Sticking throttle?

So, I got my carbs rebuilt and put new plugs in, and was overly eager to see if my bike would finally start. So eager, in fact, that I neglected to attach my choke and throttle cables. I put them both on, started it up, and realized I put the throttle on improperly. Then I had a friend come correct it properly (to the best of my knowledge), it starts and runs, but the throttle will stick, even if the right grip is all the way in (what is supposed to be) closed position. Occasionally, it will get stuck up around 4000, and i'll have to just shut the bike off to get it to go back down. Any idea whats wrong? Does it have something to do with the fact that I improperly connected the cable first?

 

To clarify-you mean your revolutions are staying high right? not that the throttle assembly or grip is actually sticking.

Adjusted your idle knob out? Its a big knob sticking backwards below and in the middle of your carbs. Either reach in with one or both hands and screw your knob counter clockwise-or if your like me and your hands won't fit-use a long handled flat blade from the left and push on the very bottom lip of the knob.

You can easily check to see if your throttle cable is correct. There should be a small amount of play from all the way off (forward) before it starts to pull up on your carb throttle assembly-about 1/10 full rotation of throttle. And when you release it there should be a metal spring 'clunk' sound.

Are your mixtures set correctly?

 

I'm not sure if its the throttle assembly or the grip or what. I twist the handle, and the grip will sometimes stick. Then, if I try and manually twist the grip back, sometimes the RPM's will go down with it, sometimes not.

 

The grip is just hollow and slips around your throttle tube. Unless you had this apart for some reason it's your cable, or throttle assembly on your carbs.

Let me ask you a few questions:

Are your cables new or old? Did you thoroughly lubricate the cables before putting them back on?

Is your carb throttle assembly moving freely? It's spring loaded and will return to "off" very forcefully if its proper. Use your right hand and twist your throttle on (bike not running), with your left reach in and hold your assembly (in-between #3 & #4 Carb body)-begin to let off on your throttle at the grip and feel how much force the assembly is pressing down with-it should be a lot-if not your springs aren't working right.

 

Or your throttle cable and/or enrichment cable is routed incorrectly

 

Make sure the Geometry isnt causing the Cable to bind.

Check the Cable-end Bracket.
It sometimes gets bent during the removal jostling.

 

Awesome, thanks for the help guys. I'll go take a look!

 

Well, I finally got out to check. The springs on the carb seem to have plenty of strength to re-close the throttle (though they do make a strange click as the throttle is closing its last little bit). The cables are looking old and worn. and i'm not totally sure where on the bike that throttle cable bracket is to check it.

 

There are a great number of reasons for Sticking Throttle:
Handlebar Control Placement
Idle Adjuster too tight
Cable Slack Adjuster too tight
Cable Installed Improperly
Cable needs Lube
Cable has broken wire
Cable Sheath not anchored
Sheath not seated in Ferrule
Ferrule not seated in Carb Mount
Wrong Cable

 

Well i'm pretty sure its the plastic throttle sleeve that was sticking, because there was no lube at all on the handle bar. Is there a recommended lubricant for such a job? I also ordered a new throttle cable just in case that isn't the problem.

 

Also, is there a trick to get the right hand grip out of the throttle sleeve? I bought some new grips to replace the old shredded ones.

 

The others know much more than I do, but I just did this yesterday- I used a very light sheen of tri-flow lubricant (Sprayed it on, and wiped most of it around and off with a paper towel)

 

Compressed air, and it will still require some tugging. The stock grips (if that's what's on there) have grooves molded in the inside that engage with ridges and "lugs" on the barrel. In most cases, when switching to aftermarket grips, you'll need to take a Dremel to the square lugs at the very least; and maybe "soften" the ridges a bit.

The original grips were molded rubber; if what's on there aren't, then they're not stock. In which case who knows how they're being held on.

I use Tri-Flow as a cable lube; but I use a white lithium grease on the handlebar/throttle drum.

 

Hmmm. Is there a proper way to lube the cable?

 

There's a tool you can use to make it easier, but it's not hard anyway.

Get a cable lube that has a straw, cut the tip of the straw at about a 45 degree angle, then holding your cable vertical wedge the straw into the gap between the cable and sheath and pulse several sprays while moving around the cable, most will go inside some won't. Spray until you begin to see lube coming out the bottom of the cable. Work your cable back and forth to fully distribute the lube. Wipe off any excess lube that got on your sheath and your done.

I wouldn't scrimp on the lubrication you use as better quality will last longer and protect your cable better. If your bike spends a lot of time outdoors, riding in bad weather, or in dusty conditions you should do this more often than the schedule.

 

Gahhhhhh. I ordered a new throttle sleeve, new throttle cable, lubed them both very thoroughly, and my throttle still wont close by its self after turning the handle. I'm almost positive my springs on the carb are fine, because when I lift them with my finger, it snaps close very quickly. Any more ideas?

