91 ST1100 High Idle

[yuncledaddy]

Hi, After sitting the winter I did regular maintenance (like changing oil, checking fluids, etc..) and went ahead and changed the plugs (iridium). She runs beautifully with the exception of high idle speed. I completely turned down the idle screw. Also, If I increase the choke, even just a little, It bogs down. My thought right now is to run some sea foam through. But I wanted to make sure all of my linkage was good and not hanging. After removing the false tank and checking the linkage free, I noticed the throttle does not close all the way. Odd, is this normal? I checked the throttle cable, it is not it. I can't seem to find any bound linkages. Just don't know.

 

[Jim Van]

Do you have any "slack" at the twist grip ?? If not, the throttle mechanism may be binding up. Try rotating the circular disk by hand to close the throttle more.

If you do have slack, maybe a slide is stuck or you have an air leak in the intake, somewhere. You could remove the rubber " snorkles" and work the slides to make sure they are all closing the same amount or tell if any are sticking. Just my 2 cents ......... Good Luck.

 

[vinny]

What he said... check the mechanism at the hand grip first, lube the cables and the twist grip.

 

[Brant]

Check the enricher cable hold down clamp screw, and make sure cable housing is held down tight under retainer clip and hasn't slipped, causing a partial opening of enricher circuit.

 

[Grabcon]

A couple of things. I just went through a big carb to do that I had issues with. I think the carbs are closed all the way, but check the cables as recommended above. Once the cables are adjusted I would throw the sync gages on and see what is happening there. What I found on mine is that I could not sync to #4 and that when I tried to the idle kept rising, in turn to reduce the idle I needed to turn the idle screw adjustment, to the point where it was completely off the throttle cam.

In my case I had to do a very thorough carb cleaning. Standard stuff and new intake boots.

 

[yuncledaddy]

Thanks Gents!! I have checked all cables and linkage, I am pretty sure it is not that (though not positive). One thing I did notice was as Brant suggested, the right side enrichers didn't come out all the way, so I adjusted that but to no avail. I am afraid I am going to need to do a thorough cleaning and syncing as Grabcon suggested. Now I just need to source new boots and a sync gauge. Thanks for all the help!

In my case I had to do a very thorough carb cleaning. Standard stuff and new intake boots.

 

[kiltman]

There is an idle adjuster at the tank filler. It's a thumb screw held in place by a rubber shield surrounding the gas cap, check to see if by adjusting the screw you alter the idle.

 

[Grabcon]

Depending on the time frame you can get the Honda intake boots from Partzilla. Reasonable price. Typically the are slow in delivery, but with that said I just ordered some parts for my ST1300 last Thursday and they are to arrive today.

Try Pro Motion for the sync Tubes (monometer). I have used gauges for the last forty years. gauges. Folks have there preferences on tubes or gauges.

I would check the sync first before you pull it apart.

 

[Brant]

My next suggestion would look for incorrectly hooked up vacuum hoses.......... definitely would suspect a vacuum leak at this point before fueling source. Just because of fact carb bank had been removed previously.

 

[afrymoyer]

I agree with Brant... Look at the choke cable hold down clamp first. Many times the screw loosens and the cable pulls out leaving the choke partially engaged. You can see it were my thumb is in the pic.



At this point, I'm also thinking vacuum leak. Did mice get up in the V, under the carbs and chew up vacuum hoses over the winter? It's a 1991. Hoses are probably dry and brittle, possibly cracked.. If PAIR valves are still installed have a good look at those hoses too. Only takes 5 minutes to remove the gas tank and have a GOOD look up in there. While running the bike, spray the boots with WD40, PB Blaster, etc... See if anything changes. One of those boots may be cracked bad. If auto fuel valve is still on bike, it too maybe leaking vacuum. Pulling / cleaning the carbs is the last resort. Do you have a service manual?

 

[John OoSTerhuis]

Guys... the OP's picture shows the throttle bellcrank's 'tab' is not returning to the throttle-stop boss on the carb body (which the idle set bolt protrudes from). I think the focus here should be on the throttle cables and linkages, not carb boots and the like. Appears to me simple mechanical binding somewheres. JMHO

John
via iPhone 4S

 

[afrymoyer]

John... Here is a pic of stripped ST1100 carbs. The throttle plates / butterflies are bottomed out in the bores and the idle cable is removed. This is normal and possible. The OP's pix show around the same clearance. Hence my opinion....



I hope that you are more correct than I am, and the OP finds something binding up-stream in the cables, or twist tube / grip. Here's to a quick fix

To confirm "cables or carbs", the OP could run the engine and manually force the bellcrank towards the idle stop and see if the engine stalls with the butterflies bottomed out.

 

[John OoSTerhuis]

OK Adam. I'll defer to your expert carb knowledge. I thought the throttle bellcrank could go all the way to the stop with the idle screw fully retracted.

John

 

[Jim Van]

Like I said in my first post, You could also have an air leak in the intake. Check for one of the small hoses connected to the intake ports ( used to balance the carbs) disconnected or cracked.