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How to fix Mcculloch MT270X starting and running problems?My now ten years old MT 270x has recently become difficult to start and when it does it will only stutter and will not pick up to run at any speed between idle and full throttle.
I have tried various carburettor screw jet adjustments but that does not seem to have any effect. Also, I have checked all fuel lines and carburettor for contamination/waxing but there is no signs of problems there. The ignition system/plug is OK (I fitted a new coil a couple of years back). I have also gone to the extreme of a strip-down and de-coke and everything now looks fine with that too.
The only thing I can now think of is a faulty carburettor, say the diaphragm (there appears to be two, one for the 'float' valve side and another with a clear plastic 'flap' on the opposite side of the carb.) and I am wondering if having used Easi-Start from time to time that has caused some porosity to the diaphragm.
Also, to the naked eye, the small spring-loaded lever which operated the 'float' valve does not seem to do very much. Is there any way of checking the setting for that.
Any ideas or recommendations please?
Rodney Elliott June 2010
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Click here if you can answer this question |
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where is the clutch located
gazbee August 2015 |
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do you have a manual for 270 x? could you send me a copy? thanks, siewert
siewert June 2014 |
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If no spark, try setting the coil to flywheel clearance down to 0.003" - the book says 0.012" but mine wouldn't work at this gap. the carburettor is a ZAMA C1u m29d -(now obsolete, but overhaul kits are available part num rb-48) or gnd -18 for gasket and diaphragm kit. ZAMA technical manual can be downloaded from their USA site. The metering needle lever should be free to move and between 0" and 0.012" clearance to the gasket flange - use a straight edge across flange to measure. The two adjusting needles are not interchangeable and, the longer one is for slow speed running -(L). After twice stripping the carb and cleaning with carb spray I still couldn't get it to run stable. There is a none return valve in the main nozzle system that you can't get at which if siezed will cause an air leak at low speed and/or no fuel flow at high speed/power. As a final measure I stripped the carb again and boiled it in a saucepan with washing up liquid for an hour. It did the trick and the unit now runs and starts well. Finally when ready to go again set H&l screws 2 turns open initially and idle screw to max speed position. You will probably find that both screws will end up about 1 turn open and idle screw backed off considerably. Best of luck, and don't give up!
Daddat August 2010 |
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