Stihl 360 Pro Won't Start

[flatnesr]

I am in need of some advice. I teach an equipment maintenance class (high school and college age students), but most of the students wanted to do some light repair work too. One girl brought in a co-worker's MS360 Pro that died last year. It has good visible spark, but flooded immediately. She said that he had cleaned the carb and had no luck, so I pulled the muffler and saw one of the worst pistons I have seen. You could not tell where the rings were in the piston. They were one solid piece. We replaced the jug and piston with an aftermarket, new filters, some new lines, and a new plug. It still flooded. I spoke with the owner and he said that he had not touched the carb, so I went to the Stihl shop. All they had was the diaphram and gasket kit in stock so I took it. The carb was full of junk. I cleaned it and put it back together. I pulled the rope with everything open and the muffler off, and it hit first pull. I put it all back together and nothing. It floods immediately. I am going to try to track down a full rebuild kit for the Zama carb tomorrow. Any advice beyond that? I have checked the flywheel key and everything is in place. I am not set up to check for air leaks if that were the problem.

I am up to $140 in the saw, but I am not going to charge him unless we get it fixed. We have brought some basket cases back to life in that class and this didn't seem that bad at first, but I may be over my head on this one.

Thanks in advance!

Rob

 

[paccity]

check the screen in the muffler, prob plugged with debris.

 

[flatnesr]

Muffler

First thing I checked.

 

[stderr]

Metering lever in the carb?
Gaskets & diaphragms on in the right order?
Air filter plugged up solid?
Choke stuck?

 

[ZeroJunk]

Needle valve may be sticking.

 

[flatnesr]

Still searching

The air filter and throttle are fine. The metering lever is an area that I thought about after I walked away from the saw. Gaskets and diaphram are correct. I cleaned the needle valve and seat, but like I said I will try to get the whole kit tomorrow.

I have done several carbs with just the gasket and diaphram kit and somtimes the needle valve. I haven't removed the welch plug on one for 15 years. What is under there and do I need to pull it tomorrow?

 

[oscar4883]

Go thru the carb again paying particuliar attention to the needle and seat as well as the metering height. Double check your gasket order. How far out from lightly seated is your low side needle?

 

[oscar4883]

Just thinking out loud, but are you usinf the de-comp to start the saw? Maybe you are missing the initial pop.

 

[brages]

Choke is in the filter on these? If so, it is working right?

 

[woodyman]

A guy at work gave me his MS210 that was doing the same thing that blew 160 cold.I cleaned and readjusted the carb and put in a new plug and it did the same thing.Put in another new plug and did not use the choke and it started.

 

[outdoorlivin247]

Check the tank vent also...

 

[stderr]

plugged tank vent = flooding ???

 

[outdoorlivin247]

plugged tank vent = flooding ???

Yep, It can also bend a rod on a MS210...

 

[redunshee]

I vote for incorrect metering lever height or stuck needle. I always replace and reset these items when rebuilding carbs. Cheap insurance. I hardly ever remove Welch plugs.

 

[stderr]

Yep, It can also bend a rod on a MS210...

I've always thought a stuck tank vent would prevent air from entering the tank as fuel is pulled out by the carb. A vacuum results in the tank which the carb can't overcome, causing the saw to lean out and stall. If loosening the gas cap solves the problem, the first place to look is the vent. I'm obviously missing something, so how does it cause flooding?

 

[flatnesr]

Flooding

I thought the same thing. Zama has online tech guides and they list a plugged tank vent as a flooding cause. There is so much that I don't understand that sometimes I just accept what is written. Not always the right thing to do, but easier.

 

[flatnesr]

A little more history

I spoke with the owner of the saw and he informed me that the saw was running fine. He ran out of fuel in the timber so he took a load of wood to the house and when he returned the saw wouldn't start.

I am going to the shop to try several things that were mentioned. Wish me luck.

 

[Chris J.]

...I am going to the shop to try several things that were mentioned. Wish me luck.

Good luck! Led us no wat happins.

 

[outdoorlivin247]

I've always thought a stuck tank vent would prevent air from entering the tank as fuel is pulled out by the carb. A vacuum results in the tank which the carb can't overcome, causing the saw to lean out and stall If loosening the gas cap solves the problem, the first place to look is the vent. I'm obviously missing something, so how does it cause flooding?

Long story short...I had an MS210 given to me that was stuck...Thought it was a lean seize, but it ended up being a bent rod that was hitting the bottom of the cylinder...

I replaced the crank and rod and went thru the carb...The saw ran great...Let it sit for several months and went to start it and it flooded?..Pulled the plug and pulled it over several times, then it started fine...Thought I must have missed the pop?...

The next time I went to use it, it lock up on me when I went to pull it over?...Thought WTF...Pulled the plug and the cylinder was plumb full of fuel...

What I discovered was the tank vent was bad and allowing pressure to build in the tank as the saw sat...This goes against everything I thought also...I would have thought the if the metering height was set properly it would have held the fuel back, but obviously not...

Replaced the vent and it has been fine since...Thats my story and I am sticking to it...If you don't beleive me just ask Brad and Thall...They will start several other threads that will get locked and all the heat will be off me...

 

[Trigger-Time]

Tank vent will not cause one to flood unless the needle will not hold
the pressurized fuel back. Needle should hold all the pressure that can build
up in tank. The vent is made to let air in tank not out as it's a one way valve.
Stihl has changed tank vent many, many times over the years.

With a good tank vent you should be able to shake the saw to build pressure
in gas tank. Then when you remove gas cap it should hiss letting the
pressure out. This also help push fuel to carb for easier cold starts.



TT