Stripping MS 171

[openspaceman]

Could someone give me a brief sequence for getting a MS171 barrel off, I've not done one with clamshell design and am a bit wary of disturbing bearings?

 

An old primary school friend has brought it round because it wouldn't spark but that was because the bore was dry and the piston had seized slightly so it wouldn't spin fast enough to spark.

[peatff]

Have a look at a parts diagram it should give you a clue how they come apart.

[bmp01]

Could someone give me a brief sequence for getting a MS171 barrel off, I've not done one with clamshell design and am a bit wary of disturbing bearings?

 

The clamshell engine only has one split line and that is horizontally through the crank centreline. ... the crank has to come out in order to get to the piston.

 

The basic strip down procedure - remove the front handle, then remove EVERYTHING attached to the engine, apart from the intake manifold and plastic divider thingee. Finally undo the 4 bolts holding engine into chainsaw body, remove engine incl intake manifold etc.

 

Just a note of warning, the engine pan (lower crankcase) is only held on to the cylinder with the sealant at this stage. (Its a s**t design imho, dunno how they are assemble them in the factory with out the worry of the engine falling apart while fiddling it in to the the chainsaw body).

 

bmp01

[openspaceman]

The clamshell engine only has one split line and that is horizontally through the crank centreline. ... the crank has to come out in order to get to the piston.

 

The basic strip down procedure - remove the front handle, then remove EVERYTHING attached to the engine, apart from the intake manifold and plastic divider thingee. Finally undo the 4 bolts holding engine into chainsaw body, remove engine incl intake manifold etc.

 

Just a note of warning, the engine pan (lower crankcase) is only held on to the cylinder with the sealant at this stage. (Its a s**t design imho, dunno how they are assemble them in the factory with out the worry of the engine falling apart while fiddling it in to the the chainsaw body).

 

bmp01

 

Thanks and I had already found everything you say is right, the clutch and flywheel have to come off along with the ignition module. The choke link once removed allows the carb to slide up with the barrel but I'd already unbolted it.

 

Lord knows how I'm going the get the AV and handles back as it was a chinese puzzle getting it off.

 

Now here's the crunch: it's a 150 quid saw, to get to the same stage with a ms261 takes 30 minutes and the same back together again, because you leave most of the saw complete. This saw involves double or treble the work so even a minor repair becomes not worthwhile.

 

Also as it's a stratified charge engine in a narrow bore, cleaning aluminium pick up off the bore is fiddly and difficult to see.

 

I've ordered an after market piston but wish I hadn't bothered.

[spudulike]

Thanks and I had already found everything you say is right, the clutch and flywheel have to come off along with the ignition module. The choke link once removed allows the carb to slide up with the barrel but I'd already unbolted it.

 

Lord knows how I'm going the get the AV and handles back as it was a chinese puzzle getting it off.

 

Now here's the crunch: it's a 150 quid saw, to get to the same stage with a ms261 takes 30 minutes and the same back together again, because you leave most of the saw complete. This saw involves double or treble the work so even a minor repair becomes not worthwhile.

 

Also as it's a stratified charge engine in a narrow bore, cleaning aluminium pick up off the bore is fiddly and difficult to see.

 

I've ordered an after market piston but wish I hadn't bothered.

 

And so endeth the lesson for today:001_tongue: Only worth doing on cold and wet days when you have nothing else to do.

[openspaceman]

And so endeth the lesson for today:001_tongue: Only worth doing on cold and wet days when you have nothing else to do.

 

I've plenty to do with building my shed and having rewired the tweeter on my ancient AR4x speakers today but in general my time has little value so I played. Just as well to warn others though.

 

Also a very good argument for hobyists to use that premixed expensive fuel in the red plastic cans

[spudulike]

I've plenty to do with building my shed and having rewired the tweeter on my ancient AR4x speakers today but in general my time has little value so I played. Just as well to warn others though.

 

Also a very good argument for hobyists to use that premixed expensive fuel in the red plastic cans

 

Acoustic Research eh, got a pair of Castle Severn floor standers myself, not quite as old but still cut the mustard:thumbup:

[bmp01]

Thanks and I had already found everything you say is right, the clutch and flywheel have to come off along with the ignition module. The choke link once removed allows the carb to slide up with the barrel but I'd already unbolted it.

 

Lord knows how I'm going the get the AV and handles back as it was a chinese puzzle getting it off.

 

Now here's the crunch: it's a 150 quid saw, to get to the same stage with a ms261 takes 30 minutes and the same back together again, because you leave most of the saw complete. This saw involves double or treble the work so even a minor repair becomes not worthwhile.

 

Also as it's a stratified charge engine in a narrow bore, cleaning aluminium pick up off the bore is fiddly and difficult to see.

 

I've ordered an after market piston but wish I hadn't bothered.

 

It's all true. T'is the way of the world. Cheap means when it breaks you DONT mend you bin it and buy another.

 

Being a sucker for this kind of thing, I've repaired a few, and tuned them too. My 211 runs a cylinder pressure of 190 psi, achieved by moving the crank centreline ! A muffler mod gives a big gain in percentage terms too.

 

To remove the seized aluminium from the cylinder i use a sanding drum and 120 grit emery cloth. I make the diameter of the drum approx 1 mm smaller than the bore to avoid a too focused abrasion. I try to move the drum around the area of deposited aluminum and at the end of the process put a cross hatch finish in the bore. Pictures of drum and a finished bore attached.

 

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[openspaceman]

To remove the seized aluminium from the cylinder i use a sanding drum and 120 grit emery cloth. I make the diameter of the drum approx 1 mm smaller than the bore to avoid a too focused abrasion. I try to move the drum around the area of deposited aluminum and at the end of the process put a cross hatch finish in the bore. Pictures of drum and a finished bore attached.

 

bmp01

 

I try and get most off with gelled oven cleaner, then just a bit with carbide paper.

 

What is the red gasket stuff, I'll need some.

 

BTW only just seen you joined last month, welcome.

[bmp01]

Red stuff is Dirko, highly rated by all accounts but expensive. I use high temp silicone sealant from Aldi I guess i need to test it for 10 years before i can say its any good.

 

Yeah thanks, been lurking a while, ditto with the US site - thats where I picked up on the different approach to cylinder cleaning. The normal abrasive approach used is emery cloth wrapped around a spindle run in an air tool, sort of flapper wheel. The abrasive cleaning is gaining acceptance there, advantages are speed and no acid to attack of the parent material. I think its ok but possibly needs more care. Oh and you need a lathe if you want to make sanding drums to a specific diameter

 

bmp01