Tech Torque

This month: Ca­ble bust or in need of re­place­ment? Gears not se­lect­ing prop­erly? Cables are the most seem­ingly in­nocu­ous item on a scooter, but when badly fit­ted or main­tained can be the cause of many prob­lems. Time to take a look at set­ting them up proper

Scootering - - Contents -

Stu Owen looks at ca­ble rout­ing and set-ups in this month’s Essen­tial Main­te­nance.

The job of the Lambretta ca­ble sys­tem is to link the hand/foot con­trols to the rel­a­tive me­chan­i­cal items which drive and stop the ma­chine, and with only six cables re­quired to do so, the sim­plis­tic de­sign works well… if looked af­ter! Quite of­ten this is not the case, and as the cables are con­stantly in use it’s usu­ally out on the road where one gives up and lets you down. How­ever, with rou­tine and reg­u­lar main­te­nance they will give the rider thou­sands of trou­ble free miles. From time to time it may be that ca­ble re­place­ment is re­quired and this can some­times give own­ers prob­lems if they are un­sure of how to route cables or set them up prop­erly.

In this ar­ti­cle we will look at the four cables re­quired to drive a Lambretta. The clutch, throt­tle and gear cables. The eas­i­est way to get started is to sep­a­rate them and fit in the fol­low­ing se­quence: both gear cables fol­lowed by the clutch and fi­nally the throt­tle. Try­ing to fit them all in one go can lead to con­fu­sion and frus­tra­tion as you strug­gle to route them prop­erly.

Gear cables

Be­fore start­ing to fit the gear cables or clutch for that mat­ter, make sure the ad­juster block is in good con­di­tion. If the ad­justers have be­come rusty or dirty clean them fully and grease the threads. At this point wind the ad­justers fully back so you have full ad­just­ment on them. Sit both outer cables in to their re­spec­tive hous­ing in the head set clamp. With the in­ner cables fully lu­bri­cated slot each one in to the pul­ley holes. If the holes on the pul­ley or the split pin fix­ing are worn, re­place the pul­ley as this will give ex­ces­sive play be­tween the gears. Feed the out­ers down the left hand side of the fork stem and cross them over the main frame tube to the right hand side just be­low the bot­tom fork bear­ing. From there they sit just above the legshield and stand sup­ports, loop­ing over the rear brake hous­ing on the frame. They then pass around the side of the head cowl feed­ing though a 10cm long pro­tec­tive shroud where they fi­nally feed into the ad­juster block.

Now to make sure you have the cables the right way round. Look­ing down at the pul­ley in the head­set, the ca­ble that sits in the top hole feeds in to the in­ner ad­juster on the block. The ca­ble that sits in the bot­tom hole on the pul­ley feeds in to the outer ad­juster on the block. Feed the in­ners through the ca­ble trun­nions on each side of the pivot on top of the cas­ing but don’t tighten up. Make sure the small disc that sits un­der­neath the grub screw in the trun­nion is present. If not it can start to cut in to the ca­ble when the grub screw is tight­ened, caus­ing it to snap over a short pe­riod of use. A good tip is to make sure all the link­age is free from wear as now would be a good time to change it. This in­cludes both pieces of the pivot and the tie bar which is the most com­mon for wear. Also make sure the trun­nions are free from groov­ing on their outer sur­face es­pe­cially the one con­nected to the tie bar. Re­place if nec­es­sary. If re­plac­ing a trun­nion, make sure the Allen key size in the top is the same di­am­e­ter; this goes for the clutch as well. Some use a 3mm Allen key and some a 3.5mm. It can be a night­mare if you are out on the road and dis­cover you have the wrong fit­ting Allen key be­cause you have mixed up the sizes.

