'84 GL1200 Low speed stumble - IDLE DROP Procedure

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Write2Paul90277

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Help! My 84 GL1200 Interstate is currently experiencing that ol' stumble-off-idle / bucking transition between 1500 RPM to 2500-3000 RPM.

Also, it takes FOREVER for the engine to warm up. I have to fiddle with the choke constantly just to get it to pull from low speeds without shuddering , and I'm not talking about the first few blocks or a miles, but halfway across town.
(Thermostat is fine, BTW)

After searching the forum and Google for the Idle Drop Procedures (and trying them) none of the solutions works.

I thoroughly cleaned the carbs (new jets, O-rings, etc.) and synchronized them using dial-type vacuum gauges. Spot on.

When I performed the infamous IDLE DROP PROCEDURE, I used an external digital tachometer, but the digits just bounced around and were of little help.

When I tried the "LISTEN FOR THE HIGHEST IDLE" technique, I really couldn't hear any difference in the engine speed as I adjusted the idle mixture screws.

QUESTION: Is there a "typical" setting for the four idle mixture screws? I've seen suggested settings ranging from 2 ¼ turns (out) to 3 or more turns. Has anyone just set their idle screws to a certain number of turns and then SKIPPED the whole Idle drop issue?

Am I dreaming? Is there an easier way out -- without converting to a single carb?

Curiously yours,

Paul
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Set the idle at 900-1000rpm. Adjust 1 mixture screw to the highest idle you can get. Adjust idle back to the previous setting. Adjust the next carb to the highest rpm you can get. Set the idle back to the original level again. Now adjust the third carb mix screw to the highest rpm you can get. Return idle to the original rpm and do the same for the last carb mix screw. Repeat the entire procedure once more. Then leave it. Forget the idle drop procedure as it leans the mix too much.
 
hmmmm id say the carbs are still the problem ...all new stuff and a good cleaning can make things come loose after it been running a while ....sounds lean ..but it could also be rich ....run it at low rpm riding or in the stubble zone and then check the plugs and see what they look like ...clean plugs first and stumble across town and back keeping rpm low ...might find the carb causing the trouble this way or carbs ...thats how i check things on stock carbs to get a clue
 
My 1200 carbs choke linkage sticks occasionally. Be sure the choke is in fact all the way off before adjusting.
 
Yup. Fresh O-rings for sure.

But it wouldn't hurt to check for leaks in the intake horns. I will look into it tomorrow.

Thanks!

Paul
 
Also...

Not to be overly persistent, but would anyone care to recommend an initial idle screw setting (number of turns out from fully seated)?

Thx,

Paul
 
General rule is 2 1/2 turns out from lightly seated. There you are pretty certain to get it running. Adjusting from there.
 
I feel your frustration. I have an '83 aspencade, paid a pretty penny for a beautiful bike with 49 k miles on it. Runs perfect and is a joy to ride. My other bike is also an '83, with a mix of parts from an interstate and a std. I carefully rebuilt the carbs with a complete Randakk's kit and book. I was thrilled when the bike started right up and ran pretty good with only a bench-synch. Did a vacuum synch and it ran a little better. I took the caps off the mixture screws during the rebuild but had to replace a broken one during this time. I have no idea if this new (used) screw is oem but it looks just like the other ones. Here is where MY frustration arises... the rebuilt bike just doesn't have that little extra torque of the pretty one for a smooth take-off. I have to give it extra rpms and slip the clutch a little more to get going without the engine protesting and shuddering a little. When I have tried adjusting the mixture to get better power, I use an external tach and can get No change in rpm no matter where the screws are! Believing the engine was running lean, I turned all the screws out another full turn and ran the bike. 800 miles later it seems to be slightly better, but still not anywhere near as nice as the pretty bike. So how come my mixture screws seem to have no effect on the idle speed. I was meticulous in making sure all the passages (idle and acceleration pump) were clear during the rebuild. It has a new fuel filter, and gets pretty good gas mileage (45mpg)? I'm stumped, sorry for hacking your thread.
 
Did you remove the mixture screws and spray carb cleaner through the passages? Most of the times I've set the mix screws I've had to go both in and out to find the highest rpm. Adjusting multiple carbs all must be adjusted twice because every carb affects the others.
 
