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Idle surging high and staying...runs ok except for...GS1100E

  • Thread starter Thread starter Anonymous
  • Start date Start date
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Anonymous

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its a 81 GS1100E with 17k miles, new V&H 421, and pod filters, 82 GS1100 stock carbs. The problem is the idle and mid throttle. First thing noticed about the idle issue. When first started and bike is warmed up nicely, it idles pretty well (1500rpm). If I give the throttle a quick turn to 4-5k and it will stay with the throttle back to normal. It did this before with another set of carbs I had on originally (they had leaky bowl connectors).
The other problem may be related but will separate issues for troubleshotting ease. When the idle is not stuck out (warming up is ok), it will rev very responsively all the time-no hesitation at all. It has alittle bit of miss, at times. The number 1 and 4 cylinders will burp back through carbs. Its not all the time, but mostly aproaching the warmed up stage.

I dont know as much as I like but would like any suggestions given. I did put on a used set of carbs that were from a running bike, the rubbers from carb to engine intake are brand new, have hi-flow motorcycle gas filter installed, and have went through all connections and cleaned then and checked for bad grounds and insulations. It does both these problems with the pod filters and will no filter at all. What I will do just for giggles, is to reinstall all the original air cleaner stuff and see how it reacts. Thanks for any help.
Chris :)
 
changing from stock to pods and free breathing four to one exhaust you will be real lean, you will need to re-jet the carbs richer.

this is the most time consuming thing on a bike and many people have pulled out all their hair (just look at Hoomies pic!) trying to get their carbs right.

with pods and pipe I would suggest starting out two sizes larger on pilot and main jets, and go from there.

folks with more experience at this will chime in soon, and there is a good chance someone has that set up already and can tell you what combination works best for them.
 
I figured I would have to rejet it for the pods for sure. The exhaust may have been the original cause of all the troubles. Previous owner installed the V&H, so it probably never ran right after that, hence the low mileage. After I got it, I was the one who installed the pod filters and it didn't change the running at all.

Just to summarize problems: idle is good at 1500, then twist on throttle up to 3-4k and the engine stays revved there. I have my hand off the throttle and it is not sticking. Now that I think about it, could it be that the opened exhaust is making the engine breathe better, and it trying to pull more air and fuel from the idle circuits. Which is why its staying at that rpm? And that carb burp thing is really getting me to think about cam timing. But with soo little miles, they are easy miles also (not hard driving at all) I wouldn't think.

What I am going to do next is install stock airbox parts back in and test it out (pain in @ss). Then do the spray WD-40 around carbs, boots, intake and see what that idle does. I appreciate the input. Also going to get new coils and ignition soon I hope.
Chris
 
The carbs will need to be sync'd with the engine hot. That should fix much of your high idle issues. Putting socks over your pods may richen things up enough to make it run better. :) I would set the hot idle at 1000 RPM, 1500 is too manic for me.

The V&H pipes were very common, I think you will be able to find the carb settings you need by searching the site.

Steve
 
Thanks, I will be playing with the carbs soon. Just gathering all info I can before all my hair is pulled out.
 
I have an 81 1100E, at one time it had a V&H 4-1 on it, stock air box, with a single foam Uni filter. The jetting that worked for me were DJ125 mains, stock needle heights (non-adjustable), 180 air jet, stock pilot and 4 turns out on the mix screws. Got a lot of popping on deceleration, but it went like stink when the throttle was open!
 
Your carburetors should be rejetted to accomodate use of the pods and aftermarket pipes. I suggest you go up 3 sizes from OEM for main jet and one size for pilot jets. Leave the jet needle as it is. If there is a flat spot off idle, use some Mikuni shims and put two shims under jet needle. You will probably find you don't need this jet needle shimming though.

As far as you idle problem, when idle shoots up high, it is because of a leak into the pilot system. Since this leak doesn't occur across all ranges of operation, it is very likely not in the intake manifolds or their seating but more likely that a vacuum cap is either missing or cracked. If you find the vacuum caps are in place or the vacuum lines properly connected and not leaking, then I believe the would want to check the o-rings on the mixture screws. You may also have poor seating on your choke plungers. When the bike idle shoots up, jiggle the choke actuation rod side to side. If the idle settles immediately, then your choke plunger pads are shot. I find this quite a bit on older carburetors where the pads have hardened or developed deep indentation and seating isn't complete or consistant.
 
All above advice is good,but you say the carb boots where new ,did you replace the O ring's on them?
Your symptems sound like a classic air leak with the rev's hanging like that, or your throttle linkage is sticking, check both.
And with those mods without uping your fuel flow, you can fry your valves.
You will need a carb sync, and with the fact you will be changeing jeting a few times just to get it right, you will be doing more than one.
 
Your slow to return idle is a lean condition/intake leak.
You should also set the idle to about 1,100 rpm's, not 1,500.
Since your manifolds are new, what about the manifold o-rings? Make sure all clamps are tight too. Check all o-rings inside the carbs. Carbs must be cleaned, floats set, bench synched and then vacuum tool synched. With pods, remove the two floatbowl vent lines too, to avoid fuel starvation. Leave the vent ports open.
Besides larger main jets, and at least richening the mixture screw settings, you WILL have to raise the jet needles for the pods.
I normally go with jet kits for re-jetting. Besides getting an adjustable jet needle, you may need the different air jets, etc, supplied. Enlarging the vacuum passage to the diaphragm chamber is generally needed and the bit and info included will help you.
You can try shimming and buying seperate jets, but I can't offer much on the shimming. Maybe raise the needles .05" and go from there?
 
