Modern Vespa

Hi,

Would like to install a CHT on my P200.
The ring that goes under the plug will not fit, there is a recess on the head where the spark plug washer sits.
If installed without modification, there is no way the plug will seal on the cylinder head.



I could reshape the piece of brass the right way (same size as the plug washer), I believe this is brass ? This piece of metal function is a heat conductor to the probe I believe.

Would it be possible to drill a hole into the fin and directly plug the probe into it ? Or the temp difference would be so off compared to the ring under the plug ?

The base of the plug is in your scenario the ideal place for it.

Looks like you will have to modify that one you have to make it work. If you were to fasten it to the fin, you would measure the fin temperature and not the cylinder temp.

To drill you would need to be much closer to the plug than you show. It's possible to shave a fin down close to where the plug sits to allow you to drill a hole and thread it. This all depends of course on your understanding of what I describe and yoir skills level to pull it off successfully 👌

Likewise, dremeling off some portion of the interfering fins might be your best bet.

Sounds clever, this is the route I chose for the head of the Polini kit, I trimmed 2 fins



It clears the 21mm socket for the spark plug



And the cap also



Hope it won't affect too much the cooling

Nicely done, it's a pain trying to stop sensor from spinning while tightening plug.

I have a sensor under plug & another on head bolt.
It's amazing how by cooling the plug doesn't cool the head!
While you can cool plug area with a few twists of throttle, the barrel & head etc will take 5min or so to cool down (ie dissipate heat) & while it's still HOT the motor is still in seize territory!

They are usually 50f difference.

Who makes tnat sensor setip? And where does one obtain such?

I have the SIP one,

Got a cheap Chinese one from Amazon

https://www.amazon.de/-/en/gp/aw/d/B0BLMFH7NB?psc=1&ref=ppx_pop_mob_b_asin_title&th=1

Just to have an idea about temps
I may invest into a sip speedo with the probes, probably better quality and integration

Nothing wrong with Function before Form


If it works, it works!!

I'll buy one of those and fit to my Mk1 T5.

The reviews are mixed, mine works as intended.

Having a separate screen is a no no for me, I will probably get a sip speedo with all the infos into the speedo.
I took this one just for test purposes

I've bought a few like that one. The two issues is it'll eat batteries (6 months or so) and the temp readout is too small and cannot be switched with the RPM readout. I've gotten used to it but it takes an extra second to check on the temp...m

True ! But as I said, it is temporary.
You can switch it off in between rides, to preserve the battery, long press on both buttons together

Cor long term use you could always solder this in place of the battery

https://ebay.us/m/X6f7HL

I have one of those branded "Runleader" with CHT & RPM. It has a 12v connection as well as the coin-type battery. From Aliexpress I think.

Links would be good if you could?

I tried to find the same thing but they didn't appear to have it with a 12v input.

While looking I decided to get one of these along with a few different fittings, and it does have the 12v input. Using the Koso-type connectors it at least gives me some flexibility over the TTO gauge I have now.
I bought a couple of different threaded senders for experimentation as well as some under-plug ones.

https://www.aliexpress.com/item/1005009195441662.html
https://www.aliexpress.com/item/1005007556294934.html