Piston Slap/Bearing Failure - How Long Will It Last?
Discussion
I guess this might end up being moved to DIY or some other obscure backwater - but hopefully can stay here as it's engine related.
Not a car engine I hasten to add; I'd do something about it if so. Said engine is fitted in a cheapo Chinese generator - one of the really small two stroke units, at a guess 35cc or so. It is used sparingly and is several years old. The whole thing cost about £40 so it's no biggie if it blows up.
Anyway of late, especially yesterday, the engine was making an appalling clattering noise at idle. The sound of a mechanism running out of true. Either the big end bearing has gone, or the piston is loose in the cylinder bore and is knocking against it. The latter is possible as the engine seized a while ago (not sure why) and I freed it by removing the head and whacking the piston crown with a piece of wood. It worked!
Bearings may also go, mainly because it's such a simple engine it doesn't have an oil sump. Any lubrication comes as part of the two stroke oil mix. Thus I don't think the rotating bits are ever going to be very well oiled.
I appreciate that it's had a hard life, but it's essentially disposable so I shall buy a new one when it breaks. The question is how long can an engine in that state run for? It still goes fine, just sounds horrible.
Not a car engine I hasten to add; I'd do something about it if so. Said engine is fitted in a cheapo Chinese generator - one of the really small two stroke units, at a guess 35cc or so. It is used sparingly and is several years old. The whole thing cost about £40 so it's no biggie if it blows up.
Anyway of late, especially yesterday, the engine was making an appalling clattering noise at idle. The sound of a mechanism running out of true. Either the big end bearing has gone, or the piston is loose in the cylinder bore and is knocking against it. The latter is possible as the engine seized a while ago (not sure why) and I freed it by removing the head and whacking the piston crown with a piece of wood. It worked!
Bearings may also go, mainly because it's such a simple engine it doesn't have an oil sump. Any lubrication comes as part of the two stroke oil mix. Thus I don't think the rotating bits are ever going to be very well oiled.
I appreciate that it's had a hard life, but it's essentially disposable so I shall buy a new one when it breaks. The question is how long can an engine in that state run for? It still goes fine, just sounds horrible.
Depends what it is. Piston slap can go on for quite a while before it breaks bits off the skirt and stops; big end bearings tend to be terminal much more quickly.
Two-stroke lubrication is always as you describe, BTW, - there's no sump of oil, all of the slippery stuff comes in with the petrol one way or another and is burnt eventually.
Two-stroke lubrication is always as you describe, BTW, - there's no sump of oil, all of the slippery stuff comes in with the petrol one way or another and is burnt eventually.
littleredrooster said:
Depends what it is. Piston slap can go on for quite a while before it breaks bits off the skirt and stops; big end bearings tend to be terminal much more quickly.
Two-stroke lubrication is always as you describe, BTW, - there's no sump of oil, all of the slippery stuff comes in with the petrol one way or another and is burnt eventually.
I had an MG once with a bad case of piston slap. The skirts didn't break up: the rings went first. Messy, it was.Two-stroke lubrication is always as you describe, BTW, - there's no sump of oil, all of the slippery stuff comes in with the petrol one way or another and is burnt eventually.
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