My take on fuel for the GY6/139QMB 50cc Engines[And all related chinese scooters]

[ds1615]

It would appear that there is a much discussed debate across the internet and across scooter nuts on which the little bugger requires in fuel, being that the scooters are of Chinese Origin and the USA vs. Others Octane rating is different.

My scoot says on the front below the seat, to use 90 or higher octane rating fuel. It also shows to be made by Jonway.

It would appear to me that, as I am a USA based rider, it is designed for only one kind of fuel. PREMIUM.

Whether you are in the UK or the USA or India, there are typically[as far as I know] 3-4 selections on most commercial pumps, and vary from store to store. Here in North Carolina, we have 87, 89, and 93.

Well upon a little research the lower the rating in the USA, the more Ethanol is used. Now I've heard it reported that a study of 1k gas stations were selling low grade fuel out of PREMIUM only selections.

Disregarding the false sales by the seller, the scooter is, as we know, of low compression. So, we know that there's not a whole lot of struggle for the engine to do a complete cycle, and it needs to be that way due to the size of the engine, especially the 50cc's.

Well, as far as I know, the higher the grade of fuel, the bigger the explosion. The lower the grade, the less UMPH per spark. Let's not get too technical here, because I'm trying to approach this simply.

Basically, with the lower compression, and not much of any power, and we know that a 2 or 4 stroke engine has only one piston, it needs as much BANG per RPM. I conjecture that if you use low grade fuel, you not only run the risk of getting poor fuel quality, but you will also have a harder time accelerating.

We know that through various parts replacing for performance, many of the stock obstacles can be overcome. But I don't have a lot of money to just start putting into buying new parts for my scoot.

if you have a better combustion, you will have a quicker rev, Imagine the engine could rev unlimited[as some CDI boxes allow] but without the engine getting too hot, lacking cool oil, or simply blowing up and warping. With this scenario we could jack the scooter up on it's jack-stand and start it up, then rev it wide open. Given let's say it wouldn't vibrate and move, you could allow and listen to it rev up. Well even if that were possible once it hits a certain RPM range, it will have a harder time continually going up in RPM's. Not that it's not capable, but that for the fuel/air mix, and the time it takes to go up, down, up, combust, up, down, up, combust, etc.

So, with a higher grade of fuel, you will get a slightly different BOOM in the block. Thus, resulting in a slightly faster push/pull on the engine to allow the new fuel/air in, and the exhaust out. So, we're not talking going from 40mph top-out to 55mph top out because you changed your fuel grade, but we are talking about better acceleration, and better gas mileage, as you won't need as much fuel to air mix to have the same BOOM.

I'm not sure what the real difference in grade is from USA to Europe, but I can tell you that 90 or higher octane, is high grade fuel, it is NOT low grade. If you want the longer life of your scoot, buy premium. If you are just a cheap skate that doesn't care if you're safe on the road, or can go up a hill in time to see the sun set, do what you will.

BUT, if you do care about your ride, as I do mine, buy the best.

Anyways, just my two cents.

EDIT: Also, my stock Carb doesn't have a low speed fuel/air mix screw, to make it lean/rich by turning the screw. Not sure if it's just wrong or what, but I do know that all my symptoms lately have been pointing to running lean. I put 87 grade in it before I found out it needs PREMIUM, so I've been having issues with acceleration and a constant, steady speed until my revs are high.

I know it's not much, but maybe it will help everyone out.

P.S. These things don't come with a 12 gallon tank, so buying PREMIUM is really reasonable. If you are just pinching your pennies so hard you can't afford it, having a little less of the right fuel, is better than more of the wrong fuel.

Why would you buy McDonalds double cheeseburger, 10 of them, if you could have 2 filet Mignon. I don't need a bunch of cheap-o sarcasm on why you have been using low grade and it's fine, etc. If you use cheap, go ahead. Ruin the darn thing. Just don't expect NOT to have to replace fuel parts after a year or less of running it daily.

[blueboy5000]

An engine will operate with it's lowest required octane, which, in the USA us usually 85 octane, hence 87 for good measure. 85 octane is for 9:1 compression. Our scoots run 10:1 compression, which means 90 octane or better.


The bikes will run on 87, but expect ping and knock under load.

A higher octane does not equal better performance. If you require 85, 93 isn't going to give you more power.

[ds1615]

Like I said, it's not so much a performance increase, as it is simply running right.

[rks]

If you want it to operate as designed, there are 550 places in your state to buy real gas...

http://pure-gas.org/index.jsp?stateprov=NC

Edit: I forgot to mention that I believe your a/f adjustment screw is just plugged, and can be accessed by drilling and removing it (the plug). Or you can go to fleabay, and buy a brand new, adjustable carb, for your 50cc for just under $23.00, that includes free shipping.

[kz1000st]

I generally run 89 Mid Grade and everything runs fine. I tried four tanks of ethanol free Premium in my 250cc. Do you know what I noticed after four tanks? Absolutely nothing. No increase in power, fuel economy or response. Nothing except the fuel cost fifty cents a gallon more than ethanol loaded Mid Grade. I use Mid Grade now and will continue. A buck a tank builds up fast for no reward.

