Fuel Mixture gas to oil ratio

[arceeguy]

As long as the carb mixture is set correctly - 32:1 is plenty. Heck, if you are running too lean, 16:1 won't save your hyde!

As long as you use a TC rated oil, you'll be fine. These engines aren't to picky.

While it is generally accepted to "take it easy" for the first coule of tanks for "break in" - I think we are just being too careful. When you buy a new chainsaw, weed trimmer, or other two stroke equipment - do they have you run more oil or at no load for "break in"? Heck no, pull the starter and get to work! Same goes for any power equipment, fuel it up and GO!

 

[duivendyk]

20 parts to one is more oil but less gas than 30 to one,which means that the higher ratio has about 2% more gas in it than before.Is that clear ?,it is 2% RICHER.If you went from 30 to one to 40 to one, the change would have been 1% richer for the 40 to one ratio, and by going from 40 to 50 it would have been another 0.5 fuel enrichment.So going from say a 20 to one, to a 50 to one micture means about a 3.5% fuel enrichment.Going from 20 to 15 would lean it out instead by 1.5 %.If the micture is adjustable with the throttle needle position,this can be compensated for but if an engine is calibrated to run at particular ratio,say 50 to one and you use 30 to one ,you will lean it out by close to 1.5 %, and by going to 25 to one by 2%.Wether this is risky or not depends on wether the engine is running rich or lean to start with.Examining the plug is helpful.
In a 2 stroke engine the principal function of the oil is to lubricate the piston as it moves up&down in the cylinder barrel.All the bearings are roller,ball or needle bearings which don't require much lubrication.If they fail it is because they are of substandard quality(quite common in Chinese engines) and not because of lack of lubrication.
The piston crown is directly exposed to the burning micture and to keep it from melting the heat must be conducted away to the cylinder wall.With a power stroke each rev. the piston in a 2 stroke leads a rough life thermally.Lean mictures tend to raise combustion temp and high cylinder wall temps may cause oil to break down and reduce lubrication.This explains the use of castrol oil for racing engines despite it's many nasty attributes.(instability for instance).In air cooled engines the critical cylinderwall temp is far more variable than liquid cooled engines and special oils had to be formulated.
Oil in the gas also gets burned of course and can foul plugs.,the more oil the more likely this is to be a problem.Consequently it has been an important factor in using higher mixing ratios and developing low ash oils.A fouled plug means a dead engine and an unhappy user,while one that suffers accelerated cylinder wear due to inadequate lubrication just gradually loses power !.So I would be inclined to exercise caution in using high ratios.
It should be taken into account that the HT engines are post WW2 designs that ware designed in England ages ago.At that time 20 to one was the standard ratio, these engines are NOT forced air cooled which exacerbates the high load, low speed cooling problem.It may well be that a lubricant containing a Castro oil component can be beneficial, but using high mixing ratios because of it would appear unwise IMO.

 

[arceeguy]

The difference in mixture due to the fuel/oil ratio is negligible when you factor in other variables like air density changes due to temperature/humidity.

 

[igore]

been running 16 to 1 synthetic and my 80cc 2 stroke runs just fine

 

[duivendyk]

It may well be that other factors mentioned override the leaning out effect of using more oil,it's a question of degree.However most engines nowadays are already set up to run on the leanish side (to cut emissions),under WOT conditions overheating which under the circumstances is quite common ,cylinder wall lube problems could be further aggravated by lean mictures.It sort of like the last straw situation.but I think that as long as you stay above 25 there is little to fear,provided the engine was not running overly lean to begin with.That is really the crux of the matter

 

[Dizzy]

What not to put in your gas...maybe

Well I've been weening my motorbycle of of the 16:1 gas oil ratio latley with each half gallon fuel-up creeping closer to 32:1, I probably have nearly 500 Miles so far. I know the bike pretty intimatley now, and have pushed close to her limits to find out where they are. Though I did have one issue: I figured that a 16:1 ratio could leave some build up in the engine. So I bought some gas treatment. It's a small bottle meant to clean carbs, fuel injectors, and valves. It's also meant for 15 gallon tanks of gas. So I just put a dab of it in. After I put it in, about 10 to 15 minutes later of riding, the bike started stalling out:bigcry:

Here's my theory, It says on the bottle to put it in an empty tank before filling, so I did, (mostly empty, with petcock closed.) and filled it with gas and oil, and shook the bike a little to mix it up. I think it stalled out because a little of the gas treatment was caught in the petcock and remain concentrated when the petcock was released and was first to hit my paper element fuel filter, which perhaps may have worsened the issue by letting the gas treatment molecules through easier than the gas and oil further concentrating it. I peddled through it and kept the throttle open through it's sputtering and coughing. The reason I think the paper element made it worse was that the next day I fired her up, after just a couple minutes started stalling, though not as bad. This would mean that, perhaps the gas treatment is heavier and smaller than the gas and oil and settled beneath it and was first to the engine in a concentrated form, and/or was not meant to be mixed in with a gas/oil mix.

I could be wrong, but that is the only thing I've done differently to the engine and the only time the engine acted that way.

 

[jtmiyake]

 

[arceeguy]

..... So I bought some gas treatment. It's a small bottle meant to clean carbs, fuel injectors, and valves. It's also meant for 15 gallon tanks of gas. So I just put a dab of it in. After I put it in, about 10 to 15 minutes later of riding, the bike started stalling out:bigcry:.....

I stay away from fuel additives with 2 stroke engines.

Why? Because a two stroke engine gets its lubrication from the premixed fuel, it is probably not wise to mix solvents (the fuel system "cleaners") with the engine's sole source of lubrication.

 

[give me vtec]

I stay away from fuel additives with 2 stroke engines.

Why? Because a two stroke engine gets its lubrication from the premixed fuel, it is probably not wise to mix solvents (the fuel system "cleaners") with the engine's sole source of lubrication.

good advice.

 

[Dizzy]

Yeah, I learned it the hard-had to peddle a bit-way