter header allows the exhaust to flow freely from the head, providing generally better overall performance.  Even "chamfering" the stock header where it joins the head to ease the exhaust flow will help. (I found improving the HEADER was far more critical to general performance than the MUFFLER).  The mufflers are not actually THAT bad...  In my opinion, it's the undersized headers that choke performance.

These are all relatively small things (affordable, and requiring only hand-tools) which make a noticeable difference in performance.  On an engine that puts out only around 10 hp (which is actually pretty good for 10 cid) even the slightest performance gain is welcome.  These mods to carb, exhaust and variator really do much more to improve general "drivability" than adding more speed, but make the riding experience much more enjoyable.

I'm an old-school big-bike guy, and these new-generation scooters are a whole different world.  Fortunately, MUCH more affordable, AND easier to fool with than big motorcycles...  There is no end to the mods possible on these small scooter engines and trannies...  It's all part of the riding experience!

Hope this info may help you out.

Ride safe!

Leo in Texas

PS: I had just totally "perfected" my 150 when local roads changed, increasing traffic speeds beyond what my 150 could safely compete with.  So...  I traded it on a used Kymco 250 simply for a little more speed to keep up with the traffic...  Somebody got the SWEETEST running Chinese 150 in Texas when they bought "Lil' Bubba" from my dealer... LOL!