Mak­ing sure that the outer ends of each ca­ble are fully seated in their re­spec­tive hous­ings, it is time to tighten them up. With the en­gine in neu­tral, get some­one to hold the gear changer in neu­tral on the head­set. You can do this your­self but it is eas­ier if some­one else is hold­ing it to stop it mov­ing as you pull the in­ner ca­ble taut. Start by tight­en­ing the in­ner trun­nion on the pivot and once that’s done check to see it se­lects first gear. Next, tighten the outer trun­nion. As it’s pulled tight, the gear changer should re­main in the neu­tral po­si­tion on the han­dle­bars. If so, you have cor­rectly fit­ted your gear cables. As a check you can push your Lambretta along with the spark plug re­moved to make sure you can get all the gears in their cor­rect po­si­tions.

Clutch ca­ble

The clutch ca­ble sits in its hous­ing in­side the han­dle­bar gear change loops across the head­set and down the right hand side of the fork stem. From then on it fol­lows the same path as the gear cables also through the pro­tec­tive shroud be­fore get­ting to the ad­juster block.

If there is ex­ces­sive pin wear ei­ther on the changer or the lever it­self this can be reme­died by buy­ing an over­size lever pin and re-drilling the hole. Take care if do­ing this and make sure you have the cor­rect di­am­e­ter drill. Where the outer ca­ble sits in­side the gear change, al­ways check in­side for de­bris. This can be old pieces of the plas­tic outer from the ca­ble or its steel end. If there are any ob­struc­tions it is pos­si­ble to cause the new ca­ble to be fit­ted with­out it be­ing seated prop­erly in the hous­ing and go­ing slack when the ca­ble is op­er­ated.

With the outer ca­ble in po­si­tion, slide the in­ner ca­ble all the way through so it ex­its the ad­juster on top of the en­gine cas­ing. Make sure the ca­ble is fully greased and more so where the clutch lever sits in the gear change. At this point fit the lever pin and tighten it up. Be­fore fit­ting the trun­nion you will want to make sure both ends of the outer are fully lo­cated in their re­spec­tive hous­ings. By hold­ing the end of the in­ner in a set of mole grips and pulling the ca­ble taut, de­press the clutch lever. If one of the ends of the outer ca­ble is not sit­ting fully home this will push it fully into place. Don’t worry if the end of the in­ner ca­ble has been crushed a bit as this will be cut off to its cor­rect length af­ter fit­ting.

Be­fore po­si­tion­ing the trun­nion, turn the ad­juster on the block out by about 4mm. This will al­low you to slacken the ca­ble off slightly just in case it is a bit too taut when fully tight­ened. With the in­ner ca­ble tight, push the clutch arm on the cas­ing for­ward till it stops. Take a marker pen and mark the ca­ble where the trun­nion will sit in the re­cess of the clutch arm. Now tighten up the trun­nion where marked enough so it won’t slip on the ca­ble. To now sit this in the re­cess the arm needs to be com­pressed. There are a few after­mar­ket tools for this pro­ce­dure but if you don’t have one it is pos­si­ble to move the clutch arm for­ward by us­ing a big set of pli­ers or mole grips. Though this isn’t the con­ven­tional way of do­ing it, it does work. If us­ing this method though, place a piece of cloth be­tween the jaws of the pli­ers and the clutch arm to make sure it isn’t marked. Once com­pressed, you can slot the trun­nion in to po­si­tion on the arm with ease.

When you are happy that it is in the cor­rect po­si­tion, fully tighten the trun­nion and check to see where the bit­ing point of the clutch is. By se­lect­ing first gear then push­ing for­ward you will be able to find the point where the clutch dis­en­gages the en­gine. If it needs ad­just­ing ei­ther way this can now be done on the ad­juster block. Re­mem­ber you don’t want the ca­ble to be taut like a piano wire or like­wise so slack that the clutch will drag. You will find that af­ter a few miles the new in­ner cables will stretch slightly and may need a slight ad­just­ment. This also goes for the gear cables and hence the need for the ad­juster block.

