Modern Vespa

Hi

Have just installed a temeperature sensor on the spark plug on my PX200 and getting some strange readings.
The temperature is reading as 118c when the weather temp is 18c and then after starting the engine the temp readings go up as follows;
119c goes to 220c
229c goes to 330c
339c goes to 440c
449c goes to 550c

Have checked the cables and changed the sensor ring but no luck, anyone else seen or heard of these strange readings?

Any help/thoughts appreciated.

Something is definitely wrong there.

With a cold engine, the CHT should basically match air temp.

Likewise, you should hopefully never see an under-plug temp above 175C if it's reading correctlly, though it won't necessarily lead to a seize if you're running an aluminum cylinder.

And while I love my gauges at least as much as the next guy, I don't let myself forget that the CHT isn't magic. An under-plug sensor's numbers lag actual combustion effects by about 45 seconds, even when it's working correctly, so it's more useful for trend detection and variation from expected readings, e.g. "My temps should be 125C for extended riding at this speed, but today they're 140C...something is off."

And welcome to NSM!

Go to Settings -> ADJ 1 and make sure you have Celsius selected and not AFR…

Else, you need to try a new sensor, they tend to fail easily…

Thanks Safis, I think youre on the right track as my Speedo is set to APR7 but instead of being able to change from C to F my only option is miles to KM (same as SPEED option).

Now I am not sure if I have a dodgy speedo or the sensor......

Really makes no sense and cant find a way to factory reset the whole speedo which may cure the fault.

Anyone had this issue or ideas?

Holding the set button will take you to the next option so eventually you will reach the temp setting…

I get the AFR7 flashing on the ADJ 1 setting but my only option is miles or KM not C or F. If I carry on holding the button it reverts back to the ADJ 1 setting flashing.

Its a bit frustrating as it should flash C or F next to AFR7 and not just miles I think. See image.

The AFR7 is actually RPM and is to set the needle for tachometer or speedometer. Press the button once to cycle through options and keep it pressed to save…

Thanks Safis but there's nothing with C or F to scroll through. The RPM setting option is only miles or km.

Will change the sensor cable and contact SIP as something isn't right.

All the videos I can find are showing RPM setting adj C to F.

Will update if I get a solution in case someone has the same issue.

Read carefully please.

Thanks Roland, unfortunately I am missing C or F above the mile or km option (see pic above).

The 3 second hold only moves the flashing options from ADJ 1 - to mile or km - to SPEED or RPM - and back to ADJ 1. No C or F option in any category.

Also have a look at my pic below which shows the temperature at 117c when the engine hasn't been started all day - ambient temp was about 17c.

Totally incorrect temperature values. The engine would seize at that temp.

Thanks all for responses, SIP believe the speedo is faulty and have requested it back to them.

Hopefully will get a new working speedo back soon.