GY-5 backfiring, popping- more information, see 2nd pg.

[Kawazacky]

I just checked the header bolts. I tightened them up some, but I wouldn't say they were exactly loose either.

Electrical problems would be ideal. It'd give me an excuse to put on a high-falutin' CDI and coil, haha.

[madmaximum]

Does it only do it when decelerating? If so it is most likely caused by a lean condition.

[Kawazacky]

No, I can sit the bike in a parking lot, rev the snot out of the throttle, and it will do it as well. But it's more pronounced on deceleration.

[Kawazacky]

I left my desk and checked the plug. (I'm at work).

According to the plug, there's no way I am running lean. It's a nice healthy colour - if anything, on the sooty side.

[IronFist]

I'm intrested too, I'm running rich and it's happened to me, in a turn and on the stand. I'm thinking as it returns to idle, the idle mix is lean. But that's my bike? Maybe try backing out your mixture screw 1/4 turn and see if it helps? Simple fix if it helps. N2r.

[Ream]

Try to screw the air screw IN ( your idle circuit is too rich) a little & go ride.If it`s better,screw IN a little more, just til it stops popping @ decel.

[Kawazacky]

Tightening the header bolts didn't stop the noise. I checked for blatantly obvious air leaks, and found none. So, I checked my valves today. The exhaust valve was tight, and the intake MAYBE a tad loose. So, I reset both.

It didn't make a difference.

After a day of fooling around with the bike, here are the symptoms:
It will pop-pop-pop at about 5000 rpms if the bike is in neutral. Sometimes it'll do this while riding as well - I was wrapping around a corner again today and heard it pop at about 5000 rpms.

Also, sharp engine braking will bring a loud snap from the exhaust - but only one. It's possible that this is just a king-sized pop I guess.

If only something on the bike would CRACKLE, I'd be on to something here....

[Q]

How about a head gasket leak or loose head bolts.

Q

[Kawazacky]

There's no oil leaks, so I doubt it's anything to do with the head gasket or bolts.

[alonzo]

I would bet that it is in the ignition, When I was younger I used to rev my old truck up and kill the ignition and turn it back to the on position. Made a really good bang, "admitidly stupid, but amusing for a 13 year old". If your ignition has some loose wires it will cause the engine to die momentarly, thus building excess fuel and when the circuit closes again,,,, BANG! now at 5000rpm these bikes have a lot of vibration and could easily shake a wires circuit open and closed.

check the plug, make sure it is secured to the plug wire

move up to the coil, make sure plug wire is connected to the coil

go the back of the coil make sure the two wires on the back of the coil are secured to the coil.

on all of these areas look for blackened connections or melted wires.

after this is all done, move on to your cdi and make sure its connections are okay.

[Q]

I haven't had a head off one of these yet but a lot of bikes use a round copper head gasket and a separate rubber piece to seal the push rod or cam chain area. On that setup it is possible to have a head gasket leak with no oil leak.

Q

[Kawazacky]

I guess the real question is, not why is it backfiring, but why is it backfiring now?

I haven't made any adjustments that should cause this. I haven't significantly fiddled with the carb (changed the idle adjustment, and since it isn't popping at idle, that shouldn't matter), which is the main reason for backfiring. Most of the other reasons (bad spark, etc.) are NOT things that normally happen after only 1000 kms. True, I took it on the highway a few times this week, but never held it for very long any higher than 65-7000 rpms. I want to get around on the bike, but I don't like to work it too hard. And, the backfire showed up when I was on a back road, NOT on a highway.

So if I haven't changed anything, why has the performance changed? That's what really puzzles me, and makes me worry that it's not an "easy" fix. Easy fixes are tweaking mistakes you made earlier, and I haven't done any tweaking that should affect this machine.

[alonzo]

make sure you eliminate all the simple stuff first. I know it is a nearly a new bike, but it is still a chinese bike. All the small problems on these bikes start when you start the bike for the first time

as far as a bad or loose electrical connections, if you can't see it right away, take off your paneling wait for it to get dark, start the engine, "make sure it is 100% dark NO LIGHTS" watch the wiring and try to get the bike to pop pop pop at the 5,000 rpm range. if there is an open connection it will light up while it is zapping the closest ground.

with one exception, if the coil is bad you will not see any grounding arc. I honestly never dealt with a bad coil not sure how one would act. unless it completly stopped sending spark to the plug I would be clueless.

[AZ200cc]

As far as I can tell from the info it will be a fuel or ignition problem...Now which problem it is will take some digging. Sorry I could not help more.

[warrior91]

Have you changed out the original plug???
I have had plugs that "looked "good but were not much good.
Champion don't last for me as they present this backfire problem after only a few hours on my Yamaha...and I have had NGK plugs with the electrode "chocolate color" and backfire some.After swapping out good looking plug for new...bike runs good. Any amount of dirty/wet fuel definatley reduces plug life.