There are two throttle cables on your motorcycle: a pull, and a push. The pull cable is the one that does most of the work - it is the cable that is under tension when you open the throttle, against the spring that is trying to snap it shut. The push cable is your safety net - should the pull cable break, or the throttle jam, the return spring break, or any number of things that could go wrong that would leave you with an open throttle, the push cable will "push" the throttle closed. Replacing the throttle cables will take between 2 and 3 hours, and requires some work in a confined area behind the carburetor assemblies. Throttle cables can be found easily, including on Amazon
. Make sure you get both a pull and a push cable.
1. Remove the side covers.
2. Remove the false tank, air filter cover, air filter, and air filter housing. Instructions on removing the false tank can be found here
, and on removing the air filter cover, filter and housing can be found here
3. Find the adjusting screw and lock nut below the throttle handgrip. The adjusting screw is on the "pull" cable only - it is the one that is closest to the front of the bike.
4. Loosen the locknut, and move it all the way up the shaft. Screw the adjuster as far up as it will go.
5. On the push cable (the one closes to the rear of the bike), unscrew the fastener from the throttle grip housing. Unscrew the lock nut at the throttle grip housing from the pull cable.
6. Unscrew the three screws on the bottom of the throttle grip housing. These screws hold the housing top and bottom halves together.
7. Optional: Remove the handgrip. You don't have to do this, but it makes it a bit easier. I was replacing my handgrips anyway, so I removed my old ones. The handgrip should just pull off, unless, as in my case, it was glued in place, in which case you may have to cut it off.
8. Separate the throttle grip housing halves. You can see how the cables link into the twist grip.
9. Remove the spark plug boots from the spark plugs on each side. Remove the four screws holding the carburetor linkage guards on each side, and remove the guards.
10. Remove the two bolts fastening each intake manifold to the cylinder head, eight bolts in total.
11. Gently lift each intake manifold off the cylinder head. Slide the entire carburetor assembly out towards the left side of the bike as far as it will go.
12. The pull and push cables are connected to a bracket at the rear of the carburetor assembly. The pull cable is on the top. This is looking down at it from the top, through the space where the air filter housing normally fits.
13. Loosen the push cable: From the left side of the bike, using one wrench to hold the long six-sided part at the top of the picture, use a second wrench to loosen the lock nut holding the cable in the bracket.
14. back the lock nut all the way off the threaded rod, and remove the cable from the bracket.
15. Do the same with the pull cable, backing its lock nut all the way off, and removing the cable from the bracket. You may find it easier to have one wrench holding the main six-sided cable part from the top, while loosening the lock nut from the side.
16. From the right side of the bike, using needle nose pliers, gently pull the cable off of the throttle bell crank, and remove the cable ends by pulling them towards the rear of the bike.
17. Pull the cables ends out the left side of the bike.
18. Now that the cables are free, rotate the twist grip back and forth to get slack, then pull the cable ends sideways out of the twist grip. Remove the cables from the twist grip assembly. You may need to unscrew and separate the curved portion of the pull cable from the cable end in order to get enough slack to unscrew it from the throttle grip housing.
19. Pull one of the throttle cables out of the motorcycle from the hand grip end. Be careful to leave one of the cables in place.
20. Tie a strong piece of string to the bottom cable end of the remaining cable. This string will be used to ensure the new cables are routed exactly the same way when they are replaced.
21. Pull the cable out from the hand grip end, carefully feeding the string through the motorcycle as it goes.
22. Tie the string to the bottom cable end of both
new throttle cables. You may wish to lubricate the cables first. Gently pull the string from the bottom end, routing the cables through the bike and out the left side at the bottom end.
23. Looking at the cable ends, the cable with the half-round washer and the shorter fastener is the pull cable. We will be working with the pull cable first.
24. From the right side of the bike, push the cable end of the pull cable into the top hole in the throttle bell crank.
25. Position the cable on the bracket, with the half-round washer on the top side of the bracket as shown. This picture is looking down from the top of the bike, through the air filter housing space.
26. Tighten the cable in place on the bracket with the lock nut. This again is looking down from the top of the bike, through the air filter housing space.
27. From the right side of the bike, route the cable correctly around the bell crank.
28. From the left side of the bike, position the push cable end in the bracket, and tighten the lock nut.
29. From the right side of the bike, pull the push cable end around the bell crank and push the cable end sideways into its hole. You may need to use your fingers to open the throttle mechanism in order to get enough slack on the cable to get it to fit easily into the hole.
30. Unscrew the curved portion of the top end of the pull cable from the cable itself. Screw the curved portion into the frontmost hole on the throttle grip housing. Leave several threads exposed for the lock nut to screw on to. Once it is installed, screw the cable back onto the curved portion, as far as it will go.
31. Push both cable ends up into the housing, and sideways into the throttle grip. Make sure the cable end holes are on the top of the grip when you do this. You will need to do the pull cable first, and then the push cable - the push cable hole is slightly elongated to allow enough slack to maneuver it in.
32. Ensure the curved portions of the cables are pointing back along the handlebar, and that the throttle grip is seated securely in the channel of the throttle grip housing. Screw the lock nuts in place to hold them. Keep in mind you are screwing into plastic - do not over torque them, or you will strip the plastic threads in the housing.
33. Close the throttle grip housing. Rotate it back and forth while doing so - it will only close completely when it is in the correct position on the handlebar. When it is completely closed, fasten the halves together with the three screws.
34. In the air filter housing area, you will see the main throttle tension adjuster. Unscrew the two larger six-sided sections from one another to adjust the free play on the twist grip. The twist grip should have between 2mm and 6mm (1/8 inch and 1/4 inch) free play when rotated back and forth. Large adjustments should be made with the adjuster under the air filter housing. Minor adjustments should be made with the adjuster at the hand grip.
35. Tighten the lock nut to prevent the adjuster from slipping.
36. Make any minor adjustments at the twist grip as required, and tighten the lock nut.
37. Gently position the carburetor assembly correctly back onto the cylinder heads. Ensure any gaskets have not slipped, and reposition them as necessary. Insert the bolts and start them in by hand - the cylinder head is very soft aluminum, and will cross-thread easily, so do not tighten them with a wrench or socket until you are sure (by threading them in by hand) that they are not cross-threaded. Use a torque wrench to tighten each bolt to 4 foot-pounds.
38. Replace the carburetor linkage guards and screw them back into place.
39. Replace the air filter housing, air filter, and false tank.
40. Test run the engine to ensure correct throttle operation.