2014 Stella Auto Vibrating Like Crazy

outtaMyBlood · Post by **outtaMyBlood** » Thu Nov 19, 2015 5:30 am

When I am going to ride my 2014 Stella Auto, I always start up the engine while its on the center stand and wait for the engine to mellow out / warm up before riding (probably takes 30-40 seconds). About 4-5 weeks ago, I noticed that when I started my Stella on the center stand that the whole scooter was vibrating so much that it started to move around, drifting a few inches from its initial spot (see video link below).

In the last 10 days, this vibration during the start has gotten so bad that I've seen it move about 1 foot away from its initial spot, and the vibrations have become increasingly intense over the last 10 days. So, I tightened every nut/bolt/screw that I could see - under the cowls, under the front wheel cover, the headset, etc. However, that did not fix the problem one bit (none of the nuts/bolts/screws were all that loose).

So, I took the scooter to the local shop. I couldn't show him the crazy vibrations that happen during the start because the engine was already warmed up. He asked me to start the engine (on center stand) and to hit the throttle a little bit, and he then said that it is normal and that all I have to do is reduce the idle rpm by adjusting the choke knob under the seat. We adjusted that and it seemed to have slightly less vibration, so I thought that we fixed the problem. However, the scooter would sometimes die at that low rpm when stopping, so I turned it back up slightly and the lovely vibrations were back in full force.

The mechanic said that if the problem persists, then I will need to replace the clutch belt (I think that's what he said). The vibrations while riding are worse at lower RPMs, and worst when I let off of the throttle after going at higher speeds. I've read numerous posts about vibrations being caused by a cracked/broken exhaust but I've looked at every inch of the exhaust that I can see and I don't see any cracks. I've read other posts that say mirrors or the glove box can vibrate, but those items are tight and the entire scooter is vibrating rather than just the front end.

Anyone experience something similar, or have any ideas of the cause? I'm currently at 1000 miles.

Video of the vibrating/drifting scooter below (pay attention to the legs of the stand):
https://www.youtube.com/watch?v=EWaOG9m ... e=youtu.be

Also, the only nut/bolt that I found to be loose was the one pictured below, on the exhaust. However, when I tighten it, it only becomes slightly tighter, and then loosens - it seems like the threads may be stripped. Does this gap between the exhaust pieces look too big? These parts don't seem to be shaking more than the rest of the scooter.

Sorry for the long post, but I figure that more detail is better!

avescoots1134 · Post by **avescoots1134** » Thu Nov 19, 2015 2:50 pm

On a normal Vespa or even a Stella there is a chunky rubber motor mount called a swingarm bushing or buffer. In the case of the Stella, this would absorb some of the vibrations of an LML-balanced crankshaft. In the StellaAuto there isn't much of one so they do buzz quite a bit. Some of this could be blamed on the engine design, but not all of it.

It varies wildly from bike to bike. It depends on who balanced your crankshaft and if your motor was built on a Wednesday or a Friday.

jimmbomb · Post by **jimmbomb** » Thu Nov 19, 2015 10:25 pm

It sounds to me like it is idling way too high. I had a an Aprilia sr50 that idled high and when I revved it on the center stand the rear wheel would spin like crazy and it would move around Vibrate move around on the center stand.
But when it idled down, and the rear wheel stop spinning it stayed in one place. I think your idle is way too high. And I would not adjust the idle by pulling out the choke. That's why it dies on you after it's warmed up.
After you got your bike completely warmed up, and the choke is off, turn the idle screw down on your carburetor until it idles pretty good without the rear wheel starting to spin. Then you should be good to go.
I think it is moving around on the pavement because the rear wheel is spinning way too fast. Good luck

OCStella · Post by **OCStella** » Fri Nov 20, 2015 2:40 am

I agree with jummbomb, idle seems way too high. My auto will do the same thing if I rev the engine while on the center stand. I would check the idle screw, but don't for get to check the throttle cable and make sure that it is not binding. I had a Moto Guzzi that once skipped across a parking lot at 8000ft (okay, maybe it was only 3 feet).

OCStella · Post by **OCStella** » Fri Nov 20, 2015 2:51 am

BTW, from your description if you can't hold the idle after warm up, you might have a vacuum leak. I've not looked the the carb yet, but if all the cracks in my new Stella rubber grommets are any indication, I would say that some seals are also prone to cracking and leaks.
If you get your idle dialed in and you drop or increase in idle, I would look to a vacuum leak.

outtaMyBlood · Post by **outtaMyBlood** » Sat Nov 21, 2015 6:19 pm

First of all, thanks to everyone for the replies!

I think what I'm describing as the choke is actually the idle screw - I adjust this small knob/screw at the end of a short cable/tube under the seat which increases/decreases the idle. The thing is, when I reduced the idle to where it was vibrating less (but still more than it did the first couple of months), it would sometimes die when I came to a stop. So I had to increase the idle a little more and now it vibrates just as bad as before, but the idle is still so low that when I come to a stop now it feels like the bike is just on the cusp of dying because the idle is so low - yet I'm still having excessive vibration while riding. Because of this situation, it seems to me that there has to be something else that is wrong - it didn't vibrate anywhere near this much during the first couple of months when the idle was actually higher than it is now. Unless this is just the way things work with the Stella's, where they vibrate more with time and its just something you have to live with. I can live with the vibration, but instead of spending my time enjoying the ride I end up worrying about the whether the scooter will make it through the day.

