Author Topic: Loud Back-Fire  (Read 181 times)

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  • Neophyte
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on: March 27, 2021, 07:48:41 am
I own a Classic 500 Euro 3. It has an AEW Goldstar aftermarket exhaust installed on it. I recently got its throttle body cleaned at a FNG. After doing that, whenever I ride the bike, it gives out a loud (read thundering) pop almost every time when I let go of the throttle or use up the entire rev band. It did not have such a problem before aside the occasional pops which weren't as deafening as these. What might be the problem? Will installing a DB killer to the exhaust help in any way?


  • Grease Monkey
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  • 2012 B5 on the original Portland Dorset UK
Reply #1 on: March 27, 2021, 08:37:52 am
a backfire could caused by air getting into the exhaust (leaking exhaust) check the header is tight up against the cylinder head as the nuts can work loose.
Also check the joint between header pipe and muffler
2012 B5 Bullet
 K&N, sport muffler, 18tooth fr sprocket, Avon style fairing, 1958 pattern British army haversacks. Mitas tyres DiD chain. Carberry plate.


  • Grease Monkey
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Reply #2 on: March 27, 2021, 09:57:45 am
I would me more concerned how your FNG cleaned your throttle body.
Did they remove the TPS and MAP sensors first?
Was the brass bypass screw removed?
Make sure the pre set throttle stop screw still has its yellow security paint on, this should not be moved.
Was the TPS voltage checked when re installed?
Off route, recalculate?


  • Grand Gearhead
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Reply #3 on: March 27, 2021, 12:58:31 pm
Isn't a loud explosion from the muffler caused by accumulated un-burnt fuel building up in the exhaust system? I seemed to recall that one way to make these explosions were for the rider (or car driver) to cut out the engine for a moment (via a kill switch) so that raw fuel would build up in the exhaust and then turn on the engine again resulting in a loud boom.  Could it be that the cleaned FI system is now causing a rich mixture?
2011 Royal Enfield B5 500, 2018 16.6 kWh Zero S, 2016 BMW R1200RS, 2009 BMW F650GS, 2020 KTM Duke 390, 2002 Yamaha FZ1