OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Trimmers and Brushcutters Two Stroke Trimmers & Brushcutters Komatsu w/snipper

Hi,, hoping for some advice.I have a Komatsu Zenoah BT 250 w/snipper which was running,, now wants to plays silly buggers..Not starting, when it eventually starts,, will only run for approx 10-15 seconds, as soon as you put it under pressure it dies. It has a Walbro carby ( K20-WYJ ) on it. Sounds like it is starving for fuel, but when you take plug out it will be flooded.
Things i have done,, checked spark plug- nice and clean.
Have good spark. Have good compression, approx 90psi. Have checked all fuel lines, cannot find any holes or cracks, filter is clean also. Have fitted new carby kit ( was suggested to do this), while apart full clean out with carby cleaner followed by air.
Now problem with carby, when primed it pumps fuel out throat of carby, abit to much i think. Also there seems to be no fuel going back down "overflow" pipe back to fuel tank.
Any help or advice is appreciated,
Paul.

Same as our Red Max BT250.

First 90 psi is not good compression on these should be more like 120+. Really surprise it even runs as most 2 cycle around here needs at 100 psi to even hit.

Also check for a clogged spark arrestor. When they are clogged they will cause flooding and lack acceleration at the same time as fuel mix can not burnt without oxygen.

No fuel on return might be a little normal as not all primer prime the same they primary meant to remove the air from the metering chamber. Now if it pushes some fuel out and then sucks it right back in then you have bad primer check valve. There is also a few other problems can happen during priming if there is a leaking main nozzle check valve or a welch plug that is leaky.

But with only 90 psi I would more worry about the PNC (cylinder(sometimes called the Jug) and piston condition).

Hi AVB ,, thanks for the reply, much appreciated. Done a heap of research on the net when i first posted my question and found a small section about these w/snippers were it stated that they needed above 110 psi to run properly.. Had me dumbfounded as i though they could run on less,, but when you posted your answer to me, and it was the same as what i had read,, i knew then it was time to retire the old girl.Had it for approx 4 years and never needed to put a spanner to it,, a good run i think.
Thanks again,,
Paul.