[dwint51]

I know from experience that ethanol does clog up carbs.

[kz1000st]

Seafoam a few times a season puts an end to that.

[skyrider]

Does anyone think one cap of seafoam per fill up is overkill? I've been doing it for years since my new carb and no problems, but perhaps every three or four fillups????

[rks]

Directions state one ounce per gallon of gas.....at that ratio, you will be adding at least $.50, if not a little more, to the cost of each gallon. I doubt that the cap holds more than a half an ounce, so you certainly aren't overdosing it, if your fill ups run about a gallon or so.

I don't use Seafoam, but something else with a similar purpose. Have always felt it is better to add a little at every fill up, to maintain a clean system, rather than using once in a while. If you can believe the claims made by the producers', you're not only cleaning the carb by using it, but keeping intake valves, and combustion chambers free of deposit build up, along with a cleaner spark plug for better, more complete combustion.

Bottom line.....do what feels right to you.....once a week.....once every 2 months.....your scooter, your call

[Dodgeme]

sea foam works by (for lack of a better phrase) steam cleaning the combustion chamber not with water but with a petroleum distillate based cleaning chemical (If I remember what is in it right). and yes ethanol is very corrosive to carburetors and carbureted fuel systems, It isn't noticeable in computer controlled fuel injection because the computer compensates for it, but I have had mechanically gasoline injected engines come in where the entire fuel system had to be replaced due to the ethanol in the fuel melting plastic filter elements, rubber fuel lines and gumming the extremely tight tolerance precision fit fuel metering systems up. So from my experiences I would recommend avoiding ethanol fuels in any carbureted or mechanically injected gasoline engine (yes those do exist for an example vw rabbit, but that's off topic). The fact is ethanol fuel can and will eventually damage a carburetor and even cause a Excessively lean condition that may cause engine damage, or detonation (aka ping, knock) this can be prevented by keeping the fuel system clean keeping air fuel in the right ratios usually between 13.7 to 14.2 works best for carbureted engines (yes stoichiometric ratio is 14.7) being a little fuel rich is better than being lean. ive even seen some Hondas that ran at 18:1 at idle, but those richened back up when put under any load examples when put into gear, ac turned on, steering wheel turned to lock which loads the steering pump, and any higher than stock electrical load for examples (yes I went slightly off topic again).

[rks]

Couldn't agree more with you, about the ill effects of ethanol. Have had to repair failed fuel systems on a couple of string trimmers, a roto tiller, and a chainsaw....destroyed fuel lines, primer bulbs, and such. Took me a while, but I finally realized that ethanol sucks. Have to believe that most of the problems encountered with our vac operated fuel petcocks, and pumps, are caused by running blended fuel.

My 2005 Cub Cadet is in it's 11th season of mowing, and has 1,070 hrs on it. I have replaced the fuel lines a couple of times, but haven't touched the fuel pump or vac line that operates it (almost identicle to an OEM scooter pump). So, kind of thinking about getting another one just in case. Searching around, I've noticed some aftermarket pump sellers stating "Not compatible with gas containing more than 10% ethanol". Seems to me what they are really saying is, ethanol will destroy the diaphram....10% will just take a little longer than a higher percentage will.

Could go on....have a close friend from my working days, who drove tanker for Hess....ah the heck with it....the sun is shining, it's warming up.....I'm going scootin'

[bandito2]

WHOO BOY!! You can rant about higher octane gas but there are some things about
higher octane that you are misunderstanding. Higher octane fuel blends are basically
better for high compression engines because they tend to prevent pre-ignition.

Premium grade and the lower grades of gas all have the same thermal energy, though
I highly suspect that ethanol blends would be lower.

BTW, there were different grades of gas before ethanol was ever introduced, so that is
not the reason for differences in gasoline grades.

Here is some information to help clear up the misconceptions about the difference between
premium and lower grades of gasoline.

http://engineering.mit.edu/ask/what%...gular-gasoline

Note near the bottom of this item here that there are different methods for determining
octane numbers. So a 91 octane rating in some country would be equivalent to 87 in the
US and Canada.
https://en.wikipedia.org/wiki/Octane_rating

Given that the Chinese are not the best at clarifying things, (service manual anyone? -
kilometers or miles on the speedo gauge? recording distance in miles or km?) it may be
hard to tell which method of octane rating they are using for the recommendation. That
is, unless it specifically gives the rating method used for that recommended fuel. If it is
not specifically given, I would wonder what the octane rating method is used in the country
of manufacture.

So if you can get by with the less expensive grades without pre-ignition problems, then
it would make sense to do that instead of needlessly paying more and not getting more
of a benefit for the expense. What most of us already know: the best gas is ethanol free.
(regardless of the octane rating) In the long run, ethanol free is worth the extra $$ IMO,
but not premium grade when regular will suffice.