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mp3 500 sport
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I've rebuilt engine new barrel and piston I've done compression test it's reading 152 psi is this good hoping it will get better when engine is run in also noticed plugs are black I think this is due to new throttle body needs setting up comment appreciated
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The Hornet (GT200, aka Love Bug) and 'Dimples' - a GTS 300
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How are you measuring the compression - did you somehow disable the valve lifting device that aids starting?

The only set-up for a new throttle body is to reset the TPS - and this is the ONLY time that should ever be done.
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mp3 500 sport
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I used compression tester no I didn't disable lifter I didn't know how I just removed plug and took ht leads off think bike will be going to derby via moto for re map
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That photo was of my piston on mp3 500
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If you're getting 152psi with the valve lifter still operational, I'd call that a good reading. It'd go up quite a bit once the engine is running.
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Cheers jimc got to book it in now for fuel mixer being off
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152 psi is 11.3:1 compression. The spec is 11.0:1 for the Master 493 engine. I'd say you're fine.

Plug chop method for mixture isn't as accurate as your ECU and oxygen sensor does automatically, even if you could change it. Just let it figure itself out, which it will do after a few dozen miles. It will run rich until it does.
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Oxygen sensor I've had trouble with from day one of having bike that's why I ended up changing throttle body . I had a broken wire in loom I repaired it using silver solder changed sensor 3 times still came up lambda sensor fault I get a reading on 02 sensor as in photo can't understand why I keep getting same fault . Been told I can get lambda sensor emulator thinking of trying this if shop can't cure fault
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Does your CEL come on? If not I'd be suspecting your home-brew diagnostic scanner is mistaken.
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You mean engine light if yes it does
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I took bike to piaggio at Sheffield which they told me same 02 sensor was at fault like I said I cannot think what to do next changed sensor three times and new throttle body . I could understand why when wire was broke but was told by a electrical engineer to repair using silver solder due to continuity of wire but didn't alter fact that Sheffield via moto said it was 02 sensor still even tho I had changed it for third time
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Piaggio MP3 500
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Normal 60/40 tin/lead solder is fine. Electronic grade silver solder isn't that much more conductive since it's 97% tin anyway.

You need to find the wiring loom problem. Ohm out the wires from the ECU (throttle body connector) to the oxygen sensor. Inspect the connectors carefully. There's still a broken wire, I believe.
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I've alreany done that I stripped wire back from 02 sensor all way back to throttle body could only find one break in wiring harness that's why bike doing my head in
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Have you checked your repair for continuity?
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I got same reading on both wires that's what I can't understand tested from 02 sensor right to throttle body same readings
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What reading - 0 ohms I hope?
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mp3 500 sport
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Can't remeber what it was but know at time I did it they was same just spoke to dealer he said it could be conector going to ecu not connecting right so I'll have another look can't very well test again as it means stripping bike down yet again to get to wiring loom
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Yeh it was in ohms when I did it not that daft some would say different lol
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Veni, Vidi, Posti
2008 MP3 500, 2013 BV350, 2020 Vespa Sei Giorni, 2008 Vespa S150
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Veni, Vidi, Posti
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novak0797 wrote:
Can't remeber what it was but know at time I did it they was same just spoke to dealer he said it could be conector going to ecu not connecting right so I'll have another look can't very well test again as it means stripping bike down yet again to get to wiring loom
You just have to get to the harness at the throttle body and at the lambda sensor to test. If not 0 omhs you have an issue with your cabling still.
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