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Scooter suddenly won't go over 30 mph: problem found
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JKJ-FZ6 UTC Ossessionato BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | |
OP JKJ-FZ6 Ossessionato
BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | UTCquote Ok, this isn't about a Vespa, but I know the experts are in this forum. I have a 2011 Zuma 125 with about 20,000 miles. It's always been well maintained and it's always run perfectly. This week, after riding about 5 miles and stopping at a stop light, it now doesn't go over about 30 mph. There is no problem starting it. It runs smoothly and apparently normally up to 30 mph. Above 30 it starts to hesitate, then won't go any faster. When I back off to 30 it runs fine again. I have no problem restarting it. The Check Engine light has not come on. I'm thinking fuel pump: it acts like perhaps the pump doesn't deliver enough fuel. But most of the fuel pump troubles on the Zuma forums refer to not starting at all, or failing to start when hot, etc. Other possible causes I've found are a dirty air filter; the belt, rollers, etc in the transmission; the coil; and the fuel injector. The air filter is clean. I will take a look at the belt, rollers, and clutch. But I'm not sure how to diagnose the other things, and I don't want to have to replace those expensive parts one at a time in order to find the problem. Does anyone have any suggestions? Thanks! JKJ ⚠️ Last edited by JKJ-FZ6 on UTC; edited 1 time |
RIP judy World Traveler
2007 LX150 Daring Plum Leonardo Da Vespa Joined:UTC | UTCquote Haven't a clue on Yamaha bikes but when we cleaned my carb (took it apart) after we reinstalled it, it did the same thing. The problem was that we didn't reseat the diaphragm properly. I'm assuming the Yamaha has one also, since it's a carbed bike. Try reseating it. Should fix it. |
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JKJ-FZ6 UTC Ossessionato BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | |
OP JKJ-FZ6 Ossessionato
BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | UTCquote judy wrote: Haven't a clue on Yamaha bikes but when we cleaned my carb (took it apart) after we reinstalled it, it did the same thing. The problem was that we didn't reseat the diaphragm properly. I'm assuming the Yamaha has one also, since it's a carbed bike. Try reseating it. Should fix it. The Zuma 125's are fuel injected and the fuel pump is electric so there are more wires than hoses. I'm checking all the connectors that I can reach. |
RIP judy World Traveler
2007 LX150 Daring Plum Leonardo Da Vespa Joined:UTC | UTCquote Bummer. I have the Vino but it's a '07. They are carbed. Haven't a clue. Good luck |
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JKJ-FZ6 UTC Ossessionato BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | |
OP JKJ-FZ6 Ossessionato
BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | UTCquote Here's an update that I posted on the Zuma forum: The air filter is clean. I've ordered a new ignition coil. Will see if that works. I don't want to buy a fuel pump or throttle body unless I have to. Thanks for any suggestions! |
Tor2ga UTC Ossessionato Looking for the next one, probably electric Joined:UTC | |
Tor2ga Ossessionato
Looking for the next one, probably electric Joined:UTC | UTCquote Does it have a vacuum operated fuel co*ck? Leakage into that vacuum hose or any other fuel hoses can cause those symptoms. Your scooter is old enough to be having cracked/broken hoses. |
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JKJ-FZ6 UTC Ossessionato BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | |
OP JKJ-FZ6 Ossessionato
BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | UTCquote Tor2ga wrote: Does it have a vacuum operated fuel co*ck? Leakage into that vacuum hose or any other fuel hoses can cause those symptoms. Your scooter is old enough to be having cracked/broken hoses. No, it has an electric fuel pump in the tank. There are very few hoses -- only the actual fuel supply hoses. It's mostly electrical wires. I may try disconnecting the fuel hose and see how far the pump can squirt the gas! (Best to do it when my smoking neighbor doesn't come over to watch. ) Maybe there's an obstruction in the tank or the fuel line. There is no fuel filter anywhere. |
WEB-Tech UTC Veni, Vidi, Posti 2008 MP3 500, 2013 BV350, 2020 Vespa Sei Giorni, 2008 Vespa S150 Joined:UTC | |
WEB-Tech Veni, Vidi, Posti
2008 MP3 500, 2013 BV350, 2020 Vespa Sei Giorni, 2008 Vespa S150 Joined:UTC | UTCquote JKJ-FZ6 wrote: Tor2ga wrote: Does it have a vacuum operated fuel co*ck? Leakage into that vacuum hose or any other fuel hoses can cause those symptoms. Your scooter is old enough to be having cracked/broken hoses. No, it has an electric fuel pump in the tank. There are very few hoses -- only the actual fuel supply hoses. It's mostly electrical wires. I may try disconnecting the fuel hose and see how far the pump can squirt the gas! (Best to do it when my smoking neighbor doesn't come over to watch. ) Maybe there's an obstruction in the tank or the fuel line. There is no fuel filter anywhere. Sure it's not a variator issue? You're not hitting the rev limiter are you??? |
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JKJ-FZ6 UTC Ossessionato BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | |
OP JKJ-FZ6 Ossessionato
BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | UTCquote WEB-Tech wrote: Sure it's not a variator issue? You're not hitting the rev limiter are you??? It could be the variator. I pulled it out and looked at the belt, rollers, and the variator ramps and surfaces. All looked okay. I suppose I could take the clutch apart for a more thorough inspection. It revs to 6700 rpm, normally it would hit about 8000 at about 55 mph at wide open throttle. |
gtsteve Member Vespa GT 200 Joined:UTC | UTCquote How about an immobiliser problem. I know on the Vespa if it's dicky it limits revs?? |
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JKJ-FZ6 UTC Ossessionato BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | |
OP JKJ-FZ6 Ossessionato
BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | UTCquote gtsteve wrote: How about an immobiliser problem. I know on the Vespa if it's dicky it limits revs?? The Zuma doesn't have an immobilizer like the Vespas. Thanks for the tip. |
Tripo UTC Addicted 2016 GTS 300 Settantesimo Grigio Pulsar Joined:UTC | |
Tripo Addicted
2016 GTS 300 Settantesimo Grigio Pulsar Joined:UTC | UTCquote This would be a long shot - but - could you have possibly topped it off accidentally with some diesel? |
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JKJ-FZ6 UTC Ossessionato BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | |
OP JKJ-FZ6 Ossessionato
BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | UTCquote Tripo wrote: This would be a long shot - but - could you have possibly topped it off accidentally with some diesel?
