Modern Vespa

I have an LX150 which I completely love. However, there is one problem that drives me crazy. At high speeds, 45-60 mph, as I am cruising, it loses power - like the gas isn't getting into the engine. I lay off the throttle and then back on and it works, then loses again. If I pull over and stop, then start again, it is usually ok again for a while. The big issue is... it is not always consistent. Sometimes it happens, sometimes it doesn't.

Here is what I have found that seems to help.

1) if I fill up with gas from a good station (91 octane of course) it seems to be better.
2) if I use gas from a station with individual pumps for each octane it also seems to help.

I asked the dealership about this and they were not surprised by it - like it was a normal thing. YET, looking through here.... I haven't seen anyone else having the problem. They indicated that when you get to top speeds, the scoot can't put the gas into the engine fast enough. It makes sense, but the sheer fact that it isn't consistent.... I think it may be a different issue.

I am guessing it may be that I just got some "bad gas" that is still working out of the scoot.

Any thoughts around this?

How many miles on your scooter? What service has been done and how long ago?

There could be a couple of causes for this. I don't know why bad gas would consistently bog you down in precisely the same range. You'd notice issues at all speeds. My stock guess (for everything) is worn rollers.

Hmmm... interesting. I will be taking it in for a tune up and ask them about the possibility of the "Rollers" (I am not sure what they are). My scoot has about 6,700 miles one it. I had it checked out last winter (tune up) and asked them about it. They couldn't get it to do it... but then it doesn't happen all the time. They didn't find anything wrong with it. Good point on the bad gas giving me problems at all speeds....

I would get some Seafoam additive and put some in the gas. You very well have gotten some bad gas. The seafoam will help. After you put it in go for a ride and let it do it's thing. I put some in after each fillup. Hope you get it sorted out

Don't know the LX150, but it sounds to me like you're hitting the rev limiter.

???

Anybody confirm?

P.

Not sure what the rev limiter is... but it is odd, cause sometime I can cruise along at 55 no problem. Other times (even on a flat road) it gives me this problem.

Have you checked the simple things first like air filter and spark plug?

based on your comments it sounds like this has been happening for a while? Since you bought the 150? When I had a similar problem on my old 150 the carb needed some serious cleaning. gunk had accumulated from sitting in the show room for an extended period. After the carb was clean by the dealer it had no problems at the 45 - 60 range. So it is definitely not simply expected behavior. There is definitely something wrong with your scoot.

Hi there KarlJens
I also have a LX150, used it for daily commute, and road it hard to keep up in traffic. never gave me problems like that, except the one time I pushed the remaining amount of gas too far and I ran out. The problem your discribing is just like that, so I am thinking it is not a bad gas, but lack of gas at the higher speeds. Something is pinching off your gas supply at high speeds. Could be gunk in carb, could be a pinched hose. But this does not sound like a bad gas problem.

Just changed the spark plug in the spring. It has been doing it for not quite a year... just got it a year ago (used '06). I don't remember it doing it for the first couple of months. Then of course, winter set in and I didn't ride it as much. I still rode it, but only on the days the roads were clear and it was "too" cold.

I will have them look at the carb a bit closer when I take it in for my oil change. I think this makes the most sense in my un-educated mind. I will also check to make sure the intake hose isn't kinked or something.

Thanks All!!

Several good suggestions so far-seafoam, plug, etc. Did your shop do a valve check at 4000 miles?

As for rollers, those are cylindrical weights in the transmission. Without getting too far into it, they're key to the automatic transmission. They're inside a disc-shaped part called the variator. As you apply the throttle, your engine RPMs increase. The variator spins and centrifugal forces cause the rollers to move outwards from the center. Rollers need replacement every 4K-6K or so depending on how you ride. Over time, they develop flat spots and won't move freely, getting stuck in certain positions. This will cause the scooter to bog down and lose power at certain RPMs.

Even if that's not the issue, you should definitely have them (and your belt) checked if they haven't been. The variator and clutch should also be cleaned up. Dirt and particles will get in there ad accumulate over time, causing all sorts of issues. It's pretty hard hit it on a stock LX. She probably wouldn't be at those speeds, which are well within an LX's abilities.

Man, I am learning a lot. Now, I can at least sound more intelligent when I go in and tell them it loses power...

Thanks!

ive had the same problem with my et4. its the overflow pipe on the fuel tank it clogs up so dosn't allow the preasure to equelize so it courses a vacum in the tank. which means the fuel cant flow properly. i fixed this by drilling a small hole in a spare fuel cap of mine and it was fie afterwards. but really you should replace the overflow pipe

The fuel overflow pipe sounds right. Thank you for your responses. This was driving me nuts and the "specialists" didn't have an answer. If that's not it then I'll go carb next.

The increased octane decreases the engine temp and allows it to run on a leaner mixture. The LX 150 has 3 fuel jets needle/pilot/main. When you are running near top speed, the top end of the fuel flow is from the main jet, that is why you are most likely not having issues at lower speeds. I would bet that your spark plug is a little on the white side if you do a read. Nothing a good carb cleaning shouldn't fix.

Good luck!

For others viewing this thread there are LX150's & LX150ie's. The latter are fuel injected. When posting for clues be sure to list the whole model ID. Best to put in your member info so you can't forget.

I bought 2006 LX 150 a month ago with only 730 miles on it. The lady I bought it from left it outside and hadn't ridden it in 7 months. The first few days it ran perfectly and I brought it in to get it serviced. After the servicing it loses power at higher speeds. I removed the evap system, cleaned air filter, and cleaned main jet. I've added gum out to gas and it just keeps happening sporadically. Is there anything the service could have done? They used 10w 30 instead of 5w, does that make a difference? Do you think it is a coincidence and maybe the fuel line has gunk in it that it's working through? Will it work through it? I'm going to go to Sea Foam as that is the choice here for cleaning engines out. Just confused as it runs perfectly otherwise. Thanks for your responses.

Several possibilities:
*Your float could possibly be hanging up.
*Crack in the carb diaphragm.
*Pressure building in gas tank.

I would say that you are on the right track with SeaFoam. It will clear up a good number of minor issues. This could be a fuel issue...did you drain the old fuel or just add on top of it? Draining old fuel is most preferable in these instances. Also, if there is a in line fuel filter that can be changed out you might want to do that. A bike that has been sitting for a while may run good at first until the sediment is released through general vibrations of operation and partially clog a filter. This could/would present it self at greater fuel demand situations. Please post when you figure it out.

I'd think the carb needs a complete cleaning. Also have the valves checked.

The fuel line going into the bottom of the petcock valve had a tiny crack at the connecting point. Tough to see without really getting a light down there and getting up close to it. Replaced that fuel line with 3/16" black rubber fuel line, $2, and the problem is solved. I'm assuming at high throttle that the engine was drawing the fuel at a rate that caused enough pressure to suck air through that tine crack and at lower speeds not a problem.