Throttle tube sluggish to move

[Salishmoto]

I'm installing Oxford Heaterz and have run into a problem. Been working on it all morning and now throw up my hands. I've spent the entire morning trying to eliminate friction in my throttle assembly since the throttle is sticking and sluggish to close when opened and though it seems I have done so, when I put it all back together the throttle sticks and at best is sluggish to return to idle. Let me list what I have done and see if any of you have any insights.

The cables themselves move very freely in their sleeves. I took the housing apart and freed the cables from their connection and they move very easily by hand, with no evident sticking. I move the throttle body and the springs seem strong and there seems plenty of pull.

On the bars, I found a little roughness and used 400 wet dry to lightly polish the bar to smooth. The throttle tube itself is cleaned and smooth. I've lightly lubed the bar and throttle tube with dry graphite spray. I've lubed the housing lightly where the throttle tube revolves within, and there is no sign of wear there.

I've adjusted the cables to seem right, with the pull cable adjusted to have just a little slack and the bike idles right at 1100 and not more. The return cable is slack, and here is a strange thing. If the return cable is slackened all the way, and I mean 100% of possible slack, and the Heaterz are not slid onto the throttle tube, then the tube itself will snap back to idle seemingly fine. But if the return cable is tightened at all, even a few turns from dead slack, the whole assembly binds and won't return if the throttle is opened. Ok, fine, I cannot for the life of me figure out why that return cable being tight causes the whole assembly to bind, but it does.

So I go ahead and put on the Heaterz and for whatever reason, though it is touching absolutely nothing!, it causes some friction in the system and the throttle tube is sluggish to return.

I cannot figure out what is happening. The throttle springs are untouched and seem strong when you open the throttle by hand at the pivot wheel. There is no friction in the cables. There is no friction on the bar. There should be no added friction with the Heaterz, and no it isn't the cable binding or anything as I checked that 100 times and ways.

I'm at a loss. Any insights?

[Dirk_S]

Is the far end of the rubber grip pressing against the bar end weight? I had a similar issue. Initially I used a smaller flat washer as a shim between the bar end weight and the tube. Recently, I trimmed the end of mine up and they move freely, no more washer.

[Huzo]

What bike is it ?
You may have mentioned it, but try disconnecting the cables and reassembling the grip mechanism, to isolate the source.
If it’s not the cables or downstream, loosen off the bolts on the clamp and see if the tightness reduces. If it does, pull the twist grip out and make sure there are no manufacturing defects like twisted or mal formed plastic parts present.
While you are looking at the cables, pull on the nipple of the opening one and make sure that it all works ok from there down.
A good test is to remove the clamps off the ‘bar and reassemble the twist grip in the housing, check for binding.

You could test by putting a thin packer (1mm) between the clamp halves and nip up the bolts, this will artificially create some clearance for the moving parts, see what happens.
It can’t be much wrong...

[Huzo]

Is the far end of the rubber grip pressing against the bar end weight? I had a similar issue. Initially I used a smaller flat washer as a shim between the bar end weight and the tube. Recently, I trimmed the end of mine up and they move freely, no more washer.

I’ll bet that’s it...!

[Salishmoto]

I appreciate the ideas. It's not the grip or throttle tube rubbing the bar end, as I've made sure of that. In fact, I trimmed the Heaterz grip when I didn't need to and there is a good 3mm gap between the grip and the bar end now. It's something in the housing, or despite all my efforts at smoothing and polishing and graphite, some friction between the throttle tube and bar. I've taken it all apart several times and everything in isolation seems fine. Like I said, the cables are smooth and easy. The throttle body springs are fine. There is something upstream of that causing this.

Oh, and it's a Stelvio NTX.

[Dirk_S]

What bike is this?

[Huzo]

What happens if you loosen the bolts off ?
Sounds like the clamps are closing too much...

You say that increasing slack on the closing cable helps. Where the metal cable guide winds into housing, it’s not poking up into the mechanism is it ?
Please tell us as requested what bike you have. Is it a V7 or similar ?
Several photo’s would be good.
What happens if you slack the cable off and fit the heaterz OR adjust the cable and DON’T fit the heaterz ?
Only make ONE change at a time.
You’re unintentionally combining two possible causes.
#1
What happens if you adjust BOTH cables and leave the grips off ?..(answer #1)

#2
What happens if you slack the cable off and install the grips ?..(answer #2)

[guzzisteve]

Wonder if the idle stop screws(magic screws) with yellow paint were moved?

Grip rubbing somewhere, seen as that's all that was changed. TILL adjustments.

