Throttle Cable Trouble
Check, lubricate and reassemble or replace outright – do the right thing.
Now, what’s a throttle cable anyway? In these days of throttle-by-wire, we’ll tell you all about it, ’cos the throttle isn’t controlled by electrical impulses but in a more classic way, that is to say: mechanically.
A vintage bike usually has a throttle cable, a thin steel wire living in a Bowden cable housing, telling the engine how much power the rider wants at any given moment in time. It opens the throttle butterfly, or the slide in a slide carb, letting more or less fuel/air mixture reach the engine. It’s a part that needs to be absolutely reliable, so a little tlc every now and then won’t hurt. If you’re on the road often, or your bike spends the night outdoors it’s a good idea to keep the cable regularly lubed. It’s supposed to glide smoothly in its housing.
Here’s our real life check list for disassembly, inspection, decision making and reassembly:
1) Jack up your bike,
eg with the Becker Minilift so you can work on it from both sides.
2) First step: relax. Not yourself,
we haven’t even started yet :) Relax the throttle cable tension by opening the throttle cable adjustment screw to maximum slack. Open all bolts on the throttle grip housing with the correct size screwdriver or hex key. Open the housing carefully, drop bolts in a magnetic bowl so’s to not lose any. Unscrew throttle cable from housing.
3) Slide out the top end
fitting on the cable from the throttle grip sleeve.
4) Slide throttle grip sleeve gently
from handlebar. This is the moment to consider the state of the grips. Get a new set?
5) Remove the air filter cover
(you may even have to remove the air filter base plate) to get at the throttle quadrant on your carb (the slide, if you have a slide carb). Park bolts, washer nuts in your magnetic tray.
6) Undo lower end of throttle cable
from throttle quadrant or slide.
7) Check the visible parts of the throttle cable
(the inner wire) for frayed or broken wires. If everything looks good, soak the cable with some WD 40 or similar penetrating oil. Moving the cable back and forth in the outer shell helps to accelerate this. Jump to 13)
8) If you find broken strands,
the cable has been bent, the outer shell’s vinyl casing is damaged, or it looks like it has been salvaged from a barn find (in a burnt down swamp hut), go for a complete replacement.
9) Remove the whole throttle cable assembly
from the bike. Try to remember how it was routed. Taking a couple of snaps of the critical points before you remove it is a good idea. You may have to remove the tank for this.
10) Order a new throttle cable.
A good selection is ready to ship from out headquarters and accessible from the listings below. Important to know: total length, year of bike, form and size of upper and lower connections. If in doubt, give our operators at wwag.com a call. For best results, send them a few snaps of your old cable.
11) Finished ordering? Now for some
well earned relaxation. Where’s the fridge? Grab a beer … Ding Dong! Oh, the parcel from W&W is here!
12) Reassembly: Route the new throttle cable
from the throttle grip to the carb, as close as possible to the original routing. Avoid tight turns and hard bends. Loosely fasten to frame with original fasteners, zip ties or the fastener of your choice. Fasten tight only after everything works snappily.
13) Place the carb end fitting
in the throttle quadrant (or the slide), place outer shell in the throttle cable support. Wait with reassembling the air filter until everything is working snappily again.
14) For smooth accelerations: give the inside
of the throttle grip sleeve a light coating of all purpose grease, connect the throttle cable to the throttle grip sleeve, insert the throttle grip sleeve into the throttle grip housing on the handlebar, gently close screws. Do this while seated on bike for best judgement. If the throttle grip moves as smooth as silk, torque down housing screws gently with the proper torque settings (see manual).
15) Reassemble the air filter/base plate.
Check fastenings along cable route, tighten as appropriate.
16) Check free movement of the throttle cable.
It should snap back instantly. Too much loose play in the cable can be reduced by turning the adjusting nut on the cable. Use two wrenches for this. Start engine. Does the engine react normally when throttling up? Don’t forget to tighten adjusting nuts.