I ended up taking it to the shop so that I could at least know that I had a professional look at it and try his best to figure it out. If he can't figure it out then I'll look into the throttle cable binding and vacuum leak as potential causes. Could someone describe what the vacuum on the Stella auto looks like and where to find it? What is the purpose of the vacuum on the Stella auto? Is it providing air to the engine for combustion or cooling? I don't know too much about engines, and the manual doesn't give much detail on these things.

Once I hear back from the mechanic I'll report back here.
Thanks!

avescoots1134 · Post by **avescoots1134** » Sun Nov 22, 2015 2:48 pm

By any chance have you let it sit unused for more than a few days with Ethanol fuel? The pilot jet in the carb is really easy to clog and will cause those issues.

Carb clean is a PITA! Since I have the right tools, the easiest way for me to pull the carb is to drop the engine out of the bike a few inches.

outtaMyBlood · Post by **outtaMyBlood** » Sun Nov 22, 2015 7:07 pm

Avescoots - I believe that most or all of the gasoline sold in California is 10% ethanol. I use my scoot usually every day Monday through Friday and less frequently on the weekends, occasionally letting it sit for 2-3 days but that has only happened a couple of times and I've never had any trouble starting the Stella up. I'm hoping its not a problem with the carb, but hopefully if it is then they can find that at the shop and take care of it. If not then I may soon be learning much more about scooter engines than I ever intended.

OCStella · Post by **OCStella** » Mon Nov 23, 2015 3:34 pm

The first thing I would do is set your RPM correctly and see if the bike can hold the idle. A simple test for your RPM can be done with a multimeter. Here's a link that shows how to check the RPMs using a multimeter. I haven't done this in a long time, but recall it was relatively easy as long as you know what the conversion rate is. once you have determined that you have the right idle RPM set (warm), then I would start ruling out some of the suggestions in the posts.

http://www.wheelhorseforum.com/topic/38 ... ultimeter/

Just food for thought. I had to clean out the garage this weekend and moved my Stella Auto out onto the cement driveway. I thought that I had ridden it in a few weeks so I might as well let it run for a while. She started fine with the choke kicking but it started scooting a few inches from the high idle choke. Oh well, must be the nature of the beast.

outtaMyBlood · Post by **outtaMyBlood** » Tue Nov 24, 2015 6:17 pm

I got a call back from the mechanic and he said that the engine is fine, and that the only problem he could find is that the front fork is bent. This is surprising because I haven't hit any potholes or any notably big obstacles. I turned right into a driveway a couple weeks ago that engaged the shocks more than I would have expected, but I would be amazed if that actually bent the front fork. I asked him if he thinks that could be the cause of the vibration while riding, and he said "maybe" or "probably", but he didn't sound too confident that this would fix the vibration problem. He said the fork is only $99 from Genuine, which was much lower than I expected, but then he said that it would take 3-4 hours of labor to replace, bringing the total for parts + labor to around $400-500. I'm gonna go take a look at it today, and have him show it to me, then think about it for a couple days before deciding whether to bite the bullet and get it fixed or not.

Does anyone else think that this could be the cause of excessive vibration during riding? I'm worried about sinking so much money into something that I feel won't even fix the problem that I brought it in for, and I find it weird that he says "it's really noticeable when your're riding it" even though I never noticed it before. Does anyone know of a tutorial about how to replace the front fork available online? Could riding around with a bent front fork cause any problems over time if I decide not to get it fixed (since I didn't even notice it was bent), or is this a vital fix?

OCStella - I have a multimeter and will try that out once I get my scoot back. Its good to know that other people experience the vibration/drifting during startup - maybe it has been happening since day one, but it just took me a while to notice.

I have a feeling that solving this problem is going to take months and $$$.

Rune · Post by **Rune** » Wed Nov 25, 2015 6:00 pm

2014 Stella Auto here... I get a vibration in the handlebars when it's idling on the center stand. When I push it forward off the stand, and let it continue to idle while balancing the scoot between my thighs, it clears right up... Not saying it's related to your problem, but just mentioning it.

outtaMyBlood · Post by **outtaMyBlood** » Wed Nov 25, 2015 6:50 pm

I went to see the scoot and they tried to show me the slight bend in the fork but I really couldn't tell. They said it's obvious if you ride and take your hands off of the handlebars - they say you can immediately feel it pull to one side... but of course that would happen... you're not holding the handlebars.

I don't get the impression that they're trying to rip me off to get me to replace the fork because when I first went to them with the vibration problem they kept saying that they would be happy to take my money and look at it, but they would recommend I just mess with the idle screw and see if that helps and if it doesn't then to bring it back. So I did that, brought it back and after they checked the engine, clutch belt, and checked for loose screws/bolts they still didn't charge me to do any of that, so I don't think they're lying to me. I asked the guy how a bent fork could cause the bike to vibrate excessively, but he just kind of dodged the question.

It vibrates slightly less than before, but that's just because they turned down the idle, but that still gives me the problem of the scooter dying when I come to my first stop sign in the morning (although it is fine at every stop after that). So I got the scooter back and I'm going to ride it around for a few weeks and decide if I'm going to actually drop that amount of money on something that I can't even notice (bent fork) that I have no reason to believe is causing the vibration problem that is my main concern. I'll also start to look into some of the other things that people have brought up here.

Rune - It's actually really helpful for me to hear to what degree other Stella riders experience vibration, so thanks for your input!

avescoots1134 · Post by **avescoots1134** » Wed Nov 25, 2015 8:54 pm

I wouldn't worry as much about the vibration issue while on the center-stand. Pretty much any scooter with the center stand mounted on the engine will have the tendency to move around until it's warmed up or if you apply some throttle.

The fork issue - not sure about that one. It's really hard to bend these forks.