Throttle cables

Throttle cables:

The throttle cables consist of two cables, that are routed from the carbs to the right hand throttle twist grip. One cable is used to pull the butterflies open against a spring tension. This is commonly referred to as the pull cable. The other cable is sometimes wrongly referred to as the push cable, but doesn't actually push, but is attached in such a manner as to pull the butterflies closed. These cables are in constant use when the bike is running and do wear out from use.

The first indication of throttle cable problems is that the engine does not respond to the throttle. A broken pull cable will not allow the bike to rev up, while a broken retraction cable may not exhibit any noticeable symptoms. This is due to the retraction spring on the butterflies providing the necessary force to pull the butterflies close. Some do operate the bike without this cable, thinking that it is redundant, but a smoother action and the safety of knowing that you can pull the throttle closed would be reason enough to keep both cables operating.

Replacing a set of throttle cables can be a half day project even tho it appears to be a very simple swap. The reason is that the clamshell containing the twist grip will need to be opened against sometimes stubborn screws, and the carbs will have to be essentially removed to disconnect and reattach the cables. The first step would be to detach from the carbs. If you are not familiar with carb removal, there are posts and directions on how to do this. After the cables are loose from the carbs, attach a sturdy string to the ends at the carbs. By pulling a string thru with the cables, you have a built-in guide as to re-routing the new cables. And proper routing is very important. Having the bike decide to rev up when the bars are turned, can lead to some interesting situations you don't want to experience. So, keep the routing original! Also, some motorcycle inspections include handle bar movement checking for change in engine speed.

When you have the cables loose to the grip, you can unscrew them from the throttle assembly. Pay attention as to which cable is wrapped in what direction before removing the old cables. Then thread the new cables into the assembly and tighten them up. Using the mentioned string, pull the cables back thru to the carbs and re-attach. Make sure you get the correct cable on the proper holder when installing. A easy way is to just twist the throttle (top towards you) at the handlebar. The cable that retracts (shortens), is the pull cable that opens the butterflies.

Final adjustments should allow some "play" in the cables at the carb and handlebar end. You want to feel a slight turn of the twist grip before the carbs begin to come into play. If you don't allow a bit of slack in the cables, you may experience binding and the carbs not fully returning to idle when the throttle is released.

Replacing a pull throttle cable. By DanCX500 (Some key pictures that were taken during the task. Some steps may have been skipped/omitted.)

Here are a few thoughts and pics of the replacement: Link to all of the pics I took...(The good, the bad, and the ugly!) 1981 CX500 pics

Pictures of the old and new cable: You can see the remnants of the broken cable in the twist grip. Here's a pic of required tools. (12mm socket....for pulling the seat and tank.) One tool I couldn't take a pic of..... LOTS OF PATIENCE! as there isn't a whole lot of room! Two screws remove the twist grip from the bar. First loosen the two lock nuts on the cables (14mm wrench) as it will be easier with the assembly anchored to the bar.

If you find one screw is too tight, try the other one.

.... Make sure to use a GOOD quality screwdriver! With ample 'downward' pressure towards the screw so the head doesn't strip out. (Note: One screw is longer than the other.) A 10mm open ended wrench to loosen the nut on the cable. It would help to have a wrench with an angle. If I was to do this on a regular bases I would customize one. A forum suggestion. Perhaps removal of the carbs would have been better. Getting the end of the cable out of it's slot on the carb takes a bit of work. Not a whole lot of room!

You'll have to put the twist grip end on first because the cable housing is required to be turned as it's threaded into the twist grip mounting.

Be sure to take a mental note on the routing of the cable. Or even a picture or two.

Work the carb end of the cable into it's slot on the carb and then the housing on to it's mount and tighten it to it's mount.

When putting the twist grip assembly back together, make sure your kill switch wires are routed correctly. It is easy to get them pinched in between the two case halves. I have probably forgotten something along the way...so..this isn't considered to be a step-by-step ..... You'll have to put a bit of thinking into it.