Stihl MS150TC...is 90PSI compression OK?

[spudulike]

10 hours ago, ChrisNewport said:

Mine failed on the crankcase mounting holes wearing oval and the engine cocking over and the flywheel rubbing against fuel and oil tank. Common problem by all accounts if not caught in time they wear through, so much so that Stihl do the crankcase kit at a reasonable price. Whilst it was apart i put on a new P+C as i thought they had made a mistake in the price when i was looking at it. Its pretty much had a new short motor for just over £100 which i thought was well worth doing.

Yup, very common. The first sign is the stop switch not working, the second is a smart arse using the choke to switch the engine off, the third is the same smart arse finding the engine is knackered from their saw tech

[Joe Newton]

35 minutes ago, spudulike said:

Yup, very common. The first sign is the stop switch not working, the second is a smart arse using the choke to switch the engine off, the third is the same smart arse finding the engine is knackered from their saw tech

I think you overestimate the capacity for mechanical engineering of your average tree worker. The lack thereoff which had paid for your last few holidays 😁

[BobbyDee]

Well the hot compression test produced a result of 75psi, worse than the cold test as predicted by Spud. The saw still cuts, especially with a newly sharpened chain, but not with any great enthusiasm so I have now ordered a new Echo CS-2511TES ( I new I probably would) and will keep the Stihl for a backup and for tinkering with.

Thanks to all those who contributed.😍

Edited July 15, 2023 by BobbyDee
wrong handle

[cuso]

I rebuild these often, have 6 90 psi is OK, when you find the saw getting  boggy or running  rough low power, do a new top end. I have a tutorial on YouTube.  Only posted the tear down so far. If you want to sell it I'm open to buying it.  

[pleasant]

90psi is very low. As spud has said it shouldnt even start that low. Minimum psi for it even begin to 'pop' let alone run would be 100+...and that will significantly lower further as it heats up once started due to heat expansion.

 

10 year old pro saw? As others have said, its done its money and on your books owes you nothing. Repair it by all means if you feel the need, but would to trust it to be a reliable saw on a job earning you money....or costing you money if it fails? Remember, even if the pot and piston are new...everything else will still be ten years old. Either repair it and keep it as a spare just in case, or sell it as it is, as you will still get reasonable money for it even as a spares machine, or buy a new one and keep it as a spares donor. 

Edited November 10, 2023 by pleasant

[spudulike]

Best just to stick a new OEM cylinder and piston on it and treat it as a winter project.

The compression gauge may not like the step down fitting to attach to a machine with a 10mm plug, it usually knocks the reading down 20psi or so and the fact the machine is that small may add to the poor reading.

I haven't tried measuring the compression on one of these saws. Usually pulling it over and inspecting the piston through the exhaust port does it for me.