We look at what to check to give your bike the best chance of starting every time
Picture the scene; you’ve had a lovely ride to a bike meet, with plenty of admiring glances towards your machine. The light is starting to diminish, so it’s time to go home; but will it start? Do you wait for everyone to go home and feel your way in the dark or do you try to kick it into life while all those onlookers quietly snigger as it doesn’t fire into life? Anyone who owns a kickstart-only bike will be familiar with this particular scenario – so let’s have a look at some simple checks that you can do to give your bike the best chance of starting first time, every time. This is aimed at British bikes, so if you’re working on a more modern bike, check your manual for exact settings.
This is the easiest check and it can also give you an idea of how the bike is running generally. Take the spark plugs out after a good run (they’ll be hot…) and check the colour. If it’s too black but dry, your bike may be running rich, so you need to lean the mixture. Try opening the air screw or adjusting the mixture screw. If they’re white, you could be running too lean, in which case you need to richen the mixture. If the plugs are black and oily, then this could show that your rings are wearing or the valve guides are tired and oil is getting into the compression chamber – that’s a bigger job. Light tan colour is perfect, too white the bike is running lean. These colours could mean you have the wrong heat range of spark plug – check the numbers against the recommended plug number. While your plugs are out, make sure the gap is correct. Bikes with a magneto like to run at around 0.018 – 0.020 thou, while coil bikes prefer a gap of around 0.020, but have a word with fellow owners and see what wisdom you can pick up. Finally, when refitting, use a little smear of copper grease to make them easier to remove next time.
HT leads and cap
A spark needs a good supply. So the HT (high tension) lead from the mag or coils needs to be checked for any splits or cracks. Then have a look at both ends, to make sure there are no issues and that they are sealed to prevent water finding a way in. Also have a good look at the plug cap. These should be non-suppressed, because the suppressed caps reduce the spark and check that it’s in good order with a tight fit to the plug. Suppressed caps are okay on electronic conversions, like bikes fitted with a Boyer or Pazon system.
Read the full story in CBG July 2018