Two stroke lubrication

I'm not sure I follow that bit. I suspect that more oil = less petrol, therefore a weaker mixture. The effect of the oil on the combustion space is negligible. My memory says that the normal air fuel ratio is about 14:1 by weight. Then consider the difference that the quantity of oil in even a 25:1 mixture makes and it's very small.

John

Picking up on a side issue from John Manders' thread, (well done, BTW!) I'd been thinking recently about two strokes (TS) & oiling. Several varieties of our Iron Toys are two strokes and built at a time when TS oils were much poorer at their job than they are today. Bearing in mind the task presented to the oil in a modern high performance TS motorcycle, it's a wonder to me that they survive at all, let alone soldiering on for decades at a time with little but abuse and neglect for company.

For instance, thirty years ago, I was always struck by the ability of a needle roller bearing in a TS small end to do it's job without dying in the first five minutes. But they worked just fine and even though the rollers never complete a full revolution, the eye of the conn rod rarely guttered.

I owned several Suzuki 500 TS twins and these had pumped lubrication to the mains (and thence to the big ends) and also to the cylinder walls. The result was the reduction of the traditional wake of smoke behind the bike to the occasional puff upon acceleration as the oil pump was linked to the throttle. Very good idea, too.

Therefore, I grow ever more convinced that the recommended ratio of oil to petrol can be drastically reduced in older engines designed to run on bacon fat lightly cut with paraffin. This year, I'll put my engine where my mouth is and try it. My next side project is a spare Homelite engine I found at the Sortout last year, so there's summut I can practice on!

Perhaps I ought to mention that oil takes up combustion space, so less oil will mean a richer mixture, just as too much results in a weak mixture.

I'd be interested in the thoughts of the esteemed Eric Brain who has had a bit more to do with experimental automotive engines than me ;o))

regards,

Kim Siddorn

Man is just an ape that shows promise ...

How much do they rotate ? I'd always thought they had to be small enough to get a full rotation in, or else they did collapse. Do they creep around gradually ?

our engines turn more slowly, with lots of force, compared to most bike engines. would that require a higher viscosity oil, or more oil? I wonder what the piston feet per second numbers are on various engines and if that makes a large difference in the viscosity or ratio required.

Rob Provins Sebring, Florida

Rob Provins - Sebring, Florida Our engines turn more slowly, with lots of force, compared to most bike engines. Would that require a higher viscosity oil, or more oil? I wonder what the piston feet per second numbers are on various engines and if that makes a large difference in the viscosity or ratio required

Whilst the pistons may be bigger, they move a lot more slowly. Compressions are lower, bearing sizes huge and parts lightly loaded for their size. We could use chip fat and the things would still last for ages ;o))

Regards,

Kim Siddorn

I must admit I'm not too fussy about exact petroil mixture. I generally have two strengths made up - 25:1 which I use in anything with plain big ends and/or mains and 50:1 for those blessed with rolling element bearings. Only for short term off/light load running though, for an engine doing a proper job of work I might think again.

Hiya Kim, Back in the old days a buddy and I were blasting across the middle of the desert when I had to stop -- actually, my bike stopped for me -- to change a spark plug. My buddy suggested that I start running Neo, a super-high-tech oil that you mix at 100:1 that doesn't foul the sparkplugs. I told him to piss up a rope and to run it in HIS bike. I'd rather foul a sparkplug than foul the bearings. He said he had been running Neo for months and his bike ran great.

Not long after that I was running Neo. I never went back to the old

32:1 muck.

Years later when I ended up with a Maytag engine, I decided the recommended ratio of 16:1 was ridiculous and mixed up a batch of Neo. The engine ran flawlessly, smoked less than some four cycle engines, and never gave me any problems.

