my mountfield HP-470 has lumpy tick over with some black smoke coming out, I have fitted a new spark plug but wonder if the spark plug gap needs adjusting? not sure, when I have removed the plug it is sooted up. ANY THOUGHTS ANYONE???

Gary, August 2008

Have a Mountfield Tuffcut Quattro 40 Which will not throttle down to a tickover please advise

rover50, June 2011

Have a Mountfield Tuffcut Quattro 40 Which will not throttle down to a tickover please advise

rover50, June 2011

Previous answer essentially correct - but there is no high-speed adjustment on most small engines. If it's the carb-on-the-tank type, change the diaphragm.

phil_saunders@bigfoot.com

Phil Saunders, August 2008

I don't know what you mean by "lumpy tick over". But black smoke indicates too rich fuel mixture. Sooted up plug is also caused by too rich fuel & air mixture. Open throttle when running, and adjust mixture screw on carburetor (clockwise and counter-clockwise) until engine runs smoother. If not, it may be carb gasket and or diaphragm. Do you have fresh fuel in tank. Any moisture in tank or carb will make it run rough. If this doesn't fix it, I don't know what else to suggest

Robert Brown, August 2008