Gas tank minimum height ?(gravity fed)

[Watts]

Just put new engine on old viza v2 gas scooter, added a 4 stroke huasheng 142f 50cc gas engine (EPA Approved Model). I currently only have my gas tank about 1 inch above the gas inlet, wondering if this is too low and would result in loss in higher rpms? I change the oil regularly and use 91 gas in the tank, but noticed when tank is down to 1/4 full it has trouble giving gas to the scooter. I can currently only get about 25 km/hr , the old 40cc 2stroke I use to get at least 35km/hr....maybe the 4 stroke will hit higher rpms when it is fully broke in. Any advice on my gas tank and its height, and any recommendations on prefered oil and gas for huasheng 142f would be greatly appreciated. Scooter runs fine at mid throttle, but cannot hit higher rpms. Also wondering if it is worth drilling out fuel mixture adjustment hidden behind the epa brass plug? Really just trying to get those higher rpms.

 

[Gordy]

Shorten up that fuel line if you can. That might help

 

[Sidewinder Jerry]

The tank is fine. Have you used a tachometer on the engine? What kind of reduction system are you using? What size tires are you using? Are you using a 100% ethanol free gas? Post pictures of your vehicle.

 

[Watts]

Its a belt drive system that works by pulling a side belt that goes up and down and pulls a rod attached to another belt that is attached to the wheel. Not familiar with tachometers, 11.5" tires. Live in Canada (Ontario) not sure if gas is ethanol free (i doubt it).

 

[Watts]

That is as short as the gas line can go without changing placement of tank or getting a new custom rear tank (not looking to spend)

 

[Sidewinder Jerry]

Since you say you have 8" wheels, I'm going to assume you ment 8" rims and the actual diameter of the tire is closer to 12" at least. If on level ground, you're doing 25 kph (15 mph) at full throttle; which should be 6800 rpm then your drive system is around a 15\1 reduction. Tachometers are fairly inexpensive and easy to install. Then you'll know exactly what your engine is doing.

 

[Flight Risk]

I'm wondering if the filter might be better up by the tank and not on its side. If you have a filter screen in the tank make sure that is clear.

 

[Watts]

11.5" tires my apologies

 

[Watts]

Sidewinder Jerry you mention using a tachometer, which i understand can help me understand the rpm better. But what I wonder if there are little to no adjustments I can make on this engine aside from boring out the fuel mixture brass plug how can I use that information from the tachometer to make any significant changes and where?

 

[Watts]

Did some research all gas in my country has to have at least 10% ethanol in it even premium gases