# Stihl FS80r trimmer slow to power up.



## Highdesignfool (May 26, 2017)

This old Pro trimmer is in great condition but at idle when I go full throttle it bogs out.


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## Highdesignfool (May 26, 2017)

Any ideas why?


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## r black (May 26, 2017)

lean ?.....i have one of these i am also working on at the same time... carb problem i am guessing ....amazon has these .....installed on mine runs like a champ .....yes it a china carburetor ....


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## GrassGuerilla (May 26, 2017)

Does it get to full rpm if "feathered" or just bogs out above idle? Either way I'd pull the muff, inspect p&c and make sure the muff is not plugged up with either carbon or even a mud dauber nest. Also check fuel line for cracks etc. Assuming all checks out try fattening up the low side about 1/4 turn.


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## Highdesignfool (May 26, 2017)

It won't let me upload the video


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## Highdesignfool (May 26, 2017)

I put the video on you tube


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## Highdesignfool (May 26, 2017)

With it being a Fs80r and the serial number is 266611323
Can someone tell me the factory carb part number?


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## r black (May 26, 2017)

WELCOME


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## GrassGuerilla (May 26, 2017)

Did you try backing out the L side?


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## Highdesignfool (May 26, 2017)

GrassGuerilla said:


> Did you try backing out the L side?



Yeah. Still does it


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## 1Alpha1 (May 27, 2017)

Have you checked the spark arrestor in the muffler?

I have an FS-250R and it was the 1st thing I removed when it was new.


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## Highdesignfool (May 28, 2017)

Free Will said:


> Have you checked the spark arrestor in the muffler?
> 
> I have an FS-250R and it was the 1st thing I removed when it was new.



Yes. That was the first thing to go in mine too.


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## Highdesignfool (May 28, 2017)

I installed a new Stihl carb today and it runs like brand new. I suspect the diaphragm plates or something else in the old carb were bad. Thanks R black for the part number


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## 1Alpha1 (May 28, 2017)

Highdesignfool said:


> I installed a new Stihl carb today and it runs like brand new. I suspect the diaphragm plates or something else in the old carb were bad. Thanks R black for the part number
> 
> 
> Sent from my iPad using Tapatalk




Glad to hear that you got it running properly.


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## Modern Marvel (May 28, 2017)

I got a couple FS 80r's ,that was one of the best pro trimmers ever to hit the public market. It saddened me when they stop producing them. but for the ones I've ran and the ones I own as long as maintenance was done on a regular basis like cleaning the carbon out of the exhaust ports and the muffler manifold fuel lines/ filter etc. The carburetor was 99% of any problem that I stumbled upon and I always have ran nothing but ethanol free fuel and synthetic oil of good quality but still problems will arise occasionally as expected from everyday use. Don't get rid of that trimmer because it will eventually be one of those old Timers that will be always talked about.


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## Highdesignfool (May 28, 2017)

Modern Marvel said:


> I got a couple FS 80r's ,that was one of the best pro trimmers ever to hit the public market. It saddened me when they stop producing them. but for the ones I've ran and the ones I own as long as maintenance was done on a regular basis like cleaning the carbon out of the exhaust ports and the muffler manifold fuel lines/ filter etc. The carburetor was 99% of any problem that I stumbled upon and I always have ran nothing but ethanol free fuel and synthetic oil of good quality but still problems will arise occasionally as expected from everyday use. Don't get rid of that trimmer because it will eventually be one of those old Timers that will be always talked about.



I totally agree. They don't make them like this anymore. I inspected the clutch recently and it looks almost new. I've never cleaned carbon out of the exhaust ports or muffler manifold. How do I go about that?


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## Modern Marvel (May 28, 2017)

There are a couple of ways to do it. You can get online a tool that is basically just a hardened plastic flat-head screwdriver the idea I guess is to scrape out the carbon with it from the exhaust port and muffler once you have removed the muffler from the engine. I think that the tool was made by Echo so that might be a good place to start a search for it online. It can be done with a metal flat-head but you have to be extremely careful to not score the piston and port. How I do it is simply by removing the cylinder head which gives you access to the inside of the cylinder and piston itself for any carbon built up there and makes it very easy to clean those parts. Use paint good chemical solvent I like to use brake cleaner to loosen the carbon up and then take a non lint rag to polish and clean everything off before reassembling it. The muffler is easy you can use the metal flat head and just scrape out the inlet manifold once you get it apart you can see where the carbon is built up at ( be sure not to damage the exhaust gasket) as well as carbon buildup on the gasket. The other way I have not tried but have seen it, if you have an oxygen and settling tank to run straight oxygen through the motor with carburetor off and the engine will scream real high like being fed with nitrous blows out all the carbon you would want to do this obviously without the muffler on and only for a very short period of time. To me it seems like a very dangerous way to do it but I have seen it done. Also if you have any spark arrestor screen that comes stock from the factory do away with that as soon as possible that will build up carbon faster than any other part. If you're running this machine every day then it becomes necessary to clean the carbon buildup every eight months or so but if you're not using it everyday it's good to just take the muffler off, you can always keep a close eye on it this way.


