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Old May 8th, 2011, 09:41 PM   #1
The Blue Rider
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Stuck throttle after Area P install & new needles

I've got a stuck throttle issue on my bike. I did some work/mods on it this past week which I should describe first. I live in apartments and I don't have a garage, so I rode to my lady roommate's parent's garage and did the work there:

- At the garage, I installed an Area P 18" Quiet Core full system, removed the snorkel, put in a Pipercross air filter, and went into the carbs from overhead (I didn't pull the carbs, just took the tops off while still on the bike) and added Factory Pro needles set to the 3rd position. I also removed the Kleen Air system and capped it off with Slingshot Racing's plate. I plugged the Kleen Air's airbox hole and top of the vacuum line "T" with some 3/16" and 3/8" vacuum caps from O'Reilly's, zip-tied tight. The only hiccup on the vaccum lines was that I had a hard time refitting the little clip on the fuel tank's vacuum line, but I eventually got it to stay in place. No changes to pilots or mains - stock pilot (#38?) and main #98. I used a couple of posts in the Jetting Database as a starting point and I was pretty confident in what I had read, that I wouldn't need to do much adjustment afterwards and that it should be set up good enough to at least ride home. Dumb? Maybe, but hey, I trust what I've been reading here.

I started it up for a test ride around the neighborhood. With full choke on the RPM immediately climbed to 4000, so I cut that down to half and let it run for a couple of minutes. Idle seemed to become stable very quickly. I went out and test-rode it around the neighborhood, and everything seemed to work OK. There was a little bit of popping and rippling on deceleration/throttle closure under load, but the bike was much smoother, more powerful and rideable, as I expected. I kept it to local environs, 1st & 2nd gear, maybe 40mph tops. I came back from about a 15 minute ride, and set the idle to 1500 and then tried adjusting the idle mixture screws. I ran into trouble here, basically I was having a lot of difficulty with the "2.5 turns and then adjust while blipping method"; the throttle kept sticking high. The bike was running for about another 15-20 minutes straight while I worked with the MOS screwdriver trying to get things right. I ended up turning idle back to what seemed like stock setting (1300 +/- 50), then turned the right & left mixture screws by ear, going all the way in and then backing out until the engine sounded smooth, and blipping yielded a smooth return to idle. Everything seemed pretty good at this point. I didn't test-ride because it was getting late and I really needed to get the bike back home (it had been at the lady's parents for a week while I worked on it every day after work). So I let it cool off, then later I buttoned the fairings back up, and rode home.

- I did not synch the carbs as planned (I have a Morgan Carbtune), because while I had the tank off I decided against cutting into the vacuum lines and adding the cheap-looking fittings I bought from O'Reilly's... I had eyeballed it and figured (wrongly) that I could probably get to the vacuum taps on the carbs while she was running. Once I was facing a hot engine and tiny access space, I realized my original plan sucked. I decided I would have to ride around during the week, then head to another friend's garage to make any changes to any issues I discovered with the new setup, and do the line cutting & synch there later.

- On the ride home, at the first stoplight after several miles of riding at higher load (45+ mph instead of puttering around the neighborhood at neighborhood speeds), the bike died after I came off the throttle and clutched in at stop. In retrospect I set the idle too low back in the garage, because it didn't exist anymore. I didn't realize that I could have just pulled off and fiddled with the knob through the opening in the fairing behind my calf, either. For the 20-mile ride home I was keeping the throttle on at every stoplight to stay running.

- On the highway and in town, everything seemed to work fine, except for the dead idle. I had tons of power on the highway, lots of pull even up top all the way through the rev range, no issues. Everything was great except for coming off of stops, which was a mess because I had to keep a little bit of gas on to stay alive.

-----

Now here's where I really ran into the stuck throttle problem full force.

- When I finally parked back at the apartment, the lady of the house came over (she followed me home in my car) and I was telling her that I was glad to get home, because I had no idle and stop & go situations had really sucked. I was still sitting on the bike, still running and in neutral, and I showed her what happened when I let off the throttle... The RPM dropped to zero and the engine died. I restarted with a bit of choke, gave it the gas to repeat the phenomenon... And the throttle stuck where I left it!

- I tried this several more times. Kill switch off, then on, push starter with choke, engine on... Take choke off, give it gas, then the RPM sticks wherever I leave it and it doesn't come back down. The idle adjustment could also trigger a stuck-at-higher-RPM condition; I turned it enough to get 1300 at startup, but if I turned it to far it would climb out of control and stick around 3-4K. It felt very mechanical, the RPM didn't come back down at all, it just hung where I left it, which suggested to me that maybe I had binding cables. I couldn't get the throttle to change by moving the cable around, though.

- Confused and thinking I needed to go hit the internet for answers, I went back inside, got my gear off, watched half of the Rangers vs. Yankees game, then came out during the 4th inning after Derek Holland lost control of his slider and the Yankees started hitting... I tried the above and got the same result. Start the bike, let it run at idle for a bit, then hit the throttle... Wherever I leave it, it stays there. 4000 RPM, 6000, whatever, it sticks and doesn't come back down. I can even get it to stick with the idle adjustment; if I turn the idle adjustment far enough (above about 1500), the RPM climbs out of control and goes up to 3-4000 and stays there. I have to kill it and restart to make it go away, the "closing" action of the throttle grip doesn't work, even though I can see all the linkages moving on the right side.