Clutch and gear ca­ble fin­ish­ing – points to note

Now that all three cables are cor­rectly fit­ted, fin­ish off by cut­ting the end of the in­ners to the de­sired length. This wants to be around 3cm where they exit the Trun­nion. Cut any ex­cess length off with good qual­ity ca­ble cut­ters. Any­thing blunt will cause the ends to fray as they tear. To stop fray­ing af­ter­wards, you can sol­der the ends of the ca­ble but it is eas­ier to place an alu­minium ca­ble cap on the end and crimp it over. These are read­ily avail­able to pur­chase from any moun­tain bike shop and sim­ple to use. Some­times a method of ty­ing the ends up in a loop is used. This can of­ten look messy and get in the way when do­ing main­te­nance. They can also come un­done and pos­si­bly rub and cut in to the outer wall of the tyre.

An­other point to note is that the rout­ing of all threes cables out of the shroud­ing comes around the head cowl at a slight curve to give them the most nat­u­ral line to the ad­juster block. At no point should they

go over the en­gine as is some­times seen. As the en­gine flexes with the rear shock ab­sorber this would cause the cables to pull taught as they pivot over the en­gine mount. This can cause the clutch to slip as it would pull the clutch arm in by it­self or put un­nec­es­sary strain on the gear link­age, caus­ing the en­gine to jump out of gear. If you have an en­gine where the car­bu­ret­tor ex­its on the right hand side, for ex­am­ple a TS1, then it’s best to make the curve around the head cowl as shal­low as pos­si­ble. This will pre­vent them rub­bing on the car­bu­ret­tor which could cause it to be pushed off or worse split the mount­ing rub­ber. To get the curve shal­lower may re­quire the out­ers to have a slightly shorter length. This is done by cut­ting a cen­time­tre off the ends and needs to be done dur­ing the ini­tial rout­ing of the cables.

One fi­nal note is the use of ca­ble shrouds where the in­ners exit the ad­juster block as fit­ted in the fac­tory. From a purist point of view they look good but can be­come a prob­lem as they com­press es­pe­cially on the in­ner trun­nion of the gear pivot. If hav­ing to change a snapped ca­ble on the side of the road it is also an­other ob­sta­cle to con­tend with as you have to feed the new ca­ble though it. Fit­ting them is a per­son­nel choice but as long as the ex­posed in­ner cables are greased there is no ac­tual need for them to be fit­ted.

Throt­tle ca­ble

The throt­tle ca­ble can be a real prob­lem as there are so many pos­si­ble lengths it can be. If you buy a ca­ble kit it will have a stan­dard Lambretta throt­tle ca­ble. Chances are if you have a stan­dard en­gine

the ca­ble will be a near enough fit. The prob­lem is though so many own­ers have cylin­der kits with dif­fer­ent car­bu­ret­tor types and po­si­tions there is no de­fined length. With the trend these days to fit a long range tank it may also be the case that throt­tle ca­ble rout­ing needs to come in at a dif­fer­ent an­gle.

The eas­i­est way to get the cor­rect length in­ner and outer is to make your own cus­tom ca­ble and it’s eas­ier than you might think. Ei­ther from the in­ter­net or any good moun­tain bike shop, pur­chase 2.5m of outer ca­ble and two steel ends. For the in­ner ca­ble use a moun­tain bike gear ca­ble, the end should fit nicely in to the throt­tle slide. As a note here if you are rout­ing round a long range tank, and the outer may be longer, it may be bet­ter to pur­chase a tan­dem gear ca­ble in­ner as the stan­dard moun­tain bike one may be slightly short. The tan­dem ca­ble will be too long but is sim­ple to cut to the cor­rect length af­ter­wards.

When rout­ing the throt­tle ca­ble outer, start from the head set first where it then fol­lows straight down the right hand side of the fork stem. It will then meet up with the clutch and gear cables and follow the same route over the front leg shield sup­port. If the car­bu­ret­tor is on the tra­di­tional side it is at this point that the ca­ble crosses over the top of the frame tube to exit above main stand strut and up to the car­bu­ret­tor. If the car­bu­ret­tor is on the right hand side then the ca­ble will con­tinue on the same path as the clutch and gear cables and be­fore go­ing up to the car­bu­ret­tor.