[Salishmoto]

Update: After fine tuning the cable adjustment tension and after everything else I've done today, it is now snapping back just great with only the Heaterz grips on. Snaps back with that nice solid "clank" of the throttle bodies closing firmly. However, I've learned that when I put my cramp buster onto the grip, that alone causes too much friction somehow and makes the system stick. So, at least part of my problem is that the OEM throttle tube, which I've found is quite thin, and especially after sanding down the ridges a bit to get the Heaterz grip on, lacks the rigidity to resist the compression forces of the cramp buster, and this causes enough friction with the bars despite everything being polished and smooth, to prevent the throttle from closing. So now I am wondering if there are aftermarket throttle tubes that might be firmer and resist this compressing force. I love solving problems and appreciate your questions and suggestions as I've worked through this.

[Huzo]

Update: After fine tuning the cable adjustment tension and after everything else I've done today, it is now snapping back just great with only the Heaterz grips on. Snaps back with that nice solid "clank" of the throttle bodies closing firmly. However, I've learned that when I put my cramp buster onto the grip, that alone causes too much friction somehow and makes the system stick. So, at least part of my problem is that the OEM throttle tube, which I've found is quite thin, and especially after sanding down the ridges a bit to get the Heaterz grip on, lacks the rigidity to resist the compression forces of the cramp buster, and this causes enough friction with the bars despite everything being polished and smooth, to prevent the throttle from closing. So now I am wondering if there are aftermarket throttle tubes that might be firmer and resist this compressing force. I love solving problems and appreciate your questions and suggestions as I've worked through this.

Had you mentioned somewhere that you had the cramp buster fitted..? (I might have missed that bit)

[Salishmoto]

Had you mentioned somewhere that you had the cramp buster fitted..? (I might have missed that bit)

No, I hadn't but that wasn't on during most of my saga. When I finally got the throttle to close quickly and smoothly, I found that adding the cramp buster made it act like it had before. My solution to that is going to be to try and find an aftermarket tube that is more rigid. On my Stelvio the tube was only made partly rigid by a bunch of ribs that were longitudinal and that had to be partly sanded off for the Oxford Heaterz grip to fit over the tube. I'm sure this removed what little rigidity existed in that tube.

The biggest remaining mystery to me is why the push cable must be fully slack 100% in adjustment or the whole system binds up. All it does is help close the throttle a bit by pushing, so even if it had no slack it doesn't make sense that it would create friction in the system at the housing or throttle tube. Head scratcher.

[Huzo]

No, I hadn't but that wasn't on during most of my saga. When I finally got the throttle to close quickly and smoothly, I found that adding the cramp buster made it act like it had before. My solution to that is going to be to try and find an aftermarket tube that is more rigid. On my Stelvio the tube was only made partly rigid by a bunch of ribs that were longitudinal and that had to be partly sanded off for the Oxford Heaterz grip to fit over the tube. I'm sure this removed what little rigidity existed in that tube.

The biggest remaining mystery to me is why the push cable must be fully slack 100% in adjustment or the whole system binds up. All it does is help close the throttle a bit by pushing, so even if it had no slack it doesn't make sense that it would create friction in the system at the housing or throttle tube. Head scratcher.

The doubling of the force pulling the winder into the housing.
Sounds lame but...who knows ?

[Salishmoto]

Final update: I'm delighted tonight as I have everything working perfectly now. With help here and from friends on advrider, I was able to get the tube to work properly through cable adjustment but then found that the stock throttle tube is too thin and flimsy to resist compression from my cramp buster and throttle lock, so I ordered an aftermarket ODI Fusion Alloy throttle tube and installed it tonight. Works perfectly. Because it is alloy it resists compressing forces from the cramp buster and operates smoothly regardless.

I tell a more complete story and post a bunch of pictures over on the Stelvio thread on advrider if you are interested. Happy to help anyone else here who has questions about heated grip installation since I have learned so damn much.

Thanks again to all who offered advice.

[Huzo]

Final update: I'm delighted tonight as I have everything working perfectly now. With help here and from friends on advrider, I was able to get the tube to work properly through cable adjustment but then found that the stock throttle tube is too thin and flimsy to resist compression from my cramp buster and throttle lock, so I ordered an aftermarket ODI Fusion Alloy throttle tube and installed it tonight. Works perfectly. Because it is alloy it resists compressing forces from the cramp buster and operates smoothly regardless.

I tell a more complete story and post a bunch of pictures over on the Stelvio thread on advrider if you are interested. Happy to help anyone else here who has questions about heated grip installation since I have learned so damn much.

Thanks again to all who offered advice.

Well done mate.
You are now a “go to guy” on the topic.