Replacing the intermittent bulb holder and checking the dimensions of that rear speedo screw.

Replacing the intermittent bulb holder.

Right, as mentioned earlier someone pulled out some wires from under my speedometer a few months back while the bike was parked, probably searching for particular wires to steal the bike. Anyway, as we saw I repaired the one broken ring clip on the one wire but was missing one of the screws to make my fuel gauge work, which got pulled out. I also developed an intermittent fuel gauge light as the one wire had got pulled from the rubber holder. Well, seeing as I was in no rush to illuminate a fuel gauge at night that wasn't working anyway, I hadn't gotten around to fitting the replacement T10 bulb holder mentioned before, as there was no real point!

However, as I need to measure the screw needed to be replaced (or it wont ever be fixed), as Lexmoto doesn't stock it as a replacement part. And need to take the speedo back off to do this, I may as well swap the bulb holder for the new one at the same time. Now of course I will have to remove one of the other 'same' screws and measure that one.

Were basically just cutting off the old rubber bulb holder as close to the holder as possible to give us more wire to play with. You could trim the wire down on the new holder if you want but, I'm leaving it at full length as there is nothing under there (speedo) anyway, it's not exactly tight for space. And should you ever need to to re-trim and re-join in future there is plenty left to do so. 

We remove some insulation and expose the copper wire on all the wires we are going to join. Not too much, about as much as I have done. Firstly we are going to turn on the riding light so the speedometer also lights up. We won't use much power with the riding light but,will with the headlight without the engine running! With the speedo on put a bulb in the new holder and touch the wires to the other wires we have prepared to check the bulb lights.

Now, because bulbs are essentially a joined electrode in gas it should work no matter which way around we touch the wires. L.E.Ds however may be different. Now here the colours of the wires are different anyway on the speedo and the new holder. The way the T10 bulb connects is identical either side as well so it really doesn't matter as you could turn an L.E.D around if it only worked one way anyway. This is probably why the wires are oddly colored, for example black or blue is usually negative polarity (-) and red or brown is usually positive (+). On the speedo we have green and brown wires, I might take brown to be positive but you cannot be sure without a meter to test. On the new holder we have blue (usually negative) and white. So since I would never join blue and brown on principal, I chose to go the other way around. Brown to white and blue to green. Another important factor in checking is to make sure the new holder is in good working condition before we hard solder it in place. 

I am going to solder them and use some heat-shrink sheathing to insulate the join as I now have some here, you could use electrical tape but it's not as good an option. It looks tatty and less professional but, is ok for a temporary solution. It's best to lightly coat each wire with solder then join them together with the heat, as the solder melts together across both wires. Not too much solder or you won't slide the heat-shrink sheath over the join. Once the sheath is in place it should be shrunk with a heat gun or strong hair dryer. My heat gun decided to give up the ghost (it's been a DIY workhorse over the years for me) so I used a hair dryer in this instance, which worked fine.

Once that's all done you can check your bulb is working properly & put it all back together again.

Checking the dimensions of that rear speedo screw.

Ok, so there's no spare part available / listed to just go and buy this part, so the only thing to do is buy a new speedo or one from an online breaker which is still about £30.00. Thirty quid for a screw! No thanks so we are going to do what we did with the bolts for the luggage rack; check the thread, measure it up and find an alternative replacement.

Now the brass screw is an electrical connector, it joins the wire by the ring connector at it's head to where the end of the screw connects inside the unit. Because of this the screw cannot have any thread lock applied or it will block the electrical signal by insulating the end. Because of this thread length is important, as it needs to make that connection.

So going through my dies I get a perfect fit for M3 x 0.5 pitch. The thread length is about 22mm overal length about 24mm with the cap but since you will find it hard to find one exactly the same just go by the thread length.

I found some steel hex cap head screws with the same dimensions on eBay and ordered them. Now electrical oriented screws generally tend to be made from brass, maybe due to conductivity but, I don't really see the steel being that much of an issue here. Even though a lot of places actually have brass down as quite a poor conductor, it seems to be better than steel. There is copper in it's make up. There are no brass screws in those dimensions with that head type, only a conical /countersink type head which won't connect to our ring connector properly. 

 (table courtesy of Metal Super Markets).

Material IACS (International Annealed Copper Standard)
Ranking	Metal	% Conductivity*
1	Silver (Pure)	105%
2	Copper	100%
3	Gold (Pure)	70%
4	Aluminum	61%
5	Brass	28%
6	Zinc	27%
7	Nickel	22%
8	Iron (Pure)	17%
9	Tin	15%
10	Phosphor Bronze	15%
11	Steel (Stainless included)	3-15%
12	Lead (Pure)	7%
13	Nickel Aluminum Bronze	7%

* Conductivity ratings are expressed as a relative measurement to copper. A 100% rating does not indicate no resistance.