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How critical is the oil/petrol ratio for a 2 stroke engine?



 
 
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  #1  
Old 30-03-2003, 03:56 PM
Jon Weaver
external usenet poster
 
Posts: n/a
Default How critical is the oil/petrol ratio for a 2 stroke engine?

I have a McCulloch strimmer which takes a 40:1 petrol/oil mix.
However, my mixing bottle (which takes 1 litre of petrol and has a
pointed top graduated in different radios) has become 'bloated'

This means that when you fill it to the 1L mark, there is actually
more than 1L in the bottle.

If I then top it up to the 40:1 with oil, I am getting a slightly lean
mix.

So, to counteract this, I have been adding a few extra drops of oil,
but the problem is that I don't know what ratio I am creating this
way.

I imagined that a slightly richer mix would be better than a lean one,
so I have made sure that I mix is on the 'rich' side if anything. I
figured that if it was too lean, then I stand the risk of seizing the
engine and doing real damage. But it is too rich, I would just have
too much oil, resulting in more smoke from the exhaust.

However, I asked my local lawnmower maintainer about this and was told
that it should be spot on 40:1.. To much or too little oil is just as
bad for the engine.

Is this really true? Is it a real problem running a 2-Stroke engine
with too much oil?

Even if too much oil is not ideal, is it so bad that you should throw
away a mix, if you added too much oil by accident?

Can anyone shed any light on this?
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  #2  
Old 30-03-2003, 04:20 PM
pied piper
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Posts: n/a
Default How critical is the oil/petrol ratio for a 2 stroke engine?


"Jon Weaver" wrote in message
om...
I have a McCulloch strimmer which takes a 40:1 petrol/oil mix.
However, my mixing bottle (which takes 1 litre of petrol and has a
pointed top graduated in different radios) has become 'bloated'

This means that when you fill it to the 1L mark, there is actually
more than 1L in the bottle.

If I then top it up to the 40:1 with oil, I am getting a slightly lean
mix.

So, to counteract this, I have been adding a few extra drops of oil,
but the problem is that I don't know what ratio I am creating this
way.

I imagined that a slightly richer mix would be better than a lean one,
so I have made sure that I mix is on the 'rich' side if anything. I
figured that if it was too lean, then I stand the risk of seizing the
engine and doing real damage. But it is too rich, I would just have
too much oil, resulting in more smoke from the exhaust.

However, I asked my local lawnmower maintainer about this and was told
that it should be spot on 40:1.. To much or too little oil is just as
bad for the engine.

Is this really true? Is it a real problem running a 2-Stroke engine
with too much oil?

dont worry


  #3  
Old 30-03-2003, 05:08 PM
John Towill
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Posts: n/a
Default How critical is the oil/petrol ratio for a 2 stroke engine?



"pied piper" wrote in message
...

"Jon Weaver" wrote in message
om...
I have a McCulloch strimmer which takes a 40:1 petrol/oil mix.
However, my mixing bottle (which takes 1 litre of petrol and has a
pointed top graduated in different radios) has become 'bloated'

This means that when you fill it to the 1L mark, there is actually
more than 1L in the bottle.

If I then top it up to the 40:1 with oil, I am getting a slightly lean
mix.

So, to counteract this, I have been adding a few extra drops of oil,
but the problem is that I don't know what ratio I am creating this
way.

I imagined that a slightly richer mix would be better than a lean one,
so I have made sure that I mix is on the 'rich' side if anything. I
figured that if it was too lean, then I stand the risk of seizing the
engine and doing real damage. But it is too rich, I would just have
too much oil, resulting in more smoke from the exhaust.

However, I asked my local lawnmower maintainer about this and was told
that it should be spot on 40:1.. To much or too little oil is just as
bad for the engine.

Is this really true? Is it a real problem running a 2-Stroke engine
with too much oil?

dont worry


If you use stihl own oil then they recommend half the amount than other oil.
I queried this and was told that extra oil does little or no harm, just oils
the plugs a bit, whereas too little oil can be very detrimental.
Cheers
John T
--
Remove the wet from towill to reply
by email


  #4  
Old 30-03-2003, 06:32 PM
Malcolm
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Posts: n/a
Default How critical is the oil/petrol ratio for a 2 stroke engine?


In article , Jon Weaver
writes
I have a McCulloch strimmer which takes a 40:1 petrol/oil mix.
However, my mixing bottle (which takes 1 litre of petrol and has a
pointed top graduated in different radios) has become 'bloated'

This means that when you fill it to the 1L mark, there is actually
more than 1L in the bottle.

If I then top it up to the 40:1 with oil, I am getting a slightly lean
mix.

But only slightly.

So, to counteract this, I have been adding a few extra drops of oil,
but the problem is that I don't know what ratio I am creating this
way.

Doesn't matter, IMO.

I imagined that a slightly richer mix would be better than a lean one,
so I have made sure that I mix is on the 'rich' side if anything. I
figured that if it was too lean, then I stand the risk of seizing the
engine and doing real damage. But it is too rich, I would just have
too much oil, resulting in more smoke from the exhaust.

