Sticking throttle cable

Replaced throttle cable 2 weeks ago.
Lubricated the new cable prior to installation.
Had this issue initially: http://www.xjbikes.com/forums/index.php?threads/replaced-throttle-cable-rpms-go-up.47644/

Today on the ride home from work the throttle cable started sticking, not all the time, just every once in awhile.

Got home and it seems that the cable may have stretched a little, adjusted the cable for less free play and still periodically it will stick. Twist the throttle and let go and you can here the butterflies snap shut - 9 times out of 10. When it sticks it slowly closes back up, not all the way but to about 1700 RPM.

When I re-routed the cable in the thread mentioned above it was recognized that the 'barrel' end of the cable needed to be turned slightly to get it to seat in the throttle grip holder. A slight twisting of the cable shouldn't be an issue . . . right? For at least ten days after re-routing there was no problem . . .
I did clean the handle bar, and inside of throttle grip; lubricated with a little bit of over spray from the cable lube (HCP9574 from Chacal).

What should I look at to remedy this disturbing issue?

 

Are you sure it's the cable? When you installed it did you clean the throttle tube, the switch housing, and the bar, then re-lube with a graphite paste? Are you sure that the grip isn't catching or rubbing on the end of the bar or the switch housing?

 

If the throttle tube is the "L" shaped tube coming off of the hand grip, where the tension adjustment is - that was new with the cable.
I used PJ1 Cable Lube on the cable and inside the throttle grip.
Cleaned the switch housing, even put a little die-electric grease on the starter button connector after cleaning it (looking a little oxidized).
There is plenty of space between the grip and the switch housing.

Confused by the delayed reveal of this situation.

Wondering if the PJ1 is doing bad things to the nylon insert?

Ah Ha moment . . . "grip rubbing on the end of the bar".
After I re-routed the cable I recall sliding the grip as far on as it could (without exsessive force), there is a small spacer (1/2" wide or so) between the MC and the switch housing and the gap was smaller than previously. . .

Tomorrow morning I'll loosen the switch housing and nudge things out a little, see if that helps.

Still puzzled by the delayed 'failure' here, the end of the bar didn't have any noticable burrs/ sharp edge to it.

 

For starters, cable lube is not the best thing for the throttle barrel/grip/bar lube.

Use a white (lithium) grease on the bar/tube and on the flange on the throttle drum. Cable lube is for cables.

But honestly, it is most likely a cable routing issue. Pop the tank off, and revisit.

Do you have/did I send you the cable routing diagrams for your bike?

It could also be something amiss with the "linkage" a return spring on one carb could be slightly out of place or something else on the rack is causing an intermittent bind.

 

Yes Fitz, got the diagrams you sent and that is what got me to re-route the cable.

Everything was good until yesterday.

Gonna slip the grip out a little this morning, clean the cable lube off the bar and get some lithium on it.

 

Did you replace the grips? With some grips you have to trim the end of the throttle return then use something (i used the wife's hair spray) to completely seat the grip. Imo follow the advice of the gurus then loosen eveything. Seat the grip/throttle return on the handle bars then locate the spacer and control to it. How did you lube the cable? There is a tool for this, however, I use a small funnel. I slip the cable through the bottom and tape it. I pour a small amount of cable lube and hang the contraption so the cable is fully extended (add a drop cloth). It takes less than 10 minutes for the lube to drip from bottom.

Gary H.

 

Well things aren't much better.

Moved original grip back away from the end of the handle bar.
Double checked the routing of the cable vs. the manual pics (thanks Fitz!).
Drove 7 miles to work and seemed ok, but thought I noticed something weird about a block away from work.

After work had an appointment, drove about 3 miles, got on the freeway for about 4 miles and noticed RPM's hanging high when rolling off the throttle. Got caught in a backup on the freeway, pucker factor elevated. RPM's holding up around 4k.

Got off the freeway and pulled over. Turned bike off removed helmet, took a deep breathe, scratched head.
Started bike back up, twisted throttle and RPM's would hang for awhile and then slowly go down, twist throttle again and released it (looks like cable is slack by carbs) yet the RPM's are slow to drop.

Cautiously work my way home (I got a new appointment now!), noticing that the RPM's shoot way up when the clutch is pulled in and mellow a bit when in gear. In fact if I could stay in 3rd or 4th long enough in 5:30 Milwaukee rush hour traffic, the RPM's would drop down close to normal (1500-1700 rpm), but not all the way down.

On the center stand at home, re-checked routing, disassembled throttle grip and switch housing, cleaned, cleaned and re-lubed cable. Fed the dogs also. Start bike back up and throttle seems to move fine. . . .

It appears that the higher RPM issue may be related to a warm engine condition. Perhaps the newish throttle cable is perfectly fine and something is going amok in/on the carbs? Carbs were rebuilt this spring and have been running sweet since the end of May.

Toying with the idea of putting the old throttle cable back on to eliminate the new one being an issue.
Not taking it into work tomorrow AM, this evening gave me a bit of a scare. Planning on doing a quick 2-4 mile ride after work and see if there is a warm engine relationship to this . . .

Any thoughts on a carb issue related to warmed up engine?
Pondering's:
Last week I noticed there was a brief 'blast' of power in 3 gear. Like hitting the power band range but at about 3500 RPM's.
This week (second time in a month) found that elusive 'false neutral' between 3rd and 4th.
RPM's are not always hanging high, the throttle twist opens the butterflies and the RPM's go up (as they should) as the bike gets warmer it seems it takes longer for the RPM's to drop. Not always, but about 70% of the time.

 

How much free play should the throttle cable have?

