Modern Vespa

Hi guys i'm wanting to screw a thermo couple directly into a cylinder head instead of the crappy aluminium rings that fit under the spark plug , does any one know what thread they are by chance ? i know they are not m4
thanks

Do yourself a favor and order the Koso branded water temp sensor.
I forget what size the are but they are wildly more robust than that pos that SIP sends with the speedo.

I broke two of the sip probes trying to install it into the cylinder head. Bought the KOSO one and had zero issues. I think it's an m10 for the Koso. The sip one is 4.5x.75 if I remember correctly. I'm not 100% on that part though

thanks for replying

Correct, it's M4.5x0.75mm. Really stupid dimensions but luckily I found a tap for it…

For future reference, I want to do same thing. Is there enough material to use a standard tap to start hole or do you need to start with a bottoming tap?

https://a.co/d/34h78E8


https://a.co/d/6YO8uvj

Question for Safis perhaps.
One thing to keep in mind - you want good contact of the tip of the unit on the aluminum hole bottom.
The larger 10mm units have a point.
I think the one you guys are opting for is a smaller diameter intended for fluid.
If it were me - I would use a flat bottom drill - or end mill - to give better contact at head of unit where it bottoms out.

Know that's not exactly the question you were asking - but something to keep in mind.

That's the tip that screws into the replaceable ring of Koso and Sip(koso) speedometers.

Not sure if you were answering a question or asking/

In any event - suspect you are well versed - but this is what I was talking about.

The one I used looks like this: https://www.amazon.com/Koso-BF100000-P1-0-Temperature-Sensor/dp/B004T8S0OW?th=1

The one from Safis looks considerably smaller - I'm not familiar with it.

that exactly what i want to do , the reason i want to use the slim thermo couple is its small size the 10mm one is quite alot of work to fit , now to get a drill bit and a tap

Here's a side by side pic of the SIP 4.5mm sensor and the Koso 10mm sensor. You'll have to get creative to sink in that 10mm sensor somewhere in the stock head.