Backfire through exhaust

[Rod Rocket]

My xl 500s Honda is backfireing through the exhaust on over run,backed off down hill,under power pulls like a train. The motor has a 95mm wiesco sleeve and hi-comp piston making it 600cc the carb is standard jets and needle setting, air filter cleaned each ride. I lost an exhaust stud from the head and gasket and split ring subsequently were also lost have replaced all part's hoping it may have been a problem for a while but made no difference. Any clue's.
Regards Rod.

[Freakshow]

your at 600cc but on standard 500cc  jets and float heights....... try changing the pilot jet, out of curiosity.

[JohnnyO]

It's too lean.. Go to a bigger pilot jet

[EML]

Could still be sucking air on over run, recheck around where the header pipe joins the head and then again if the is a join half way down the exhaust.

[bazza]

LEAN

[EML]

Listen again. It could be lean because extra air is getting into the hot system and after-burning the un-burnt fuel. Check your plugs. Ours are always black and sooty-so it's not too lean-at the chamber.

[pancho]

 Almost always air leak into exhaust.
 
 Can be lean on idle [pilot jet.]

 Can be crook plug/resistor/lead.

 Can be tiny air leak to inlet behind carby under max. vacuum (throttle closed)

 cheers

[JohnnyO]

If its recently started backfiring its probably the exhaust header leaking.. If its always done it since fitting big bore kit it's the jetting(pilot). Simple

[Rod Rocket]

Thanks for the reply's,
I have replaced the exhaust gasket's with the replaced stud in the head, I filed the face of the header pipe's to make sure they were square and on the same plane so they would seat well to the gasket's. Tightened them to firm ran the bike for a while then re-tightened them the join half way along the pipe also re sealed and tight. The bike has been backfiring for a while but has been getting worse of late. Sound's like I need to re-check tommorow.
Regards Rod.