Issues with brand new Downtown running rough and cutting out / stalling

[msolok]

Hi guys.

I'm a new rider from down in Aus. Only got my license a few weeks ago and was looking around at a few different bikes. Was originally looking at some different bikes, including the Honda CB500x and the Kymco Venox. In the end, after discussing with my partner what she was happier with me riding, I settled on a scooter. Looking at all the options I quickly determined that a Maxi size scooter was going to be what I need (as I am 182cm and 120kg). Here is Australia we only have a very limited selection of scooters (no where near what other countries can get, and usually in only 1 or 2 colours) so i quickly narrowed it down to the Kymco Downtown 300i and the Honda Forza.
I found a dealer that had both in stock and went down to compare. I quickly ruled out the Forza based on it having less power, was heavier, I didn't like the looks, and that I didn't fit (my knees where impacting with the front dash).
The Downtown, however, was perfect. Looked great, has enough power to pull my heavy butt, and was big enough and very very comfy. So I quickly made a deal for a brand new one and it was delivered to me today.

I took it out for a bit of a spin this afternoon. It started fine but I quickly noticed that it was shaking and vibrating a lot at idle and at low speed. I thought it a bit odd as the bike was meant to be very smooth, but decided to take it out anyway. Once I added a bit of throttle it seemed to be OK though, no more shuddering.

Now, being a new rider I was taking things a bit slowly. Doing maybe 30-40km/h on some backstreets around my house. I went around some corners, slowing right down to make sure no one was coming (people in my area tend to drive like complete maniacs). I got to one corner, slowed down, looked and took off and suddenly there was no power. The engine had cut out / stalled. I would have been going around 30km/h at this stage. I couldn't believe it. Luckily no one was around and I was able to pull over and start it back up. But it could have ended so badly.
I kept riding for the next few minutes and then took it home and it didn't happen again (although it almost happened when I was coming up my drive, which has a little bit of a slope).

Any suggestions on what might have happened here? I'm going to take it out for a few more trips over the next few days and monitor it. But any advice on what to look for or suggestions on what is happening before I contact the dealer would be greatly appreciated.

[sklnzl]

I would suggest you check your filling station, it might be a bad batch of fuel , sometimes it is contaminated with water.

[msolok]

Thanks for the suggestion sklnzl. The petrol in it is whatever the dealer has put in. The bike only has about 10Km on it, so I haven't had to put anything in there. I will have to wait for the petrol to drop a bit more before I can refill with some known good stuff.

[CROSSBOLT]

Welcome to this forum, msolok! You will find a real mix of scooter nuts of all ages! You made a good choice in the DT300i but I am biased since I have one.

There seems to be a universal thing the dealers do not do and that is INITIALIZE. It is easy to do and usually stops any bad behavior of most of the EFI Kymco's with idling and unexplained throttle transition problems. This does NOT rule out bad gasoline! Here is the procedure: bike on center stand, side stand UP. Kill switch to run, key off. Open throttle to wide open stop and hold open. Turn key on but do not start. Time or count 8 seconds, close throttle, key off. Yer done! This will initialize the TPS and ISC (throttle position sensor and idle speed control). I do not know what "spooks" these two but I have solve ALL my crummy idle problems this way. Do let us all know what happens. I ain't the only one on this forum that knows this and most of us have used the procedure to fix our DT300i bikes.

Karl

[msolok]

Hi Crossbolt.  Thanks for the advice. I remember reading about this previously but couldn't find it again. Tomorrow I will give it a try as it is, try your procedure, and then compare how it runs. Hopefully it fixes the issues right up. I shall let you know how I go!

[sklnzl]

Here it is :

[msolok]

Thanks guys. I gave that procedure a test today. It seems to have helped a bit with making it smoother at idle, it didn't stall when I was out for a ride today, and acceleration and throttle response seems to be far improved. The bike still seems to be a bit rough when sitting idle, but not too bad now. I might work my way through the petrol left in the tank and fill up with some known good Premium petrol and see if that helps it more.

Thanks again guys!

[sklnzl]

You're welcome 

[Stig / Major Tom]

Thanks guys. I gave that procedure a test today. It seems to have helped a bit with making it smoother at idle, it didn't stall when I was out for a ride today, and acceleration and throttle response seems to be far improved. The bike still seems to be a bit rough when sitting idle, but not too bad now. I might work my way through the petrol left in the tank and fill up with some known good Premium petrol and see if that helps it more.

