# FS-76 is kicking my A$S!!



## Undy (May 24, 2015)

I thought I had this fixed, but not yet...

This thing won't stay running at WOT. Sometimes it runs fine for a few minutes, but then he rpms vary and it bogs down and dies. Doesn't seem to matter if it's hot or not. So far I have:

Used premium gas that was new about 2 weeks ago.
Checked spark, which seemed fine.
Tried adjusting H & L settings.
Installed new Bosch plug.
Disassembled, cleaned and reassembled carb.
Pressure and vacuum tested case and turned crank while testing.
Tested compression at 120#. (I don't know what it should be, but as old as it is I'd guess this is okay.)
Checked for a bad flywheel key.
Tried running w/o fuel filter inline.
Still didn't fix it.
Installed carb kit, even though everything looked good and the carb was new last summer.

Thought it was fixed, but tonight it's cutting out again. When it bogs and begins to die, a quick blip of the choke usually gets it to catch, which tells me it's fuel related. (???)

I thought I'd try some new gas just in case. Next step, maybe pull off the throttle line carb base mount to see if there's some sort of leak under that. Any other ideas?


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## lone wolf (May 24, 2015)

Undy said:


> I thought I had this fixed, but not yet...
> 
> This thing won't stay running at WOT. Sometimes it runs fine for a few minutes, but then he rpms vary and it bogs down and dies. Doesn't seem to matter if it's hot or not. So far I have:
> 
> ...


Needs a new coil. I had a pole pruner that did that and drove me crazy.


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## Undy (May 24, 2015)

Update. I drove to town and bought fresh gas, and it runs much better. The rpm fluctuation seems to be cured. Stupid me for ASSuming new gas would be good gas. But...

It still occasionally will slow and die. Blipping the choke sometimes cures this, but not consistently. Warm or not. I took off the gas cap, and it seems to be okay. Which would make me think the cap is bad, but...

It doesn't seem to be a vented cap that I can see. Can someone tell me whether it needs to vent through the cap? If not, is there something vent-related within the carb which I'm somehow missing??? (I've been through it repeatedly.)

And then lonewolf may be right that it's a coil. Perhaps a thermally intermittent one? (do they do that?)

Thanks.


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## lone wolf (May 24, 2015)

Undy said:


> Update. I drove to town and bought fresh gas, and it runs much better. The rpm fluctuation seems to be cured. Stupid me for ASSuming new gas would be good gas. But...
> 
> It still occasionally will slow and die. Blipping the choke sometimes cures this, but not consistently. Warm or not. I took off the gas cap, and it seems to be okay. Which would make me think the cap is bad, but...
> 
> ...


Do you have another machine you can swap the coil from? I think they are only 40 bucks anyway. And I stand by my assessment.


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## Undy (May 25, 2015)

Thanks lonewolf. No, I don't have a spare coil, unless one from a Stihl saw would work. (I have several to choose from.) I guess I can start disassembling and looking or checking part #s.

I hate the WAG (wild-assed-guess) system of diagnosis, but perhaps I'll have to spring for the coil anyway.

Checking flea-bay, I'm seeing used and aftermarket coils for 15-30$, but only one OEM NOS coil, and it was $90. Lots of used pull-offs, so there must be a lot of parted-out 026s out there. Any opinion on these?

Thanks again for any input.


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## lone wolf (May 25, 2015)

Undy said:


> Thanks lonewolf. No, I don't have a spare coil, unless one from a Stihl saw would work. (I have several to choose from.) I guess I can start disassembling and looking or checking part #s.
> 
> I hate the WAG (wild-assed-guess) system of diagnosis, but perhaps I'll have to spring for the coil anyway.
> 
> ...


The dealer wanted 90.00? I could call mine if you want and see? Post a pic of that coil I bet someone on here will have one off another machine try to show the numbers.


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## Undy (May 25, 2015)

Thanks much. I'll see what I can do about a picture.
I was wrong on the ebay search. (I think I entered the number wrong.) I looked again and I only found one coil, from France. I'll call my local guy and see if it's available and how much.


