Odd tick over issues

[Bibio]

might be lifting ok but the rear might not be returning and seating properly. was the rear plug dry and sooty black or black and damp/wet when you took it out?

yes just post it up on youtube and then link it in your reply.

Black and damp. Worth whacking some fuel cleaner in the tank or just getting carbs off and cleaned?

[Bibio]

black and damp suggests its not firing properly or too much fuel, since you are getting backfires/pops its more than likely the unburnt fuel igniting in the exhaust.

first thing is swap the spark plugs or get new ones. if the rear continues to foul then its the ignition system. so nutz might be on the money with this one and the HT lead is fubar. pop the tank up and check the connections to the coil if they are ok then pull the spark cap and twist it off the end then check that its good and clean if it is then check the other end on the coil. if the copper core is not nice and shiny then bets are the HT lead is past its best so get some nice new stuff and pop it on. you can chop a bit off the end if needed but if you do and its still not shiny copper then new leads. new HT lead dont cost much and a cheat is to just get a nice long length (usually coil to cap on cars) out of halfords that will do both coils and make new ones. be careful that the HT lead is not the carbon filament type as they look black. you can replace with that type if you like.

if its still fouling after that then its carb related.

Lovely, thanks very much for your help. I'll get a new set of plugs and change the HT leads in the next few days and update.

[happysv]

Go out to the bike when it's dark start it up and keep blipping the throttle whilst looking round the coil/ht leads for blue sparks.
My curvy developed a miss as you described and was easy to spot doing this method.

Managed to have another fiddle today (girlfriends very poorly). Took rear coil off, cleaned up the contacts and chopped 20mm from each end of the ht lead. Copper core wasnt black but couldnt see hardly any core at all.
No more back firing Thanks for the help all.
I'll get leads changed when I service it over winter.