Question about Stihl Saws

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I have a 420 stihl saw I installed a new carburetor new gas lines won’t start if I pour gas in cyclinder runs for a minute then cuts off need help figuring this one

Posted by Wakeen on

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  • Cal Fedak Oct 03, 2019

    You will need to find a compression tester to check compression and see if the compression stays up

  • Chester Allen Oct 09, 2019

    Try removing the in tank gas line filter, it may be plugged

  • Chester Allen Oct 09, 2019

    Make sure the lines are set correctly, I had a similar issue. It's most likely a carb issue, if you can get it running set your air screws.



3 Answers

Ralph Shah

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  • 37 Answers

Pump not working

Posted on Oct 09, 2019


Cal Fedak

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Check the cylinder for compression if no compression there Courbet a bad Piston ring in the cylinder and it won’t stay running

Posted on Oct 03, 2019


toot tall

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Obviously it's not getting gas. remove the carb and recheck it. some have a plastic piece over the intake and output to keep the interior clean during transit. Forgetting to remove it will cause it not to get gas. Either that or the float is stuck closed, something like that. If the carb is new out of the box, they sometimes have a piece of plastic or something inside the float bowl to keep the float from banging around during shipping ect. Check that too.

Posted on Oct 01, 2019

5 Related Answers

Savu Mihai

  • 211 Answers

SOURCE: Stihl MS 260 Pro wont run wide open or idle.

Hi brandon First change the sparkplug with the same heat range,Check and clean the gas filter with compressed air.Remove the carb and very carefully disassembly entirely.Check the gaskets and the diafragms.At the fuel pump side there is a fine screen(clean it).Check the needle,the spring and lever.Unlock the screws L and H(note how many turns are they).Put the corp of the carb in a special clean solution for 12 hours and then clean it with compressed air(something is clogged there).Put all back together and try to start the engine. regards savumihai71

Posted on Feb 12, 2009


  • 1 Answer

SOURCE: Chain Saw, Stihl Model 011, cutting off

I've been messin with my poulan 2150 that was doing the same thing. Good, fresh gas, good spark,etc. I noticed whenever I loosened the fuel cap it would literally spray gas out! alas, I removed the muiffler assy and the darn thing fired up the first pull! I've got the muffler parts soaking in gas right now and I'm sure this the problem. It just makes sense especially if you use the same 'mixed fuel' can for weed eater, blower,etc. Check your's out, it could very well be your problem too! GOOD LUCK

Posted on Apr 29, 2009

Brian Anderson

  • 399 Answers

SOURCE: Stihl MS290 only runs if the gas tank vent valve

sounds like you have a plugged vent either in the gas cap or the vent valve of which you speak. Without the vent working properly, the engine running and drawing gas from the fuel tank causes a vaccum inside the tank making it harder for the fuel to draw to the carburator. this would cause the symptoms that you are talking about.

Replace the gas cap if it is vented or check to see if the vent valve you mention is working properly.

Good Luck

Posted on Dec 21, 2009


Joseph Mueller

  • 346 Answers

SOURCE: where is location of serial number on a 420 stihl

The Serial is engraved into the aluminum right next to the muffler. Look from the top down and you will see it. Good luck

Posted on Feb 22, 2011


frank thomas wilson

  • 10319 Answers

SOURCE: Ts420 stihl cut off saw

the jets in the carburetor need to be cleaned out very well to operate this engine
the holes in the jets are very small and clog up easily with in a year or two

Posted on Jun 22, 2011

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Stihl ts 420 run fine idles good but on half choke changed filter replace line repace carbureator cut off when switch is placed in no choke position what could be the problem

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I have stihl saw stone cutter i have rebuilt it with new cylinder and piston it will only run for short time when i pour petrol in plug hole it sound good when running

This indicates that you have carburetor or intake setup problems. If the saw had sat a long time then most likely your going need clean and rebuild it. Please note that cleaning these with carburetor cleaner and especially the drip can destroy the carburetor. It is best to use an ultrasonic cleaner on these carburetors.

Also check intake gaskets placement as you may have installed either out place or backwards.

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Check the boot between the carb and the cylinder, it could be an air leak. also check the compression. If the piston rings are damaged then it wont have the compression to pull the fuel through. Could also be a damaged fuel line, or plugged filter.

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Take the saw and open the gas tank. There should be two lines going into the tank, one for the primer bulb and the other (with a line-end filter) feeds the engine while running. Make sure that the line-end filter is submerged in the gas in the tank. If the saw still won't start or run, you probably have a diaphragm in the carburetor that is torn (from letting the saw sit for a long period of time). You may need to rebuild the carburetor. A carburetor rebuild kit can be bought for very little $$ at a lawnmower repair shop.

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This was very common, they say it was because the screws were too long and prutruding through the nut the thread then gets covered in concrete dust and when trying to unscrew locks in the thread. You will probably have to destroy the cover to get it off.

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How do you fix as carborator for saw that has gas mixed to rich one of my employees thought it would be good to mix it 8 ounces to a gallon

First pour out all of the old mixture. Put in the right mixture. Pour an ounce or two of raw gas down the throat of the carb or inject it wit an eye dropper.(what ever works the best. The raw gasoline will run for a few seconds but will not hurt the engine. Let saw run for a while until the blue/white smoke clears. Running a saw on too much oil mixture is much better than running it on too lean as that is the way the piston is lubricated. The problem with too much oil is that the oil is sticky and clogs the exhaust ports of the 2 cycle engine, but running it on the correct mixture should correct that.

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1 Answer

Stihl 420 - continues to cut out , we purchased 4 new saws and have problems with all of them. We thought it must be gas , ethanol, vapor lock any suggestions

If the unit is running for a short amount of time but never gets to a high rpm then it could be that the needle is sticking open, or another carburetor problem. Might also blow the fuel tank completely dry, I have seen where the water would stay in the fuel tank even after it has been drained out. And when the tank is empty I would check the fuel filter. Take the fuel filter off of the fuel line and dry it off. IF the fuel filter is dark, like a coffee stain on white, then you need to replace the fuel filter. If it is a white color when dry the fuel filter is O.K. and the problem is elsewhere.
I would also suggest that you take it to a Stihl dealer that has a Gold Certified Technician, the technician will be able to diagnose and fix the problem. Usually in a timely manner. You can go tot the dealer that you bought the units from or you can go to the Stihl website and they can direct you to the nearest dealer.

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1 Answer

I have a Stihl Ts400 cut-off saw. I just replaced the piston, piston rings and Cyclinder due to no compression. Now I can't get it too fire. Need some advice on what to do now.

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1 Answer

Hi there; my stihl ts 420 does not start easily

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