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Post by jdf7tc on Sept 12, 2019 7:37:17 GMT -5
Hi! I have just bought a 2013 Metropolitan after owning a Yamaha and a couple of China clones. The Met will only run 29 MPH on flat ground and makes an odd rrrrrrrr-------rrrrrrrr------rrrrrrrr sound at top end (sorry for the sound effects but imagine almost a muffled sound of it being cranked over without starting).
I don't expect it to run 50 but 35-40 would be nice. I have replaced the belt and checked oil and tire pressure. Any suggestions as to where I should be looking?
Thanks in advance.
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Post by benhonda on Sept 16, 2019 0:13:02 GMT -5
check the airbox...make sure the filter is good and that the pipe going to the carb is attached.
If that is all good, then maybe a partly clogged main jet?
Specs online say it should be doing 35-38mph top speed.
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Post by jdf7tc on Sept 17, 2019 18:41:46 GMT -5
Thanks for the help. I have checked the filter and it is nearly new. This particular scooter is fuel injected, it would not have a jet like an older carb scooter, right?
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Post by GrumpyUnk on Sept 17, 2019 22:49:28 GMT -5
Check that the throttle is opening all the way. Check tire pressure. The EFI must have a TPS, throttle position sensor, to tell it how much fuel to send to the injectors. If the TPS is reporting the wrong info, the computer won't send enough fuel for the amount of air passing the throttle plate, limiting engine power. To figure out, you really need access to the service information so you know what to check. It is possible there is a tiny filter inside the injector. If plugged, it will affect power. It is also possible the fuel pump is not producing pressure or volume as designed, or a pressure regulator is cutting pressure below design specs. Did you check fuel pressure and delivery volume?
Really need some technical documents to do much besides throw darts at a target in this case...
tom
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Post by jdf7tc on Sept 18, 2019 7:24:19 GMT -5
Thanks for the reply Tom. The throttle is cable is opening the the throttle fully and tire pressure is good. I have no idea how to check (or even find) the throttle position sensor. I will start pulling it apart this evening but a problem will have to be obvious for me to be able to spot it I'm afraid. Thanks again.
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Post by GrumpyUnk on Sept 19, 2019 13:03:38 GMT -5
If you have computer controlled EFI, the computer has to know how far open the throttle is to be able to figure out whether you are 'driving' or 'coasting' so it can inject the proper amount of fuel. A MAF- Mass AIrflow Sensor - will tell it how many lbs/Kg of air is flowing into the engine at a given time, which helps make the mix closer to perfect. A MAP - manifold absolute pressure - sensor can tell the computer if the engine is idling or under low/no load when the vacuum is high, or hard at work, where the manifold vacuum is zero or close to it. Based on that load information, it can trim the fuel injected or plop in more fuel to a hard working engine.
So, I think if you look near where your throttle cable connects to operate the throttle, you should find a sensor that reflects throttle plate opening. If not, they are working using methods I know nothing about.
tom
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