Question about Husqvarna Chain Saw 20" Bar

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Spear and jackson chainsaw. runs for a few seconds then stops. needs choke all the time. primer bubble seems to **** back fuel when priming. fuel is clean. saw is 1 month old. plug is fine. saw will not rev. squeezing throttle knocks off choke then saw dies.

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  • Anonymous Mar 13, 2014

    have rebuilt the carb. Float valve, gaskets, both diaphrams and circular disk plates over ports.

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OK - let's work through this. If you need choke all the time then the mixture is too weak when the choke is off. Putting the choke on literally chokes off the air supply to the engine by lowering a small shutter across the entrance to the carburettor. That means either there is too much air getting to the engine (don't see how!!) or too little fuel. So, how do we get too little fuel? You could check for this as follows;
- before we do anything tricky let's check the obvious things - is there a fresh fuel mix in the tank? Petrol does go off, especially if there is 2 -stroke oil added to it. If it's over a month old from the pump mix up a fresh batch. Is the idle speed set too low so the engine stalls when the choke is knocked off? You can see this screw to one side of the carburettor (you need to remove the top lid in front of the handle on the chain saw, and then remove the air filter to see it). Turn the screw half a turn clockwise to speed the engine up. Be warned - if the engine starts it will run faster than normal and that means the chain may start to spin around. Also - check that the chain brake is off (i.e. the safety lever is pulled backwards, and that the chain is free to move BEFORE you attempt to start)
- is the fuel filter blocked? To get to this, make a wire hook (e.g. thick fuse wire) and gently hook out the fuel filter that's sitting at the bottom of the fuel tank, and take a look at it (be gentle - you can damage the gauze if you are clumsy). Does the gauze look clear? I.e. if you dip it into petrol it will freely run into the filter and of course drain out when you lift it? If not, replace it.
- next stop - are the jets in the carburettor set right? I don't have a service manual for this (and I know the manual says unhelpfully "return for service") but basically you will have seen two holes on the side of the chain saw (below the handle) two small 0.8cm holes; one marked 'L' (for low speed) and the other 'H' (for high). Put a fine flat screwdriver down the L hole and feel for the slot of the low speed jet. Once engaged turn it out half a turn and this will enrich the mixture - if this seems to help and you can start the engine then adjust the L jet in or out until the engine is idling comfortably. If it idles too quickly then you can also turn down the idle screw (see previous paragraph).
- no luck still? Well, it could be fuel pump or a blocked jet in the carburettor but this really is a 'return to the service centre' task!

Good luck!

Posted on Jan 12, 2009

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Needs adjustmennt on those two screws on the carburator

Posted on Dec 31, 2008

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