95 St1100 Runs on choke only and stumles from idle to mid range

ChrisSt1100 · May 16, 2011

I thought I would post this just in case someone else had the same problem and was contemplating the same fix. I have owned my ?95 1100 for three years now and it has always been a little cold blooded. Last year the bike sat for about a month or so and the problem got significantly worse. It wouldn?t run unless the choke was on and it had a severe stumble going from idle to mid-range. The first thing that was suspect was the low speed jets. Ran out of time last fall, so I stored it with stable in the gas and tried again this spring. Even worse. Tried the Seafoam for a tank of fuel, but that didn?t get it.
So I pulled the carbs out and sure enough all of the low speed idle jets were completely plugged. I couldn?t blow or see through them. I disassembled each carb and dropped the high speed and the low speed jet into a small lid of carb cleaner. After about 2 minutes, I used compressed air and blew them out. They were perfectly clear. I could blow through them and using a proper light see through that small hole. Put it back together and it solved the problem 100%. Idled perfect and didn?t have any stumble while transitioning from idle to mid-range.
If you are having the same issue and need some more input, let me know. There are a few little bits of info that would of made the job easier the second time around.

Chris

stgolfer · May 16, 2011

Did you drain the fuel as well, or keep the same fuel and clean the carbs? I need to clean my carbs on the 'wing. It's been sitting too long and only runs on full choke. It has about 1/2 tank with no Stabile.

Tom P · May 16, 2011

Having a similar problem on my 1999, though I ride mine every day and it has 152,000 on it. It started about six moths ago and happens around 1800 to 2200 rpm. Have run Techtron and Seafoam to little avail. I changed spark plugs, fuel filter, have cleaned K&N filter
changed thermostat and check the vacuum on what I could including fuel shut off, synchronized carbs and still there. I guess I am going to have to pull the carbs, clean them and hope it fixes the problem. Any tips you have Chris would be greatly appreciate.

ChrisSt1100 · May 16, 2011

STgolfer
I started with a fresh tank of fuel and changed the fuel filter.
Tom P
If you decide to clean the carbs yourself, you will want to put some time aside. It only takes about 1 1/2 hours to get everything apart and about another 45 minutes to clean the carbs, but putting it back together can be a little tough. Make sure you pay attention to how everything comes apart. Some of the simple things like the indexing of the clamps at the carb bases or some of the vent hoses. On some projects I shoot a quick digital picture as a reference. It's always good to have a few bread crumbs to find your way home. I replace the carb to cylinder boots because the originals were sagging a little and they are fairly inexpensive. When going back together, do yourself a favor and put the throttle cable back onto the carbs before mounting them to the cylinders. Mostly have the time set aside and be patient. It took about 5 hours by the time I was done.

Bigmak96 · May 16, 2011

Hi Chris, I missed your into. Welcome. If you have not done so yet, take a look at the events and plan on joining us in Lanesboro in Aug.
Mark

Silver Bullet · May 16, 2011

Went through the same issue on a 700cc Sabre and had to clean the idle jets, and boy that hole is small ! Ran perfect after also !

MIKE

cptgrits · May 16, 2011

I had the same problem on my '98 CB750 after it sat too long a couple winters ago. It was a bear to start and would only run while choked. I overdosed it with Seafoam for 4 tankfulls of Shell premium before it cleared up. After that it ran fine. Now I seafoam all my equipment before storing it.

Tom P · May 17, 2011

cptgrits said:
I had the same problem on my '98 CB750 after it sat too long a couple winters ago. It was a bear to start and would only run while choked. I overdosed it with Seafoam for 4 tankfulls of Shell premium before it cleared up. After that it ran fine. Now I seafoam all my equipment before storing it.

Ah... to Seafoam or not to Seafoam .... that is the question.

I have run 2 tanks through...
seems a little better. Maybe another 2 stronger shots. Would be worth it if it worked.

Uncle Phil · May 18, 2011

It does usually indicate stopped up idle jets. Just beware that if you use too big a dosage of Seafoam at one time, it will coat the sparkplugs and they will become useless. Don't ask how I know that ... ;-) I could never get mine cleaned out on Frost (the passages were clogged as well as the jets - it set for several years). This current 'excuse' for fuel (ethanol mix) goes south a lot quicker than the old stuff from what I can tell.