- Choke doesn't seem to create this problem. I have to double-check this, but if I start the bike with choke, and then close the choke, she drops back to 1300 like normal. It's only when the RPM gets pushed above 2000 by the throttle grip or the idle controller, that it sticks high and doesn't want to come back down.

- The gas is fresh Chevron 87 Octane with a can of Seafoam. I hadn't ridden in a couple of weeks before starting work, due to some personal issues, and I wanted to make sure on the ride over (about 20 miles, mixed highway, main streets, and small back streets) that I took the opportunity to burn out any crud, so I filled the tank to the top and added the whole can of Seafoam before departing for the garage.


---

I realize I changed too many things at once, and I'll have to go back over everything and do some methodical detective work. Based on my description, is there something I should check first that might be the culprit? From what I've read, it could be any one of several things... Vacuum leak, internal carburetor hangup or leak, or an intake leak at the carb boots, or stuck throttle cables... Any ideas?
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Old May 8th, 2011, 10:10 PM   #2
setasai
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Yikes. A lot of things happening here. My first guess is a vacuum leak and anything that might be associated with the carb. I seem to be having a vacuum leak issue as well and it's also causing the rpms to hang around and drop down slowly regardless what the idle mixture screw is set at. Makes me wonder if you have a larger leak than I do if it's not coming down at all.

kkim has suggested that I get the bike running and spray water around different areas of the bike and if the idle changes then it's a leak in that region. Idea is that the water plugs up the leak for the split second and seals it until the water gets sucked in.

I would take the fairings off and methodically just follow all the tubing to make sure everything is on tight and check each and every change you did one at a time to see if there's something obvious. Did you check binding of the throttle assembly?
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Old May 8th, 2011, 10:13 PM   #3
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first, does the throttle return to a closed position when you open it and let it go?

second, down by the carbs, does the throttle linkage mechanism return to the fully closed/stopped position when you open and let the throttle go?

in this pic, I'm using my hand to turn that linkage mechanism...
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Old May 9th, 2011, 08:38 PM   #4
The Blue Rider
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I played with the throttle handle while looking through the gap in the fairing when I got home from work; both opening & closing cables are in place, both are moving, and the throttle snaps shut when I let it go, from any position. I don't see anything that looks like binding. The circular spring is in place and everything mechanical looks to be functioning as normal.
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Old May 9th, 2011, 09:07 PM   #5
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if you're sure the throttle cables are not binding and the carb linkage plate is closing to its stop, I would do as setasai mentioned and look over your work for a vacuum leak. are you sure you capped and reconnected all the vacuum ports/lines properly?
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Old May 10th, 2011, 06:20 AM   #6
bdavison
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Im guessing the needle's are getting stuck due to the shims, or the slides are getting stuck.
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Old July 25th, 2011, 09:01 PM   #7
The Blue Rider
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FIXED!

The problem was that the idle mixture screw for the right-hand carburetor fell out, probably right when I came to a stop at my apartment at the end of the ferry ride from the garage where I first did the carb work.

I've had the bike up on stands for a while at a friend's garage... He trailered it to his place for me and we ran it a bit on stands. He said the exhaust smelled very rich.

I took the carburetors out, and as soon as I got them clear of the frame I turned them over, and the right hand idle mixture screw was missing. Yeah, that screw is kind of important... Having one missing might be a problem, no? I unscrewed them both too far when I was doing my half-assed "carb tuning by ear" and the right one eventually fell loose, thankfully AFTER I had stopped, and not at any point on the 20-mile ride home (I actually found the entire screw assembly, complete with rubber washer and spring, in that deep dark gap between the starter and the upper part of the engine case on the right hand side).

So... I cleaned the carbs, replaced the float bowl gaskets (they were dry and crushed almost flush with the top edge of the float bowl lip), installed the #40 pilots per Factory Pro's instructions, and very carefully set the idle mixture screws to 2.5 turns out apiece, which, by the way, leaves the idle needle tips exactly flush with the carburetor throats on the engine side.

I also cleaned and lubed the throttle and choke cables, installed new Iridium plugs, put in fresh gas, added stainless steel brake lines, and now she runs great... I had my friend ferry the bike back to my place for me since he's more experienced and I hadn't ridden in three months, and he agrees that it's a huge improvement all around.

So the verdict is that a #40 pilot, stock #98 main, Pipercross air filter minus the snorkel, 2.5 turns on the mixture, and full Area P is a winning combo on my bike.

I need to do some riding to write up a more detailed review for the jetting thread, but for now, I'll just say "be careful" with those idle mixture screws... If you lose one, the symptoms are very strange. This time, I put a couple of tight-fitting vacuum caps over the idle screw towers to prevent loss in case one or both of the screws ever worked loose in the future.
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