Classic temp: gauge

[johnbirchjar]

Hi guys,The engine temp: gauge needle on my Classic never goes down to the 50c when the engine is cold,just sits above it (10 degrees?)does this mean that the temp gauge is reading "fast"? e.g.engine cooler than temp gauge indicates?answers quickly please,I'm off to Spain on Wednesday and would feel a lot happier if the old girl was running a bit cooler than the indicated 150c that was reached on a run out in Devon recently,hope to see some of you guys on the ferry or at the rally,ride safely,regards,J.B.

[MrB]

Hi John,Is this with ignition on or off? My temp gauge was reading higher than usual. It would fluctuate when hot and the bike was moving and I noticed that switching the lights on increased the temperature by 10 degrees! I traced the fault to a poor instrument cluster earth.By the way, Graham sells a lower temp thermostat and also a lower temp fan switch. I had some trouble getting the thermostat housing to seal properly until I noticed that the ridge on the new stat was taller than the old. A quick squash in a vice and filing the edge back to size solved that. With a deeper matrix rad to boot MrB (that's the bike) now sits at a steady 85 degrees even in slow traffic and 28 degrees ambient air temp.I'll be going on the Santanader ferry but on Friday from Plymouth and in the car! Start day of the family holiday. If you (or anyone else) is taking a later crossing and fancies meeting for a beer on the ship my number is 07919 216824.Johnny

[johnbirchjar]

Hi Johnny,The guage reads the same,ign on or off,and the Classic is air cooled, so no fan!!and I dont think a lower temp thermostat would be the answer,enjoy your vacation,and have a safe trip.regards,J.B.

[Interpol2471]

John it sounds to me that you have a damaged Thermocouple wire. I have seen it on a couple of air cooled bikes including my own IP2 where the wire that runs over the top of the engine has broken down and the insulation melted. This caused the bikes to give inconsistent readings but was fixed by replacing the thermocouple (easier said than done) with a Norton item or on my IP2 with a Thermocouple bought from a known aution site for a couple of quid that worked to the same standard as the original. If I remember correctly it is the 'F' British standard Blue and Brown wire type but I made notes and can check if this is the case. The fountain of all knowledge Mr. Negus also told me that the Temp gauges are often damaged by people putting 12v across them which damages the needle winding causing them to read high so this may be the case also.Regards Paul

[Richard Negus]

Paul is correct that the VDO gauge requires a thermocouple wire which is no longer an industry standard. The correct wire is available, but only if you're very lucky finding a small piece or can afford a 100metre reel.However, just having fixed a broken thermocouple wire on a 1983 bike, I found that you only need a short length of thermocouple wire at the engine end and the remainder can be ordinary copper wire. It's the 'hot' junction of the two wires that creates a voltage and makes the gauge work ; length of the wire is not important.The original wire had broken just above the engine and, as is usual, the brass end fitting sheared off in the rotor housing. I modified an oil pump banjo bolt by drilling straight through, silver soldered the ends of the thermocouple wires into a brass nipple, sleeved with heatshrink and fitted bullet connectors at the other end. It worked fine - suppose I should have taken a photo before installing it in the engine.

[Interpol2471]

There's a First

[Richard Negus]

Well, you can't be wrong ALL the time.Quiet in 'ere, innit. 'Spose the noisy ones have all bu@@ered off to Spain.

[Interpol2471]

I found the thermocouple type that I tested the link is :-http://cgi.ebay.co.uk/10-ft-K-Type-Ther ... e534Cheers Paul

[commando-rotary]

Hi Richard this noisy bugger now back from spain it was very hot but the commander behaved itself till the the daft sod sitting on it fell off dohD G

[Richard Negus]

Photographs ??

[johnbirchjar]

Hi Guys,another noisy bugger back from Spain(and France,)the memsahib & my sister rented a car and I joined them in southern France for a week after the rally, thanks for the input on the temp:gauge,I shall explore all avenues.I hope you and bike are o.k.D.G. and all the rallyist returned safely, and Richard,I did roughly the same miles as you on your trip round the Isles,but used less oil (3.1/4pts)but more fuel I would think.ride safely,J.B.

[johnbirchjar]

Hi Guys,I've had a good look for the thurmothingy on the Classic and could'nt find it near the spark plugs,found what I think is the engine probe,and along side that is a round hard plastic thingy(a bit smaller than a 5p piece in diameter, and about 3/8" deep) with two blue wires fixed to it with spade connectors,this sits in a round cage, secured with two small screwdriver headed bolts,this and the probe are situated on the casting on the right hand chamber where the carburator intake enters the chamber,no burnt or broken wires,the plastic thingy and cage are all of a one item,and when I took it off the casting the plastic thingy had a chrome bottom!! which was covered in that crap one gets on battery terminales(the casting under the cage was well coated also)I gave them both a good clean and put them back.I fired the old girl up,she ran o.k.I will give her a good run tomorow and see if the plastic thingy is the thurmo thingy,sorry if I'm not very technical,I just can't remember the names of things anymore(It's me age guv!)regards,J.B.

[Interpol2471]

John what you found is the temperature thermistor that controls the fast idle, all this does is switch in an earth to tell the ignition module to change the retard that controls the slow idle once the engine is at temperature instead of a fast idle while cold. This has nothing to do with the temperature gauge on your instruments this is controlled by the thermocouple which is a small brass coupling with a brown coated wire that is just above the right hand spark plug when viewed from the front.Hope this helps to sort your thermistors from your thermothingies

[Richard Negus]

covered in that crap one gets on battery terminales,J.B.

And that 'crap' is the white heat conducting paste to ensure the best conduction of heat from the casting to the switch! Doesn't make much difference though, it works just as well without, as you've found. R.