Strimmer learning curve question

[ipbr21054]

Replaced the following today.
Tank grommet.
Inlet & Return fuel pipes.
Inlet filter on pick up pipe.

Question 1
Why when pulling the cord 10 times it doesn’t start BUT small squirt or wd40 with air filter off & down the port pulls & starts straight away ?

Question 2
When making a mix of fuel / oil every time will not be exactly the same.
I understand about seizing it up or white smoke BUT does this also affect the way the strimmer runs in respect of having to adjust the mixture ?

Question 3
Tick over is controlled by the screw that touches the throttle plastic piece on top the carb.
On the carb just above the inlet fuel pipe what is the name of that screw adjuster. This is the one I adjust when setting the mixture / tick over whilst holding down the throttle.

 

[Burnerman]

A couple of pics of the carb would help but I guess its either a Walbro or Ruixing item by your description.
Anyway -
1). The carb needs a new metering diaphragm.....its not providing a squirt of fuel when needed. The metering diaphragm has the round metal disc on one side.
2). On engines like these, the oil / petrol ratio should be around 50:1. A 40:1 mix or whatever won’t require Mixture adjustment. (On racing two strokes - 20,000 rpm plus the oil ratio does make a difference which is why Yamaha developed Autolube, a mechanical oil injection system).
3). Pilot or slow running mixture screw.....anticlock to richen. If its the carb I’m thinking about, full throttle running is altered by a screw on the throttle operating quadrant.
John

 

[ipbr21054]

Green I adjust for Tickover.

Blue I hold down the trigger and turn clockwise & anti clockwise and find the sweet spot in between.

 

[Burnerman]

That'll do - effectively the blue screw is for low speed running but it does have an effect on full throttle performance. The green is the tickover adjustment screw.
As you increase throttle, notice the plastic throttle quadrant lifts up slightly.....this is lifting a needle out of a jet increasing fuel flow.
John

 

[ipbr21054]

I dont think it lifts up as i only see it rotate but i see what you mean now.

 

[Burnerman]

Looking down the carburettor venturi, you'll see the cylinder that rotates when you open the throttle.....if you can see a needle too, it will rise a fraction at the same time.
John

 

[ipbr21054]

You are correct.
Other than that it’s plenty of holes and a rubber gasket.

Started 3rd pull and used for 2 hours no issues.
Thanks.