Mpg

[hect75]

Fellow zongites,

I´m getting around 59 MPG on the vento, what about your zongshen?

[katoranger]

That sounds reasonable, but on the low side. Most get 60-70mpg.

[Pliskin]

@ hect75
Your figures seem high. I am getting 83mpg if I did the conversion correctly or 2.8 litres per 100km or 59mpg would be 3.9 litres per 100km
http://www.fadainc.com/mpg_100l.html

[SpudRider]

I think Pliskin means your mpg figure is low. How hard are you racing the Vento? If the carburetor is jetted properly, you should be getting 75 mpg, or higher, unless you are either flogging the bike, or constantly fighting strong headwinds.

[hect75]

The fuel tank capacity is 8L including the extra (1L). I filled out the tank with 7L and drove about 150 km before the vento stop (without using the extra). I ride between the 80 and 90 km/h when commuting about 35 mins (not always is windy when riding and don't flog the bike). I think, the carburetor needs to rejet.

Thanks for your comments

[hect75]

For increasing mileage, jets with small or big holes? ( I'm thinking small hole) brand to fit on vento's carb? what about the jet needle? I haven't taken a look on the spark plug but will do it this weekend to check the color.

Cheers

[SpudRider]

Your Vento Mountrack uses the same, Teikei MV28 carburetor as my Zongshen 200GY-2 motorcycle. You will learn much about your carburetor, and how to select the proper carburetor jets, by reading the following threads.

http://www.chinariders.net/showthread.php?t=6501
http://www.chinariders.net/showthread.php?t=6528

[Weldangrind]

The jets don't necessarily dictate the fuel economy. The efficiency of the engine in good running condition determines the fuel economy.

As you indicated Hector, the plug colour is a very good indicator. If you intend to check the plug, one way is with a plug chop. Find a level road (on a day that is not windy), cruise at whatever speed you would normally use (80km/h is a good baseline) and shut the bike off without letting go of the throttle until the engine stops. Once the engine cools, remove the plug and you'll see the colour for that specific condition. If it is tan-grey in colour, you're right where you should be.

The way to increase economy after that is by making changes that improve effiency on the intake and exhaust side, removing weight, using synthetic oil; stuff like that. Every time you make a change, it's wise to do another plug chop.

Ideally, you'll increase efficiency to the point where you can cruise at the speed you wish with less throttle than you do now.

[hect75]

I inspected the spark plug yesterday and found the vento is running lean and there is burned oil in the ceramic. I drilled 4 small holes in the airbox to let air flow more freely to the carb but probably this is causing the leaning. I don't remember but probably the spark plug has 600 miles. I will replace it this month as soon as my vacations begin. Here is the link for the spark pics. http://s123.photobucket.com/user/hrm...y/Spark%20plug

[Weldangrind]

I would say that plug is dangerously lean. I'd increase the main jet size at least one step.

[bogieboy]

given the color of that plug i would grab both 1and 2 steps larger... it may need to be bumped up that much...

[hect75]

You guys think this is causing the poor fuel economy on my vento? Increasing one or two steps will increase fuel economy? what about if get one notch down (jet needle) and see what happens while I get the main jet (I will stop by the Yamaha)? It's difficult to find the jets down here, I could get them in El Paso, TX but is too expensive traveling only for some jets. I will figure out where to get them.

[Weldangrind]

You could move the clip one notch down, but that only affects mid-range throttle. If you were running at wide open throttle when you did the plug chop, the needle position would have no effect.

[hect75]

Originally Posted by Weldangrind

The jets don't necessarily dictate the fuel economy. The efficiency of the engine in good running condition determines the fuel economy.

As you indicated Hector, the plug colour is a very good indicator. If you intend to check the plug, one way is with a plug chop. Find a level road (on a day that is not windy), cruise at whatever speed you would normally use (80km/h is a good baseline) and shut the bike off without letting go of the throttle until the engine stops. Once the engine cools, remove the plug and you'll see the colour for that specific condition. If it is tan-grey in colour, you're right where you should be.

The way to increase economy after that is by making changes that improve effiency on the intake and exhaust side, removing weight, using synthetic oil; stuff like that. Every time you make a change, it's wise to do another plug chop.

Ideally, you'll increase efficiency to the point where you can cruise at the speed you wish with less throttle than you do now.

Hi Chineros, I've been buying different used main jets (mikuni, dynojet, and keihin) trying to get the right plug color and best acceleration. I haven't found the mikuni 132.5 but found the mikuni 137.5 with poor results (can't reach 80 km/h or full throttle) white plug. Bought the dynojet 142 equivalen to mikuni 132.5 and could not reach the 75 km/h, white plug. I used the keihin 140 equivalen to mikuni 122.5 and could reach the 80 km/h but start to stall after the 80's,, white plug. One step down, right know using the 120 mikuni with no problem (can get 100 km/h and full throttle with no problem), start tan-grey in color. My conclusions, the bigger the jet (132 and beyond), the poorest the acceleration. Check the pics below after running at 80 km/h and done the plug chop (used plug 'cause is sunday and nobody opens).







I wonder if I can conmute to my work (46 miles round trip) at a cruising speed of 60-70 km/h (half throttle) without causing engine damage. I will order the mainjets online and pick them up in Cruces 'til late June when picking my PhD's diploma at NMSU.

[hect75]

Hola, I bought 3 Mikuni mainjets (130, 132.5, 135). I got them from rockymountian atv but they sent OEM jets instead of original ones (the square within square simbol is not carved on the mainjet) which I totally disagree . I tried first with the 132.5 but I could not ride beyond first shift `cause the engine turned off. Then, I tried 130 and could ride ´til full throttle but only for less than 15 mins ´til the vento started to feel slow with out power, did the plug chop and got a black plug. Then, I tried with a dynojet 136 = mikuni 127 but could not ride beyond 3rd shift. It seems dynojet convertion is not accurate. I will try with a Keihin 140 = mikuni 122.5 which i tried in the past (can get only 80 km/h). I´m not sure what is going on cause I ´m going one step backward (decreasing the size) instead of sticking with the 132.5. I forgot, the muffler was packed with lexx 4T before using the 130. There is no air leakage in the inlet or outlet carb pipe, air filter is clean, compression? I think is good ´cause been riding with the mikuni 120 with excellent results but white plug.