The rev limiter ideas do make sense. It runs well up to about 6700 rpm, then starts to hiccup. What could affect the rev limiter but not throw a FI fault? |
kz1000ST UTC Molto Verboso Dongfang 170cc, CF Moto Fashion 250 Joined:UTC | |
kz1000ST Molto Verboso
Dongfang 170cc, CF Moto Fashion 250 Joined:UTC | UTCquote I remember a problem and maybe even a recall for fuel pump issues on 125 Zuma. You may want to check with a dealer. |
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JKJ-FZ6 UTC Ossessionato BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | |
OP JKJ-FZ6 Ossessionato
BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | UTCquote So I finally got around to checking the valve clearances. These are the two intake valves with a broken rocker arm. Guess this explains a lot: sudden loss of power as in one moment it was good, the next it lost half its power; no fuel injection trouble indicated; no problem found with the ignition; nothing wrong in the transmission. The compression checked out okay -- because the valve is closed. I can't see the other half of the rocker arm. Hope it isn't damaging something else. Now that I've found the cause, I'll think about whether to try to fix it myself or have someone do it for me. Thanks for your ideas and encouragement!
Positive |
Madison Sully UTC Veni, Vidi, Posti MP3 500, GTS 250 (both 2008 MY), 2013 Piaggio BV 350, 2014 Can Am Spyder RT Joined:UTC | |
Madison Sully Veni, Vidi, Posti
MP3 500, GTS 250 (both 2008 MY), 2013 Piaggio BV 350, 2014 Can Am Spyder RT Joined:UTC | UTCquote That's a new one. |
tdrake Ossessionato
2006 GT200 Joined:UTC | UTCquote |
old as dirt UTC Veni, Vidi, Posti 2007 GTS Joined:UTC | |
old as dirt Veni, Vidi, Posti
2007 GTS Joined:UTC | UTCquote looks like a great time to do some cal and head mod upgrades. in the voice of Tim Taylor oh oh oh. |
Madison Sully UTC Veni, Vidi, Posti MP3 500, GTS 250 (both 2008 MY), 2013 Piaggio BV 350, 2014 Can Am Spyder RT Joined:UTC | |
Madison Sully Veni, Vidi, Posti
MP3 500, GTS 250 (both 2008 MY), 2013 Piaggio BV 350, 2014 Can Am Spyder RT Joined:UTC | UTCquote Yeah, on further thought that's not really a motor-in-scooter sort of job.... |
Motovista Veni, Vidi, Posti
GT 2.4 Joined:UTC | UTCquote Years ago, I had an Opel GT and one of the intake rocker arms broke. It's a hard thing to track down, because it's something you just don't think about. Good that you found it. |
Tierney Veni, Vidi, Posti Joined:UTC | UTCquote That broken piece has to be in there up top - unless in dropped down the cam chain tunnel. In which case, the fun will really starts and you will have to drop the oil pan at a minimum. At the least, these engines are not that bad to pull out the back and will be a lot easier to work on then. Good luck. |
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JKJ-FZ6 UTC Ossessionato BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | |
OP JKJ-FZ6 Ossessionato
BV400, Primavera 150, Yamaha Zuma 125 Joined:UTC | UTCquote Tierney wrote: That broken piece has to be in there up top - unless in dropped down the cam chain tunnel. In which case, the fun will really starts and you will have to drop the oil pan at a minimum. At the least, these engines are not that bad to pull out the back and will be a lot easier to work on then. Good luck. The broken piece was safely nestled in the exhaust valve cover. I managed to get the rocker arm out without removing the engine. Next, the hardest part will be to get the timing chain back in. |
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