I am working on a 150cc GY6 engine that is practically new. It has a little over 100 miles on it, but was made in 2009.
After warming it up, when I rev the engine and hold it there for a few seconds, I get a "sneeze", or backfire, similar to the sound of a suppressor letting out air, or a ricochet. It's sort of a high pitched "pachooo!" sound. It sounds like the muffler is shooting out a nut or something. hehe.
It's not constant. In my tests it happens once, sometimes twice while the engine is running at high rpm.
I tried to record it but my phone's sound is horrible. It sounds like a garbled mess. I tried to find a sound like it on youtube but I couldn't find it, although it is similar to the echo of a rifle or a ricochet sound effect. I'm worried it might be something bad.
I have adjusted the valves and replaced the vacuum lines and it still does it.
What is this chuffing or sneezing sound and what causes it?
Post by newbscootdude on Oct 21, 2014 13:08:41 GMT -5
i had that sounds happen to me like you said it sounds like it coming from the muffler right? what i did was take the muffler off inspect the gasket make sure thats good then i tightened everything back up and the sounds went away. im pretty sure the bolts i had in there (stock studs broke) loosened up and i didnt notice hopefully its something easy like that for you as well. it could also be a backfire into your carb and the sound is coming out of ur air filter not sure what to do about that one im sure someone will chime in on that tho.
139qmb 80cc bbk
big valve head
24mm carb w/ 125cc manifold
115 main jet 38 pilot jet
performance clutch W/ 1k springs
unlimited CDI
K&N style air filter
8g rollers
iridium plug
red hot coil
bando belt
stock but drilled exhaust
currently running rich (need 112)
From your explanation sounds more like pinging detonating put in a higher octane gas. I mean you cannot make a mistake if it is backfiring that is a (POW) sound, and other sounds are BRAT and POP sounds. Alleyoop
...BAD TO THE BONE.. PST150H 62mm BBK, 60mm Crank, 16/37 Tranny Gears..MOW-POWER
WATCH OUT...THOSE WHO DO NOT KNOW, DO NOT KNOW THAT THEY DO NOT KNOW
From your explanation sounds more like pinging detonating put in a higher octane gas. I mean you cannot make a mistake if it is backfiring that is a (POW) sound, and other sounds are BRAT and POP sounds. Alleyoop
I put some new high octane gas in it and ran it a few minutes. I don't know if all of the old gas is out yet, but I was able to get the sound to repeat by revving it up, holding it, then letting off. It makes the noise just as I let off or a little afterward. It reminds me of a backfire but with the explosion being squeezed out of a tiny hole, making a high pitched chuff and a hiss like air letting out, like something is blowing up, then quickly the air is squeezing out. I'm going to try to put up a video, but it doesn't sound much like the ral thing. I think the rattly noise is the shop fan blowing, and the siren-like noise is electrical noise coming from the ignition. You can't hear that sound in real life. The explosion sounds different too, but for what it's worth.. You'll hear the chuff at 13 seconds. Aslo I noted that the engine bogs down a lot if the air filter box lid is open. It's not open here in the video though.
i had that sounds happen to me like you said it sounds like it coming from the muffler right? what i did was take the muffler off inspect the gasket make sure thats good then i tightened everything back up and the sounds went away. im pretty sure the bolts i had in there (stock studs broke) loosened up and i didnt notice hopefully its something easy like that for you as well. it could also be a backfire into your carb and the sound is coming out of ur air filter not sure what to do about that one im sure someone will chime in on that tho.
I put up a video. I think it's a backfire but it doesn't sound like when my scooter backfires. In the video it sounds like a pop, but in real life it's more 3 dimensional, like a fast high pitched sound followed by a whoosh. Still, I'm now thinking backfire. Weird sounding backfire.
i had that sounds happen to me like you said it sounds like it coming from the muffler right? what i did was take the muffler off inspect the gasket make sure thats good then i tightened everything back up and the sounds went away. im pretty sure the bolts i had in there (stock studs broke) loosened up and i didnt notice hopefully its something easy like that for you as well. it could also be a backfire into your carb and the sound is coming out of ur air filter not sure what to do about that one im sure someone will chime in on that tho.
I put up a video. I think it's a backfire but it doesn't sound like when my scooter backfires. In the video it sounds like a pop, but in real life it's more 3 dimensional, like a fast high pitched sound followed by a whoosh. Still, I'm now thinking backfire. Weird sounding backfire.
did you try inspecting the studs to your exhaust if its leaking it can cause backfires like that i had the exact same problem i heard it in the video sounded identical to what was happening to me.
