Thruxton Backfire

i am running my 15 plate 900 thruxton with the arrow 2 into 2 exhaust system with the baffle's out,it had the remap to suit,i use premium unleaded petrol,mainly on starting up it will occasionally produce a backfire,apart from that it seem's to be running fine,i may try the cheaper standard unleaded,this all started when i never used it for a while over the winter month's & ended up dumping the fuel in the tank as it was running rough to say the least.i've ran the fuel tank LOW & refuelled about 4 time's since.it doesn't backfire every time i start it, it's only occasional.

 

Not sure what causes the problem but I run the same set up but only use normal unleaded, not the premium stuff. Never had any issues with back firing nor any issues with the fuel going off over winter?

 

you really mean backfire ie through the airbox? or just a big bang from the exhaust? that banging is probably a weak charge not igniting in the cylinder, then firing off in the exhaust.

 

just a BIG bang from the exhaust, like a gun going off.

 

so it's a weak mixture igniting in the pipe.

 

The spark fails to ignite the mixture which then ignites in the exhaust ( I think)

 

would

would it be down to operator error,ie not starting using the choke.

 

@youngy

 

I had a backfire caused by a dodgy sparkplug