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HB: Handlebars electro tach

vibrac

Well Known and Active Website User
VOC Member
#2
You need one with the correct color spot we have a white spot on our comet racer I think it is brown for a twin It should be supplied with a charging plug and lead with a blue ( resistor?) in the lead and a keeper plug which I keep wired to the bars
make sure you also get the thin alloy mounting which should come with it I have got through 3 set of mounting rubbers over the years they crack and disintergrate -does no-one make decent rubber components anymore...?
 

davidd

Well Known and Active Website User
VOC Member
#3
It is a widely used and very reliable tachometer. Assuming it is battery powered there is only one wire coming out of the body, which is an antenna wire that is wire tied onto the front plug lead. It only needs to know about the spark. The back of the tach is a particular color that is shown in the chart below. For example, I would use a white tach for electronic ignition or a yellow one for magneto ignition on a Comet.

http://www.scitsu.com/selecting-a-tacho-3-w.asp

Tim's advice is good. I made new rubbers every year with an exacto knife and some sheet rubber I had. They may last quite a while longer, I just did it as a seasonal thing.

100_1570.jpg

David
 

Nulli Secundus

Well Known and Active Website User
VOC Member
#4
I have a battery power Scitsu on my Rudge and wonder if these small Norton Commando oil tank rubber mounts, with appropriate nuts and washers, could be used as an alternative rubber mount. It might need a new, or modified alloy mounting bracket, but the rubber might be a little too rigid. What do you think?

https://andover-norton.co.uk/en/shop-details/15339/oil-tank-rubber-mounting
 

Nulli Secundus

Well Known and Active Website User
VOC Member
#5
Having now studied the Norton Commando oil tank rubber mounts I think they are far too stiff for mounting a light delicate instrument like the Scitsu, so a rubbish idea.

I have a battery power Scitsu on my Rudge and wonder if these small Norton Commando oil tank rubber mounts, with appropriate nuts and washers, could be used as an alternative rubber mount. It might need a new, or modified alloy mounting bracket, but the rubber might be a little too rigid. What do you think?

https://andover-norton.co.uk/en/shop-details/15339/oil-tank-rubber-mounting
 

greg brillus

Well Known and Active Website User
VOC Member
#6
They are very prone to vibration, not unlike most instruments. You need to be specific in telling them exactly the type of ignition you are running, as there are several versions dictated by the colour wire that goes to the HT Leads. Do not wrap the wire around the HT lead........It is taped or zip tied for about 75 mm in line with the HT lead.
 

MartynG

Well Known and Active Website User
VOC Member
#8
They are very prone to vibration, not unlike most instruments. You need to be specific in telling them exactly the type of ignition you are running, as there are several versions dictated by the colour wire that goes to the HT Leads. Do not wrap the wire around the HT lead........It is taped or zip tied for about 75 mm in line with the HT lead.
On my Comet I have an el cheapo electronic tach from ebay. At first I installed it as per the instructions with the pickup wire wrapped around the HT lead and found the tach reading to be unstable. After Gregs post I changed it to in-line with the HT lead and now the tach readings are stable. Good one Greg!
1523411744878.png
 

Howard

Well Known and Active Website User
VOC Member
#9
I've got Daytona clocks from Digital Speedos. They worked fine for 12 months, then following a bit of engine tidying the tacho needle sat quivering in the "corner" and the speedo acted like a rev counter. Somehow (old brain) I'd fitted non resistor plugs and caps, and one or the other has to have a resistor. Just a heads up if anyone else has this problem.
H
 

davidd

Well Known and Active Website User
VOC Member
#10
They are very prone to vibration, not unlike most instruments. You need to be specific in telling them exactly the type of ignition you are running, as there are several versions dictated by the colour wire that goes to the HT Leads. Do not wrap the wire around the HT lead........It is taped or zip tied for about 75 mm in line with the HT lead.
I think I agree with Greg, but I have found the Scitsu tach to be almost universal at the races. If kept on the original mount they are nearly indestructible and the batteries last forever. In contrast, I have had Elliot tachs that lasted a few minutes. The Scitsu on the racer is 10 years old and has never missed a beat.

The tachs are coded by the color of their backs. For a single with a magneto it is yellow and for a single with an electronic mag or ignition it is white. I would use what they specify so that they will stand behind it. The tachs are "potted" and cannot be taken apart.

David
 
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