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CHT Sender route?

Technical help for Series one, two and three Lambrettas. Models include the Li, Li Special, TV, SX, GP, Serveta and API/SIL models

CHT Sender route?

Postby LateAgain » Wed Feb 11, 2015 12:37 am

My first attempt routing my Skydrive CHT sender cable didn't last very long. It's an 'under-plug' mount and to get it back out of the plug hole means bending up the mount 60-90' for the cable to exit. This causes hassles when doing up/undoing the plug as the plug spanner fouls the cable mount. I think this subsequently caused the sender to fail as the wires came away from the mount.

So with a replacement sender FOC :D from Skydrive I'm looking for a different route under the plug... anyone else had to do this without bending up the 'under-plug' mount, and how have you done it? I'm thinking of following the horizontal head fins away from the plug hole and then bring the cable out of the cowling... but not sure of best way to cut the cowling. Thoughts? Cheers, Paul.
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Re: CHT Sender route?

Postby peejay » Wed Feb 11, 2015 1:37 am

i'm using a gamma RT 1000
it comes with under plug mounts in the kit, didn't like the look of them one bit, knew i would have the agro you mention with yours.

went for fin mounting instead.

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using the standard plug spanner there is loads of room

Image

with plug cap fitted there is at least 10mm clearance

with probe removed it is easy to remove head cowling over the fixing point to check head nuts
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Re: CHT Sender route?

Postby coaster » Wed Feb 11, 2015 9:46 am

If you are going to use the sensor under the plug (best place for it tbh) you need to modify the head by cutting a channel to allow the sender lead to lay flatter. However, the rings are not very robust and don't survive many plug removals as they are made of very soft metal. I read recently that the ring can be placed over the porcelain insulator so that it is in contact with the metal part of the plug and held tight against it with a short offcut of petrol pipe. I've not tried this myself yet but it was said to be almost as effective as under the plug. As already mentioned, some people bolt the sensor to a fin which will work but the readings you get will be significantly lower and more importantly, will be slower to react to temperature changes.

One other point with the skydrive sensors, they have 2 sections of stiff single strand wire at the sensor end which are twisted together. The wires are of different metals which when in contact with each other will produce a small electrical current which rises with temperature. The twisted ends are simply 'crimped' onto the ring so if yours have pulled out, it is possible to re-crimp them. Mine actually snapped but under instruction from Skydrive I managed to straighten out the original ring and re-crimp using a pair of mole grips. That lasted ages until the ring split whne replacing the plug one time too often.
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Re: CHT Sender route?

Postby LateAgain » Wed Feb 11, 2015 12:48 pm

Cheers lads. I was thinking of a route thru the head Coaster but do like the idea of the sensor sitting over the top of the plug and resting on the metal section held in place with pipe, less fettling to be done. Would this in effect though be measuring the heat of the plug as opposed to the head temperature?

When speaking to Skydrive they said the two wires required 'welding' together but not conventional welding so resupplied one. Bloody nice bloke.
Last edited by LateAgain on Wed Feb 11, 2015 12:51 pm, edited 1 time in total.
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Re: CHT Sender route?

Postby LateAgain » Wed Feb 11, 2015 12:49 pm

PJ, does your probe just sit in the bracket then?
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Re: CHT Sender route?

Postby coaster » Wed Feb 11, 2015 4:24 pm

LateAgain wrote:Cheers lads. I was thinking of a route thru the head Coaster but do like the idea of the sensor sitting over the top of the plug and resting on the metal section held in place with pipe, less fettling to be done. Would this in effect though be measuring the heat of the plug as opposed to the head temperature?

When speaking to Skydrive they said the two wires required 'welding' together but not conventional welding so resupplied one. Bloody nice bloke.


I'm sure he told me they were twisted but either way, that's what I did, only two twists was enough and dangled in a kettle of boiling water is still read 100 degrees afterwards.
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Re: CHT Sender route?

Postby jonashford » Wed Feb 11, 2015 7:47 pm

coaster wrote:If you are going to use the sensor under the plug (best place for it tbh) you need to modify the head by cutting a channel to allow the sender lead to lay flatter. However, the rings are not very robust and don't survive many plug removals as they are made of very soft metal. I read recently that the ring can be placed over the porcelain insulator so that it is in contact with the metal part of the plug and held tight against it with a short offcut of petrol pipe. I've not tried this myself yet but it was said to be almost as effective as under the plug. As already mentioned, some people bolt the sensor to a fin which will work but the readings you get will be significantly lower and more importantly, will be slower to react to temperature changes.


Correct, modify the head and the sensor sits perfectly under the plug, mines been that way for 2 years no problem with seating etc.

Did anybody read the sip speedo article in Jetset???? Very good idea to sit the sensor on top or the plug next to the metal that contacts the head, secured with a piece of pipe, very simple and it works
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Re: CHT Sender route?

Postby Cheersdude » Wed Feb 11, 2015 8:21 pm

Here's the method I used (well the guy who built my engine used) the sensor came with a koso temp gauge
Image
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Re: CHT Sender route?

Postby coaster » Wed Feb 11, 2015 9:21 pm

jonashford wrote:
coaster wrote:.........................I read recently that the ring can be placed over the porcelain insulator so that it is in contact with the metal part of the plug and held tight against it with a short offcut of petrol pipe. I've not tried this myself yet but it was said to be almost as effective as under the plug........


Did anybody read the sip speedo article in Jetset???? Very good idea to sit the sensor on top or the plug next to the metal that contacts the head, secured with a piece of pipe, very simple and it works


Yes, I did ;)
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Re: CHT Sender route?

Postby LateAgain » Thu Feb 12, 2015 5:15 pm

Set up the sender mount over the top of the plug method yesterday and held in place with a rubber tube. Trouble is that this doesn't leave much room for the plug cap to 'hug' the porcelain part of the plug to hold the cap in place. I haven't taken the bike out yet but don't think the plug cap feels very secure perched on the top of the plug after cutting down the shroud. Might have to re-visit this eve?
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Re: CHT Sender route?

Postby dscscotty » Thu Feb 12, 2015 10:53 pm

Trim the pipe to allow the cap to fit properly, I've done thousands of miles with this method (plug) I recently sent an article to jet-set with pics etc. It'll also be in scootering sometime some as they requested the article to. I'll post them on here sometime soon,
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Re: CHT Sender route?

Postby LateAgain » Thu Feb 12, 2015 11:58 pm

Cheers Scotty, pics would be good, not been in garage since but having trouble thinking how the small length (10mm?) of tight fitting tube is easy to get hold of and take off when you want to get the plug out. Any thoughts on a jubilee clip?

I'll have to dig out Jet Set...
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