2 stroke anomaly

[fred]

Pulled out two hedge trimmers from the shed for first use this year. First one wouldn't pull. Cord ran so far and no further. Second one was the same except it pulled past the first stop so I worked it a few times and away it went

Went back to first one again and gingerly pulled it through the stopped position and eventually it performed fine also.

I have never experienced this before What might the cause be ? Is there anyway to remedy it ?

Presumably the long lay up caused the problem but it never did before and I don't fancy having to start them every 4 weeks during the off season.

Can you still get Redex. Would a squirt of that down the plug hole at lay up time be a good idea. Or possibly just a shot of plain 2 stroke oil ?

Or are both engines on the way out ?

[newshound]

Rust formation on piston rings and/or cylinder can give this sort of symptom. The usual fix is to remove plug, add some oil, put plug back in, leave to soak with cylinder vertical and plug at the top. Not terribly critical what sort of oil you use IMHO. Once it frees up, remove plug, drain surplus, give a few firm pulls to clear remaining oil otherwise there is a risk of the plug oiling up when you come to start it. For starting, often helps to remove the plug and heat it up maybe to

200C with gas torch or hot air gun. Or you can just heat up the cylinder, heat will conduct to the carburettor and help overcome loss of volatiles in the fuel. May or may not be necessary to use "fresh" fuel, seems less necessary with modern than older engines. I suspect sparks have got fatter with better magnets, or electronics in the low tension side.

[Caecilius]

Lubrication is the achilles heel for two strokes. So adding a teaspoon full of oil through the plug hole and turning the engine over to cover the bore before putting them away at the end of the season is a good idea.

[Brian Gaff]

It depends on what was jamming up. I personally doubt it was the cylinder itself, quite honestly. Brian

[Tim Lamb]

In message , Brian Gaff writes

I have had a similar odd experience with an electric start 4 stroke lawn tractor.

This turned out to be fuel leaking through the carburetter from the over head tank. Cured by a shut off valve in the fuel supply pipe.

Piston would approach TDC and jam. By the 3rd or 4th. attempt it would shunt the excess fuel into the exhaust and then start.

[Harry Bloomfield]

Brian Gaff expressed precisely :

Rings are a form of cast iron, bore is likely cast iron, so the chance is good of between them their leaving a rusty mark part way down the bore. On the first attempt to turn the engine over, the rings will likely bind on the rusty mark until it is cleared.

Adding a few drops of oil via the spark plug hole is always a good idea, before laying up an engine, especially true for a 2T.

[fred]

Thanks for the suggestions. ISTR that Volvo recommended squirting some oil into the cylinders of their marine petrol engines before laying up for the winter. Never bothered of course.

[newshound]

Hydraulic locks like this fairly regularly wreck big marine diesels and stationary engines, I am told. One of my old colleagues investigated a case on a megawatt sized emergency generator.