Gas consumption

Coval_PL · Aug 2, 2009

Hi everybody. I have 80cc Skyhawk motor installed in my MTB. I wish to now gas consumtion of this engine. Has anybody idea how can I mesure gas amount in a standard gas tank? I ask aobout it becouse I feel there is something wrong with my engine. It's quite new, I ride about 26km and it took around half of a tank. Am I too heavy or something...

motorbiker · Aug 2, 2009

I am about 160 and I don't think I ever got over 100 mpg.

Then again I think a 2 stroke doesn't sound right with the throttle less than wide open.

Cabinfever1977 · Aug 2, 2009

I am around 120lbs and im getting around 180mpg or more.

Finfan · Aug 3, 2009

I put a speedometer/odometer on my 48 cc and I figure I get about 120 - 130 mpg (roughly). I weigh in at 180 lb.

Maxvision · Aug 3, 2009

There are many variables to gas consumption. Do you run throttle wide open all the time, are the roads you ride flat or hilly, are your tires properly inflated, are your tires wide or thin, gear ratio, fuel mixture, cheap gas, old gas, carb needle setting, exhaust bore narrowing with deposits, type of exhaust, dirty air filter, altitude, wind direction, worn rings, chain too tight, wheel bearings too tight. Probably more if I think hard enough.

Cabinfever1977 · Aug 3, 2009

i run full throttle on flat roads and dont know how air in tire,i hope theres enough and i have wide cruiser tires with a 44t sprocket on a 26" bike with a clean airfilter and i mix my oil/gas in da tank around 20-25:1 with cheap gas+cheap oil and the carb needle is at the very top and i live near mountains and is windy half the time. i weigh 120lbs.

180+mpg

TheE · Aug 3, 2009

I'm about 170 lbs, and ride with a standard sprocket, usually cruising at 50-80% throttle. I get pretty crappy gas mileage, around 80km/gal =/

Still better than a car...

Coval_PL · Aug 3, 2009

Maxvision said:
There are many variables to gas consumption. Do you run throttle wide open all the time, are the roads you ride flat or hilly, are your tires properly inflated, are your tires wide or thin, gear ratio, fuel mixture, cheap gas, old gas, carb needle setting, exhaust bore narrowing with deposits, type of exhaust, dirty air filter, altitude, wind direction, worn rings, chain too tight, wheel bearings too tight. Probably more if I think hard enough.

My weight is around 220lbs (100kg). I have MTB with 1.95" off-road tires. I'll try to inflate then more.
I have standard (big) sprocket, Shell gas with 1:16 Statoil 2T oil, long exhaust. I thing rest of listed below its ok. Maybe excluding carb. Regulation bolt is about 3,5 rounds (thats what manual say) on the idle works fine. I dont know how to set needle or throttle rope, there is no word about it.

Junster · Aug 3, 2009

Your milage will get better as the motor breaks in. I seem to get better milage riding hard than easy. I'm averaging 120mpg.

Coval_PL · Aug 3, 2009

I thing I have an answer. Half hour ago (in Poland is no 2:00pm

) I met one guy with motorbike and I've ask him about this problem. He told me, he had the same problem if the lever loaded valve at the gas tank is on the full-open position. I have also full open so I have to reduce gas flow I hope will be fine.
One more question. Which valve is beter to to that: at the tank or at the carb?

Maxvision · Aug 3, 2009

Coval_PL said:
I thing I have an answer. Half hour ago (in Poland is no 2:00pm ) I met one guy with motorbike and I've ask him about this problem. He told me, he had the same problem if the lever loaded valve at the gas tank is on the full-open position. I have also full open so I have to reduce gas flow I hope will be fine.
One more question. Which valve is beter to to that: at the tank or at the carb?

I honestly dont believe the shutoff valve at the gas tank would affect gas mileage. The float in the carburator bowl acts as another shut off valve, but I guess it would be worth a try to see if it changes things.

