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

[Kawazacky]

SEE 2ND PAGE FOR MORE INFORMATION!

so my bike is making a pretty decent backfire (sounds like its out the exhaust, not through the carb) at high rpms, say around 7000ish. I noticed this on a hard engine brake today, and did it a few more times to make sure. Also, if the bike is sitting, idling, and I crank the throttle, it takes some trying, but the bike will backfire then too. The bike doesn't always backfire, just occasionally. I tried quite a few times to see if it would do it again, and it was intermittent. Mileage is only 1100 kms.

SO!

Any ideas?

Here's some possiblities:
Rings - I'd think it'd happen more often if it was rings, and that it would be burning significant oil, but rings are (to my pessimistic mind) the likeliest suspect.
Valves - I set them last week, and they were fine for the first 195 kms my 200 km trip I just finished.
Spark plug - There's 1100 kms on the NGK plug that came with it, so its a possibility.
Bad gas - no such luck.
Carburation - I haven't noticed the backfires before (except when decelerating when cold, and I attributed that to leaning out) and I haven't really changed anything with the carb, so I don't think that's it!

Sooooo...... I've guessing bad rings. Anyone else? What's compression supposed to be on these anyway?

[katoranger]

Possibly a weak coil.

Allen

[Q]

Any chance the exhaust pipe is loose where it connects to the head?

Q

[Dragon]

What does it sound like?

[Kawazacky]

It's just a sharp backfire.

I have to work to get it, but it's there, and it's not cool. I don't want my rings to melt down a hundred miles from home. It happened on my old XS650 once, and that really sucked.

[katoranger]

Check the headpipe bolts at the head like Q mentioned. I remember having that on mine now.

10mm wrench and tighten them up.

Allen

[Dragon]

Does it sound like: putt-putt-putt-putt-putt...?

[DesertDog]

Originally Posted by Snake

Does it sound like: putt-putt-putt-putt-putt...?

8O or pop-pop-pop-pop

[Dragon]

Originally Posted by DesertDog

8O or pop-pop-pop-pop

Mine sounds like that. I thought it's normal.

[DesertDog]

if you dont hear a tapit (ticking noise up front during idle or normal running) everything tight , then your runnin to lean on the main jet
more than likely.? what is the spark plug color, light brown to white is to lean, that is your back fire, caramel brown in color is about perfict
if that is not satisfying ......
hold on the big guns will give there answer shortly 8O
DD

[Kawazacky]

Well, last time I checked, the plug was sorta brownish, but there was some carbon too. it's making a sharp cracking noise.

Except for the first time, it only backfires once, it's not a pop pop pop. The first time it happened, I was winding around a corner hard and heard three sharp snaps, and thought it came from my suspension. But, upon hard deceleration, I realized it was coming from (I think) the exhaust. Im not 100% sure, but I don't think it's going through the carb.

[Kawazacky]

And I am hearing a tappet noise, but I don't think it's anything abnormal (I'm running a pushrod engine, btw).

I will have to check the valves though. It just seems that if it was valve problems, it would be evident across the power band, not just occasionally at high rpms.

[katoranger]

Check those bolts on the exhaust and let us know. They tend to work loose.

Allen

[Kawazacky]

Um, they aren't obviously loose. I check them regularly. But I'll look at them if I get a break from the desk here for a few mins later tonight.

I don't THINK this'd be the issue, though, as, once again, an exhaust leak should be noticeable at all RPMs, not just at the high end...

[katoranger]

If if is high end then the coil may be cutting out or cdi box is faulty. Check the connections.

Allen