Just thought I'd give a heads-up regarding a fix for Fly By Wire TPS sensors that feel "sticky" in operation, somewhat like a binding or dry throttle cable.
I've had the problem for about 18 months on my 2008 FLHRC Road King. It made it irritating on take-off and low speed work, creating jerky operation of the throttle. I finally got around to attending to it. I removed the handgrip, thinking it must have been dry against the handlebars and causing the problem. The handgrip lube was okay. I then checked the operation of the TPS in the end of the LHS bar and that was the problem. There was a pronounced sticking, resembling plastic-to-plastic binding.
I slipped the TPS out of the bars to see if I could examine it and found that it was a non-serviceable item. So, I tried a few drops of WD40 between the exposed moving parts. No better. I'm now thinking that this bugger is going to be a fair handful of dosh to buy, so I searched the 'net so see if there was a replacement available aftermarket. No such luck, so today I bit the bullet and decided to attempt a dimantle & repair, thinking that it's going to need repair or replacement anyway.
The TPS assembly is housed within a thin-wall metal tube. The electronics, spring tensioner & rotating drive are retained withing the tube by indents pressed into the tube (centre-punched). To gain access to the assemblies I used a 3mm drill bit to drill out the indented sections of these retainers. Care must be exercised here to only drill through the metal casing and not drill deep into the plastic of the inner sections. A slight "witness" of plastic is okay. Drill out all 12 of the indents.
Now, starting with the geared (handgrip) end, grab it securely with your hand and wiggle it back and forth until it's clear of the metal tube. The insert will still be a bit firm because of the indents which are not completely removed with a 3mm drill, but it will come out. Be careful to mark the orientation of the two end sections so they go back together correctly later. This end retains a spring, spring seat and a "return ramp", as well as the rotating section of the TPS. You will not damage any of this when removing it, but just make sure the spring, etc doesn't take flight.
Whe you have removed those items from the metal tube, select a 1/4 drive socket and bar that will sit down inside the other half of the "return ramp" and drive the other half of the TPS assembly out of the tube from the inside. You won't damage the TPS doing this. There is no carbon track or fine sweep arm like you would expect to encounter with a regular automotive TPS, This utilises a magnet contained within the geared section first removed, to move past two solid-state pickups, which are separatel encased in flexible plastic and sit in formed hard plastic retainers. I've never encountered a TPS like it before.
Okay, when it's all apart, it will be obvious where the problem lies. The two interocking "return ramps" are pushed apart as the throttle is rotated and the spring tries to push them back together, creating force to return the throttle. These two ramps are not lubricated, being probably manufacture from a self-lubricating plastic. Major fail. The bloody pieces bind against each other, so the fix is to apply a lubricant. I used a small amount of Nulon high temp, waterproof grease containing teflon (PTFE). a small smear on the contact faces of the ramps and around the trust washer of the geared outer piece and the assembly is ready for reassembly.
First thing you'll need to do is flatten the remaining parts of the indents to make assembly easier. I used a socket bar secured in a vise , slid the tube over it and gently tapped the indented areas until they were smooth. Now, before assembly you'll have to mark some guide lines at the correct spacing so you'll know where to repunch the new retaining indents. I just rotated the metal tube 90deg, slipped one of the sections in until the indents formed in the plastic were near the edge of the metal tube and scribed 4x parallel lines along the length of the tube, in alignment with the indents.
Although not absolutely required, I found the reassembly easier by first fabricating a simple jig to hold all the parts together. It's much easier to repunch the indents if the assembly is sitting in a small piece of steel angle.
Firstly, refit the wired section of the TPS into the metal tube, making sure that the indents in the plastic body are in line with the scribed lines. Whilst using the drilled holes in the tube for distance measurement, use a centre punch to indent the metal tube at the 8x points and retain this section. Once that is done, reassemble the opposite end of the TPS and do the same with the remaining 4x indent points. Make sure that the assembly is compressed into the tube to the correct depth before punching these indents. Again, the simple jig made this operation much easier and only took about 15 mins to fabricate out of scrap items. Now check the operation of the assembled TPS. It should now be smooth, free of binding, firm against the spring and should return to the stop position strongly.
You will now need to seal up the 12x holes that were drilled in the metal case. I just used some "5 Minute Araldite", filling each hole and trimming off the excess with a scraper razor blade when dry. Job done.
The attached photo shows the rotating section of the TPS on the handgrip end. Half of the "return ramp" is easy to identify in this view. I tried uploading a series of photos to show more of the repair and also the jig, but I could only upload 1 photo with this post. If anyone needs more detailed photos, contact me with your email address and I'll send them to you.
I too like pulling stuff apart but that little green connector did me head in so I bought the cvo version of the sensor which doesn't have the green connector. I liked the fact of one less connector sitting inside the bars and not knowing how much I stretched the wiring pulling the wiring through. Good write up though.