Where the ca­ble goes up to the car­bu­ret­tor try to make sure it has a nice curved loop. If the loop is too short or sharp this can stop the ca­ble run­ning smoothly and stop it from re­turn­ing on its own. Once happy with the rout­ing of the ca­ble, cut it down to its cor­rect length and fit the steel ends. Now feed the in­ner in to the outer from the slide in the car­bu­ret­tor up to the head­set. On the throt­tle pul­ley use a small brass trun­nion with a screw ad­juster and feed the in­ner ca­ble through the pul­ley grove and trun­nion. Make sure the throt­tle is in the fully closed po­si­tion and pull the in­ner ca­ble taut. Now tighten the trun­nion and you will have the cor­rect length throt­tle ca­ble. Note that when pulling the in­ner taught don’t overdo it as the throt­tle will start to open. As a check, if you turn the head­set to the left hand lock look at the throt­tle slide. If it is too tight you will see it open on its own even if the throt­tle re­mains in the closed po­si­tion. It is al­ways best to fine tune the length of the ca­ble with the ad­juster on top of the car­bu­ret­tor to get the de­sired length rather than have it too short in the first place.

Pe­ri­od­i­cally lu­bri­cate the ca­ble at the pul­ley end ei­ther with a small amount of grease or a spray lu­bri­cant. If the throt­tle ca­ble is go­ing to snap then this is usu­ally where it hap­pens. Like­wise if you see any fray­ing of the ca­ble in this area re­place it im­me­di­ately as it could let you down at any point. From a safety point of view, if the in­ner is frayed badly then it can catch on the outer ca­ble which may cause the throt­tle to stay open – which can be dan­ger­ous.

Words & Pho­to­graphs: Stu Owen

1: The clutch ca­ble on the right ex­its the gear change and takes a gen­tle curve in the head set over to the other side of the frame. 2: A clear view of how all the cables route down the fork stem. 3: While the clutch and throt­tle cables follow a nat­u­ral line down the frame tube the gear cables cross over un­der the forks as can be seen here. 4: Once passed through un­der the legshields the clutch and gear cables loop over the rear brake hous­ing into their pro­tec­tive shroud­ing. 1

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3

2

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5: Ex­it­ing the shroud­ing, the cables take a nat­u­ral line to the ad­juster block. 6: Al­ways make sure the cables go un­der­neath the en­gine mount, not over it. 7: Try to make the curve around the head cowl as shal­low as pos­si­ble if your car­bu­ret­tor ex­its on the right hand side to pre­vent the cables from foul­ing it. 8: Fin­ish the in­ner ca­ble ends off by ei­ther sol­der­ing them or, more eas­ily, fit­ting with an alu­minium cap to pre­vent fray­ing. 9: Though rub­ber ca­ble cov­ers give that gen­uine fac­tory look, they can get in the way. If fit­ting a ca­ble on the side of the road they are an­other ob­sta­cle to get around. 8

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6

5

12

10: If the gear link­ages and ad­juster block are worn, ca­bling is the per­fect time to re­place them. 11: When the car­bu­ret­tor sits on the tra­di­tional side then the throt­tle ca­ble crosses over the mid­dle of the frame tube to exit on the cor­rect side. 12: If the throt­tle ca­ble doesn’t sit cor­rectly in its hous­ing then chances are it will pop out in the head set. This is the same for any ca­ble. 11

10

13: No mat­ter what type of car­bu­ret­tor you are us­ing and what­ever side of the frame it is ex­it­ing, make sure there is a nice gen­tle loop where it goes in to the top of the body. Not only does this make the throt­tle eas­ier to use, it will help in mak­ing sure it re­turns nat­u­rally on its own. 13

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