Stihl FS85 fuel, spark, no start

michaelharris1333

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Got a real puzzler. I've got an FS85 that I bought new, and it has pretty low hours. I have an old FS44 for the work around my home, and the FS-85 for some larger lots that I own. I've used the FS-85 2 or 3 times this summer, and it's been great. Most recently used it about 3 weeks ago, and had no problems. When I was finished, generally hang it up(blade up). However, this time, I set it in my basement with the blade down at about a 40 degree angle. During this time, it was tipped sideways(slightly).

Anyway, when I got ready to use it, started to attach the harness, and fuel began to drip/pour from somewhere near the carburetor area(not sure exactly). I cranked it several times, and got no start, or even a good sounding fire from the engine. I removed the plug, and it was extremely wet. I dried it, and tried again, no luck. I did this several more times, and still not one good crank. I checked for spark, and saw a strong spark. I decided to use an air compressor to dry the cylinder. When I turned the cutter up, gas poured from the cylinder. I removed the carburetor and the muffler and tried to dry these with compressed air. I also raised the piston so that I could blow underneath it as well. I also had to remove the air filter since it was soaked. I left it off. After all this, still no luck.

On the first crank, it will have a slight bit of ignition(very little), after this first crank, nothing, and the plug is always wet after I crank. I don't prime it, and the throttle is not locked open. Today, I decided to buy a new spark plug, and still the same. It has a very nice spark, and it's getting gas. As I mentioned earlier, Iused it 2 or 3 weeks ago, and the carb was adjusted perfectly, and all was well. I suspect when it tipped sideways, the fuel flooded the cylinder and the whole saw.

I really hate to take the carb apart since it was fine, but I can't even get it to start. Any ideas?

I saw several FS85 threads for other issues, so I hope starting this thread was ok.

Thanks so much.

Michael
 

Darryl G

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My no start procedure for 2 stroke equipment is full throttle, choke off and pulling the cord as rapidly as possible. Often times once it starts in a cloud of smoke it's fine afterwards.
 

bertsmobile1

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Before you go ripping into things, do a pressure / vacuum test.
If you cranked it and it was full of fuel then good chance you have broken the rings, or blown out the crankcase seals.

If it passes the test then pressure test the cab, you can do that on the engine.

This is a lot more common than you think.
Hand held engines pressurise the fuel tank and it is always good idea to loosen the cap when you have finished to release the pressure.
The metering valve has a pop off pressure at about 15 psi which is about twice the running pressure but it does no reseat till about 3 or 4.
Even with such a small tank, bleeding off 9 psi can pump a lot of fuel through the main jet.

And for all those who believe this is garbage,
run your hand held for 10 minutes , turn it off then pull the fuel intake line off the carb.
Enjoy the petrol bath
 

SidecarFlip

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I have the same trimmer. Sounds like the carb is suffering from ethanol gunk up.. I don't bother taking them apart, I just bolt on a new one If you forced cranked it, chances are the lower crank seal is gone (so long as it didn't pop at all). If it did, could be a broken ring too. tiny piston, thin rings but a good Japanese built engine. Sure like mine.
 

michaelharris1333

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I have the same trimmer. Sounds like the carb is suffering from ethanol gunk up.. I don't bother taking them apart, I just bolt on a new one If you forced cranked it, chances are the lower crank seal is gone (so long as it didn't pop at all). If it did, could be a broken ring too. tiny piston, thin rings but a good Japanese built engine. Sure like mine.

Thanks for the response. I'm 100% sure that it's not ethanol gunk. I've used only ethanol-free fuel since I took the carb apart and cleaned it about 3 or 4 years ago. Did you go with a Zama carb, or one of the $10 knock-offs being sold on ebay? I actually thought I'd give it a try, but wasn't sure if the knock-offs were any good. Looks like the original ZAMA has that written across the bottom.

Don't think I force cranked it. It was a regular crank.
After letting it set for a couple days, I bought a spark plug, and went back at it today. There was still a lot of fuel from beneath the piston, and some coming from the exhaust when I cranked it. Something is letting lots of fuel come into the cylinder. After removing the carb, I used compressed air, and dried everything very well. Turned it up and let all of the fuel drip from underneath the piston.

It cranked, and I ran it for 2 or 3 minutes. After I let it die, I tried to restart it, but it flooded again. It seemed to run fine when I started it. I now suspect something going on with the carb letting fuel pour into the cylinder.
 
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