Fs400

[spudulike]

Thanks everyone for your help and advice.

 

Stripped the carb, cleaned it and then discovered that the valve lever was about 1/8" too high. Sorted it, put it all back and hey ho it starts and runs.

 

Now perhaps someone could tell me where to get a tachometer so that I can set the max revs correctly

 

Welcome To Tiny-Tach. Small and economical rev counter tachometers for petrol and diesel engines from ITCO I have the TT20K workshop model, a fine piece of kit and no induction wires:thumbup:

[aquatoo]

Welcome To Tiny-Tach. Small and economical rev counter tachometers for petrol and diesel engines from ITCO I have the TT20K workshop model, a fine piece of kit and no induction wires:thumbup:

 

Thanks very much Spudulike. I have emailed for a price just now.

[Logit]

Thanks very much Spudulike. I have emailed for a price just now.

 

 

Hi aquatoo, I took Spuds advice (thanks Spud) and bought a TT20K a couple of weeks ago. It arrived in 48 hours and is a nice bit of kit which works well.

[Hill-Billy]

Sounds like issues in supplying fuel on the low speed part of the carb - I would normally wind the idle screw right in until it DOES idle but am guessing that this isn't working.

 

Try turning the L screw 1/2 turn out and the idle screw 1-2 turns out from fully in and try again - you may find it hard to start but the leaner mix may give you a better idle speed.

 

Failing this, you may have a bad fuel filter, bad or holed fuel line, a carb fault, leaking welch plug, air leak etc

 

HI Spud, I'd like to make some carb adjustments but only have an LD setting on my STIHL FS 400!

[Maico490]

HI Spud, I'd like to make some carb adjustments but only have an LD setting on my STIHL FS 400!

 

Hi Hill-Billy

The carb you have is fixed jet so there is not a lot you can do. The one adjustment you have is actually an air screw rather than a fuel screw. By being reverse threaded it behaves the same as a conventional one by making the idle mixture weaker when you turn it clockwise and richer anti-clockwise. About all you can do is make sure the screen under the needle is clean but don't go blasting the whole carb with compressed air or you will ruin the check valves.

As regards adjusting wind the screw in and the tick over should increase then back it out until you get good response to snapping the throttle open. It is also worth checking that the carb butterfly is actually fully open when you have the throttle fully pressed. If it isn't you lose a lot of power and the choke doesn't operate properly in the start position. Adjusting the cable varies with which cable/hand grip set up you have.

Edited April 20, 2014 by Maico490
spelling

[Stihl dealer in Scotland]

Hi aquatoo. Any Stihl or Husky agent should be able to get you one. I use one I got through Husky years ago, does a good job.

[Hill-Billy]

Hi Hill-Billy

The carb you have is fixed jet so there is not a lot you can do. The one adjustment you have is actually an air screw rather than a fuel screw. By being reverse threaded it behaves the same as a conventional one by making the idle mixture weaker when you turn it clockwise and richer anti-clockwise. About all you can do is make sure the screen under the needle is clean but don't go blasting the whole carb with compressed air or you will ruin the check valves.

As regards adjusting wind the screw in and the tick over should increase then back it out until you get good response to snapping the throttle open. It is also worth checking that the carb butterfly is actually fully open when you have the throttle fully pressed. If it isn't you lose a lot of power and the choke doesn't operate properly in the start position. Adjusting the cable varies with which cable/hand grip set up you have.

Thanks Maico. I've done what you said and the engine now runs Ok(My mower broke so I had to strim nearly an acre of garden yesterday!) . The only odd thing is that when I fully open the throttle the engine dies so I only squeeze the throttle half way.

[Hill-Billy]

I should add that my FS 400 throttle works normally for up to 1/2 hr before it starts to choke up slightly. I'm guessing this is a fuel blockage or carb issue? If the engine starts to die on me I simply let go the throttle to tickover and then ease it back up again. Gives me a break while i wait!

[Maico490]

Hi Hill-Billy,

 

From the symptoms you describe I would almost guarantee it is the gauze in the carb. I've had a few like this that start up and run OK then fade out over several minutes although you would expect the problem to be there straight away. I would be wary of using the strimmer until you fix it as running lean could ruin the piston and cylinder. The carb comes off really easily and you only need to take the two covers off and the lever arm and needle. Full instructions here if you aren't too sure:

USA Zama : Service Tips

While you are in there a new fuel line and tank filter would only be about a tenner.