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openspaceman
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Has anyone any observation or technique for discriminating between ring seizure from overheating/lean mixture or poor lubrication/neat petrol?

 

Next question as I have dealt with a number of MS262 and 260 seizures recently; which high quality 2t oil is dyed red or highly visible when poured from the petroil container?

 

I ask because I have trouble seeing blue dyed mix in some lights whereas red appears obvious.

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I think you may find that a lean seize tends to mark the piston up more on the exhaust side, whereas a lack of lube seize will tend to mark all round.

 

Also, a lean seize should have the damage limited to the piston and pot. The crank, con rod and bearings should be OK and should still be covered in an oily film.

 

If the crank, crankcase and con rod are bone dry and rattly, and the piston is marked all round then its a fair chance thats its due to lack of oil / neat petrol.

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Has anyone any observation or technique for discriminating between ring seizure from overheating/lean mixture or poor lubrication/neat petrol?

 

Next question as I have dealt with a number of MS262 and 260 seizures recently; which high quality 2t oil is dyed red or highly visible when poured from the petroil container?

 

I ask because I have trouble seeing blue dyed mix in some lights whereas red appears obvious.

 

Had a few seized saws this year , no fault found with the machines bar poor quality fuel , all damaged on exhaust port side , all had toxic smelling gunk for fuel in the tank .

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Had a few seized saws this year , no fault found with the machines bar poor quality fuel , all damaged on exhaust port side , all had toxic smelling gunk for fuel in the tank .

 

I've done 2 261s (typo in original post) and on my 3rd 260, these latter are probably over 7 years old now but use on railway work is fairly moderate as it's shared with strimmers and hedge cutters. This is around 50% of the small ground saws.

 

I've never seen seizing other than by the exhaust port apart from when my FS360 ingested a steel pin. In all cases the rest of the saw seems fine with no leaks around the crank seals on those I tested.

 

The 261s were both running weak, which I believe is common on this strato engine, as received they seem to rev over 14krpm but a sensitive user would compensate for this.

 

So far the 260s have run fine after rebuild and self limited at around 13.5k rpm which I think is fairly safe.

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Old stale fuel can be the culprit even if it was mixed at the correct ratio originally . Not a problem with Aspen though .........

 

I've never noticed much issue with old fuel, I recently repaired the ignition on a husky 136 which stared fine with its 5 year old fuel.

 

One thing about leaving old fuel in 2t engines is if there is any leak into the crankcase the petrol evaporates leaving oil, when the engine turns over this can foul the plug but if it fires then the problem clears before the engine is hot enough to cause a problem.

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I've never noticed much issue with old fuel, I recently repaired the ignition on a husky 136 which stared fine with its 5 year old fuel.

 

One thing about leaving old fuel in 2t engines is if there is any leak into the crankcase the petrol evaporates leaving oil, when the engine turns over this can foul the plug but if it fires then the problem clears before the engine is hot enough to cause a problem.

 

Your repairing seized saws with no obvious air leaks ect and you have not noticed much issue with old fuel ? on a big saw you might hear it start to detonate before its to late .

Edited by njm
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