bmp01

Piston is just as soft as the cylinder. So as Spud said if something has gone through the engine you'd expect to see a damaged piston too. So either piston has been replaced or it's a dodgy cylinder from the off. Could be aftermarket  parts,  do you know the saws history? 

Regarding assembly issues - the need to assemble the engine lose and bolt it all up in situe is a truely shite idea. I don't have any respect for Stihl for employing this design. Compound that with making it almost impossible to position the engine in the saw body.... just stupid.  I've done a few now and it's not easy, best way I've found is to have the engine upside down and position the body over it. 

Well, the truth is you're not expected to rebuild these saws.

Personally I'd just run it,  you've changed and/or inspected all the bits that leak.

If it's an old saw expect the carb to be a pain. ...

bmp01

9 hours ago, spudulike said:

Pitting on the combustion chamber tends to mean metal fragments have been smashed repeatedly between the piston and squish band but the piston would also have damage in this instance.

Replacement piston? Saw history.

My punt - it's the roughness of the cast surface compared with smoothness of machined surfaces. 

Mr Rainford, is the squish band in the cylinder pitted ? (Squish band is the 2-3 mm wide ring around the periphery of the combustion camber).

6 minutes ago, peatff said:

First thing to do would be to check the H & L screw by screwing them in till they seat gently then turn them out 1 full turn each then try to get the tick-over fairly even when you have warmed up the saw.

Saws in bits already. ...

26 minutes ago, John Rainford said:

The reason I am stripping the saw down is to find what is causing it to conk out soon after starting, only starts on cold start and engine reved extremely high without me touching the throttle. I didn't attempt to start it again after that.

Right, that's a decent starting point. 

So this is the normal starting procdure (below), can you confirm at what stage your saw revved up "extremely high" ? This might help people to offer advice. 

1) cold saw, so set to choke position, saw cranked, saw coughs at this stage,

2) control set to fast idle, saw cranked, saw starts and revs high (assuming chain brake not applied),

3) throttle trigger squeezed momentarily to disengage fast idle, saw should idle.

Your air leak diagnosis could well be right, certainly if the saw revved madly while on choke (1 above).  It'll be a big air leak in that case, inspect parts and replace as you are doing.

The only example I can think of where this happened was with a MS181 where some of the screws - engIne to saw body came loose. These screws double up to hold the two halves of the crankcase together (clam shell engine) so the air leak was where you have the liquid gasket. There was a lot of grey paste from worn aluminium. ...

It's a bit difficult for peeps to comment on a problem when there's not much info to go on.

What exactly was the problem that caused you to pull the saw apart ?

I'd expect there to be an oil film inside the engine,  especially if it wouldn't start and/or has been "cranked" lots with the choke on. It's typical of 2 stroke fuel to evaporate the petrol and leave the oil behind. ..

Similarly, carbon on piston and combustion chamber is normal, within reason.

And what is pitted? If it's the combustion chamber, after you've cleaned the carbon off - are we talking about the cast surface? That's normal.

If the original piston and cylinder are genuine parts, they need to be wrecked before its worth looking at inferior aftermarket parts.

Post some good pictures.

On 18/04/2019 at 13:43, John Rainford said:

Does anyone know how to remove it at the throttle trigger end? I tried to take the top of the handle off, but can't see any screws holding it on. Maybe it just pops off, but I dont want to force it.

If you look from underneith, you'll see a slot at the operator end of the handle. The top cover has a clip with a barb on it which you can access in that slot. Flat blade screw driver in the slot to release the clip. 

Be super careful with the front end of the cover, there's a stupid flimsy piece of plastic ...

Put it back together with some Loctite, it'll be fine ?     (...or not).

I tried separating a knackered crank once (MS180) just for interest, tried all sorts of abuse, mostly involving hammers,  couldn't shift it at all. You've been unlucky there. 

Vaguely remember some story about tuned 2 stroke bike engines being assembled and then welded to stop the crank becoming misaligned with use. Don't suppose you need too many degrees of rotation before the crank would seize on a multi cylinder.

1 minute ago, peatff said:

 

If you don't got none just say so, right ?

But that wouldn't be truthful. ...

I got loadsa 200T bits .... they is blinkin stuck together in one lump. Might be available for an elevated ebay price....?

Does anyone have. ...

Or,

Has anyone got. ....

But not, 

"Does anyone got. ..."

???

bmp01

Threads in cylinder for the exhaust bolts look a bit suspect too, might need helicoiling... 

Same logic as above,  fix it properly now or it will be unreliable just when you need it. 