Yes, when cleaning the carbs I removed everything and proved the passages were clear by seeing the spray cleaner exit at the appropriate orifice. I dipped the carb bodies in carb cleaner liquid for 24 hrs each. I'm sure all the passages were clear at least at the time of reassembly. since then, I have been unable to detect any change in engine speed due to adjusting the mixture screws from all the way in to almost out of the hole! Rebuilding was not difficult, sychronizing was actually quite satisfying, but mixture adjustment is my nemessis!
 
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Sorry to hijack your hijack, but were ALL of the rubber parts removed before the 24-hour carb soak? I believe it's Randakk who warns us to never use a dip solution if there are any rubber parts involved. I'm guessing that deteriorated o-rings and such could lead to air leaks.
 
Try starting with the engine warm at the lowest idle it will run. In fact lower the idle until it quits then raise it just a 1/4 turn. So it will continue to idle. Then set the mix screws. Changes there should be very obvious. Be sure after each carb is adjusted you return the idle to the original minimum rpm. Once all have been set twice. Set rpm 900-1000rpm and test ride.
 
Paul, yes, all rubber parts were removed prior to any carb cleaners. I have lost too many expensive rubber parts while learning that "carb and choke" "cleaners" are actually eliminators. On a side note I couldn't be happier with Randakk's stuff.

Unfortunately, all of this is just conversational till spring. The bikes are in storage to make room for another project at the moment.
But while i'm still hijacking...does an 84 carb have accelerator pumps to cover the transition from idle jet to main jet? Are we sure those passages are clear? I'm going off to re-read the carb thread I saw last night on the stumble situation.
 
Ok, I found the post on off-idle stumble. It is on Randakk's site, HOWEVER...the info refers to gl1000 carbs! Maybe the repeated claims that these bikes are set up from the factory to run lean also includes the 84 gl1200 carbs too. You say the bike takes a long time to warm up. Could this be a reduction in the power available from ethanol-tainted gas. Maybe having a little more gas available would help the stumble situation. How do your plugs look? Do they give any indication of lean vs rich?
Keep in mind that these observations are from someone who has difficulty working with mixture screws! But I did find a way to make mixture screws really easy to adjust.
 
all it takes is slides that are a bit sticky or vacuum leak and carbs go way lean...1200 carbs are usually better at not being lean ....still there couldnt be a more piss poor set up to try and keep dial in right .... at there best CV carbs start off lean ...CV carb are always late reactors by design ....the motors always need the gas way before they get it ..this cuts power at low rpm hugely....and if they get off any at all it stumbles and spits and can hardly get going cause there right at the edge at there best ... yes the crap alky gas of today makes it even worse ...atf in gas helps this some and also cleans things up while running.....pretty much and i hate to say it ....the design for the boxer oldwing motors is just poor ...just about anything trips them up....not trying to discount just trying to point out how difficult this can be ...as passages and jets float valves are all small and that means there a small window where all this works ok...certainly not a clean and go and be happy deal x4
 
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THE LOW SPEED STUMBLE IS GONE! posting.php?mode=reply&f=36&t=11934#

Thanks, people for walking me through the idle drop / low speed stumble problem on my 84 Interstate.

You are not going to believe what the problem was:

The idle jet on the #4 carb had FALLEN OUT. No wonder all that excess air was getting sucked in. Apparently when I was at my most confused point in the idle drop fiasco, I lost track of the number of turns on the various pilot screws and #4 must have been totally loose.

Luckily I had a spare pilot screw, spring, washer and o-ring which immediately corrected the problem.
This time I started with 2 ½ turns out on all four carbs, then did a sync and got good results. There was a nice smooth transition from idle, off the line, and transitioning to the primary jets. No more stumbling or bucking! The idle was a bit rough (sort of a loping beat) so I tried 3 turns out and the transition got even smoother.

What a difference! THIS is the Goldwing I know and remember.

Keep in mind that all I did was set all four screws at 3 turns out. I did not actually do the idle drop procedure, since I had previously had no luck in making the idle speed go up or down no matter how many turns in or out. With such smooth throttle control, I am willing to live with a slightly rough idle.

My plan is to leave everything as it is and enjoy the bike once again. Should I feel guilty for skipping the idle drop altogether?

Thanks again everyone.

Paul
 
Nah no guilt, I might not either after spending a lot of time futzing with it already lol.

Glad you got it straight. Sure is nice when these old beasts run like they should and very gratifying knowing you got it there with your own hands!
 
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