139qmb 80cc bbk
big valve head
24mm carb w/ 125cc manifold
115 main jet 38 pilot jet
performance clutch W/ 1k springs
unlimited CDI
K&N style air filter
8g rollers
iridium plug
red hot coil
bando belt
stock but drilled exhaust
currently running rich (need 112)
You guys must have never heard a backfire. That is not a backfire you will know when it backfires SOUNDS LIKE A GUN GOING OFF. All I heard was what sounds like a leaking muffler making a whistling sort of sound but other than that RIDE RIDE RIDE . Alleyoop
...BAD TO THE BONE.. PST150H 62mm BBK, 60mm Crank, 16/37 Tranny Gears..MOW-POWER
WATCH OUT...THOSE WHO DO NOT KNOW, DO NOT KNOW THAT THEY DO NOT KNOW
I'm with Alley and think there's something going on with that muffler. Possibly a manufacturing defect. Don't spose you have a spare muffler laying round to swap with Heck just take it off and see if you can get anything like that to happen without it on. That right there will tell you if it's the engine or the muffler. I usually prefer to use the process of elimination if you don't know right away what the problem is.
2008 Lance Vintage 58.5mm BBK
Port and Polished Performance Head w/1200 RPM Springs and Titanium Retainers
Hand Matched Intake Port w/30mm 3 inch Tunnel Ram Intake 30mm carb 130 main 42 pilot Cold Air Intake w/Uni Filter
A-Eleven Cam Variable Timing CDI Hot Coil Irid Plug
Custom Shorty Performance Exhaust
Hoca 115mm Variator w/10g rollers Hoca clutch w/drilled bell houseing Custom Cut CVT Cover
Custom Leather Seat/Back Rest
I put up a video. I think it's a backfire but it doesn't sound like when my scooter backfires. In the video it sounds like a pop, but in real life it's more 3 dimensional, like a fast high pitched sound followed by a whoosh. Still, I'm now thinking backfire. Weird sounding backfire.
did you try inspecting the studs to your exhaust if its leaking it can cause backfires like that i had the exact same problem i heard it in the video sounded identical to what was happening to me.
I checked my nuts and they are tight. I tried another approach to the video though, with clearer results. Check it out. Also check out my post to Alley. I'm including pictures of what I think is an EGR valve?
I'm with Alley and think there's something going on with that muffler. Possibly a manufacturing defect. Don't spose you have a spare muffler laying round to swap with Heck just take it off and see if you can get anything like that to happen without it on. That right there will tell you if it's the engine or the muffler. I usually prefer to use the process of elimination if you don't know right away what the problem is.
As I mentioned, the siren/whistle noise is the camera picking up the engine's ignition signal. Check out my new post to Alley below along with some new info.
You guys must have never heard a backfire. That is not a backfire you will know when it backfires SOUNDS LIKE A GUN GOING OFF. All I heard was what sounds like a leaking muffler making a whistling sort of sound but other than that RIDE RIDE RIDE . Alleyoop
That whistling is the camera picking up the engine ignition. Check out this new video. This time you can see the flame come out.
Also, could this little doodad have anything to do with anything? As you can see, the outlet goes nowhere. This is an EGR?
Yes I heard the sound you were talking about, but now looking at that vid in the dark I see it's not the muffler. Other than either something going on with some of the emissions crap they put on new scoots or your carb adjustments...I dunno. Still if it were me I would start the processes of elimination. If you can bypass the emissions junk,, I would, then if the problem persists, check your carb settings. Then if it still gave me problems I would look at the ignition. After that, there's not much else that could be causing this. These engines only have so many parts....as you know
Either way keep us posted..I'm curious as to what it is myself.
2008 Lance Vintage 58.5mm BBK
Port and Polished Performance Head w/1200 RPM Springs and Titanium Retainers
Hand Matched Intake Port w/30mm 3 inch Tunnel Ram Intake 30mm carb 130 main 42 pilot Cold Air Intake w/Uni Filter
A-Eleven Cam Variable Timing CDI Hot Coil Irid Plug
Custom Shorty Performance Exhaust
Hoca 115mm Variator w/10g rollers Hoca clutch w/drilled bell houseing Custom Cut CVT Cover
Custom Leather Seat/Back Rest
Ok I did see it backfire , if the EGR is not connected to anything and it does not have a Vacuum operating a valve THEN PLUG that outlet on that EGR Valve it is allowing some air to be sucked in JB weld it. Remember Backfires are caused by a Lean condition the motor is sucking in air from someplace contrary to what everyone thinks that is it to RICH(NOT).
Normally that EGR would go to a Canister operated by Vacuum and have a hose going to a connector on the tubing between the Air Filter and the carb to send the unburned fumes back into the motor to be reburned. I have seen where the Canister and or Vacuum failed and the canister started on fire. Alleyoop
Last Edit: Oct 21, 2014 23:11:39 GMT -5 by alleyoop
...BAD TO THE BONE.. PST150H 62mm BBK, 60mm Crank, 16/37 Tranny Gears..MOW-POWER
WATCH OUT...THOSE WHO DO NOT KNOW, DO NOT KNOW THAT THEY DO NOT KNOW
(need 112)
..BAD TO THE BONE..