5 hours ago, peatff said:

I had MS180 (similar carb setup) that had similar problems and a carb kit plus raise the metering arm cured it. It was checked for air leaks etc and It seemed alright till you touched it against a log then it just died but after the fix it worked like new. Someone on here, billpierce probably, said you can get proper adjustable carb for it which would be a big improvement I think.

The carb on the 170 / 180 is completely different to the 171 / 181 / 211. The latter are strato engines and their carbs have 2 ports through them, 1 fuel and air, 2 air only......

(They already have Hi and Lo fuel screws).

8 hours ago, DCS6800i said:

 

You lucky lucky git!!

 

Cherish it for the rest of your days, they are mighty saws ? my one is my pride and joy

Ditto, I really like the old school design and feel of this saw. 

I think I've now ironed out all the gremlins left behind by previous owners. ..  

Carbs on these have an accelerator circuit that turns to sh1t on well used examples....

2 hours ago, DCS6800i said:

+1

Bought a saw a while ago which wouldn't run... did a good once over then stripped the carb - somebody had put a new diaphragm in upside down ?‍♂️flipped it over, she's been a great saw ever since ?

Bought a DSC6800i for 50 quid as a non runner, that needed a fuel line. Good condition saw too. Still haven't found a saw in a skip though.

...engine too small to drive the chain, buy a bigger, pro model saw....

20 minutes ago, Ratman said:

No, its a 7t, does fine for me, but i’m not a pro user.

So thats the whole point. ....

Going to 8 tooth will increase chain speed by a multiple of 8/7 but it will reduce the torque by the same ratio. As is the way,  you can't have something for nothing.

59 minutes ago, Ratman said:

I run .325 on my 026 with a 16” bar and its merry all day long.

On an 8 tooth sprocket ? 

4 hours ago, sfl said:

Thanks to all for your responses, coherent or otherwise ?.

 

I thought I was a long shot but worth a try. I'll ask Rob as well.

 

From what I've read and seen, my 260 should cut faster with the 3/8picco chain than the .325 even with a 7t rim. The 8t would be a bonus though.

Whether it cuts faster or not with 8 tooth will be dependant on a multitude of factors. Most important will be if you've got enough torque from the engine for the bar length you are using. A 260 with 8 tooth 3/8 maybe ok on 12 - 14 inch bar in soft wood, don't expect it to cope well with longer bar or hard wood. 

Also I'll state the blinkin obvious,  you will need to change chain, sprocket and bar with a pitch change (nose sprocket in bar is pitch dependant).

Have fun with it.

43 minutes ago, spudulike said:

VEC - Indian, Hyway - Chinese

As above. 

Sawbits - M Jones - goes by the name of tesgol on e bay. His listing there is consistently VEC, origin India and no mention of Hyway. He must have hundreds of products listed - easy to make a gaff when cut 'n paste and editing. .... or maybe he changed source for that part. Worth an ask. 

Genuine piston price? ... about what I paid for the 'spares or repair' concrete saw in the first place?.  Barrel has cleaned up ok 2 scores but not deep. It's getting an after market piston and liking it (for personal building project use) or its going for bits.

Yet another seized 2 stoke. ... ?

Out of these two piston brands, which would you go for,  Hyway (China) or VEC (India)? Price is more or less the same, I can't find a Meteor...   L and S also do one but it's a no name piston. 

I'm leaning towards VEC but for no good reason. 

I'm hoping the answer of which brand might be useful to people here but I should state the piston is for a Makita concete saw DPC6410.

And yeah, split impulse line probably... 

Thanks for any input.

BMP01

Was that Bumstead or Bumsteer ..... ?

19 minutes ago, richy_B said:

Is just touching the cables enough to do this? You don't need to break/damage them? 

Yep. Wires in the air have no insulation on them. Have a look at where the wires are held, you'll see a isolator between wire and support.

Proper scary stuff. ....

3 minutes ago, Ratman said:

Am i reading right..... No you want a top handle? Think you might struggle finding a solid tidy one at £200 (stihl) you might av to be nearer £250. They go real quick when they come up. Where you based? Sure most and myself included will keep our eyes peeled

 

Don't think so, he said "No" to the top handle.... 

Google (or t'other search engine or your choice), type in

" Arbtalk battery saw "

You'll get plenty of hits and answers straight away. In particular Battery chainsaw recomendation was done quite recently.....

HTH.

9 hours ago, Byndy said:

I would like to mod the carb and the muffler only. Please write me, how to do it, and attach pictures too!

Or you could do your home work. Search here and elsewhere, find out what's possible and recommended in general with carb and muffler mods... just as everyone else does.