2-Stroke

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Original submission by T Apr 2nd 2007:


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The North South Engine orientation gives this Victa Monaro nice manouvering manners. This is because the Cylinder (the heaviest part of the Engine) is closest to the Rear Axle giving optimum leverage by the Handle. It also avoids the Spark Plug end being bashed when mowing up against the Fence. Photo by Scott4571. Click to Enlargen.


2-Stroke Engines:

The occasional lawn mower question appears.

2-Stroke Starting Problems:

Failed De-Compressor Valve:

Submitted by T on Mon, 02/04/2007 - 08:56. A common problem with any modern 2-Stroke is the decompressor valve having carbon under it. I've seen it on many brands/models. Cleaning/replacing the valve is often all that's needed. 160 Victa's can start and run with significantly less compression than the early 125 cc engines because of the action of the decompressor.

This North-South Engined Victa Monaro has nice manouvering manners. Later Victas had East-West mounted  Engines which are harder to manouvre because the Cylinder is further from the Rear Axle. It also results in the Spark Plug end being bashed when mowing up against the Fence because the Spark Plug stick out the side of the Mower. THis happens despite the fact that they are fitted with Spark Plug covers. Photo by Scott4571. Click to Enlargen.


Proper Fuel Management:

2-Strokes need proper fuel management, not only the correct oil ratio, but the age of the fuel. Fuel more than a couple of months old breaks down the oil and causes engine failure within minutes of a start (the exhaust side of the piston melts, becomes demetalled, the bore becomes scored and all compression is lost).
Submitted by HG383PREM on Thu, 03/05/2007 - 10:33.
I agree with turning the fuel off and running it dry, making for easy starts.
T - Edit (One of) The reason(s) why is Victa plastic carbys have a plastic needle that seats on a brass ring inside the primer cap. If the fuel is left on fuel leaks past the seat and floods the motor. A victa will quite often drain the tank contents into the motor because of the poor sealing between the needle and seat over a period of time.
End of submission by HG383PREM on Thu, 03/05/2007 - 10:33.

Proper Shutdown Technique:

Also, turning the fuel off and running the engine dry is vital for easy starts. If the engine is stopped by the throttle (ignition killed) the carburettor will be left full. Over time the petrol will evaporate and leave a layer of pure oil on the bottom of the carburettor. The next start will be impossible because the engine will draw pure oil from the carburettor and no fuel.

Spark Plug:

The spark plug will become laced with oil and no start will be possible.

Starting Technique:

Always add new fuel to the fuel tank prior to turning on the fuel tap and attempting a start.
If the engine has been unused for more than a week, try to add only as much fuel as you will need for the current job, less is better than too much you can add the rest as needed. The new fuel will dilute the oil rich mixture in the fuel tank.
Running the engine on stale fuel will cause a piston/bore failure in a matter of minutes. Stale fuel
breaks down the oil and causes it to lose its lubricating abilities.


Links:

Scott4571's Shed

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