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## Highdesignfool (May 29, 2017)

I'll have to try the scraper method


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## Modern Marvel (May 29, 2017)

You may want to have the engine stabilized up at a high bench level with good lighting keep the engine upright to avoid carbon scrapings getting on to the piston. And you shouldn't have any problems with it.


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## GlynnC (May 30, 2017)

I use popcicle sticks to scrap the exhaust port. Easy to obtain, and you get to enjoy the yummy to prepare the tool for use!


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## Modern Marvel (May 30, 2017)

Sometimes the carbon deposit may be to hard to remove with a Popsicle stick. but I suppose that could work for some of it. Close to the inside of the jug though you're gonna need something that's got more of an edge( if you're not going to take the cylinder jug off) like a flat head or something of that sort.


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## Highdesignfool (May 31, 2017)

Would a flat piece of brass stock be ok?


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## Highdesignfool (May 31, 2017)

I pulled the muffler off today. The exhaust port looked surprisingly clean. I scraped off a little built up carbon and used carb cleaner on Q tips to clean off the residue. It's all buttoned up and running strong. I don't notice a difference but I'm glad I know it's done. Thanks for the tip. 


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## 1Alpha1 (May 31, 2017)

Of all the O P E I've owned over the course of 50 years or more, not once did I have to remove any carbon build-up on anything.

Just lucky I guess..............


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## Modern Marvel (Jun 1, 2017)

Free Will said:


> Of all the O P E I've owned over the course of 50 years or more, not once did I have to remove any carbon build-up on anything.
> 
> Just lucky I guess..............


Yeah I would say you were lucky because carbon buildup is one of those things that is not talked about much or noticed that much but has been blamed for many problems. I myself had a catastrophic failure on a saw. It's no secret what clogging up the exhaust flow will do to an engine.


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## Modern Marvel (Jun 1, 2017)

Highdesignfool said:


> I pulled the muffler off today. The exhaust port looked surprisingly clean. I scraped off a little built up carbon and used carb cleaner on Q tips to clean off the residue. It's all buttoned up and running strong. I don't notice a difference but I'm glad I know it's done. Thanks for the tip.
> 
> 
> Sent from my iPad using Tapatalk


No problem glad you were able to get it cleaned out. The main cause of carbon buildup is just from a crappy oil or improper mixture so if it's for the most part clean then you're using a good 2-cycle oil and mixing it correctly if you were to have had a big build-up and got it clean that may have been the only time you would have noticed any difference in power.


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## Highdesignfool (Jun 1, 2017)

Modern Marvel said:


> No problem glad you were able to get it cleaned out. The main cause of carbon buildup is just from a crappy oil or improper mixture so if it's for the most part clean then you're using a good 2-cycle oil and mixing it correctly if you were to have had a big build-up and got it clean that may have been the only time you would have noticed any difference in power.



Looking at the plug, it was running too lean. Maybe that's why no carbon build up.


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## Modern Marvel (Jun 1, 2017)

Highdesignfool said:


> Looking at the plug, it was running too lean. Maybe that's why no carbon build up.


That's possible. Was the spark plug looking like it had a white residue on the electrode.


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## Highdesignfool (Jun 1, 2017)

Modern Marvel said:


> That's possible. Was the spark plug looking like it had a white residue on the electrode.



The ground electrode was light tan


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## Modern Marvel (Jun 1, 2017)

Highdesignfool said:


> The ground electrode was light tan


Besides the spark plug being old that doesn't look too bad I do notice a little carbon deposit on the bottom rim but overall not too bad a little on the lean side it should be a light charcoal color but shouldn't have a significant amount of deposit on it. Warm the engine up for a couple minutes and then hold the throttle wide open at the same time take screwdriver and back out the high jet about 1/8 of a turn you'll hear the motor sightly decrease in RPM at WOP. A correctly tuned engine will have a four stroke fire in between the powerband with no load.


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## Modern Marvel (Jun 1, 2017)

Highdesignfool said:


> The ground electrode was light tan


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