THE GURU IMPARTS MORE OF HIS KNOWLEDGE OF MECHANICS
LAST ISSUE I WAS LOOKING AT THE MECHANICS OF ELECTRICS, SO TO SPEAK, AND AS LUCK'D HAVE IT THE NORTHERN GIT'S TRACTOR DEVELOPED AN OCCASIONAL RELUCTANCE TO START. THIS ISN'T UNCOMMON ON HARLEY-DAVIDSONS,
AND THERE'S A LOT OF INFORMATION OUT THERE ON THE INTERNET, NOT ALL OF IT OF ANY USE.
mefore getting too deeply into the subject, it might pay to clear up a little terminology. Evolution-engined Harley Davidson Softails from around the mid '90s have a starter relay and a starter solenoid (but, then again, so does a Yamaha R6). The terms aren't interchangeable; a relay is a switch that uses a low current signal to switch a different, normally higher current, circuit, and they can be used to turn one thing off when another thing is turned on or vice versa, or they can be arranged into banks to make odd things happen (some of the very first computers were built out of relays). A solenoid, on the other hand, works in much the same way as a relay, but what makes it a solenoid is that it draws a rod into a coil of wire, and it's the movement of the rod that makes it a solenoid. This can get a little confusing as, quite often, the movement of the rod's used to close a pair of electrical contacts, and switch something on. That might sound like splitting hairs but, in the case of the Harley and BMW air-cooled twins to name but two, the motion of the rod's used to engage the drive gear with the driven gear before the starter motor is powered up. Even if the solenoid isn't moving any gears, and just closing an electrical circuit,
then typically a solenoid will bridge two contacts with a separate piece of metal, whereas a relay closes (or opens) a single pair of contacts, so a solenoid's capable of handling a lot more current than a relay simply because it can deal with the increased mass of the contacts. Because the coil winding in a solenoid can be drawing quite a lot of current, it's not unusual to find a relay used to activate the solenoid, which is what the Harley has. So what happens when you start the thing is that your thumb presses a button, and closes contacts in the handlebar switch, which send current to the relay's coil - this creates a magnetic field that attracts a piece of steel, bending a spring, and causing another pair of contacts to close, and send current to the solenoid's coil, which creates yet another magnetic field that draws the moving part of the solenoid into the coil, which causes the starter gear to engage with the ring gear on the clutch drum just before the copper ring on the end of the rod meets the two hefty copper terminals inside the solenoid. Following that through, if you push the button on the switchgear, and nothing happens, the chances are that it's either the handlebar switch, or the relay. This, of course, assumes everything lit up when you switched it on, the battery isn't flat, and all the connections in between are good? More usually, though, you get the 'click of dread' where the solenoid gets power to its coil, and the rod gets drawn in, but doesn't actually make a decent contact. Sometimes it's more of a death rattle, as the solenoid does its thing and the battery voltage drops too low to keep the coil energised, so the rod returns to its rest position, which reduces the load on the battery, re-energises the coil, and the whole cycle starts again.
While all that's going on, the contacts inside the solenoid are likely to be arcing and pitting, making it harder to get a decent
contact. The normal cause of this is that the battery's past its sellby date, and repeatedly trying to start the motorcycle while the solenoid's buzzing is just storing up trouble for later - it's better to stick a set of jump-leads on it and start it. If jump-leads don't work, it might be time to look at the battery leads (and you probably need a battery anyway). Assuming all the easy stuff's been dealt with, and it's a good battery, then it's worth taking a look inside the solenoid. You can probably do that with the starter in place, but since we were doing an oil change, and having a look inside the primary drive, we opted to remove the starter since the oil tank was getting drained, and the primary was coming off anyway. The bolts that hold the starter to the inner primary can be undone with the oil tank in place if you need to remove the inner primary - I use a cut off 5/16"
Allen key held into a 5/16" AF 3/8" drive socket, and a ball-ended extension bar that lets the socket run at an angle to the extension (Figs.1&2). Then again, if you drain the oil by unplugging the drain hose (Fig.3), and take the tank off, getting at the starter bolts is simple.
Take note of the way the pipes from the oil tank are routed (Fig.4). The tank's held in by two bolts, accessible from the battery compartment (Fig.5), and two more bolts with nuts at the front that attach the tank to the frame brackets visible in Fig.4.
Either feed the positive battery lead through the oil tank (Fig.5), or remove it from the solenoid (Fig.6). The primary outer cover needs to come off to access the starter gear, and remove the bolt holding to the starter motor shaft (Fig.7). As far as I recall, you can't get the gear out without releasing the clutch, but unless it's damaged it can stay in place. With the starter on the bench, the three bolts holding the
solenoid end cover were removed (Fig.8), and the rod and its return spring pulled out to reveal the two contacts. Both the contacts and the rod were badly pitted (Figs.9 &10), and while they would've probably cleaned up, the Northerner'd spent money and bought a rebuild kit so that was installed (Fig.11). Spending money like this is probably why he's exiled to this end of the country.
With the rod out, and the retaining nut removed, the contact for the battery leads gets pushed into the housing, and removed (Fig.12). Then the short lead from the solenoid to the starter motor is dismantled in the same way.
The terminals will knock out of the contacts (Fig.13), and can be pressed into the new contacts in a vice using a suitable socket as sleeve. When refitting the contacts, check that the insulators are present, undamaged, and correctly positioned (Fig.14).
At this point the new rod and spring can go in (Fig.15), and the end cover can be re-installed, and everything should work as the factory intended. We fitted an aftermarket end cover that features a push-button that allows you to engage the starter motor manually (Fig.16) by pushing the button to move the starter gear into engagement, and close the contacts between the battery and the starter motor. Also it's shiny. It goes without saying that refitting the starter motor is the reverse of disassembly, I'd imagine.