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Stihl trimmer blowing out oil.

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CK82

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Discussion starter · #1 ·
I have a Stihl MS 70 trimmer that constantly is spattering oil out of the muffler and spark arresting screen. When I first purchased the trimmer it was new and I dropped it off of the wheel well on my trailer. Not until its second season did I start to notice oil spatters on my arm after trimming. I took the trimmer in and told them my problem. They took it apart and cleaned everything out and told me my oil mix was too strong. That may be so, but after that I made sure to not over mix and well the problem remained, it may have even gotten worse. I have multiple Stihl backpack blowers and 4-mix trimmers that dont seem to have any issues. Any ideas what is going on here?! I am ready to dump the trimmer and buy new.

Thanks
Chris
 
#2 ·
When running the unit at WOT does it seem to flood. Carb may need to be leaned out on the High side. MS 70? MS means chainsaw don't you mean FS 75?
 
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#3 ·
As Ron said it could be too rich. Some units develope loose welch plugs in the carb and they will run rich. Sometimes the plugs come out and they will hardly run. Over rich on the metering lever could also do it.
 
Discussion starter · #5 ·
Thanks for correcting me. Its not an MS, my fault. Its an FS 80 I believe. Its not a four mix as I stated. I have an FS 90 and 110 as well and they are 4 mix.

Anyways, Im not sure what a welch plug is in the carb. I will have to look into that. The dealer had it for a day or so and they couldnt figure it out, just told me my mix is too rich. Appreciate the information though.
 
#6 ·
CK82 said:
Thanks for correcting me. Its not an MS, my fault. Its an FS 80 I believe. Its not a four mix as I stated. I have an FS 90 and 110 as well and they are 4 mix.

Anyways, I'm not sure what a welch plug is in the carb. I will have to look into that. The dealer had it for a day or so and they couldn't figure it out, just told me my mix is too rich. Appreciate the information though.
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The welch plugs are used to seal the passages in the carb body after machining. I guess you could also call them expansion plugs. They are cup shaped aluminum disc's that are set into the cavity and hit in the center to expand them and make them fit tightly. They also use sealer on these plugs. The alcohol in the fuel will eat at the sealing material and fuel will leak around the plug. Some fall completely out of the cavity. You can get an over rich condition when they leak. When they fall completely out it will usually be so rich that it will hardly run.
 
Discussion starter · #7 ·
The trimmer will run, it just spits oil alot. the engine cover has splatters and definite oil residue on it at all times. I just have a hard time believing my mix is too rich. I mix it with a pre-measure (1 gallon mix) with the top cut off so I can fill it exactly to the 2.6oz line on the side.
 
Discussion starter · #10 ·
The filter is clean, I do store it hanging sometimes. Im probably going to just dump it and buy a new FS90 or something. Sometimes its not worth the time or money. I took it in paid almost a $100 they did a few things to it, cant recall exactly what. I dont think any new parts were added, but it went back to spitting oil within a week.
 
#11 ·
CK82 said:
The filter is clean, I do store it hanging sometimes. Im probably going to just dump it and buy a new FS90 or something. Sometimes its not worth the time or money. I took it in paid almost a $100 they did a few things to it, cant recall exactly what. I dont think any new parts were added, but it went back to spitting oil within a week.
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and I would have went back to them the next week wanting my $ back.:drinkup:
 
#12 ·
Checking the welch plugs sounds like a good idea. Are you using the proper oil spec'd for that piece of equipment? Not by brand or ratio, but Jaso rating. Have you tried different brands of oil? I would try some others before giving up on it. Synthetic oils that use a 100:1 ratio are a lot cleaner burning, leaving virtually no spooge or carbon buildup. Don't worry about the oil ratio seeming too thin at 100:1, as they are in effect doubly concentrated over a 50:1 and provide just as good or better protection over a petroleum oil. Also, you should be running it at full throttle more often than not. Low throttle settings will typically be messier.
 
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