Thanks again guys!

Just a thought .....my newish LIKE200i's "stop light idle" became a lot more reassuring when I put in an Iridium spark plug. The Denso Iridium and NGK Iridium have both worked well for me. They won't 'fix' anything - but they gave me a smoother idle and a few more RPM's while at the lights in traffic. A nice sounding idle is 'good' when sitting surrounded by tons of iron.

[zombie]

[/quote]

Thanks guys. I gave that procedure a test today. It seems to have helped a bit with making it smoother at idle, it didn't stall when I was out for a ride today, and acceleration and throttle response seems to be far improved. The bike still seems to be a bit rough when sitting idle, but not too bad now. I might work my way through the petrol left in the tank and fill up with some known good Premium petrol and see if that helps it more.

Thanks again guys!

You could also adjust your idle mix / speed screws. If the "test ride" at the dealer takes more than 15 minutes it's alot so the carb. adjustments are more often than not, mis-adjusted. (Is that a word?)
Adjusting the fuel system is the first thing I do on every engine I touch. Known good fuel is first. You can adjust all day w/ bad fuel, and not even start when you put in good fuel.

~Just a thought~

[msolok]

Hey guys. Got another update on my bike. Like I said earlier, after I did the throttle reset yesterday the bike seemed a bit smoother, but it was still noticeably rough when idle. Things where still pretty shaky when I turned it on or was sitting at lights. But being new to riding and the Downtown being my first bike I was a bit unsure as to what is normal or acceptable. All I could really compared it to was the Honda CB125 that I did my training on, and it was noticeably smoother at idle.

So anyway, I have been riding it around and getting used to it. Today the fuel gauge starts flashing at me to say the tank is low. I wanted to use up as much of the suspect petrol as I could before refilling to make sure all the containments had been cleaned out, but I had no idea how much petrol was actually left. So I did a bit more riding and then filled up. Using the Premium fuel that they had (98ron, no ethanol) it took just over 10.5L. Jumping back on it I notice a just about instant improvement. Idle just after switching on was still rough but by the time I had driven 1 hundred meters out of the petrol station and to the lights it was idling very smooth. It was a huge difference.

Clearly something was up with the petrol the dealer had filled it with. Thankfully they seemed to put less than half a tank in, so hoping nothing has damaged the engine. Going to be speaking to them tomorrow about it!

Thanks again all for the advice!

[CROSSBOLT]

Probably more fuel than Initialize but maybe a little of both, eh? We otta present you for posting the results since all of us were waitin' on the fence rail to see whose diagnosis was right! Good on ya and don't be a stranger!

Karl

[CROSSBOLT]

Oh, boy,oh, boyoyo! It is not often if ever one can get one on Zombie, if ever, UNTIL NOW! But here is the chance, right here on this thread: Hey, Zomb! There ain't no adjusting screws on this thing! No carb! Throttle body! OK, there might be a throttle stop that is threaded but it has some kinda bullet-proof epoxy paint on it which says, "Don't touch me!"

This is on a par with me yellin' at that guy about what kind of bike he had and his posted question was in the Agility 125 column! HE got ME GOOD on that one!

Karl

[zombie]

You've been a pain in my a_ _ since the day you joined.

Just messing... I love ya Bro! I thought about it being injected as I was posting. That throttle stop is the idle air break, and does have a specific setting in thousandths inch opening. I just got lost in the glow of your holiness, and kept posting blindly.

For future reference the piece on EVERYTHING that has the "DO NOT TOUCH" tag... is the problem. Smash off the safety seal, and turn that thing with a pipe wrench if you have to because that is ALWAYS the part that needs to be tweaked.
Obama put those tags on things so we all have to go back to the dealers. Part of his "Back to Work" program.

I think I am having a stroke!

[maxhush]

I'll second the suggestion of switching to an NGK iridium plug. Cheapest "upgrade" you can do. Also, at a stop, your rear (left) brake will cause the bike to shake more than the front (right) brake. I generally use both brakes to come to a stop and then switch to just the front brake while sitting at a light.