Killswitch Backfire

Sebastian666 · 03-29-2018, 09:59 AM

My Hawk backfires pretty loud when I use the killswitch. This happens every time I shutdown my bike. I've checked the exhaust head gasket & adjusted the valves. What causes this? Can it damage anything?

Weldangrind · 03-29-2018, 11:22 AM

Do you still have the catalytic converter in place? Do you have the air injection device still connected? Is the carb in stock configuration? What is your elevation?

The short answer is a lean mixture causes backfiring, but you can certainly correct it.

Weldangrind · 03-29-2018, 11:24 AM

To respond to your other question, I'd be inclined to think that any damage would be aft of the cylinder head. I suspect that if the backfire was substantial enough, it would knock a hole in the cat or break welds loose in the muffler.

Megadan · 03-29-2018, 12:13 PM

Quote:

Originally Posted by Weldangrind

Do you still have the catalytic converter in place? Do you have the air injection device still connected? Is the carb in stock configuration? What is your elevation?

The short answer is a lean mixture causes backfiring, but you can certainly correct it.

No PAIR system on a Hawk.

To the OP. I just want to clarify so I can diagnose moving forward.
Backfire = the engine has an ignition even that sends fire] that goes back up the intake.
Afterfire - An ignition even that fires through the exhuast after the combustion chamber. (yes, this is the actual term for it).

Anyway, if it is the after fire scenario, this almost always happens due to a fueling issue. What does the spark plug look like?

03-29-2018, 09:59 AM	#1
Sebastian666 Join Date: Mar 2016 Location: Glenwood, NY Posts: 6	Killswitch Backfire My Hawk backfires pretty loud when I use the killswitch. This happens every time I shutdown my bike. I've checked the exhaust head gasket & adjusted the valves. What causes this? Can it damage anything? __________________ 2016 Hawk 250, Ebay exhaust, Mikiuni clone VM26 w/#120 Jet, 42mm Uni Pod Filter, Shinko 705 front & Shinko E-805 Crossfly rear, 17T/45T Sprockets, IX24B Iridium spark plug, Aftermarket LED turning signals, OPT7 Fluxbeam LED Headlight, Digital Cluster/Speedo, RK Racing Chain 428MXZ
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03-29-2018, 11:22 AM	#2
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	Do you still have the catalytic converter in place? Do you have the air injection device still connected? Is the carb in stock configuration? What is your elevation? The short answer is a lean mixture causes backfiring, but you can certainly correct it. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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03-29-2018, 11:24 AM	#3
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	To respond to your other question, I'd be inclined to think that any damage would be aft of the cylinder head. I suspect that if the backfire was substantial enough, it would knock a hole in the cat or break welds loose in the muffler. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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