jkkl

Its the black box under the seat (cdi unit). I had the same problem with myne and i changed that box and then it was fine

Turns out the problem was the CDI unit.

Hi Everyone. My local yam dealer is supplying me Monday morning with some figures so i can check the coil and stator plate readings,so at the moment progress has ground to a halt. We did start it this morning it started easily on the button ran for about 5 minutes perfectly and suddenly just cut out. It wouldnt restart at all. We went back to it about 20 mins later it started easily but within a minute ran really rough misfirng, and only running on mid range revs and so we put it back in the garage fed up. I feel it might be a ignition coil breaking down any opinions welcome.

Anymore ideas anyone?

Hi its a gravity petrol tap and the flow is good. I have thought about fuel starvation but the carb is spotless inside and supply from the tank is good. I do use the choke from cold and have even tried a squirt of easy start in the air intake when not running to no avail. I have just tried starting it today it started reluctantly on the button but did so i let it warm up for 5 minutes it ran sweetly on tickover then suddenly cut out. I unscrewed the plug cap and held the lead about 5mm from the plug. Pressing the starter i got a weak erratic spark sometimes not at all, when it appeared stronger it tried to fire. I have tried 2 new plugs and changed the plug lead still no change. Last night i took it out for 30mins and it was fine.

many thanks i have checked the earth on the battery and will check the rest. i have have just been working on and it bumped again instantly but did not go on the starter until hot. if left for more than 10 mins it has to be bumped again. the starter doesnt always seem that lively and varies.is it possible the starter is pulling to much current and hinders starting.i have put a new clutch in as it was dragging and thought it might cure it.

i have a 92 sr125 which will bump start easily but wont start on the starter. it has a new battery fiited.it has stood unused for 6 years. i have cleaned out the petrol tank, tap, and carb it occasionly fires on the starter but wont pick up. another day you go to it and it starts instantly on the button. when it is idling sometimes it just cuts out suddenly and then wont restart unless bumped. i have renewed the air filter reground the valves checked the rings were'nt stuck on the piston, the bore is like new. it has good suction on the inlet manifold. it also seems to have a spark when not starting.the bike has done 7000 miles from new.i have also sprayed wd40 on every connection i could find.