Stihl MS361 help for a newbie

[chopchop]

Good morning all. I'm brand new on here and was hoping some might be able to assist me please?

 

I recently bought a cheap used 026 and with lots of detective work, a new bar and a chain got it running well. I enjoy tinkering tbh.

 

The other day I bought a very cheap used MS361. First inspections after dusting off reveal that it appears barely used. Piston at inlet and exhaust looks perfect with zero scoring. BUT it won't start.

 

What I've done so far:

 

Cleaned everything up.

Blown out the carb.

Inspected fuel line and impulsive.

Checked air filter and air intake boot.

Checked for spark (all seemed good)

Checked piston is correctly orientated.

 

So I'm wondering about the next diagnostic steps.

 

One thing I'm unsure about is the decompression valve (having never used a saw with one). When out the compression feels excellent...very hard to pull over. With it in it feels like there is very little compression at all. Pulls easy and piston can be heard moving up and down with a hiss from the valve. I'd this normal? I have a compression tester on the way. 

 

Upon trying to start it seems that little fuel is getting to the cylinder despite the checks mentioned. Little smell of fuel, dry spark plug etc. Anything I should check that I haven't?

 

Finally, I tried starting with some fuel through the spark plug hole. Nothing doing. Surely that points to a spark/timing issue?

 

Any help to get me started would be very much appreciated. Thank you

 

 

[spudulike]

How did you check the piston orientation? Have you inspected the piston from the exhaust port? I ask as if the saw has seized, the inlet side is often perfect with all the damage being on the exhaust side being the hottest side.

When you try starting it, leave the decomp valve out as the extra compression will help. Once the saw is running, it is up to you whether you use it or not.

Most issues on this type of equipment are carb related so it is worth taking the carb covers off and checking both voids under the covers are full of fuel.

[Stubby]

4 hours ago, chopchop said:

Good morning all. I'm brand new on here and was hoping some might be able to assist me please?

 

I recently bought a cheap used 026 and with lots of detective work, a new bar and a chain got it running well. I enjoy tinkering tbh.

 

The other day I bought a very cheap used MS361. First inspections after dusting off reveal that it appears barely used. Piston at inlet and exhaust looks perfect with zero scoring. BUT it won't start.

 

What I've done so far:

 

Cleaned everything up.

Blown out the carb.

Inspected fuel line and impulsive.

Checked air filter and air intake boot.

Checked for spark (all seemed good)

Checked piston is correctly orientated.

 

So I'm wondering about the next diagnostic steps.

 

One thing I'm unsure about is the decompression valve (having never used a saw with one). When out the compression feels excellent...very hard to pull over. With it in it feels like there is very little compression at all. Pulls easy and piston can be heard moving up and down with a hiss from the valve. I'd this normal? I have a compression tester on the way. 

 

Upon trying to start it seems that little fuel is getting to the cylinder despite the checks mentioned. Little smell of fuel, dry spark plug etc. Anything I should check that I haven't?

 

Finally, I tried starting with some fuel through the spark plug hole. Nothing doing. Surely that points to a spark/timing issue?

 

Any help to get me started would be very much appreciated. Thank you

 

 

Has the fly wheel key sheared putting it out of time ? You say there is a spark but it might not spark under compression if the plug is duff or the ignition unit has failed .

[chopchop]

Thank you very much guys...

 

Checked piston through spark plug hole. Arrow on the top points to exhaust side. Both sides of piston, thru exhaust and spark plug hole look flawless. The piston moves freely with no unusual noises.

 

Stripped the carb again and fuel in both cavities. Also spun the flywheel with a drill but no firing, but did confirm good spark. Flywheel appears totally intact and 'new' like the rest of the saw.

 

One thing I have noticed is that when pulling over with decomp in a fine mist of spray comes out of the tiny hole. Normal I guess. But with the valve out there is a significant mist of fuel escaping the decomp from around the pin/stem especially noticeable with the drill on the flywheel. Could this be a cause? A comp test tomorrow should make things clearer.

 

Many thanks guys 👍

[chopchop]

A few pics may help...

[Bolt]

12 minutes ago, chopchop said:

 

 

 

I think I’ve bought brand new saws that have been dirtier than than.

[adw]

It certainly looks like new, have you actually removed the flywheel to check the key as Stubby suggested? It also sounds like it’s completely flooded if fuel mist is coming out of the deco valve, how much fuel did you tip into it? Too much and it will just soak the plug before it gets chance to fire.

[chopchop]

40 minutes ago, Bolt said:

I think I’ve bought brand new saws that have been dirtier than than.

I know! Ridiculous. Piston doesn't like it's been run...nor does the rest of the saw! Not bad for £40 (if I can get it to run)

[chopchop]

9 minutes ago, adw said:

It certainly looks like new, have you actually removed the flywheel to check the key as Stubby suggested? It also sounds like it’s completely flooded if fuel mist is coming out of the deco valve, how much fuel did you tip into it? Too much and it will just soak the plug before it gets chance to fire.

Yes i did flood it! Thought it wasn't getting fuel but then had in peeing everywhere with the c head off.

 

One thing I haven't done is the flywheel removal as never attempted it before. Is that side righty-tighty or righty-loosey? And do you mind explaining what I'm looking for once it's removed please? Appreciate the kind help.

[ChrisNewport]

is the top end genuine? My first thought when i saw the first picture was that piston looks aftermarket and and the gasket between the crankcase doesnt look right for such a clean saw giving me the impression someone has been in there before you.