Stihl scratchin' my head

[jinman]

Two days ago, my Stihl 021, 16" saw just quit working. Earlier this year, I found the fuel line had dissolved and replaced it. The saw has worked perfectly since, up until now.

I have a 1-1/2 month-old mix of fuel in a 1-gallon can that has been stored inside and is a perfect mix with Stihl 50:1 oil. I filled the saw and went to cut some fallen trees on Wednesday morning. The saw started normally, but wouldn't gain full rpm. It seemed to be struggling and finally died. After a few more attempts to start it with no results. I returned to the house to work on the saw.

I pulled the plug first thing and it was wet/soaked. I used my air hose to blow it off and also blew air into the cylinder to clear any fuel. I dumped the fuel out into a can and then used my Mr. Funnel to refill the saw about half full. With everything dry, I gave the saw about 10 more pulls. NUTHIN'!

I again removed the plug to find it soaked. I dried the plug then put the wire on the plug and shorted the body to ground. It had a very hot spark when I pulled the rope. Ignition works perfectly.

So, I dumped out the gas again and dried out the saw. Just to be sure, I changed the plug with another used one I had laying around. With no gas in the tank, I pulled the rope and that silly saw fired off and ran perfectly, drawing gas from what remained in the pickup hose. I swear it ran like a new one. I ran it long enough that the engine got pretty hot, and then I shut it off and added fuel to the tank. When I pulled the rope, NADA! NUTHIN'! The plug is again soaked.

Okay, time to look at the carb. I disassembled the carb and it is clean as a whistle inside. Even the needle valve seemed to be working properly, but I didn't have a rebuild kit, so I'm not sure that all the gaskets and diaphrams are working properly. It still acted the same way when I put it all together, so I decided this saw was going into the shop. I emptied out all the fuel and yesterday morning I took it to my New Holland dealer who is also a Stihl dealer.

I felt sort of silly telling the mechanic that my saw only ran perfect when there was no gas in it. Yep, he looked at me like I was from another planet and took the saw and checked the gas tank. I told him it would probably start up the way it was, but if he added gas it would flood. He took the saw back to the shop and in a few seconds I heard it running perfectly. Then nothing, no more sound. I bet he put gas in it.

I'm waiting to hear the outcome of this one. I know it's probably going to cost me at least the price of a carb kit and maybe a whole new carb. I just can't believe it is anything else from the way it performed. If it were bad gas, it should have acted the same whether it had a little or a full tank. I'm having difficulty accepting that the gas could have been the reason, especially after refiltering through the Mr. Funnel.

Ideas are welcome, but I'll surely soon know what is ailing my saw.

 

[Western]

That is strange! I bet your right on the carb kit. I wander if, when the tank is full it is saturating something (diaphragm, seals), or the added volume of air in the tank with only the pick up line full is an indicator of starving for air. I had a similar problem to this on a lawn mower, only ran on a 1/2 tank, shop put a new gas cap on and it was good, I felt really stupid..Of course it was a Briggs and Stratton so I was thinking it could be a problem from the handles to the blade!!!

Hey Jinman good time fer a NEW saw..

 

[jayste]

Thanks, Jim, now I'm "stihl" scratching my head! Maybe it's your gas cap...bad vent? OOPPS! I sew Western beat me to it!

 

[mwb]

There must be diaghram or gasket damaged or the needle is not seating correctly. Pretty sure a carb kit would fix it.

Trade it in on a Husqvarna!

 

[mwb]

Three posts in less than three minutes! Now four...

 

[RobertN]

Guesses, but

- Needle is not seating; it is getting too much fuel. Maybe gunk from bad fuel hose
- Tank vent is clogged. Pressure buildup in the tank
- Ethanol in gas softened the needle/set so now it flows too much

I'm thinking carb kit. Flush the tank. New filter. Check impulse line. New spark plug

Oh, and check the air filter...

I have been seeing some TBN'ers over on arboristsite.com Bet you could have a quick answer there. You'll have a good answer from the shop soon though.

How is the lead time at the shop? Around here, they are busy busy. We had 1.5' of snow here in December; lots of trees down and/or branches broken. LOTS! Local shop have been selling small to medium size homeowner chainsaws as fast as they can get them. And, fixing lots of saws that folks grabbed out of the garage/shed, only to find they needed service...

 

[jinman]

Right on! Right on! Right on! All you guys are right on target with what I'm thinking. I don't think it's the fuel cap because the Stihl has a vent line separate from the cap and I could see it bubbling with air coming out of the tank as it warmed up. I think it's far more likely to be a faulty diaphragm or ethanol deteriorated "something." I haven't heard anything yet, so I'm pretty sure they are ordering parts and waiting on arrival from Stihl.

This saw is several years old, but it is practically new. I'd bet I don't have 10 hours of cutting time on it. It still has the original price tag on it like it was sitting on the shelf in the store. It would kill me to have to buy another saw. Plus, it has been super reliable over the years and only recently started giving me problems, which I'm sure I'm probably responsible for.

Thanks for all the suggestions. I'll surely tell you what I find out.

 

[beenthere]

And, don't use any more gas with ethanol. It is not good stuff.

 

[powerpace]

All small engines now come with a warning not use ethanol fuels. It will degrade most rubberized parts. But who reads the instructions?

 

[om21braz]

Probably no cure here, but every piece of Stihl equipment I have has it's own sequence to start. One you turn choke on, pull 3-4 times until it tries to fire, turn choke off and one more pull starts it. On others this method is slightly different. But if you vary the start method in the least they will flood every time and then it's time to let it set or remove the plug and slowly pull the starter rope a few times/dry off plug/replace. The easiest piece to start is a BR400 blower - the above method will start it every time. But it is used very often, at minimum twice a week and during grass cutting or leaf season it is daily. Also, the most difficult to start and most cold-natured is a 028 chainsaw - it gets the least use. Hope the shop gets you cutting soon jinman !