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Hi , I've just fitted a spark plug temperature gauge. I started it up to see it working but the engine started racing so much that the scooter was moving around on the stand with the vibration. The only thing I did engine-wise was to remove and refit the spark plug to fit the sensor ring.

I'm baffled - anybody got any ideas ?

Sounds like you've got an air leak ?

Have you tried taking the sensor off and trying it ?

Yes Mick , I did but was still the same. Should've said in the original post that it was running fine until today.

The clue is in the actions that you performed.
You have an air leak at the spark plug.
Take the sensor off and refit the spark plug and push the sensor ring down on top of the metal part of the plug and secure with a piece of rubber fuel pipe or similar overy the porcelain part of the plug. It was in Jetset a while back. It won't be entirely accurate but you will have a reference point.

Maybe a leak test required ?

Have you checked to see if the slide/throttle is stuck open on the carb' ?

Cheers Chris , I'll try that and yes Mick I did check throttle & carb and they were fine.
Thanks for your replies - I'll let you know how I get on.

SILGP wrote:Hi , I've just fitted a spark plug temperature gauge. I started it up to see it working but the engine started racing so much that the scooter was moving around on the stand with the vibration. The only thing I did engine-wise was to remove and refit the spark plug to fit the sensor ring.

I'm baffled - anybody got any ideas ?

Sorry to not be able to offer any advice, but where did you get your sensor ring for spark plug from? I've been looking everywhere and for something so simple, I ain't found anywhere that sells them.

Cheers fellow SIL lover

If you google 'A C Services trail tech' you should be guided to their website. They have a page with extension leads for the spark plug rings.

Cheers SIL

Try a new spark plug,you may have damaged the sealing ring on the old one when you tried to fit it with the temperature gauge.

The TTO sensor fitting instructions advice to remove the ring!
Cheers Shane.

Cheers Shane , I did remove the ring and also tried another spark plug with the ring still in place but it made no difference. I'll keep checking things to try & suss it out.

Thanks for all your replies.

How did you get on with this problem.
Stag

SILGP wrote:Hi , I've just fitted a spark plug temperature gauge. I started it up to see it working but the engine started racing so much that the scooter was moving around on the stand with the vibration. The only thing I did engine-wise was to remove and refit the spark plug to fit the sensor ring.

I'm baffled - anybody got any ideas ?

Coincidentally perhaps with your issue, I set about having a go @ this pressure testing malarkey as I happened to have a 20 x 2.25 inner tube with punctures so that is where I made the cut & fitted it on to the inlet & exhaust pipe (quite a stretch!) Unlike other Forum User’s versions, I kept the Schrader valve in & just put some air in...So my version is probably the cheapest of the cheap because I found the whole bike in the street!

However, the only point I found to leak was @ the spark plug!

A brand new plug & seal leaked, but I must mention that the cylinder head has a threaded, ‘solid’ insert that does result in a raised shoulder.

I managed to cure the leak there by refitting another plug with one of those solid copper washers that you get specifically for that purpose.

It may be all that you need! BTW under-plug heat sensors are notorious for leaking in the air-cooled VW World as well as ours...

If you get stuck, I’ll send you a washer that I speak of FOC. Let me know, eh?

(Hi Kenny! )

Hi all , In the end I took it to Chiselspeed as I was getting nowhere with it. Turned out to be a knackered carb rubber - nothing to do with the sensor ring / plug - just a coincidence that it happened as I took the plug out.
Thanks for all your replies & offers of help.
Tony.

Just to add to what WT said above, I did a leak down test on a GT240 that I'm building last week and also had trouble with the plug sealing with an SIP eht sensor ring or a new plug with its sealing washer. I ended up smearing Copper Slip lightly on the thread and also the sealing ring and that cured it.