Replacing Throttle Shaft “Felts” on GL1000, GL1100, GL1200, DOHC-4, CBX, CX500, etc.
Throttle Shaft Felt Replacement (photo courtesy Aaron Williams of Dude’s Garage)
(See below for “How-to” video.)
Keihin carbs of this vintage have felt seals on the choke and throttle shafts ostensibly for sealing the shafts, providing wicked lubrication while maintaining good throttle feel.
But – the carbs have to be excessively disassembled to access the felts which are “inboard” within the body. This is why I never recommend removing the throttle (or choke) butterflies / shafts on early ‘Wing carbs. Ditto for immersion cleaning with harsh chemical agents. The felts are easily lost or damaged. Plus, amateur mechanics typically have difficulty reinstalling the butterflies in the correct orientation with respect to the beveled edges and without introducing binding
My video and booklets do not cover felt replacement for these reasons.
“False air” entering around the choke shafts is inconsequential. It allows a small amount of unfiltered air to enter the equation, but this occurs before fuel metering so it has no effect on air/fuel mixture.
“False air” entering around the throttle shafts does affect air fuel mixture – The extra air leans out the mixture. All Keihin carbs of this vintage (especially Honda GL1000) will show “false air” at the throttle shafts if you bother to check. The good news is that they will tolerate quite a bit of “slop” and still run very well. Honda apparently anticipated this. Plus, most of these carbs are jetted a bit rich in the mid and high ranges as extra insurance to to ward off warranty claims from overheating in various markets and climates around the world.
There are many more common causes of “hanging” high idle as detailed are here.
Honestly, replacing these felts is beyond the skill level of most amateur mechanics and is a task best left to professional carb rebuilders.
If you decide that you want to replace the felts (against my best advice), here’s some tips:
- Do not be tempted to substitute rubber o-rings instead of felts. This will yield an unacceptably “hard” throttle pull (too much friction).
- This supplier offers correct, improved felts that are superior to OEM:
Aaron Williams
Dude’s Garage
(Square outer edge felt: 8 x 11.5mm)
There other suppliers, but Aaron’s version is made to a higher standard and is my preference.
Here’s a nice video by Aaron Williams that shows how to replace the felts:
Randakk i own a 1984 1200 Wing which i rebuilt from the ground up, the bike has been running great but i”ve noticed that she wont go over 85 M.P.H., it still has more twist to the throttle but doesnt make any differance, i rode the bike for about 3 years now after 10 minutes of warm up it spits and has no accel. unless i slightly close the choke, then it runs like it never has before, the pump and relay, fuel filter and plugs are new, i thought of rejetting but this wont fix the root problem, do u have any info. that could help me with this issue?
Carb rebuild time I think. Something is making your bike runs too lean.