TOOL OF THE MONTH
Ralph on multimeters.
If you have an electrical fault on your bike the only realistic way to find it is with a multimeter. When I was a lad the Avo 8 was the meter to have and was well beyond my pocket. Even then there were cheap and cheerful multimeters, but they were not especially accurate and weren’t in the slightest bit robust. There is still a massive range of meters available, from the high-end professional apparatus to the cheapest for occasional use. For this article I have chosen a range from the cheapest at a fiver (+VAT) to my own, which set me back around £300 (plus VAT Bastard’s pound of flesh) and they basically all do the same job. I am addicted to nice tools so always want to have the best quality tools I can afford. To be fair I do use my meter far more than the average classic bike enthusiast and being of such good quality it will probably see me out.
The cheapest one in the group actually has an
impressive range of functions including transistor testing for PNP and NPN semiconductors, though I reckon that if you had the skills to use that function, you would want a better quality instrument. If you are only ever going to do the most basic testing, very occasionally and don’t like spending money, this is the meter for you. Sealey gave me a meter, which jumped out of their range for me. It is the perfect test meter to take touring where space is at a premium as it folds away into an integral small case, with the test leads, not much bigger than a smart phone. It is cheap enough that you wouldn’t be distraught should something happen to it on the journey, but it has all the functions you would need to diagnose an electrical problem on a trip. I have already told Sealey that I want to keep it because I travel to rallies on the continent on my classic Kawasakis and due to its diminutive size, it will be ideal. A couple of years ago on my way back from Germany my 1977 Z1000A1 had a total electrical failure and I had no meter. One of the boys did have one, which he broke out for the first time ever. Sadly he had packed it assuming that it came with batteries; it didn’t (eh Chris?) Luckily another Zeddist had one complete with batteries and I was able to diagnose the problem – a glass fuse had failed, not blown, just fallen apart. Fortunately, I had a spare. Without a meter I would have been stuffed. I have tried all the basic functions of the little Sealy pocket meter and I was impressed by the accuracy and it will definitely be in my packing when I ride my Z1300 to the German Warsteiner rally in June.
Next up in camera is the Laser 5989, which is an eminently affordable meter covering all the functions a classic bike fettler will need at a very affordable price. An extra feature that seems to be becoming more widely found on meters is a thermocouple temperature sensor. You plug in a sensor wire and the end of it which measures temperature which is displayed on the meter when the correct range is dialled up. My meter also has this function and I have used it many times. Checking the coolant temperature on my Z1300 being one application. I also used it to check the temperature of my domestic oven in my workshop as temperature is critical when powder coating; far more so than cooking the Sunday roast! One thing I didn’t like about the cheaper meters is the necessity to select the correct range as you used to on analogue meters. The more expensive meters are auto-ranging, which means that you only need to select what you are reading, i.e. DC Voltage as opposed to DC Volts 0-20 volts.
The Laser 5990 is a serious automotive multimeter with loads of functions not found on regular meters, which you might find useful. It has dwell ranges set up for engines with 2, 3, 4, 5, 6 and 8 cylinders, but oddly not singles. Dwell is the time that the points are closed during a crankcase rotation. I personally consider contact breaker points to be the spawn of Satan and always replace them with electronic ignition on all my bikes, so this range would be superfluous to me. This meter also measures the engine speed in rpm, if suitably connected to the ignition circuit. For me, leaving the excessively expensive Fluke out of the running, this is the best workshop instrument as it has a lovely big display, which doesn’t require reading glasses to interpret, and has excellent build quality.
Classic motorcycle electrics are pretty simple and a multimeter makes tracing a fault within the remit of most DIY fettlers. The bike looms only look complicated because there are a lot of wires, but it is only a collection of very simple circuits, unlike the modern bikes controlled by computers.