 

and can someone please tell me where on the bike this is?

 

On top of the bank of carbs, up under the tank. The best way to be able to see it clearly is to pop the fuel tank off.

The bracket itself is attached by a couple of one of the carbs' hat screws, the part Rick is talking about is positioned just above the throttle linkage itself.

 

Also, you may not have a binding throttle at all. I went through all of the linkage checks and lubricating as well, and it turned out on my bike that the "throttle" hanging was actually caused by a bad crack in the intake boots causing a vacuum leak and keeping the revs up. The bike would rev to 4-5k, and hang for a while and very slowly creep back down.

 

Its not just the rpms that stay high is the problem. The right grip will not physically snap back to closed when I want it to. I have to turn my wrist back up to close the throttle.

 

Sounds like you're on the right track; it's binding somewhere.

Did you pull the tank when you replaced the cable, or just "chase" it with the new cable?

It could be the bracket we've been discussing, a routing issue, or a bind at the throttle drum/switch cluster assembly.

Again, you'll probably need to pop the tank off and pay close attention to the routing and the cable's relationship with the bracket.

 

The only thing I can think is the throttle drum/switch cluster. The only parts up there that i've lubed are the actual handle bar and the inside of the throttle sleeve. Is there something else I should be lubricating?

(link to a video i made that will hopefully help)
http://s24.photobucket.com/albums/c3/yo ... -00000.mp4

 

The cable.

Have you pulled the tank, checked your routing for proper "gracefulness" (no sharp bends) and checked the alignment of the bracket we've been discussing?

This isn't a "lubricate." You've got an actual bind somewhere; the linkage return springs are strong enough to overcome mere "stickiness."

PULL THE TANK. Check bracket / relationship with cable / cable routing.

Did you install lower bars or do something that might be exacerbating the situation?

 

The tank has been off the whole time. you can see the whole line and the bracket in the video up there. Can you see somewhere that it might be binding?

 

Did you recently glue those hand grips onto the bike? I found that when I installed new hand grips (my bike came with ONE), I accidentally got some glue too close to the housing on the handlebar for the throttle and starter. The end result: I had a sticky throttle that the springs would NOT recover. Yours is acting almost exactly like mine was. Peel back the grip from the housing and see if the glue is causing extra drag.

Did the stock throttle cable run over that support racket at the back of the gas tank? That seems odd, maybe try zip-tying that to the bottom of one of the frame supports there. Maybe that is a pinch point putting extra stress on the cable and preventing it from snapping back.

Also, try to shoot some powder graphite lubricant in both ends of the cable cover. It will help lubricate it without attracting dirt and grime that would impact cable movement later on.

That's just my two cents on the matter.

 

I just ordered a new throttle housing, and they come from the yamaha factory with a black grip installed. However, there is some residue on the handle bar which appears to be dried glue from when the previous owner put on some (ugly) aftermarket grips. I've since lubed it to death, so I dont think thats it.

When i took the tank off, that is not how the cable was routed down to the carbs. However, the throttle was sticking back then as well, so i've tried numerous different configurations in an attempt to make sure there is no binding.

I also bought some lubricant specifically designed for cables, and have used much of the can.

I appreciate all the ideas, though.

 

Try disconnecting the throttle cable from the carbs. Turn the handle back and forth moving the throttle cable and housing around. Make it completely straight, bend it at different points (like where it comes off the handlebars and down to the frame, where it bends down to the carbs and so on) to find the spot where it is binding. IF it is binding when completely straight, then I would suspect it would be the throttle housing itself.

Let's see what the seasoned experts think, but once again just my $.02. No matter what it is, good luck!

 

Sounds like a good idea, i'll go give that a try

 

Howitz, I attached a couple of pics. Mine is an 82 750, but cable routing and bracket location should essentially be the same. The bracket for the throttle cable is positioned on the 3rd carb hat from the left as sitting on the bike. The cable is the one on the right side of the bike, it runs down the bar in front of the head tube, and then along the right frame tube under the tank. Not a whole heck of a lot of bends there, just gentle curves. It sounds like you (if you haven't already installed the new cable you ordered) that the old cable had broken strands that are binding on the inner sheathing of the cable housing. Hope it helps...

 

This is a good idea at this point. Disconnect the cable at the carbs, operate the throttle while YOU pull on the end of the cable in place of the rack of carbs, and see if you can "feel" where it's binding. You should be able to figure out whether something is binding the cable, or the throttle, or even the linkage itself.

If there's "residue" on the RH end of the handlebar, get some lacquer thinner (or sandpaper) and get it off. The handlebar should be smooth and clean for the throttle drum to pivot on.

 

From looking at the video and the way the cable is routed, I'd have to go with the throttle housing itself. You have it routed pretty straight-forward and if it was doing this before, I'd have to believe that it's the glue on the bars.

