Backfire?

HanShan · Post by **HanShan** » Thu Jun 29, 2017 7:05 pm

Blur 220!, 2013

Sometime, when I let go of the throttle, I hear a little "phoopht" sound. Assuming I am backfiring.

Plugs are clean and gapped at about .65.

Could it be the 93octane gas? Should I step down a grade?

Maybe not enough air, so maybe a new air filter?

PhillyKick · Post by **PhillyKick** » Sat Jul 01, 2017 10:06 pm

My kick makes a sound that would appear to be backfiring when I decelerate. I think it's pretty common with small engines, especially one with no o2 sensor. Octane has nothing to do with it. I kinda want the sports exhaust for my kick so I can hear it better.

HanShan · Post by **HanShan** » Sun Jul 02, 2017 12:21 am

PhillyKick wrote:My kick makes a sound that would appear to be backfiring when I decelerate. I think it's pretty common with small engines, especially one with no o2 sensor. Octane has nothing to do with it. I kinda want the sports exhaust for my kick so I can hear it better.

Cool. Weird thing is I never heard it before, just recently started. I have about 8000 miles on it.

Dooglas · Post by **Dooglas** » Sun Jul 02, 2017 5:29 pm

PhillyKick wrote:My kick makes a sound that would appear to be backfiring when I decelerate. I think it's pretty common with small engines, especially one with no O2 sensor. Octane has nothing to do with it. I kinda want the sports exhaust for my kick so I can hear it better.

That has been my experience as well. Also true, though, that a bit of an air leak between the exhaust manifold and the muffler can cause backfiring.

PhillyKick · Post by **PhillyKick** » Mon Jul 03, 2017 2:25 am

Dooglas wrote:
PhillyKick wrote:My kick makes a sound that would appear to be backfiring when I decelerate. I think it's pretty common with small engines, especially one with no O2 sensor. Octane has nothing to do with it. I kinda want the sports exhaust for my kick so I can hear it better.
That has been my experience as well. Also true, though, that a bit of an air leak between the exhaust manifold and the muffler can cause backfiring.

I had a car (two, actually) that after a full throttle acceleration and letting off the gas, the engine mounts would flex enough to open a small air hole in the flex pipe, and it would backfire somewhat loudly (with visible flame, on occasion). After I replaced the flex pipe and motor mounts, no more backfires, even muffled by the exhaust system. I doubt that these engines are flexing that much, it may just be because of the smallness of the engine and the simplicity of the tuning and sensors.

HanShan · Post by **HanShan** » Sat Jul 29, 2017 2:00 pm

PhillyKick wrote:
Dooglas wrote:
PhillyKick wrote:My kick makes a sound that would appear to be backfiring when I decelerate. I think it's pretty common with small engines, especially one with no O2 sensor. Octane has nothing to do with it. I kinda want the sports exhaust for my kick so I can hear it better.
That has been my experience as well. Also true, though, that a bit of an air leak between the exhaust manifold and the muffler can cause backfiring.
I had a car (two, actually) that after a full throttle acceleration and letting off the gas, the engine mounts would flex enough to open a small air hole in the flex pipe, and it would backfire somewhat loudly (with visible flame, on occasion). After I replaced the flex pipe and motor mounts, no more backfires, even muffled by the exhaust system. I doubt that these engines are flexing that much, it may just be because of the smallness of the engine and the simplicity of the tuning and sensors.

That is interesting though, since mine seems to do the exact thing, only after full throttle.

What would a similar location be on my bike to look for a leak? Somewhere before the muffler? I need to check my pipes anyway because they are kind of rusty.

chickdr · Post by **chickdr** » Tue May 08, 2018 4:34 pm

Mine does this sporadically (9,800 miles). Came on the site to see if others had the same issue. Typically mine runs very well. On my way home this past Friday I had loud backfires as I slowed and noticed the idle was running higher than normal (around 2k-2,100 vs 1500-1700 as normal). It did this for a while then went back to normal on Wednesday during my ride to work. It returned on the way home Thursday and was doing it today when I left the house today then settled down on the way home again. I was wondering about a possible cold start valve being sticky, but am not aware if the Blur 220 has one, or not. I don't understand why it comes and goes on my bike.

GregsBuddy · Post by **GregsBuddy** » Tue May 08, 2018 6:45 pm

Almost certainly not a backfire as that causes flames to enter the intake system. Likely a exhaust pop from unburned fuel ignited by flames coming out of the exhaust into the exhaust pipe and muffler.

chickdr · Post by **chickdr** » Mon May 14, 2018 8:41 pm

GregsBuddy wrote:Almost certainly not a backfire as that causes flames to enter the intake system. Likely a exhaust pop from unburned fuel ignited by flames coming out of the exhaust into the exhaust pipe and muffler.

Is there a solution to this issue? I may have to DIY as my dealership answered my email saying they don't do any engine work - only routine maintenance. Great CS eh?

GregsBuddy · Post by **GregsBuddy** » Mon May 14, 2018 8:47 pm

Not a simple solution.