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## lone wolf (May 25, 2015)

Undy said:


> Thanks much. I'll see what I can do about a picture.
> I was wrong on the ebay search. (I think I entered the number wrong.) I looked again and I only found one coil, from France. I'll call my local guy and see if it's available and how much.


I should think about 40.oo.


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## backhoelover (Jun 5, 2015)

vacuum test gas tank shout not hold at all 
also check nozzle check valve pull high screw and remove metering diaphragm and cover supply hole for high needle put small fuel line in where high needle goes should be about to blow but you shouldnt be able to suck back 
also damaged adjustment need seats could cause this problem


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## lone wolf (Jun 5, 2015)

Update?


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## Undy (Jun 5, 2015)

Maybe, I hope. Things have been busy here. By day, I fight wrongs by our DOT. In my spare time, I've been building a tracked wheelchair for a friend of mine. But I've gotten a little time on this trimmer.

I think I finally got it nailed. I fixed the tank. Still had the issue. I just couldn't pull the trigger for a new coil, since some signs still seemed to indicate fuel problems, so I kept at it.

Finally found a YouTube video of a guy who professed to "fixing" a carb problem with a FS76. His fix? Replace the carb. FWIW, I did that last summer. But in his video, he mentioned that the carb had a metal inlet tube on the side by the primer bulb which he claimed were known to leak. He said the Zama replacement carb had fixed this issue. PLUS, on mine the return line fitting on the carb was able to swivel. I always figured this wasn't good, and assumed it _had_ to leak there, but wasn't sure enough to try something crazy.

After seeing the YouTube video, I broke out some RTV sealant and goobered it on around where both fittings met the carb. It'd either fix it, or F. it all up for sure. I haven't yet run a full tank of fuel through, but so far, it seems like it's fixed. It fired on the second pull. RPM's seem dead steady. It hasn't died out once yet. Top end RPM's seem better than ever, or at least recent.

I didn't post yet because I really hadn't made up my mind that it was for sure fixed. But let's say it's fixed for now, and I'll update if things go south again. My fingers are crossed...


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## backhoelover (Jun 5, 2015)

was it mower medic one who made video?


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## Undy (Jun 6, 2015)

No, Jeremy Fountain. (nobody I know)

Not that helpful of a video, except for his comments on why the old carb commonly failed.
Hoping for the best here...


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## backhoelover (Jun 6, 2015)

lol that is mower medic one guy


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## lone wolf (Jun 6, 2015)

Undy said:


> Maybe, I hope. Things have been busy here. By day, I fight wrongs by our DOT. In my spare time, I've been building a tracked wheelchair for a friend of mine. But I've gotten a little time on this trimmer.
> 
> I think I finally got it nailed. I fixed the tank. Still had the issue. I just couldn't pull the trigger for a new coil, since some signs still seemed to indicate fuel problems, so I kept at it.
> 
> ...


You should not use silicone RTV it will not hold up to gas and deteriorate, use JB weld on the outside.


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## Undy (Jun 6, 2015)

Looks like I'll be redoing it then. Thanks.

I got a tank through it today, and it looks as if that was where the leak was. Now to fix it right.


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## lone wolf (Jun 6, 2015)

Undy said:


> Looks like I'll be redoing it then. Thanks.
> 
> I got a tank through it today, and it looks as if that was where the leak was. Now to fix it right.


If it acts up again and does it at random times it is the coil.


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## backhoelover (Jun 6, 2015)

does readjusting the needles help needle seats could be back also nozzle check valve could be bad


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## backhoelover (Jun 6, 2015)

here you go


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## Undy (Jun 7, 2015)

Sweet! Thanks backhoelover! I'd never seen those before. I'll keep those handy for the future.

I'm pretty certain that it was leaky connections on the carb. It's running like a champ right now. But Lonewolf is likely right that the RTV sealant will fail and I'll have to redo the fix with JB weld.


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