Bigmak96 · May 18, 2011

Uncle Phil said:
This current 'excuse' for fuel (ethanol mix) goes south a lot quicker than the old stuff from what I can tell.

I was going to say that if you can find some straight gas with out ethanol AKA non-oxigenated, it may help wash things out.

Tom P · May 19, 2011

Bigmak96 said:
I was going to say that if you can find some straight gas with out ethanol AKA non-oxigenated, it may help wash things out.

I don't think that we have ethanol added in California, though I might be wrong. I have use gas all over the nation and rode the bike many miles with no problems so it just might be its high miles and I have done a lot more around town driving recently (last 3 yrs.)
I think it might just be time to pull them. Other than this problem, it has been a faultless ride. A few of the valves are a thousandths or two out and I will adjust those at the same time.

By the way Chris, good information. Boy it is so great to have this and more from the rest of the site, at our finger tips. Makes the job go so much easier.

stgolfer · Aug 29, 2011

I just put some Seafoam and a little gas in my 1500 Wing. I got it running, but can't get off of the choke completely. Good throttle response from mid to high rpm's, but horrible idle and if I goose the gas from idle, it will stall.

It will idle on 1/2 choke, but not full choke and not without choke. I figured I'd let it idle for awhile and left the garage so I could breathe some clean air for awhile and hopefully it would clean out the low speed jets while idling. When I came back 5 minutes later, there was a big pool of gas under the bike, coming from the overflow line.

Where to go now? Taking this fairing apart makes the ST's a piece of cake!!!

kanem · Dec 6, 2011

Just for clarification the jets you are talking about are #17 & 19 on page 5-9 of the Service Manual. The "h:igh" speed being called the main jet and the" idle" jet being called the. Slow jet?

DrummerDrew · Mar 12, 2012

Well, well, well . . . I find myself in the same boat, er, uh, bike? I purchased a 1991 ST1100 with 84k miles. The PO said, "She's cold natured; you'll need to choke her for a long time until she warms up." and "Watch out, man; when she gets up around 6,000 rpm, she'll jump out from under ya."

I adjusted the idle up to 1100/1200 rpm and it helped. But I'm experiencing the mid-range stumble. I checked the air filter and there's no sock. I checked the compression and it's even on all 4 around 165 on a cheap guage. I replaced the plugs. Still low power mid-range and popping when the aircleaner assembly is removed.

I just checked the Sea Foam website and that's what I'm going to do next.

Thanks!

George · Mar 12, 2012

ChrisSt1100 said:
I thought I would post this just in case someone else had the same problem and was contemplating the same fix. I have owned my ?95 1100 for three years now and it has always been a little cold blooded. Last year the bike sat for about a month or so and the problem got significantly worse. It wouldn?t run unless the choke was on and it had a severe stumble going from idle to mid-range. The first thing that was suspect was the low speed jets. Ran out of time last fall, so I stored it with stable in the gas and tried again this spring. Even worse. Tried the Seafoam for a tank of fuel, but that didn?t get it.
So I pulled the carbs out and sure enough all of the low speed idle jets were completely plugged. I couldn?t blow or see through them. I disassembled each carb and dropped the high speed and the low speed jet into a small lid of carb cleaner. After about 2 minutes, I used compressed air and blew them out. They were perfectly clear. I could blow through them and using a proper light see through that small hole. Put it back together and it solved the problem 100%. Idled perfect and didn?t have any stumble while transitioning from idle to mid-range.
If you are having the same issue and need some more input, let me know. There are a few little bits of info that would of made the job easier the second time around.

Chris

Chris, I first went thru that process in ~95 on my first 91. Done it several times since on various STs, including my 01 ABS when I first bought it. I think the plugged jets probably save me $500 on the price.

Those jets are small and plug easily unless ya keep the gas flowing regularly.

95 St1100 Runs on choke only and stumles from idle to mid range

ChrisSt1100

stgolfer

Tom P

ChrisSt1100

Bigmak96

R.I.P. - 2021/08/07

Silver Bullet

Retired

cptgrits

Tom P

Uncle Phil

Bigmak96

R.I.P. - 2021/08/07

Tom P

stgolfer

kanem

DrummerDrew

George