Low Idle Speed - New to me 2000 ABSII

Gymbo

Gymbo

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Low Idle Speed & Other Carb Weirdness - New to me 2000 ABSII

I just bought a 2000 ST1100ABSII. It is in pristine condition other than it has a carburation issue. I got a great deal as a result of the carb issue, so I am happy but I am also resigned that I may need to pull the carbs and service them.

This is my 6th ST1100 in the past 22 years....but I've never had the carbs off one before......so before I do that I thought I'd share the symptoms and see if the collective wisdom here can give me an idea of what might be going on.....

Symptoms: The bike runs strong and smooth above idle once warm and gets decent fuel economy in the mid-40s at 75mph. The bike starts right away cold with the choke on but doesn't rev as high as my previous ST1100's did with the choke on. With the choke on, it revs only to around 2K...my previous ST1100's would rev up more than that. Once warmed up with the choke off it idles at around 700 rpm. If I try to adjust the idle with the adjustment knob it jumps from the 700 to about 3000 rpm with just a fraction of a turn.

With the engine warmed up and idling at 700 it stumbles slightly when the throttle is opened and then revs great the rest of the way.

So with that, anyone have any idea of what might be going on? Idle jets?
 
Last edited:
Roger. said:
Jimbo,
Could be pilot jets, but can you connect a set of balancers to see if there's a mismatch on one or more cylinders first?
Click to expand...

I don't have one of those. I had a SK flowmeter i used on my previous ST1100's....going to have to buy a new one. The previous owner synched the carbs at 4K rpm, which unfortunately doesn't help at idle.
 
My hunch is the low speed/idle jets. When those things get stopped up, the ST1100 does not idle much at all.
Not a lot of expense to fix, just some time.
It could be a torn diaphragm in one or more of the carbs.
BTW, I would recommend pulling the gas tank before you pull the carbs.
It doesn't take much extra time, but it sure makes getting to the carbs easier.
 
Re: Low Idle Speed & Other Carb Weirdness - New to me 2000 ABSII

I just had my ST carbs rebuilt by Billy Carr in Canton, TX. He seems to be the goto guy for Honda V4 carbs. Did a really good job on mine for about $275.
 
probably wouldn't hurt to throw a little Seafoam in the tank and see if that helps.
 
I just redid a set on a bike I just sold. It sat up for about a year an a half. Had infrequent use over that period. So it's still fresh on my mind. Bike should idle higher than that with fuel enrichment lever fully engaged. It should also kill the bike when fully warmed up an running correctly if you try to apply it. It should not stumble at all when applying the throttle. All of this I'm sure you know.

If it idles well at that low a speed I'm sure its a good sign. If slow speed jets were completely clogged it simply would not. I have not had much reason or experience running an 1100 that low, but, would not be surprised if it didn't cause a slight hesitation when applying throttle from 700 RPM. Try taking the top shelter off so you can get a better hold on the adjustment cable. Hold firmly in one hand while rotating the knob with the other. See if it gives you a bit more control.

Since it will start and run you could try some fuel cleaner. See if it clears up within a few tanks. Just add a bit more than the directions state. It could work, but progress would be slow and difficult.

If it were my bike I would just remove the carbs and clean them well. On my latest rebuild I got away with only buying fuel bowl gaskets. You on the other hand will be out a bit more money. Since it is a new to you bike I would buy carb boots, fuel bowl gaskets, slow jets, air cut off valves, maybe float needles/seats, and coolant elbows/o rings. Since you have the carbs out replace the coolant elbows and check all hose clamps for tightness. Some clean/ disable pair valves. I just cleaned em.

There is a good write up on the ST-Riders site. Pic heavy and good descriptions on what to do. I can lend you the proper Honda tool to adjust the pilot jets an also the sync tool. If/when you decide to do the work yourself. It's not terribly difficult, just labor intensive. Good luck.
 
I had this exact problem on my 2000 back in 2008 when it would run fine when warm (so a minor stumble off idle but would run fine at speed and when accelerating) but at idle wouldn’t run over 500 rpm or so (so it always felt like it would stall at idle, even with adjusting the idle speed up with the thumb screw next to the gas filler- couldn’t get it over 750 rpm or so even adjusted all the way). I pulled the carbs, cleaned the pilot jets with compressed air (running Gumout Regane and Seafoam didn’t help) and I cleaned the diaphragm slides- after I was all done, bike fired as new, then I had the carbs balanced and it runs great to this day. I’m not of the opinion that the chemical approach is best (could be a cheap attempt and in rare occasions might work)- probably better just to pull the carbs and do a little cleaning. The key with these bikes is to use them and use them often.
 
Oh, I should also say that my slow speed jets were completely blocked on two carbs. So much so that a soak in carb cleaner overnight, a 30 minute ultrasonic bath, a second overnight soak, second round through the ultrasonic didn't clear them. I had to find my tiniest drill to physically removed the tarnish. Which is why I said just replace em. Cheap enough on ebay for a new set. Which is where I got the gaskets btw.
 
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