Noisy and not quite right

[bcolladay]

So I have a 2006, I bought it last September with 3500 KM on it. Recently (3 months ago) I took it on a longer trip, curvy county blacktops, cruising at between 50 and 60 MPH 150 miles with several breaks. Usually below 6500 rpm. No problems to speak of but the last stop I made I noticed the scoot was louder on acceleration. Almost like the airbox was open. It would quiet down when I settled into cruising speed.

It didn't seem to run any different but the loudness concerned me enough it got a ride home in the back of a pickup. I parked it for a few days and when I had time I gave it a quick once over. It seems like all of the air cleaner connections are secure and the engine sounds fine. It just gets loud under acceleration, kind of a throaty rumble. Again similar to running an open carb with no air cleaner.

Since then I've taken it out on 2 - 40 Mile round trips and put another 800 KM in the city. I have noticed a little hesitation on slow accelerations and maybe the hint of a miss or fuel problem sometimes when at cruising speed. But mostly just the noise.

It doesn't seem to be the muffler but it could be. Also it is getting poorer and poorer fuel economy each time I fill up. I went from 67 MPG city before the trip, the next tank full was 62mpg and today it was 57mpg and I'm driving it more conservatively now than I ever have.

One other thing, and this may sound weird, but since buying the bike I've sensed something loose or grumbly in the drive case. Starts have always had a bit of a slightly jerky feeling.

For full disclosure Prior to the long trip I changed the oil and had two new tires installed.

Any ideas, before I tear into this fairly low mileage bike?

[zombie]

It sounds like the header pipe has broken at or near the muffler. Torque will go down, and DB's will go up.

Put it on the center stand, and let someone else rev it up. FEEL around for air blowing out. It could also be loose at the manifold. The studs do break.

One sure way to test is block the exhaust w/ a rag or whatever, and the bike should stall in a few seconds. If it is leaking it will run.

[bcolladay]

I initially checked the exhaust manifold bolts, due to the fact that I had the exhaust off for the tire change. I''l check that again. and the rest of the pipe, although it sounds louder from the left side of the bike.

Thanks.

[zombie]

Did you replace the exhaust seal?

If it's not there It may be cracked. Also it is important to loosely fit the pipe, and tighten the manifold bolts FIRST.

If you tighten the frame bolts first it may torque the pipe, and break it near a weld, or never seal at the manifold.

[bcolladay]

So I Checked again, I can neither hear nor feel air leaking out near the manifold or anywhere on the pipe. I plugged the tail pipe with a towel at idle and it died within about a second. I did notice that the rumble sound doesn't seem as pronounced on the center stand. Almost like it has to be under load. Although I accelerated on the center stand with the rear brake applied and it wasn't too loud that way either.

[BettinANDlosing]

Did you pull the carb access hatch under the seat and see if the air box actually is still attached well? Unscrew the clamp and reattach it just to make sure.

[bcolladay]

I haven't, I could see and feel it from the back left side. I'll do that. Thanks.

[BettinANDlosing]

Or go one step not and take your seat bucket out, that way you can inspect everything.

[bcolladay]

I was able to check it out, doesn't seem to be coming from the carb either. I may try spraying some starting fluid around the connections to see if there is a leak.

in the mean time here is a short clip of the noise. I', beginning to think it may be in the drive system.

[BettinANDlosing]

Damn yeah I can't two what that might be from the video. Is it that kind of cracking noise your talking about? My variator wore out and got louder kinda sounded like that, have you adjusted the valves recently? It'll quiet your engine down a bit.

[zombie]

Could you perhaps make another video? I'm not quite sure what we heard either...

[bcolladay]

It is the noise at 8-9 seconds. It is hard to record I have to be moving and the wind noise covers it up pretty quickly I will try again when the wind settles down a bit.

I'm leaning toward variator area now as well, anything I should know about these cases? Before this I had only dealt with gy6 150cc cheaper chinese machines.

I have listened near the head area and it is nice and quiet. Just feels and sound more like the variator.

[bcolladay]

Here's another. I'm not sure if it is any better... the sound I'm talking about starts at 6 seconds and goes until 9. Kind of a whirring rumble noise. Anyone else's kymco make noises like that?  Again it goes away once you settle into a speed. Only happens on medium to heavy acceleration.

[zombie]

I'm at a loss. I can't hear the noise you describe.

In re reading your post I do think you may have a flooding issue. Perhaps just a simple Idle Mix screw adjustment or a bad auto choke. When it floods it will sound lower in tone.. 

Since the bike was used it is possible you could have some wear in the cvt as well. I would open it up, and remove the clutch bell, and the variator so you can inspect it all. This is addressing the jerky feeling only

[BettinANDlosing]

One thing I noticed, these 250 engine make a distinct noise under load like a growl that ©an sounds mechanically rough. Is normal, and I couldn't hear anything but that and wind in your vid.