my makita brushcutter

[tammo5151]

my makita brush cutter stops after 20 minutes and i cant start it again for hours afterwards

 

[Mursal]

Just cant see it from here, so if I might ask is it, petrol or electric?

If electric probably an over active thermal cut-out

If petrol, change the spark plug and or check to see if you have a spark just after it stops.

 

[tammo5151]

its petrol and i have changed spark plug,used it for 20 miutes at 10 this morning it stopped i went back to it at 1oclock it stared fine then cut out again after about 20 minutes.

 

[Burnerman]

Twenty minutes is a fair old run time really - so any obvious fault should have shown up long before then.
I think the fault is related to fuel starvation because the machine is getting to hot, and vapourising within the carburettor.
Just check that the cooling fins are clean around the cylinder, and that the air ports at the recoil starter are clear. Keep the petrol tank brim full too!
John

 

[r896neo]

tank breather/ tank vent? probably running too long for it to be that.

 

[Burnerman]

Its always worth hooking the tank fuel filter out too...I've had one or two of these breaking up on their own.
Excess running with a lean mixture can also cause excess heating but a plug colour check should identify that one.
I guess if the spark disappears after 20 mins, then its the igniter breaking down internally.
John

 

[kbdiy]

I'd go along with the fuel starvation theory.

I have a similar problem with my Qualcast petrol brushcutter and find that the engine starts to lose power before it finally cuts out. When it looses power I find that by loosening the fuel filler cap it allows air into the tank and performance is restored.

Even if it does cut out, loosening and refitting the cap allows it to be restarted right away

I have tried clearing and even enlarging the breather in the cap but that doesn't seem to cure the problem.

Annoying, but at least it overcomes the problem. Might be worth a go on your's?