 

I am so F'd in the A.
Went for a ride after work, just about at the 6 mile mark she starts hanging high again with the RPM's.
Doesn't stay there but takes about 3 seconds to drop down. That is waaaaayyy too long for me.
Stole an infra red heat camera from work, all 4 exhausts are running within 10F of each other.

I can see the top of the linkage at the carbs dropping down (loosened the cable extremely). Yet the RPM's are staying high. Sounds like I need to pull the rack and start looking at springs. . . . Does that make sense?

Would radiant heat on the springs expose a weak/ cracked spring for the butterflies?
Would the butterflies hanging open be the only thing to cause elevated RPM's ?
Pondered the idea of a stuck float and low fuel level causing the gas to start to 'atomize' early - creating a larger/ hotter combustion . . . But that logic doesn't sound sane.

I'm drinking tonight.
This is some of the greatest riding weather of the year.

 

when you did the carbs did you put in new throttle shaft seals? new vacuum caps on the ports?

 

What he ^ said and before you remove the carbs re-install the throttle cable, remove the air boots and visually inspect the butterflies. See if all four are snapping shut when you release the throttle. Hope this helps.

Gary H.

 

So if you apply the troubleshooting technique of what was the last thing I did to this working device (an assumption), then the throttle cable is number one on the list. However, during that process what else was done? Was the tank removed? Was the vacuum line disconnected from the petcock and consequently created a vacuum leak because it is now sealing poorly? Over and over again you read on this site hanging idle – carb sync and or vacuum leak.

So:

What about revisiting carb sync? If a butterfly valve is hanging on just one carb, then a noticeable change in sync should be evident.

Also, with an auxiliary tank hook-up you would have much a better visual of the throttle linkage and access to try forcing the butterfly’s closed as you duplicate the hanging idle. Additionally, some chemical spraying to chase down a vacuum leak would be much easier.

 

I certainly appreciate the thoughts. An extra set of eyes always helps one to keep an open mind.

Throttle shaft seals are new, vacuum caps are old. Tanks was removed, etc. . .

Sounds like I should get the propane torch out and check for leaks. Makes sense that when things get warm expansion of components could create a leak. Will need to re-borrow the vacuum sync gauge from co-worker; however that should clearly reveal if there is an issue with the whole rack or if one or two butterflies are acting up.

 

Further ponderings whilst stuck at work . . . .

If it was a vacuum leak, wouldn't the RPM's stay elevated and not drop down - or is my reasoning flawed?

 

I would say so. Sounds like a out of sync issue as rooster suggested. One or more of the carbs is letting more fuel/air mix through than needed. Could be a few things if the "air leak" test shows nothing including diaphrams, needles, springs, emulsion tubes, air and fuel jets and float heights. If the o-rings, springs and washers on the mixture screws get swapped or don't seat in the holes correctly problems will occur. Also debris on the tip of the mix screws will also cause problems. I'm not trying to scare you just going over in my head issues others have had with no air leaks and erractic reving. Hope this helps.

 

did you adjust the idle at all?
could some crud have gotten in one of the carbs only partially blocking a idle jet and the high rev is when it's working. this got me on that track
"Last week I noticed there was a brief 'blast' of power in 3 gear. Like hitting the power band range but at about 3500 RPM's."
kind of like something brought a lazy cylinder back to life. hot engines like a leaner mixture. Could a plug be misbehaving ?
look at your plugs and put the tank on prime and open the bowl drains, catch the gas in a clean jar and check if any crud comes out. I do this when i change the oil.

 

I'd suspect a vacuum leak somewhere too......very possibly the vacuum caps are too loose. But yeah, get your propane tank..

dave

 

Old vacuum caps are often rock hard whilst appearing to be fine. Better yet, if you have one that's not always leaking, you won't necessarily find it with the propane test. I speak from experience.

Take them off, and see how pliable or not they still are. You cannot go by appearance.

Also, check to be sure that a vac spigot hasn't come loose in its manifold. I've had that happen too, and fixed it with an application of JBWeld.

 

Think I got it.
Took an 8 mile ride yesterday, 7 mile ride to work and 12 on the way home and she is purring like a kitten again.

Did the following yesterday, interspersed with test rides.
Checked float levels.
Drained bowls and inspected gas for debris.
Checked for vacuum leak with propane.
Verified cable was loose at carb linkage.
Put old throttle cable on.
Checked gas cap vent.
Checked for vacuum leak with propane.
Checked spark plugs.
Verified cable was loose at carb linkage.
Drained bowls again, looking for debris.
Put new throttle cable back on.
Pulled rack.
Noted that all 4 bowls were slightly loose (using short end of Allen wrench got 1/16" turn) figure new gaskets shrunk instead of expanded . . . Can't believe any leak at the bowls caused hanging RPM's???? Tightened up all screws.

Bowl #2 - this bowl had a stuck drain screw when carbs were rebuilt. Old screw was drilled out and threads were re-tapped. There was an ever so slight leak, didn't want to over torque so carefully (so I thought) applied thread tape to The new drain screw. Turns out the thread tape unraveled inside of the bowl and there was a 'tail' floating around. Cleaned that up verified the bowl jets were clear; reassembled and bada bing!

So - if fuel was being blocked going into carb #2 by the thread tape tail, would that create a scenario that would cause the RPM's to hang high (and slowly drop down)?
And wouldn't a 'mis-firing' as such have shown up when I checked temperatures at the exhaust?

Or maybe the removal and re-installation of rack, freed something up?

I don't like having a mystery . . . Planning on a longer ride tomorrow, but as she stands I think it is good; historically symptoms were showing up at 6 or less miles.

Thanks to all for the tips and tricks!