workshop time

[openspaceman]

Could anyone say how much workshop time would the book say it took to swap a pot and piston on an ms261?

[Johny Walker]

Could anyone say how much workshop time would the book say it took to swap a pot and piston on an ms261?

 

hourish , if youve done it before

[openspaceman]

hourish , if youve done it before

 

I'd never seen beneath the top cover of the 261 before, just had the exhaust off to verify a seizure.

 

It took me considerably more than an hour and I didn't have tools to remove the carb but the flexi induction manifold has enough give to remove the three torx screws and separate the cylinder.

 

I still cannot figure the reason it seized but I am also used to employees being economical with the truth.

 

I was trying to work out the economics of repairing a 2 year old saw that retails at £500. Using new OEM parts at a Stihl dealers I judge it not worthwhile.

 

Cleaning the bore and piston and replacing the rings: we'll see...

[openspaceman]

 

I still cannot figure the reason it seized but I am also used to employees being economical with the truth.

 

I was trying to work out the economics of repairing a 2 year old saw that retails at £500. Using new OEM parts at a Stihl dealers I judge it not worthwhile.

 

Cleaning the bore and piston and replacing the rings: we'll see...

 

I rebuilt the ms261 with new rings and it ran fine but it revved to 14800 on high idle.

 

My colleague built a pressure testing kit, sealed the inlet and exhaust and pressure held fine, quite amusing to see it cycle as the crank was rotated.

 

So tonight I decided to strip the carburettor; all as good as new inside but I blew it all out just in case.

 

Now I suspect it has revved this high from new and ordinarilly it would not have seized if kept in work but we do a lot of rashing down...

 

So I've pulled the HI adjustment limiter cap off and I'll see if I can tone it down to about 13500 for a longer life.

[MATTMOSS]

Mmm... I'm don't know off the top of my head what the 261 high revs should be. But I would make sure that it's not got an air leak which would also make it rev high, you say you have done a pressure test but a vacuum test would also be good to do for peace of mind.

[openspaceman]

Mmm... I'm don't know off the top of my head what the 261 high revs should be. But I would make sure that it's not got an air leak which would also make it rev high, you say you have done a pressure test but a vacuum test would also be good to do for peace of mind.

 

He's a clever chap, I'll ask him if he can create a vacuum

 

The thing is reading on the US forums these early 261s do seem to be sent out lean

[openspaceman]

I rebuilt the ms261 with new rings and it ran fine but it revved to 14800 on high idle.

 

My colleague built a pressure testing kit, sealed the inlet and exhaust and pressure held fine, quite amusing to see it cycle as the crank was rotated.

 

So tonight I decided to strip the carburettor; all as good as new inside but I blew it all out just in case.

 

Now I suspect it has revved this high from new and ordinarilly it would not have seized if kept in work but we do a lot of rashing down...

 

So I've pulled the HI adjustment limiter cap off and I'll see if I can tone it down to about 13500 for a longer life.

 

I've had a chance to revisit this saw to cut some timber for logs, It definitely has a fuelling problem as it revs too high, the exhaust is showing very light brown and there is crackle on the over run. I just ran it for one fill. I shall replace the fuel line and filter as a matter of course but feel the problem is fundamentally in the carb.

 

Does anyone know off hand what other carbs will fit so I can see about swapping one out with another saw to see if it improves?

[Eddy_t]

If the mixture is lean, just richen the screws slightly (1/8 of a turn anti-clockwise should be enough)

[openspaceman]

If the mixture is lean, just richen the screws slightly (1/8 of a turn anti-clockwise should be enough)

 

I'm a bit further down the line than that: The saw was apparently a bit of a screamer from new but the dealers said it was okay. It had a clutch failure rebuild under warranty and worked for a year. Then it was seized, not badly. I suspected the main fault was carburation/weak mixture, so cleaned the bore and bought new, genuine, rings.

 

After the rebuild I ran it up and checked the revs which were 14800 on high idle. Limiter caps fitted to carb so no scope for further adjustment. I stripped and cleaned the carb but no obvious problems, while it was off a colleague pressure tested the engine which showed no leaks.

 

I removed the HI limit cap and there was little improvement on richening this, so I suspect either a restriction in fuel flow (possibly in the needle valve if arm too high) or a blockage in the gallery to the main jet.

 

Easiest to test by swapping the carb with another but none of the gangs will lend me a 261 for the weekend:001_smile:

[openspaceman]

I've had a chance to revisit this saw to cut some timber for logs, It definitely has a fuelling problem as it revs too high, the exhaust is showing very light brown and there is crackle on the over run. I just ran it for one fill. I shall replace the fuel line and filter as a matter of course but feel the problem is fundamentally in the carb.

 

Update on this; I removed the high screw and diaphragm and squirted some petroil through from the screw end, I also gently raised the fuel metering lever arm. Set the screw to 1.5 turns out and put it all back together, I found to get high idle down to 13800 rpm I needed to screw the needle another half turn out. Saw seems to hold this for over 10 seconds without wavering, tickover is a bit fast now.