If you think your engine is getting more gas than it should it would be easy enough to verify by looking at your spark plug tip. If its black and sooty, your fuel mixture is too rich. This is a good way to figure which notch to put the clip on your carburator needle. The closer to the flat end of the needle, the less gas will be mixed with the same volumne of air and the cleaner your plug will show. However, if the plug is so clean that its white, youre running WAY too lean causing your engine to run too hot and possibly headed to a melt down. Spark plug tip should be a light brown.

robin · Aug 3, 2009

I installed a new HT 2 cycle. It is still new so i hope fuel consumption improves. On my old engine i ran a high speed carb and expansion chamber-i weigh 210-fuel consumption was 150 mpg now about 75 mpg everything else is the same.

Coval_PL · Aug 4, 2009

Thanks for advices, but is anywhere some step-by-step carb tune-up procedure?

Bikeguy Joe · Aug 4, 2009

Coval_PL said:
I have MTB with 1.95" off-road tires. I'll try to inflate then more.
I have standard (big) sprocket, Shell gas with 1:16 Statoil 2T oil, long exhaust. I thing rest of listed below its ok. Maybe excluding carb. Regulation bolt is about 3,5 rounds (thats what manual say) on the idle works fine. I dont know how to set needle or throttle rope, there is no word about it.

Off road tires will affect your mileage quite a bit.
I don't kow what the "big" sprocket is, but if it is a 48 or 50 tooth, that's a problem. A 41T is about ideal, 44 O.K.

BEFORE YOU ATTEMPT TO "DIAL IN" THE CARBURATOR, GO TO 24:1 OR EVEN 32:1 FUEL TO OIL MIX.
To set the needle, remove it from the slide, and move the clip up for a leaner setting, down for a richer setting.
The throttle cable should be just free with a fractional amount of free-play in it. Adjust it at the top of the carb.

Coval_PL · Aug 4, 2009

Bikeguy Joe said:
Off road tires will affect your mileage quite a bit.
I don't kow what the "big" sprocket is, but if it is a 48 or 50 tooth, that's a problem. A 41T is about ideal, 44 O.K.

BEFORE YOU ATTEMPT TO "DIAL IN" THE CARBURATOR, GO TO 24:1 OR EVEN 32:1 FUEL TO OIL MIX.
To set the needle, remove it from the slide, and move the clip up for a leaner setting, down for a richer setting.
The throttle cable should be just free with a fractional amount of free-play in it. Adjust it at the top of the carb.

Grubee's home page says that standard sprocket for this engine has 50T, so this one I have.
Seller told me to use 16:1 fuel to oil mix during first 500-600km. Is this wrong? Should I use less oil?

Coval_PL · Aug 4, 2009

I recieived a reply notification email, but there is no reply on this topic

Bikeguy Joe wrote:
It is very easy...you move the little "C" clip up on the needle to make it run leaner (start at the 2nd from the top).
You are getting poor fuel mileage due to an overly rich setting.
Also change your fuel to oil ratio to 24:1 before you do anything else.

I move the clip from midddle to second from the top position. Engine works much better. It starts at first kick (or spark

). Thanks a lot

I'll burn out the rest of mixed fuel and then try 24:1.
dance1

Cabinfever1977 · Aug 4, 2009

some of the websites people buy there kit from will avertise that the kit comes with a
50T sprocket but they usually send you a 44T sprocket.

Bikeguy Joe · Aug 4, 2009

A 50 t will not get you a real high top speed, probably around 25-30 mph tops.

azbill · Aug 4, 2009

when I was running a 50, my mileage was 40m/tank (approx 80mpg)
changing to a 40 got me to approx 120mpg

livefast 66, same Jag

Coval_PL · Aug 5, 2009

azbill said:
when I was running a 50, my mileage was 40m/tank (approx 80mpg)
changing to a 40 got me to approx 120mpg

livefast 66, same Jag

So fuel consumption is lower becouse of lower engine's RPM? Maybe I should change this sprocket also..?

Gas consumption

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