Rob

=-=-=-=-=-=-=-=-= Rob Skinner La Habra, California

Well, I know that on a Petter two stroke, if you put in the recommended number of drips per minute whichever lubrication system it has, then an oily spray is emitted from the exhaust pipe which anoints all and sundry in the vicinity. About half of what Mr. Petter says seems about right with modern lubricants. The cheapest and nastiest oil nowadays is better than anything they had in the

1920's and 1930's. The only caveat is do be careful of what cylinder oil you use in your hot bulb four stroke, i.e. Blackstone, Hornsby, etc. Some of the cheaper oils are not very resistant to oxidation, and they do gum up the piston and rings something wicked. Been there, done that :-)

Regards

Philip T-E

Big Snip

Hey Rob, I hope nobody from the ATIS list catches you being complementary about Maytags. 8^)

-- Dave Croft Warrington

I tend to run cheap 2 stroke oil in cylinder lubricators on open cranks, it clings to the bore better and you end up using less and have less thrown all over the place. Still use the cheap rubbish on the exposed works as most of it just runs off anyway though I have also been using Duckhams Multigrade (the nice green stuff) that our local discount motring emporium still sells at less than a tenner a tin!

Regards

Dan

It was a twinge of memory from my days as an occasional racing mechanic. I remember that Shell Racing made a big thing of weak mixtures caused by adding an extra splodge of oil "just for good measure". Whilst our engines are hardly stretched mechanically, one never knows who is reading stuff wot one has writ ;o))

OTOH, water injection makes a big difference to combustion temperature, flame front travel and actual compression ratio, yet is only a slow drip or fine mist spray.

Regards,

Kim Siddorn

Still use the cheap rubbish on the exposed works as most of

Have you thought of using chain saw oil? It's very tacky and designed not to fling off.

John

My Johnston outboard has always used 100:1 mix of the marine 2t oil, I know it has low ash but assumed the water cooling also had something to do with the lower oiling requirement.

AJH

Water injection cools the cylinder charge due to evaporation. That reduces compression pressure but cannot reduce compression ratio. That's a fixed mechanical ratio of volumes.

John

Now there's a thought. At least it's bio-friendly. This was just becoming a requirement for chainsaw oil used in forestry when I left about 5 years ago. My chainsaw handbook says to use the manufacturers own oil (naturally) but then goes on to say that gear oil could be used as an alternative. I only use the machine occasionally but use whatever gear oil is handy. Just to keep on topic, the chain saw has a 2 stroke engine.

John

By cooling the incoming charge, more mixture (by weight) can be drawn in. During compression, further evaporation causes more cooling so pre-ignition is reduced. This means that higher CR can be tolerated, hence more power. The evolution of knock sensors and ECU's mean that the norm now is to simply retard the ignition timing to stop pinking.

John

If it does, there is something very wrong. The chain oil should only go on the chain and bar. The 2 stroke oil goes in the engine on mine. An electric one uses WD40. That reminds me of a demonstration of WD40 type of spray that I say a few years ago. The salesman was in the workshop and asked to borrow an electric drill. We gave him a 240V machine (they were acceptable then and cordless was a term for clunky telephones). He sprayed his magic spray all over the drill, inside the switch and by onto the brushes. He then showed that the drill still worked. The drill was then immersed in a bucket of water (still plugged in) and removed and it still worked. He then put the drill into the water and pulled the trigger. The drill worked with much thrashing of the water by the fan. This was also before RCD's were around. Everyone agreed that the salesman was very brave and very stupid. We did by his product though but I never tried the drill trick. There you are Martin, just the thing for your electric chain saw when it rains.

John

Dave, I was extolling the virtues of the oil, not the engine.

=-=-=-=-=-=-=-=-= Rob Skinner La Habra, California

Now there's a thought... Has anyone any experience of doing this? I tend to use domestic cooking oil for the chain saw chain as I never get round to buying proper oil!

An unguent I would recommend is Bituminised Grease as used on Railway points and buffers, sticks to anything (particulary pets and small children ;-) and brilliant for protecting exposed metalwork. The drum I have has a warning 'May cause Harm' which gives unlinited possibilities...

Regards

Dan