[Hybrid]

I started up my second sierra after a year of sitting. It's a g13 WT. It was running smooth as silk last it ran. Now it's running really rough. The only thing that has changed is I swapped in a g16 alternator I had lying around. Things I've checked.

1. Spark at the end of each lead
2. Timing
3. Pulling each lead to try to identify a specific cylinder miss
4. Swapping leads, rotor, dis cap off my running sierra

I've just pulled the plugs this morning and checked one on number one lead and though there is blue spark it seems pretty weak

Could the alternator swap be causing the weak spark? Even when its running rough its still charging at 13-13.5v which I thought should be ok. Can a grounding issue cause this? Any other main culprits?

[steak_knife]

1 yr old fuel will cause it to run shit..

check the earth at the back of the head to..

[weaves]

i've had a few earthing dramas, to the point where it would earth through my clutch cable, turning things to poop!, oh and having it earth between my carbie and head.

chuck a few decent size and well mounted earth cables on there. see if that helps, also check your coil pack, and the earth to your coil pack.

[Hybrid]

Thanks Guys. I'll try fresh fuel and run a new earth lead. See if that helps.

[Hybrid]

Well changed out the fuel and cleaned up the plugs. After about 10 mins idling rough and blowing smoke it's back to smooth as silk. I've always been wary of 2 stroke and premium fuel going bad. I didn't realise regular unleaded did.

Thanks lads! I feel noob all over again hehe.