Cyclinder Kit change

[JimWix]

Cutting a long story short my Stihl MS170's piston is shot. On the web I can see cylinder kits for £20-30 for this saw or over £70 for a Stihl one.

I've stripped and cleaned the carb on my mower before but that's to limit of my engine experience and I've a few questions I hope someone can help with;

 

Firstly, what are these 'copy' cylinder kits like, are they OK? Good enough?

Then, how easy is a cylinder and piston change?

and finally, the piston's proper knackered - what do I need to learn to avoid this again. The saw's about 7 years old and only gets used a few times a year, but I probably haven't maintained properly and I probably have over worked it sometimes.

 

Thank you for your help and sorry if I've got you slapping your head in despair...

Jim.

[logedd in]

I have heard old stale fuel mixl is a killer of engines and modern fuel mix goes stale about 2 to3 months in 

[billpierce]

What caused the piston to get like that? No 2 stroke oil? Check the butterflies on the carb. Looks to me like some metal has got I to cylinder and crunched piston. Maybe the screw on carb butterfly.

Give me 2 mins I'll check if I have a usable 170 cylinder.

Chinese ones are wick. Meteor are good.


These saws are only 170 quid new so I def wouldn't buy a new oem cylinder

Sent from my SM-G390F using Arbtalk mobile app

[JimWix]

7 minutes ago, billpierce said:

What caused the piston to get like that? No 2 stroke oil? Check the butterflies on the carb. Looks to me like some metal has got I to cylinder and crunched piston. Maybe the screw on carb butterfly.

That's what I thought I must have done, used the wrong fuel, but when I emptied it out I was actually surprised to see it was 2 stroke mix.  It certainly went pretty quickly, I'd got through half a tank of fuel then it cut out, it restarted and went for about a minute then wouldn't start again and I could feel there was no resistance on the starter chord. I'll check the carb but unless it's obvious I may not be able to tell if something's missing.

 

I'm am guilty of using old mix.

 

7 minutes ago, billpierce said:

 

 

[billpierce]

Yes have a spare cylinder that should be usable if you got a piston.
Link to new oem cylinder kit for 55 quid.
https://www.lsengineers.co.uk/genuine-cylinder-piston-assy-for-stihl-ms170.html

Good luck.

You will need some gasket sealent

Sent from my SM-G390F using Arbtalk mobile app

[billpierce]

This one ate a screw from butterfly. Piston was shot but cylinder looks ok. And is smooth.



Sent from my SM-G390F using Arbtalk mobile app

[openspaceman]

I started a similar thread and BMP01 told me how to start, this one was run with no oil, I don't believe old petroil mix would cause lack of lubrication though it could cause other problems, principally poor starting.

 

 It's uneconomic unless you do it yourself as the saw has little value. I only replaced the piston with a chinese one as meteor weren't available. NB the piston skirt slightly fouled the bobweights so needed relieving. I used Hylomar blue for the gasket sealant.

 

It's long-winded and fiddly compared with changing the piston on a conventionally barrelled engine as, being a clamshell, everything from front handles to flywheel, ignition coil and clutch has to be removed before the two halves of the clamshell are separated and then the whole crank and piston reorientated to slide out of the casing.

 

Good luck

 

[DuncanH]

On 8/27/2017 at 15:43, JimWix said:

That's what I thought I must have done, used the wrong fuel, but when I emptied it out I was actually surprised to see it was 2 stroke mix.  It certainly went pretty quickly, I'd got through half a tank of fuel then it cut out, it restarted and went for about a minute then wouldn't start again and I could feel there was no resistance on the starter chord. I'll check the carb but unless it's obvious I may not be able to tell if something's missing.

 

I'm am guilty of using old mix.

 

 

We recently had a problem getting out 660 to start. Took it to the dealer and he guessed with a couple of pulls that it probably some serious work, due to water in the fuel. He took it out back, tipped some of fuel into a jar and brought it back out. Within a minute there was an obvious, fairly deep layer of water in the jar. They've had to deal with a growing number of machines down to problems with ethanol in fuel.
Not necessarily caused by old fuel (we get through it fairly quickly), but a growing problem caused by the amount of ethanol in petrol these days - apparently it draws water from the atmosphere into the fuel and he claimed he could cause it to happen within half an hour just by blowing a fan across the top of some fuel.
We've always used the cheaper Stihl red 2 stroke oil but he suggested moving on to the green Super as it has an additive which will slow down this water production.
Another option if Aspen or Stihl's Motomix - an expensive way to go (although cheaper than costly work on a 660!).

[spudulike]

Very generally, you can usually clean the bore on 660s and get away with a quality piston rather than the £200 OEM pot and piston.....done a fair few now. 

[DuncanH]

On 8/31/2017 at 19:04, spudulike said:

Very generally, you can usually clean the bore on 660s and get away with a quality piston rather than the £200 OEM pot and piston.....done a fair few now. 

If it was down to me, or my own saw that's what I'd do, possibly getting it ported as well (I think that's the term, for getting more power out of it). The boss has decided to get the dealer to do it as we get a good discount off them when buying new equipment and supplies so good to keep in with them.