High idle after carbs clean and gasket replace

I just rebuilt my carbs and got them all clean. I replace the gaskets from head to intake boots. I am idle around 3k and sometimes jumps to 5k. The choke is not sticking. I bench synched the carbs when i had them off. I am not sure where to go from here. the idle adjustment knob is all the way backed off. Any ideas what to check

 

did you check the throttle cable for proper adjustment.
are the carb to manifold boots new?
you need to do a propane test to look for leaks you said rebuilt so I will assume you changed the throttle shaft seals.
use an unlit propane torch and check around the intake boots and vacuum port caps. vacuum line to petcock.
if no results use carb cleaner.
it could be your petcock is leaking fuel into the vac line. pull it off and see if there is gas in it or leaking from petcock
did you check your wet fuel level after installing carbs and running bike?
are your enrichment plungers fully down ? push on them to see if something changes

we had a member who misinstalled (i think thats what the problem was) one of the manifold boot gaskets and it cased this problem

 

Sorry I am just getting back. I have a non vacuum petcock and have all the vacuum caps on. The boots are not new but are in good shape. The plunger are all the way down. I was working it today and may have found the problem but not exactly sure how to fix it. It will be idleing at 4k then I push down on the sync screw and that takes it down to 800 rpms. I did propane and starting fluid test and nothing changed

 

Disconnect the throttle cable. Does the problem persist?

 

Did you bench synch your carb rack prior to installation?
You should have some wiggle room with your idle adjustment knob.

Did you tighten down your butterfly's prior to tightening the bolt on synch screws? This could cause the butterfly valve to bind . . . .
Don't ask me how I know this.

 

I disconnect the cable last night and still had the same problem. Yes i bench synced the carbs. Are you saying the butterfly could be to tight.

 

Ding Ding..Your carbs are out of synch ...if you push on one of the sych screws and idle drops you need to go thru adjusting . I'm in process of setting mine up now after full carb rebuild . I have a 4 gauge vacuum set up , got it close ,but keep running out of time to finish oh well . One more are your mixture screws set at 2.5 out? that is a good starting point. In other words do the sync first get it to idle , check plug color if it is white adjust out half a turn ,and recheck . If it is real black half a turn in.

 

The idle is dropping because pressing on the synch screws closes the butterflies. While he certanly should do a running synch, it's not necessarily the cause of the problem. I still think there is a vacuum leak somewhere, because with a bench synch the idle should be very close to spot on, and easily adjustable at the idle screw.

When I test for vacuum leaks I spray one specific area at a time (say just one throttle shaft seal) and wait for a few seconds. It takes time for the carb cleaner to vaporise, and a bit more time for the vapor to be sucked into a leak. If I just spray all over the leak never becomes apparant unless it's really big.

 

I had this recently too.

I replaced the intake manifolds, and gaskets were supplied by the vendor (this is what happens when you order parts from a guy who isn't Len...) Anyways, the intake manifold gaskets were the wrong size. So they leaked air, but because the gaskets were the wrong size, it made the leak difficult to detect. I could see the gaskets, which for those boots, made me think something was wrong. I looked up a pic of the OEM gaskets, and they looked nothing like the ones I installed.

Long story short, I got the proper gaskets, and the problem went away.

My vote is for air leak.

 

Yes could be ....I make my own gaskets for intake boots , the material is thicker and yes used propane to check for leaks...no leaks !!! I have done this for years on my Virago, Kawasaki ,Honda ... trace around boot use a new sharp exacto knife check contour and a quick smear with grease and good to go.

 

Yes, if you tightened the butterfly to the shaft and then tightened the nut that holds the synch screws on the outside of the carb, it can pull the butterfly slightly to one side and cause it to rub/ bind.
With the bike off and throttle cable connected, twist the throttle full open and then let go - you should hear those butterflies snap shut, test different throttle positions and if you don't hear the "snap" then verify that pressing the synch screw down closes the valves all the way.
Best way to do this is to remove the rack and open the valves with the throttle cable linkage as you can then visual see the valves closing (and/or binding).

HOWEVER - with that all said, it would be wise to do a thorough check for a vacuum leak prior to running down the afore mentioned road, as a vacuum leak will certainly cause a hanging high idle situation.

Good luck

 

I am sorry for just getting back I have been very busy and went on a mission trip to Haiti. So I have not been on for a while. I check for leaks with propane again and found nothing. I have the carbs off the bike. If I open the throttle half way with my finger on the linkage and let go I can see the butterfly does not close all of the way. Then I have to push down to close it. Could it be the nut on the shaft that is to tight or to loose. I have located the problem just wondering what direction I should go now. I made sure the 2 screws to the butterfly were tight also

 

Loosen the screws and reset the throttle plate.

Gary H.

 

I reset the throttle plates and it is running perfect now. Thanks to everyone

 

I agree with you that it seems like an air leak, my issue is the air is coming around the edges of the butterfly valves. While bench syncing the carburetors the butterflies do not completely seal when I close the throttle. This doesn’t seem to be an adjustment rather the butterflies appear to be oval (this is a great exaggeration, but it tells the story).

 

I am using the MotionPro SyncPro which balances the four carbs. I have used the SyncPro in the past (not on this bike) with excellent results. The SyncPro shows the carburetors are in sync.

 

Butterflies are not round. Follow the instructions in the other thread. Easiest way is to break the rack, loosen the two screws, adjust so that the plate comes in contact with the carb body, snap closed several times, tighten screws while plate are in contact with sides so there is no wiggle room.

 

I appear to have resolved the hanging idle. The engine returns to idle within a second or two from 3000-3500 rpm. My issue now has moved from the hanging idle to the engine not idling smoothly - or too low to remain running. The pilot jet circuits appear to be clear inasmuch as turning the pilot jets does impact idling smoothness.

I have varied the pilot jet circuit from 2 to 4-1/2 turns out with the engine idling smoothest at 3-1/2 or 4 turns. With the idle set a bit higher to achieve a suitable idle speed of ~1000 rpm the bike is responsive and returns to idle so long as engine speed stays below 2500 rpm; speeds higher than 2500 rpm and I am back to a high hanging idle condition. Interestingly, if the idle set screw is backed off a tad, the hanging idle condition disappears (even at higher rpm’s) but of course then the bike doesn’t want to idle.

The bike accelerates quickly and acts like I would expect it to, but when I come to a stop, the idle is too low and the bike wants to die.
The carbs have been sync’d using the MotionPro SyncPro.

To recap: Using the idle set screw the bike will idle at 1050 rpm but will hang if engine speed exceeds 2500 rpm (engine speed does not hang at engine speed below 2500 rpm). If the idle set screw is backed off, the idle does not hang at higher rpms BUT then the engine speed is too low to idle.

Suggestions?

 

Problem solved.
The fast idle condition was resolved by adjusting the pilot circuits. By opening the pilot circuits, idle smoothed out, allowing the idle set screw to be backed off a bit. Backing off the idle adjustment screw eliminated the fast idle condition. The bike runs like it should.
Dave