It seems that I should use a jet kit to find the sweet spot and the suggestions give me a good median to start out at. Yes the intake boots and o-rings are new. The throttle itself goes back to normal, but will stay at the 3k rpm. I tried to wiggle the choke bar and it offers no help. Also tried to move the carbs around and check for seal leaks, none found. That I am thinking is the o-rings are bad and its just pulling the fuel on its own, buts its funny that it stays at 3k like its getting the correct a/f ratio. The throttle blades are closed for sure in that event. These carbs are worse than my kids, hehe.
 
Well, you'll find it if you check all the things listed.
It's usually an intake leak, but a very lean mixture will cause it too.
Lean mixtures burn so unevenly that it takes the pistons a bit longer to settle down again. The combustion cycle/timing is just screwed up you might say.
Pods and a pipe and a stock jet needle position make your bike a candidate for this.
 
The high idle does not return back to normal. If I give it another twist on the throttle, it will follow and stay there. I have to hit the kill switch and start it back up, sometimes it will return to normal and sometimes will go back to the high rpm spot. It did this on another set of carbs I had actually. Well, and to say that these are all 25 y/o carbs and suffer the same kind of things. I'm begining to think the jet o-rings and seals are bad inside. So I think I will need to start with a solid set of carbs, before I start the tuning. These tips are really helpful. Thank you.


KEITH KRAUSE said:
Your slow to return idle is a lean condition/intake leak.
You should also set the idle to about 1,100 rpm's, not 1,500.
Since your manifolds are new, what about the manifold o-rings? Make sure all clamps are tight too. Check all o-rings inside the carbs. Carbs must be cleaned, floats set, bench synched and then vacuum tool synched. With pods, remove the two floatbowl vent lines too, to avoid fuel starvation. Leave the vent ports open.
Besides larger main jets, and at least richening the mixture screw settings, you WILL have to raise the jet needles for the pods.
I normally go with jet kits for re-jetting. Besides getting an adjustable jet needle, you may need the different air jets, etc, supplied. Enlarging the vacuum passage to the diaphragm chamber is generally needed and the bit and info included will help you.
You can try shimming and buying seperate jets, but I can't offer much on the shimming. Maybe raise the needles .05" and go from there?
Click to expand...
 
OK, if it's hanging up and you have to turn it off (removing all vacuum) to get the rpm's back down, then it's something to do with the throttle plate(s) and the piston/diaphragm/spring assembly. A sticking throttle plate can stay partially open until all vacuum is removed, allowing it to fully close. Check operation.
A failing diaphragm/spring assembly can do the same thing. If you have any pin holes or an incorrectly seated diaphragm, the assembly wouldn't rise at all above idle, so a leaking diaphragm isn't the cause, but the spring/piston not operating smoothly would cause your problem. Check them too.
The throttle plates and diaphragm assembly work almost simultaneously, with the throttle plates actually opening first.
 
So theory of operation is that: when you twist the throttle, the plates open and then vacuum raises up the diaphram/needle to let the air siphon the fuel from the jet. Which is regulated by the needle raising and lowering. The pilot and idle circuits bypass the main system when no throttle is on to keep the engine going with a decent a/f ratio. I should be able to tell with the pods off, if a piston is sticking. Gives me some direction to go into :)
 
To maybe save you the trouble of reinstalling your stock airbox, I ran my 750 for a few miles without the airbox just to get it home, after troubleshooting what turned out to be a starter problem. It ran fine unless I tried to open it up a little, in which case it would bog down - too much air for the stock carburetor and exhaust setup I assumed. No rpm racing or hanging though. With the restrictive stock box and paper filter back in, it ran/runs great again.
 
As I have already suggested, the choke plunger pads may not be sealing. Next time your idle shoots up, jiggle or bump the choke rod to the shut position. If the idle drops at least for awhile, you know that the pads are either hardened or indented badly and not allowing a consistant seal.
 
Heheh...I had this same problem when I built my GS750L ratbike.
After putting the carbs on and startng it up the bike would immediately jump to 3500 rpm and stay there.

I couldn't figure out why! I cleaned and reinstalled everything and doublechecked it all.

Turns out I had the throttle cable adjusted too tight at the carbs!!
It was pulling the throttle plates partially open as if I was twisting the throttle!

:lol:

A minor adjustment of proper slack amount cured everything.

:P
 
well I am perplexed abit now. I do have about 1/8" of slack in throttle cable, I could totally loosen it back off and try it. It just has to be getting the air from somewhere. I know I will need to jet it. It has good throttle response and snap, but its not as stong of power as it could be. Its play time for me.
 
I know I will need to jet it. It has good throttle response and snap, but its not as stong of power as it could be.
Click to expand...

Your setup is pretty close to mine. I have an 82 1100E with Kerker 4-1 pipe and pods. It is a Canadian model and comes with adjustable needles stock. I am at:

pilot jet - 47.5 (stock)
mixture screws 3 turns out
main jets - 142.5
needles on #3 of 5 grooves

If you have the adjustable needles on your bike these settings will get you to a decent starting point to work from. If you do not have adjustable needles, try shimming them about 0.020"-0.040" and use the other settings as a starting point. I live at 3400ft, so if you are lower than that, you may want to work from a slightly richer starting point.


Mark
 
Great, thanks help. I think I have alot of backup now to go through and do a full check of everything. Just need alittle cool time to work. Its been hitting over 100 degrees here in sacramento. No delta breeze and humid, feels like 120!!!
 
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