THE GURU IM­PARTS MORE OF HIS KNOWL­EDGE OF ME­CHAN­ICS

Back Street Heroes - - CONTENT - WORDS & PICS: MR. BRIDGES

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.

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