And an oiled up plug if there is really too much oil.

However, I asked my local lawnmower maintainer about this and was told
that it should be spot on 40:1.. To much or too little oil is just as
bad for the engine.

Certainly too much or too little is bad, but there's no 2-stroke engine
made which will suffer if you use 39:1 or 41:1, or even 35:1 or 45:1.
The ratio is not *that* critical. The instructions for my Flymo strimmer
say to use the correct ratio but they don't make a song and dance about
it having to be exact.

Is this really true? Is it a real problem running a 2-Stroke engine
with too much oil?

It will smoke a bit more and the plug may get oiled up.

Even if too much oil is not ideal, is it so bad that you should throw
away a mix, if you added too much oil by accident?

Tip some out and add some more petrol.


--
Malcolm
  #5  
Old 30-03-2003, 07:20 PM
Rod
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Posts: n/a
Default How critical is the oil/petrol ratio for a 2 stroke engine?


"Jon Weaver" wrote in message om...
I have a McCulloch strimmer which takes a 40:1 petrol/oil mix.
However, I asked my local lawnmower maintainer about this and was told
that it should be spot on 40:1.. To much or too little oil is just as
bad for the engine.

Is this really true?


iirc this is what McCulloch dealers are told to say. Too much oil isn't a big deal - too little could be. Quality of oil
is important. Engine maker's oil (any maker) is usually OK at 40 or 50:1. Cheap no name - oil follow the instruction on
the can often 25:1 and smelly ;~(((

Rod


  #6  
Old 30-03-2003, 07:56 PM
len brauer
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Posts: n/a
Default How critical is the oil/petrol ratio for a 2 stroke engine?

g'day john,

all you need do is get it as close as you can to the recommended
ratio, as stated too little is going to be the worst, too much will
fowl spark plugs and lead to the clogging up of the muffler. plus your
machine will blow more smoke and could be down a little on power
depending on how much the oil ratio is above that of the fuel.

len

snipped
--
happy gardening
'it works for me it could work for you,'

"in the end ya' gotta do what ya' gotta do" but consider others and the environment
http://hub.dataline.net.au/~gardnlen/
  #9  
Old 31-03-2003, 07:33 PM
Brian Watson
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Posts: n/a
Default How critical is the oil/petrol ratio for a 2 stroke engine?


"Jon Weaver" wrote in message
om...
I have a McCulloch strimmer which takes a 40:1 petrol/oil mix.
However, my mixing bottle (which takes 1 litre of petrol and has a
pointed top graduated in different radios) has become 'bloated'

This means that when you fill it to the 1L mark, there is actually
more than 1L in the bottle.


Can anyone shed any light on this?


I used to ride a Lambretta two-stroke scooter and frequently took liberties
with the petrol/oil mixture, persuading myself that it went faster with less
oil in the mixture.

I didn't blow it up and changed plugs no more frequently than my more
cautious fellow riders.

Therefore I would say that a little bit (say 20% error) in either direction
is not going to make any appreciable difference.

If you are still bothered, treat yourself to a metal measuring jug.

--
Brian
"I know about kittens and knitting. Will that do?"


  #10  
Old 22-05-2012, 10:29 PM
Registered User
 
First recorded activity by GardenBanter: May 2012
Posts: 1
Smile

Quote:
Originally Posted by Jon Weaver View Post
I have a McCulloch strimmer which takes a 40:1 petrol/oil mix.
However, my mixing bottle (which takes 1 litre of petrol and has a
pointed top graduated in different radios) has become 'bloated'

This means that when you fill it to the 1L mark, there is actually
more than 1L in the bottle.

If I then top it up to the 40:1 with oil, I am getting a slightly lean
mix.

So, to counteract this, I have been adding a few extra drops of oil,
but the problem is that I don't know what ratio I am creating this
way.

I imagined that a slightly richer mix would be better than a lean one,
so I have made sure that I mix is on the 'rich' side if anything. I
figured that if it was too lean, then I stand the risk of seizing the
engine and doing real damage. But it is too rich, I would just have
too much oil, resulting in more smoke from the exhaust.

However, I asked my local lawnmower maintainer about this and was told
that it should be spot on 40:1.. To much or too little oil is just as
bad for the engine.

Is this really true? Is it a real problem running a 2-Stroke engine
with too much oil?

Even if too much oil is not ideal, is it so bad that you should throw
away a mix, if you added too much oil by accident?

Can anyone shed any light on this?
ratios mix is not too critical in most two stoke engines in particular your strimmer as allowances are made in the tolerances when manufactured a few ml here and there will not harm the engine so long as your close enough ,there are however a few things to consider too much oil causes smoke and runs the petrol mix lean which will over heat the engine this is not so good for the engine, and too little oil will cause the petrol mix to richen which washes away the little oil thats being left behind no need to say what happens then ,i think you need not worry about the method your using it is allways prudent to err on the more oil than the less oil approach
 




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How critical is the oil/petrol ratio for a 2 stroke engine. Jon Weaver Gardening 3 31-03-2003 04:20 AM


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