No power at low speeds in cold weather
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Lx 150
Joined: 27 Dec 2017
Posts: 8

Tue Dec 03, 2019 4:48 pm quote
LX 150 circa 2007 with approximately 5000 miles on it.

Colder weather here on the east coast and I was driving my LX 150 home from work today and a minute or two into my ride and while going up a very shallow hill, the scooter seemed to lose all power when I gave it gas. It didn't stall completely but did seem like it was about to stall. But then if I was stopped and not giving it any power it would idle fine without any chance of stalling. This went on for a block or two until I pulled over. Turned it off for a few minutes and restarted it. It restarted fine. Let the engine warm up for a few minutes and tried again and the same issue. Finally turned it down the hill and took a more flat way home and it was still having problems. Basically a really rough/no power ride anywhere between 5-20 mph. But actually had normal responsiveness over 20 mph when it was running. This is probably the coldest day we've had thus far this year but it was running fine this morning.

Any ideas of what I can do to avoid this situation in the next few months?
Ossessionato
Yamaha Tricity 155 Urban 2019 - MV Agusta 125 RS 1956 - Moto Guzzi Airone 250 Sport 1951
Joined: 21 Jul 2007
Posts: 2306
Location: Latina (Italy)
Tue Dec 03, 2019 10:58 pm quote
Try changing the candle with a new one, the combination of climate change with the problem could be a misleading factor, to me the idea of a problem related to the leakage of electricity. From a distance they can be many things, when did you change the air filter last time?
Enthusiast
Joined: 14 Aug 2019
Posts: 96
Location: Bermuda
Wed Dec 04, 2019 3:28 am quote
Sounds like gunk in the carburetor. Clean it carefully, particularly the jets and the throttle needle, consider replacing fuel lines and fuel filter, and also check valve clearances.
Addicted
2009 LX 150, 2008 GTS 250
Joined: 19 Jun 2011
Posts: 726
Location: Birmingham, Alabama, USA
Wed Dec 04, 2019 3:48 am quote
I had a similar condition and found the rubber diaphragm of the carburetor piston assembly to have some tears in it. It's easy to remove and check without removing the carb. Just 4 screws on the cap. Be prepared for the spring pushing the cap up. Use a strong lamp to look for tears.

Bill
Enthusiast
Joined: 14 Aug 2019
Posts: 96
Location: Bermuda
Wed Dec 04, 2019 4:48 am quote
Cosmos wrote:
I had a similar condition and found the rubber diaphragm of the carburetor piston assembly to have some tears in it. It's easy to remove and check without removing the carb. Just 4 screws on the cap. Be prepared for the spring pushing the cap up. Use a strong lamp to look for tears.

Bill
That's a good idea but FWIW when this happened to me (mis-seated diaphragm due to careless reassembly), the problem persisted all the way up the throttle position, and didn't get better over a certain speed.

I guess there are a lot of ways that diaphragm can be less than perfect, but mid-throttle issues to me suggest problems with the throttle needle. Not the needle valve that the carb float controls, the needle that the throttle itself pulls up and down inside the carb, that meters fuel out of the main jet.

Likewise with Attila's air filter and candle (I think our word for it would be "spark plug") suggestions - the confinement of the symptom to mid-throttle would point me elsewhere. Those issues usually simply get worse at higher throttle levels.

Interesting problem, though. It's likely to be something very simple once you find it.
Ossessionato
Yamaha Tricity 155 Urban 2019 - MV Agusta 125 RS 1956 - Moto Guzzi Airone 250 Sport 1951
Joined: 21 Jul 2007
Posts: 2306
Location: Latina (Italy)
Wed Dec 04, 2019 5:16 am quote
... in fact it is a candle ... but if I write like that here they start laughing; too many of our terms are derived from commonly used objects but we understand that on an engine the meaning is unique.
As for the problem described, without trying the vehicle it is a little like guessing; the symptoms are sometimes ambiguous and the inexperienced doctors often do more damages to do try to save the patients that to leave them like this but it's an engine and nothing bad happens.
Molto Verboso
Kymco AK550
Joined: 09 Feb 2008
Posts: 1136
Location: UK
Thu Dec 05, 2019 12:43 am quote
The only clue here is the weather/temperature so my money would be icing. This is normally only a carburettor issue but injectors can sometimes ice up too. If everything returns to normal when you stop and let some heat soak through the engine at idle that would reinforce this guess. In most cases, once normal engine temperature has been established throughout, the problem won't recur on the same journey. Some carburettors have built in electric heating elements to combat this.
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