If the bars aren't perfectly clean, the housing will hang up.

 

Well i've now sanded down the handle bar and used wayyyyyy more lube than I thought I needed, but it made a little difference. It now will stick some times, but not every time. I also disconnected the cable from the carbs and bent it in several ways, seeing if it was binding, but it seemed to be just fine.

Side note: I also switched from using the white lithium lube on the handle bar to wd-40. I think that sliding the throttle sleeve onto the handle bar was pushing all the thick lube off the bar, and wd-40 stays on a little better.

 

Is there anything inside the grip housing? Any grit or grime inside there will interfere with the operation also.

WD is a good cleaner, not a good lubricant.

I always used graphite powder (for locks) on the motocross bikes.

 

The grip housing was brand new from the factory. I removed it 2 or 3 times and used white lithium grease (a large amount), and it didn't rotate as freely as it did when I used WD.

 

Then use a thinner lube, like Tri-Flow. WD40 was formulated to displace water. Its use as a cable or other lubricant on a motorcycle is downright dangerous. WD40 gums up quickly once exposed to heat; it's fine for house door hinges. Use it as a motorcycle lube and it can wreck you. Seriously.

I have used Tri-Flow for years and highly recommend it: http://www.triflowlubricants.com/Tri-Fl ... icant.html

 

Best advice yet. WD40 is more trouble than good. Try to clean that out soon and use a graphite powder lubricant. Take your time with it and make sure everything is clean before inserting it.

WD40 also is great for attracting dirt and other particles that make excellent rust catalysts and snag points.

 

How do you guys feel about PB Blaster as a lubricant for cables or anything else?

 

Which Triflow lube should I get? Theres normal, dry, or grease

 

I use the regular aerosol lube; ("normal") plus I have a tube of the grease.

PB Blaster is a penetrant for breaking stuff loose (like Kroil) I don't know how well it would hold up as a lube.

 

GAHHHH! I got the lube in the mail today, went out and re-lubricated the handle bar, and the problem seemed to be fixed! The throttle wouldn't stick, and the grip would go right back to the original position after I let go...

unfortunately, I went back inside for a couple hours, came back out to check if it was still good, and it went back to sticking about as bad as it used to

Could it possibly be the cold thats causing it to stick? It was a little warmer earlier today when It seemed to work..

 

Is your bar bent maybe? Tweaked in such a way that it's no longer a conic section? or maybe what haven't you replaced?

+1 to the WD verdict-I only use it for cleaning away dust and dirt from parts that don't like water.

There are different types of lubricants including dry based ones that won't attract dirt/grime.

 

try "lock ease" - available at fleet farm, its a great graphite based aerosol lube.

http://www.amazon.com/AGS-LE5-Lock-Ease/dp/B000CIJUGA

 

Its not affected by the cold at all, as its what i use in my car doors over winter as well.

 

gahhh. I hate the thought of buying another lubricant for the job. I've now tried 3. Hmmm, the bent bar could be an idea. I plan on trying some superbike bars in the future (maybe more near future), hopefully that will solve my problem.

As far as what i've replaced in this area, i've replaced the throttle cable, throttle drum (sleeve, whatever you want to call it), and well...thats it. Those seem like the two most likely candidates for my condition.

 

After rebuilding my carbs I had a similiar intermittent throttle sticking issue. After dinking with it for awhile I pulled the carbs off and realized the new o-rings were too tight. I switched types of o-rings and now it works great with no sticking. This might be something you wanna check. Just an idea.

 

Hmmm. Where exactly on the carbs are the O rings? And would that result in the throttle grip itself sticking in place?

Btw, thanks guys for being patient with my seemingly stupid problem. People on other forums are less than nice when I ask ignorant questions.

 

I think he might be referring to the throttle shaft seals, and no it wouldn't.

Have you made sure it isn't something in the perch/switch cluster assembly that's binding on the throttle drum and/or its flange?

Quite honestly, you should be able to assemble the whole thing DRY and it shouldn't stick like you're describing. Changing lubricants isn't going to fix it; there's an actual bind somewhere.

 

Hmmm, i'll be sure to go out and look at the cluster tomorrow. This was my first time disassembling the cluster, so I made sure to focus on how it was put together so I could reassemble it properly, but its very possible I could have put it together wrong.

 

If you even push the grip on too far, you can cause a bind between the "flange" on the grip/throttle drum and the housing. You should have a thin, plastic/nylon washer there too.

Try moving the whole assembly a few MM toward the end of the bar; maybe the bar itself is binding on the inside of the end of the grip. Add some clearance, Clarence.

 

How can you say no it wouldn't? On my carbs this was the problem. Two of the carbs throttle seals were too tight and caused the butterfly's to stay open.
It depends what kind of o rings you used during rebuild. I switched
From standard o rings that were too think to thinner double seal o rings and boom no sticking.