MS361 - Can barely pull w/plug - possibilities???

[davefr]

Hi,
I bought a MS361 at a garage sale yesterday super cheap as an "as-is saw". It looks like it's only had minimal use.

When I pull the rope with the plug installed it'll barely turn over. With the plug removed it'll free wheel with minimal friction just fine. Compression says 125 PSI but that's because I can't even get a good spin.

The cylinder/piston look perfect as viewed from both the exhaust port and intake.

I'm racking my brain trying to come up with theories why compression would be so tight but freewheel effortlessly with no plug? Has anyone run into this problem before? The cylinder gasket's there and it looks like the saw was never worked on before.

TIA

 

[shawn022]

Does it have the correct plug? Will it pull over with the spark plug installed and the decomp pushed in?

Another thought would be severely flooded. Pull the plug and turn it upside down and pull it over.

Also with the plug out how do the bearings feel when you turn it over by hand?

 

[lone wolf]

Does it have the correct plug? Will it pull over with the spark plug installed and the decomp pushed in?

Another thought would be severely flooded. Pull the plug and turn it upside down and pull it over.

Also with the plug out how do the bearings feel when you turn it over by hand?

Flooded was my first thought.

 

[shawn022]

Just following the kiss rule. I had a 361 that sat on the shelf for 7 months with fuel in it. It somehow flooded the crankcase and rusted the main bearings. I pulled the cylinder to change out an aftermarket piston for oem and the crankcase was full of fuel. Needless to say it got a full rebuild.

 

[davefr]

I'm testing it with the muffler and carb removed. Even if I push in the decomp valve it feels abnormally tight.

The bearings feel just fine when I remove the plug and free wheel it. (nearly frictionless)

Could a clogged or collapsed impulse line from the crankcase to the carb seat cause this condition? I'm thinking maybe the crankcase is in a high vacuum condition causing excess effort for the piston's upstroke. Just an idea??

 

[lone wolf]

I'm testing it with the muffler and carb removed. Even if I push in the decomp valve it feels abnormally tight.

The bearings feel just fine when I remove the plug and free wheel it. (nearly frictionless)

Could a clogged or collapsed impulse line from the crankcase to the carb seat cause this condition? I'm thinking maybe the crankcase is in a high vacuum condition causing excess effort for the piston's upstroke. Just an idea??

Is the plug gap closed from getting hit by chance? Is the pullstart rope and pulley in good condition? You may have to rip it down if all this fails to answer the question. Maybe the base gasket was deleted and its too much?

 

[Mad Professor]

Just following the kiss rule. I had a 361 that sat on the shelf for 7 months with fuel in it. It somehow flooded the crankcase and rusted the main bearings. I pulled the cylinder to change out an aftermarket piston for oem and the crankcase was full of fuel. Needless to say it got a full rebuild.

And if it was flooded with E10 that was the source of the corrosion. Does just what it does to carbs.

I am blessed we finally have pump prem non-E10 nearby

 

[davefr]

Well surprise, surprise!!

The saw only cost me $7.50 so I guess I can buy a new top end.

 

[lone wolf]

Well surprise, surprise!!

The saw only cost me $7.50 so I guess I can buy a new top end.

Now that is something you dont see happen a lot.

 

[Rx7man]

That'll do it.. I guess with pressure the piston was going cockeyed in the bore...

 

[ELECT6845]

I think I have a 361 cylinder that has a blown out bolt hole for the muffler. You can have it if you want to try and repair the hole and use it. PM me if you are interested and I will dig it up.

 

[fearofpavement]

Now, you need to ensure that the broken cylinder is a cause of the saw turning over hard and not a symptom. Ie, check the top of the piston and make sure it doesn't have any signs of contacting anything. For instance, if someone put too long of a plug in it, the piston could hit the plug and break the cylinder.
The damage you have is not typical and something is amiss somewhere...
Were all the cylinder base bolts tight?

 

[fearofpavement]

Could have also been caused by hydraulic lock which wouldn't mark the piston but may bend the rod.

 

[davefr]

The damage you have is not typical and something is amiss somewhere...
Were all the cylinder base bolts tight?

I think what happened is the previous owner dropped the saw or maybe a tree fell on top of it. The brake handle has been patched, a top fin is also broken from the cylinder, the decompression button is bent and the shroud is cracked. What took out those parts also must have cracked the base of the cylinder. Fortunately everything else looks great. The crankshaft, piston and connecting rod look and perform fine on the bench. I ordered a cylinder kit and new brake handle. Hopefully that'll get her running.

The piston and cylinder wall looked like new. I don't think this saw has more then a few hours on it.

I think I have a 361 cylinder that has a blown out bolt hole for the muffler. You can have it if you want to try and repair the hole and use it. PM me if you are interested and I will dig it up.

Thank you for the offer!! I'm just going to get the whole top end kit.

 

[drf255]

Well surprise, surprise!!

The saw only cost me $7.50 so I guess I can buy a new top end.

Should buff right out.

I'll double your money if you send me that saw.

 

[LowVolt]

I think what happened is the previous owner dropped the saw or maybe a tree fell on top of it. The brake handle has been patched, a top fin is also broken from the cylinder, the decompression button is bent and the shroud is cracked. What took out those parts also must have cracked the base of the cylinder. Fortunately everything else looks great. The crankshaft, piston and connecting rod look and perform fine on the bench. I ordered a cylinder kit and new brake handle. Hopefully that'll get her running.

The piston and cylinder wall looked like new. I don't think this saw has more then a few hours on it.

Thank you for the offer!! I'm just going to get the whole top end kit.

Please go oem with it. If you are patient a good oem will pop up on eBay for $100 or less.

 

[fearofpavement]

Ah, now more of the story comes out. With all the physical damage, it would have been good to include some of that info in the original post which would have resulted in less head scratching and useless advice.

 

[RAYINTOMBALL]

Ah, now more of the story comes out. With all the physical damage, it would have been good to include some of that info in the original post which would have resulted in less head scratching and useless advice.

Yeah that's what I was thinking. It was like what could of cracked the jug and piston like it was hit with a sledge hammer. Well I guess that's pretty much what happened .

 

[davefr]

Yeah that's what I was thinking. It was like what could of cracked the jug and piston like it was hit with a sledge hammer. Well I guess that's pretty much what happened .

I'm just trying to imagine how an impact to the top of the saw could crack the base of a cylinder where it's attached to the crankcase. Are these cylinders real brittle?? I wonder if the saw was running when this happened?

 

[Red Amor]

I think what happened is the previous owner dropped the saw or maybe a tree fell on top of it. The brake handle has been patched, a top fin is also broken from the cylinder, the decompression button is bent and the shroud is cracked. What took out those parts also must have cracked the base of the cylinder. Fortunately everything else looks great. The crankshaft, piston and connecting rod look and perform fine on the bench. I ordered a cylinder kit and new brake handle. Hopefully that'll get her running.

The piston and cylinder wall looked like new. I don't think this saw has more then a few hours on it.

Thank you for the offer!! I'm just going to get the whole top end kit.

You can do a nice job of plastic welding that cover using an electric soldering iron Idve done a couple if them now
drive the hot point into and along the crack as you drag the iron along it will produce two wind rowes of multon plastic , use the iron to push these back into the trench and smooth over makes a good fix
If you can find a same type of plastic to use as a filler rod you can maybe do a better stronger well ;O)