As I started my scoot this afternoon, I heard a rather loud noise, coming right from under the engine. Luckily enough, the engine itself is OK, but one of the nuts that attaches the muffler to the engine exhaust port went loose.
There are two long screws sticking out of the engine, and the muffler is held in place on these by special long cap nuts. One of these nuts was gone. Well, I was stupid enough to go for a coffee and later to ride home on this. That last part of the trip was most special, as the engine rocked and rumbled like some sort of Harley. Scared off a pack of freshman that are being herded around the campus for the orientation these days.
Well as I got home it turned out the other nut was gone too, and the muffler was just hanging down there, completely off the screws.
Here's a short video just to show what is sounded like on the idle. The flash inside the engine is probably some kind of misfire. I could clearly see fire coming out.
So I loosened the muffler sleve nuts just to be able to move it around, and put the muffler onto the engine port. The screw protruding from the engine are standard M6 thread. I tried to tie it down with M6 screw, washer and a block washer:
Too bad I tried too hard - and broke one of these screws! Now the muffler is sort of in place, still making the noise, but not as much. It appears that as the nuts came off during the ride, a gasket that must have been b/n the muffler and the engine fell off. Now I'll be on the lookout for this piece. The broken screw may be just a stud, a sort of screw without head that can screw both ways in. I really hope to be able to extract and replace it.So if you hear any weird noise from your exhaust, or simply for maintenance, check those nuts. I I am now at 2800km. And for Pete's sake, just don't drive it if it's loose! Gently fasten it up. It takes 10mm wrench or hex socket to operate a standard M6 nut, and so may be the same for those long nuts that fell off.
12 comments:
This happend to me about last week..ahh such a problem!! i couldnt find that nut anywhere not even in pepboys or autozone !! i went almost every single hardware place all over the city ( I live in philly) turns out ...regular bicycle's breaks screws have the same nut size as the muffler and works perfect! now i still have that little poppy sound but not as bad..but my dad told me (he use to be an engineer) that its not really a problem instead it makes air flow a little faster and freely which makes the bike accelerate a slightly better and also i think it makes people notice the bike a lot more which is always a plus
Yes, its a standard metric M6 bolt and nut. Most bicycles these days use metric parts. I got mine at Ace Hardware.
Yarko
This happened to me too. I tried to screw the bolts back, one is tight, but the other doesn't want to stop turning. It still makes the noise.
This JUST happened to me today. I have an Eagle/Aquila 150-T, and I try to change the oil (regular & gear) every 1000km on the bike. Well, I went 2000km just to be lazy, and noticed the bike started making a bit of a whiny rattling noise. I checked the oil, and it wasn't even registering on the dipstick. I thought for sure I must have blown a seal or something, and the oil leaked out without me knowing. So, I thought the whiny noise was the engine and I was pretty much screwed. (I always run the bike around 50mph to keep up with traffic around here...it gets a beating every day, so I figured it was perhaps too much for it). Well, I did the oil change anyways, and there was still plenty of oil in it. It was still running ok (before and after), but the whiny noise was still there; couldn't figure out where it was coming from. Could swear it was coming from the muffler, but it seemed like it was coming from the engine, too. I'm riding home today, and in the midst of traffic I hear this really loud BRAPPBRAPBRAPBRAP noise all of a sudden. I look around, and I thought it was the car next to me with a squeaky belt. The noise goes away as that car drives on, so I figure no problem. Then I'm coming up to a light, my Spidey-sense kicks in and for some reason I just know something's up with my bike. Sure enough, right as I start to stop the bike makes a loud brappy noise as if I'm riding a Harley. I pull over, and look underneath. Both nuts are missing from the exhaust mount to the engine, and the O-ring that fits between exhaust pipe and engine is stuck in a plastic shroud covering the two. I figure the first noise I heard must have been the O-ring breaking free, and then later on it swished right out the gap between the exhaust and engine and jammed into the plastic. I rode it home with it loud, and got strange looks, but it all seemed ok. I hopped on the net and searched for "chinese scooter exhaust pipe nuts", and stumbled across your blog. You pointed out the exact problem I had, the type of nuts I need, and the commenters helped isolate where I could go get them! Super thanks, Mate!
Side note, I should have realized it was this issue before, because during the oil change, the bottom of the engine was really black. I thought it was leaking oil, but it was more like burnt oil. The scooter has a tendency to burn it, but since the exhaust mount was loose, it was just blowing right out of the gap onto the bottom of the engine and coating it. Likewise, the scooters exhaust was white not grayish like it used to be. I should have seen the signs, and recognized what was up. But I guess hind-sight is 20/20.
I had the same problem. Found a kit on Ebay that actually worked. Factory design allows single cylinder vibration to back-out the header bolts. It's a fastening system of hardened alloy steel and an improved gasket. This must be common enough that someone designed a kit. Here is the Ebay listing number. Cut & paste into their look-up. 250547631247 And scoot on!
I guess it's an Ebay thing, but the exhaust repair kit I spoke of has a new listing number. Use 260533211007 and there it is. This guy explains the whole issue. An exhaust leak is a drop in back pressuer which might sound neat, but the exhaust valve now runs too hot and burns at the edges and results in loss of compression in the cylinder. Bad, very bad.
I have exactly the same issue as you guys but I think mine kind'a needs major repair.
Both screws broke in half leaving the other half inside and the inner thread is already worn out, so no screws will fit anyways.
Bummer ...
hello.
is it dangerous to ride a scooter with the muffler opened like in your situation?
what is the risks?
thx
pls reply to my emel: fiezati@yahoo.com
Thank you for posting this. It was exactly what I needed today!
My little 150cc Roketa has been making these loud exhaust noises ever since I dropped it on its side 5 days ago. I know f-all about exhaust and motors and was dreading taking it to a shop.
But these pics were exactly what happened on mine. The M6 bolt is exactly what I have too. I picked up two M6 nuts and locking washers from Ace Hardware for 59 cents. After loosening the bolts on the muffler, I could get it back in place to line up with the M6 studs. A little coercion with a hammer and it slid right on. The space for sliding in a nut driver is a little awkward on one side, but workable.
Now the scooter sounds almost like it did before. It has just a tad more pop and growl to it, but is so much quieter than before. I don't even know if there's supposed to be another gasket there, but it sounds pretty darn good.
Thank you for helping me with the 59 cent fix to an embarrassing problem!
Thank you for your comment! This worked OK, but in fact I had later removed amd replaced the stud. This was also quite simple. Perhaps now I will finally get to posting about that! It is nice to hear that these posts are still useful, after several years since I made them.
YL
hello, I stumble across this post and pictures in search for a solution to my exact problem as your pictures, my question is I have one broken exhaust bolt and one complete and the scooter is still making the loud noise and leaking oil from I have no idea so the other exhaust bolt is broken and not enough thread to put another screw top so how do I remove the half threaded bolt and is it dangerous to ride around with only one in place? it seems tight but still crazy noisy
I really screwed up this weekend. I was torquing on my exhaust bolts and got to the final one and I happened to snap it off. There's still about three quarters of an inch sticking out of the head.
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