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ST 4175 string Trimmer

#1

G

GM Guy

Hello All.
I have a ST 4175 string trimmer that dies just off idle. I replaced the fule lines and it was running normally and then it studdered and died.
I can restart it easily but it dies as soon as I open the throttle.
Any ideas??


#2

B

bertsmobile1

If the tank is full. tip 1/2 of it out .
If it will not start at all then the lines you just replaced are wrong way round


#3

G

GM Guy

bertsmobile1 said:
If the tank is full. tip 1/2 of it out .
If it will not start at all then the lines you just replaced are wrong way round
Click to expand...
Thanks for your reply.
It will indeed start and idle with less than a full tank. It simply will not rev and dies .
The new fuel lines are clear and I can see that they’re full of fuel.


#4

B

bertsmobile1

Now comes the hard bit
If it has a rotary valve carb then the check valve on the high speed circuit is probably stuck closed and that ie a fatal flaw as they can not be replaced
If you have a butterfly valve carb then the High speed circuit is out of adjustment
If it goes fluffy , blows a bit of blackish smoke then the H is too rich
If the exhaust sounds sharp the stops abruptly the H is too lean

Some times if you take the carb off but leave the fuel lines on, turn it sideways & blow compressed across the venturi a lightly stuck check valve will start to flow
You should see fuel mist blowing out the carb .


#5

G

GM Guy

bertsmobile1 said:
Now comes the hard bit
If it has a rotary valve carb then the check valve on the high speed circuit is probably stuck closed and that ie a fatal flaw as they can not be replaced
If you have a butterfly valve carb then the High speed circuit is out of adjustment
If it goes fluffy , blows a bit of blackish smoke then the H is too rich
If the exhaust sounds sharp the stops abruptly the H is too lean

Some times if you take the carb off but leave the fuel lines on, turn it sideways & blow compressed across the venturi a lightly stuck check valve will start to flow
You should see fuel mist blowing out the carb .
Click to expand...
Thanks very much!
It has the rotary valve carb.
I suspected that it was a carburetor problem although it happened so suddenly, I had never experienced a carburetor problem like this. I’ll search for a carb kit or a new carburetor.


#6

M

mitchel232

I know people use trimmers to maintain trims and hedges; however, I prefer Hedge Shears over them in order to maintain my garden.


#7

StarTech

StarTech

Walbro WYL-240-1 carburetor.

Check the metering diaphragm for stiffness, If stiff replace it.


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