Free up your throt­tle

Get your twist­grip snap­ping back and forth like new

MCN - - HANDS ON -

1 Sticky sit­u­a­tion

A stick­ing throt­tle is a prob­lem that creeps up on you and it’s easy to learn to live with it, but it’s a huge safety risk as well as an MoT fail. The prob­lem can of­ten be traced back to a few ba­sic things: the throt­tle tube rub­bing on the han­dle­bar, old ca­bles, poor rout­ing, or the grips bind­ing on the bar end weights.

2 Need a new ca­ble?

To re­place the throt­tle ca­ble you’ll first need to re­move the tank and air­box from the bike. Care­fully de­tach the vac­uum pipe and fuel line from the fuel tap, as well as any elec­tri­cal con­nec­tors and breathers. To re­move the air­box, undo the clamps that se­cure it to the carbs, as well as any breather pipes.

3 Open hous­ing

Undo the screws that se­cure the throt­tle grip, of­ten these will also hold the switchgear in place. Once un­done, loosen the ca­ble ad­justers on the body of the hous­ing; our Suzuki SV650 is fit­ted with two ca­bles, one to pull and the other to re­turn. Be­fore you pro­ceed, make sure the re­place­ment ca­bles are cor­rect and iden­tify which is which.

4 Get some slack

Turn your at­ten­tion to the carb or throt­tle body end of the ca­ble. Undo the lock nuts then screw in the ad­justers far enough so that the ca­ble nipple can be popped out of the link­age or pul­ley. The other end of the ca­ble can also be popped out of the plas­tic throt­tle tube on the han­dle­bar. Re­peat for the re­main­ing ca­ble if fit­ted.

5 Time for the tube

With the ca­ble re­moved, the throt­tle tube is al­most free, but the bar-end weights need to be re­moved be­fore it can be slipped off. This SV650 has some af­ter­mar­ket an­odised weights which have de­formed the throt­tle tube over time. Re­place them with new OE end weights.

6 Rolling free

Clean the han­dle­bar with con­tact cleaner and slide the new throt­tle tube into place. Make sure it ro­tates freely. If it does bind, re­move it and find out why: it could be that the bar is bent from a low-speed tum­ble in the past or it might just need a more thor­ough clean.

7 Re­move and reroute

Re­move the throt­tle ca­bles one at time and make a note of the rout­ing as you do so. On older bikes don’t al­ways as­sume that the rout­ing is cor­rect as it is. Check against a work­shop man­ual to be 100% sure the ca­bles won’t foul or snag. In­stall the ca­ble on the carb/throt­tle body but keep the ad­justers loose.

8 Con­nect the tube

When both ca­bles are fit­ted to the carb/throt­tle body, fit the other ends to the cor­rect side of the throt­tle tube. In the case of this SV650, the open ca­ble is at the front and the re­turn ca­ble is fit­ted to the back. When they are lo­cated, screw the hous­ing back to­gether mak­ing sure that the han­dle­bar lo­ca­tion dowel is lined up cor­rectly.

9 Ad­just freeplay

When the throt­tle hous­ing is tight­ened up, turn the throt­tle tube to make sure it moves freely then as­sess how much slack is in the ca­bles. First, tighten up the lock­nuts at the carb end then ad­just the play at the grip end us­ing the ad­justers just be­fore the throt­tle hous­ing. Play on the open ca­ble should be 2-4mm; the re­turn ca­ble should have no play.

10 Re­fit and check

Do a fi­nal check, mak­ing sure that the ad­juster lock­nuts are tight. Re­fit the air­box and tank, en­sur­ing that all the breather pipes are fit­ted back in place on the air­box. Fit the tank, mak­ing sure the fuel gauge sen­der, fuel line, vac­uum, and breather pipes and con­nec­tions are all in place. Check that the idle speed is cor­rect and the throt­tle ac­tion is smooth.

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