SIP temperature sensor. A warning.
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Hooked
PX125E
Joined: 06 Oct 2018
Posts: 146
Location: Gravesend, Kent, UK
Thu May 30, 2019 9:24 am quote
Hello. I fitted a SIP speedo which includes a temperature measuring device which screws into a special Spark plug washer.

I thought a better idea was to screw it into a cooling fin. (Best would screw it into the Head). I drilled a hole and a a gap in the fin next to it.

I bolted it up and discovered the 4MM bolt is in fact hollow and the sensor is right at the end. How? By snapping the bloody thing off and now weighed out £18 for another one. I Lightly tightened at the end using Locktite and tight as I dare go.
Member
Joined: 15 Mar 2010
Posts: 45

Thu May 30, 2019 1:48 pm quote
Your other mistake is attaching the sensor to a fin. The important temperature to read is at the head, where the plug is. If your fin gets hot enough to give you concern, your cylinder will be much, much hotter, and probably seized by then.
Ossessionato
05 Stella, '62 VBB, 76 Sprint V, 63 GL
Joined: 16 Jun 2011
Posts: 2268
Location: Chicago. Well, Evanston, but that's almost Chicago
Thu May 30, 2019 2:43 pm quote
I belive the SIP speedo will also take the Koso sensor that's designed to be threaded into an M10 tapped hole in the cylinder head. I don't love the fact that the Koso sensor chews through CR2032 batteries, but it's accuarte and has a great display.
Hooked
PX125E
Joined: 06 Oct 2018
Posts: 146
Location: Gravesend, Kent, UK
Sun Jun 02, 2019 10:20 pm quote
jambretta wrote:
Your other mistake is attaching the sensor to a fin. The important temperature to read is at the head, where the plug is. If your fin gets hot enough to give you concern, your cylinder will be much, much hotter, and probably seized by then.
Thank you. Plan B. I drill a hole and screw it in directly. I don't like those spark plug adaptors.
Hooked
PX125E
Joined: 06 Oct 2018
Posts: 146
Location: Gravesend, Kent, UK
Mon Jun 03, 2019 11:23 pm quote
Help
Hello.
Iv'e decided to screw it into the head but I'm not sure what the thread size is.
they're made in Canada by Koso and it's between 4 and 5 mm. would it be UNF?
Ossessionato
1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 4902
Location: So Cal
Tue Jun 04, 2019 6:09 am quote
It is an odd thread ... takes a special tap.. be careful. Just use the spark plug sensor, it gives a more accurate reading. I donít see why people donít like them, Iíve never had any issues.
Hooked
Bodgerific 150 Super, 50s in progress
Joined: 18 Aug 2016
Posts: 265
Location: Melbourne, Way Downunder
Tue Jun 04, 2019 6:42 am quote
I bought the special M4.5 tap.

Trimmed a fin for clearance.

Measured thrice so I wouldn't break through or create a hotspot.

Taped off a long drill bit to make the hole the exact length.

Carefully drilled and tapped.

Hand screwed in the Sip sensor, with a little high temp Loctite.

Pulled out a teeny tiny spanner to nip it up.

Snapped the bastard before I got close to finished.




gone to a spark plug sensor. (On a TTO gauge, 'cos SIP speedos are great for everything except trying to read CHT outputs at speed.)
Ossessionato
2 matching N.Z. '69 VBC Super, 177cc Racer, VespaCross Bodge, Puch SRA150, Piaggio Zip 100! & others
Joined: 26 May 2013
Posts: 3839
Location: Millbin, Ostrayleea, mate
Sun Jun 09, 2019 12:44 am quote
jambretta wrote:
The important temperature to read is at the head, where the plug is. If your fin gets hot enough to give you concern, your cylinder will be much, much hotter, and probably seized by then.
I don't agree fully... Having overheated & seized many engines, & having brought/broken numerous sensors, i had an extra TTI display, so got another sensor...

Now have: 1 under the PLUG, & 1 on head-stud bolt (on the extension bit that holds the cowl on)...
During a 3500km ride there was lots of nothing to do, but i was having continual overheating issues, so learnt the following;

SPARKPLUG area/sensor heats up QUICKLY.
A heap of on/off the throttle dramatically REDUCES the PLUG/COMBUSTION area TEMP... this is due to adding lots o cool FUEL (someone can correct that "fact")
50f temp drop was possible pretty quickly!
BUT.... this in ONLY A TEMPORARY MEASURE!

The HEAD BOLT area/sensor is much SLOWER to HEAT UP...
It is also (dramatically) SLOWER to COOL DOWN, as it is relying on AIR to cool it.

After a long time running there was exactly 100f (unusually it was generally 100f, possibly 102f, so i guess its a minor difference depending on ambient temp)...

By using FUEL to cool the plug worked, BUT the (plug) temp would go back to pretty much the same place a minute later... it needed the entire CYLINDER (bolts etc) to cool down before the "overheating" was resolved, this took about 10min.
Member
PX 125/Polini 177
Joined: 07 Jun 2019
Posts: 22
Location: Gloucester UK
Sun Jun 09, 2019 2:24 am quote
Spark plug sensor
Just fitted a TTO sensor, as the actual sensor sticks out to one side of the washer part, it would not drop to the bottom of the recess around the spark plug, this on a Polini head. If tightened up it would no doubt break the sensor. I needed to remove a bit of metal to allow it to seat properly, the trusty Dremel grinder did this. You need to plug the spark plug hole securely so no bits get into the cylinder, of course. Not sure if this would be necessary on a SIP unit.
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