Family was out this morning, and there's only a couple more weeks of mowing (if that, we've had some frosts so far, but it's the warmest May on record)...so I decided to test some of the stuff that's been here the last few weeks.
First was the weedwhacker. My 15 year old homelite 2 stroke has become unserviceable, so I mixed up some 25:1 the old fashioned way with SAE30, stole parts off the new one, and did the edging.
It didn't start as well as usual, and blew huge clouds of stinky smoke until the machine was running at full heat.
Conclusions
* Two stroke oil is definitely part of the combustion process, it wasn't burning until the unit was well up to temp, then was mostly consumed.
* Proper two stroke oil is way better regarding smoke during the warm-up.
* SAE30 is a stinky mess as a two stroke oil.
* I'm going to steal the parts of my new machine to keep the old one running...old one doesn't have a clutch, is lighter, and more usable.
Second was the mower proper...it was an age since I changed the plug, so I bought a new one, and cut the side electrode off the old one.
Starting was incredibly difficult, but happened. When it started to run, it was very hit/miss, like a hit and miss stationary engine, but accelerated slowly.
Eventually it gave two very sharp "knocks" and went to full noise, and ran perfectly after that.
Changed yards, and the hot start was very similar to the cold.
Pulled the plug, and the centre electrode had a clear rim, with the previous carbon deposits indicating that it was firing from the sharp edge (to be expected), but fairly evenly around the electode (was a surprise, I was expecting a more defined ignition point).
Which made me look in the plug hole, and I worked out what I think caused the behaviours demonstrated.
It looks like the spark found the least path of resistance to Earth was onto the piston crown....which means that the path has to have included either passage through the oil film on the bearings (very bad), or through the oil film/piston ring interface (probably nearly as bad).
Conclusion
* Mower will start and run with no side electrode, and apparently be just as powerful and stall prone;
* Mower won't run like this for very long, as the current passage through lubricated clearances is (will be) very detrimental.
First was the weedwhacker. My 15 year old homelite 2 stroke has become unserviceable, so I mixed up some 25:1 the old fashioned way with SAE30, stole parts off the new one, and did the edging.
It didn't start as well as usual, and blew huge clouds of stinky smoke until the machine was running at full heat.
Conclusions
* Two stroke oil is definitely part of the combustion process, it wasn't burning until the unit was well up to temp, then was mostly consumed.
* Proper two stroke oil is way better regarding smoke during the warm-up.
* SAE30 is a stinky mess as a two stroke oil.
* I'm going to steal the parts of my new machine to keep the old one running...old one doesn't have a clutch, is lighter, and more usable.
Second was the mower proper...it was an age since I changed the plug, so I bought a new one, and cut the side electrode off the old one.
Starting was incredibly difficult, but happened. When it started to run, it was very hit/miss, like a hit and miss stationary engine, but accelerated slowly.
Eventually it gave two very sharp "knocks" and went to full noise, and ran perfectly after that.
Changed yards, and the hot start was very similar to the cold.
Pulled the plug, and the centre electrode had a clear rim, with the previous carbon deposits indicating that it was firing from the sharp edge (to be expected), but fairly evenly around the electode (was a surprise, I was expecting a more defined ignition point).
Which made me look in the plug hole, and I worked out what I think caused the behaviours demonstrated.
It looks like the spark found the least path of resistance to Earth was onto the piston crown....which means that the path has to have included either passage through the oil film on the bearings (very bad), or through the oil film/piston ring interface (probably nearly as bad).
Conclusion
* Mower will start and run with no side electrode, and apparently be just as powerful and stall prone;
* Mower won't run like this for very long, as the current passage through lubricated clearances is (will be) very detrimental.
