Stihl spits gas out of exhaust

jotul8e2

Minister of Fire
Feb 2, 2008
580
Ozarks
I have a Stihl GT225 string trimmer that will only run for 15 seconds or so. It will run a little longer if I keep the choke full on. And significant amounts of raw fuel is being blown out of the exhaust.

Replacing the carb with a new one did nothing. The fuel line and return are clear and the filter is good.

I am at a loss here.
 

greg13

Minister of Fire
Jan 5, 2012
907
CNY
Pull the muffler and check the cylinder for scoring.
 

jotul8e2

Minister of Fire
Feb 2, 2008
580
Ozarks
The cylinder is clean and shiny - no scoring. I am open to any suggestions.
 

xman23

Minister of Fire
Oct 7, 2008
2,080
Lackawaxen PA
Did you try new mixed gas?
 

jotul8e2

Minister of Fire
Feb 2, 2008
580
Ozarks
I tried fresher fuel from a different can. It runs smoothly when it runs at all. It even idles nicely - for a few seconds. Then it very quickly becomes super rich. But why.
 

SpaceBus

Minister of Fire
Nov 18, 2018
4,105
Downeast Maine
It's a two stroke there's not much to it. You must be getting too much fuel as the system warms up, so check the fuel side of thing again.
 

salecker

Minister of Fire
Aug 22, 2010
1,044
Northern Canada
Check the tank vent...
When the trimmer dies,loosen the cap and listen for pressure release.
 
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jotul8e2

Minister of Fire
Feb 2, 2008
580
Ozarks
Solved.

It was the fuel - but only because of my location.

Some explanation is called for. This trimmer is used at almost 9,000 ft of altitude. Apparently the EPA did not consider - or did not care about - the effects of this thin air on their mandated and unajustable carb settings. So, not only is fresh fuel required, it must be FRESH fuel. Given the remoteness of our location, the local gas stations do not pump enough fuel to keep their stock fresh enough. And of the two stations I seem to have been using the one known to be the worst offender. So, while I had just purchased the gas a few days ago, it was likely already past its best date for a finicky two cycle at high altitude. The local small engine repair, and source for this information, drives down the mountain a fairly considerable distance to purchase gas from a much higher volume dealer.

The fuel I had been trying to use is out of the same can I use for my old Stihl 025 chain saw. I have been using it daily with no issues.

There is undoubtedly a moral behind all this, but it beats me as to what it is.
 
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xman23

Minister of Fire
Oct 7, 2008
2,080
Lackawaxen PA
I had water in the fuel. Did a lot of stuff before i figured it out.