Newbie ST1100 carb question

Gentlemen, thanks for your wisdom. I will take the fuel shutoff valve out. I will plug the vacuum line (and inspect it). I am getting a 3/4" inch spark at idle, I am leaning to the carbs as the problem....it has gotten worse with seafoam. I guess I am taking the carbs off to get to the reality of the situation. I will checkout the water hose and casting situation while I'm in there. Probably change that stuff out. Im at 33K miles. I may do that idle jet #40 mod too, depending on whats in it. I was wanting to do all this in the fall, but here we are. I need this fixed pronto because I am short of cars and need this to get to work.
I am liking how this bike rides.....it does seem like I have a hard time consistently getting a clean shift from first to second gear. Should I be concerned about that?

I agree with everyone here that pulling the carb bank and cleaning the pilot jets and the diaphragm slides would be good cheap maintenance and it might correct quite a bit (it's easy to do and as you indicated, while in there, go after the hoses, O rings, and elbows as well- might as well get it all done in one shot). Some here feel repairing the vacuum valve is the way to go- others just eliminate it (if mine was defective, I'd likely just fix the diaphragm by replacing it). As for not getting a clean 1-2 shift, it might also be a good idea to see if the linkage to the transmission from the foot lever is notchy or not- there's a pretty easy fix for that as well that involves lubing the linkage:

http://koczarski.com/mmartin/Shifter.htm

When you reassemble, the nylon lock nut can't be too tight otherwise it'll cause binding in the shift linkage (I overtightened mine a bit and when the linkage warmed and I assume expanded just a hair, I couldn't fully downshift to 2nd or 1st)- drove the bike home, loosened just a touch (like an 1/8th of a turn of the nut) and its been perfect since then.

I wouldn't try to balance the carbs until after you've done the carb work- also, use new boots for the carbs as the old ones are likely more brittle and hard and it may be much more difficult to reinstall the carbs after popping them off).

Good advice above. I’ll just add — N.B. don’t try to sync the carbs using the Haynes manual with its egregious error! The ST1100 carbs are sync’d to the base carb (#4, left rear) individually, in any order. There is no sync’g one “bank” to the other!

John

Oh yeah, I meant to mention the fuel shutoff valve and forgot. I think he said he already checked the plugs, but if not, the #3 cylinder (right rear sitting on bike) supplies the vacuum for the valve. If you get enough leakage past the diaphragm that plug tends to foul, so he should check that if he hasn't already. Other than that, I doubt it has anything to do with his performance issue, but wouldn't say its impossible either. While he's at it, he should do the bypass and be done with it.

Click to expand...

I also doubt that is the problem but if it is leaking, it is another problem to go with the other problem. Fix them as you find them.

Carb removal under way.....
Is moving to a #128 main jet a good idea?.....
It sounds like moving to a #40 pilot jet is a good idea.....

trying to pry carbs out now.....

Before you think about re-jetting, be absolutely sure the ignition system is up to snuff. While the carbs are out, right now is the perfect time to check the resistance values of the plug caps and coils. Also a great time to remove the coils and clean the mounts for a perfect ground and all power connectors checked. The bikes main ground should be cleaned and pasted too. Regardless that it's shooting a 3" of spark on a tester, be certain everything is perfect for firing under cylinder pressure.

Is this an ABS bike, or a California emission bike? 49 State bike? Need to know this for proper jetting.

Sounds like great advice on the electrical....do you know offhand what the values should be? It is pretty clean under the carbs, and clearly the PO was in there and also cleaned the carbs up. I am finding minimal junk in there...it looks like very fine dirt. I took a pilot jet out of one of the carbs to a non firing cylinder. It looked a bit gunked, just enough to be a problem. This is not an ABS bike, not sure of difference between CA or 49 state. It has #38 and #125 jets in it. Under the seat it says ST1100Y and conforms to year 2000 US EPA and CA standards. Looks like CA? It has the PAIR system and lots of junk hooked up to carbs. I have some #40 and #128 jets coming.
I took the gas tank out and it was dirty under there.....wondering if I can borrow a pressure washer to blow it out. Am also thinking about emptying tank and examining for crap in the bottom. The fuel filter looks original. I have a new oem one. I am wondering if the fine stuff in the carbs came from the tank or from alcohol in gas.....I think PO had stabil in it over the winter. I added seafoam when I got it.

If you plan on keeping this bike, I strongly recommend getting a service manual for all the specifications. I've included a link to an online manual. It's an older one, but many things still apply. In it are all the specifications and testing procedures for the ignition system. This I can tell you... If ANY of the the plug cap or coil readings are anywhere over the specifications, even just a hair over, they're no good. throw them away and get new ones. Also install fresh plugs.

http://www.sharetheexperience.co.uk/ST1100/

You have a California emission bike. You'll need to be very careful with the jetting. The USA ABS/emission bike's have lazier camshafts and cam timing. You can swap out the pilot/slow speed jet to the #40 successfully, but I recommend against changing the main to the #128 for your area. It's too fat for your STOC bike. Stick with the #125. When it comes time for set-up and initial tune, start off with 1 3/4 turns out with the idle mixture screws. this should get you real close of were you need to be.

It runs pretty good on the top end.....seemed just slightly lean to me at #125. Would #128 be doable if I switch to a K&N air filter?
I will defer to your experience.....
Thanks for the link!
Bummer on the CA cams!

Techman said:

Bummer on the CA cams!

Click to expand...

You can find used ST cams on eBay and such. :wink:

Techman said:

It runs pretty good on the top end.....seemed just slightly lean to me at #125. Would #128 be doable if I switch to a K&N air filter?
I will defer to your experience.....
Thanks for the link!
Bummer on the CA cams!

Click to expand...

Even with a K&N it will still be too much fuel with a #128 main. The only way an emission bike can handle the fuel is if you had a modified exhaust with straight through baffles in conjunction with the K&N. But then you will loose low end torque and gain "MAYBE" 5HP at 7000 RPM.

Personally, I don't care for the K&N filter. While it lets in a little more air (and leans out an already lean running emission engine), it also lets in more grit. The carbs I've done in the past that have had a K&N, all had a lot of grit down in the plenum. One bike was a rally rider, with a ton of miles. The additional grit allowed into the system, wore out the plastic diphragm slides. Pick your poison....

The main circuit doesn't "start working" until roughly 3500rpm. At 4000rpm the needle is lightly lifted, but at this point your already doing 80mph. The larger #40 pilot is "always working" through the entire rev band. This will also provide the additional fuel needed for mid-range and top end. One of the reasons you won't need the #128, and will be over fueling if you do.

OK. I was just going by what you said in your extensive rebuild article (thank you for it, by the way).....

http://www.st-riders.net/index.php?topic=10249.0

With what you are saying now, do you still recommend 1 shim on the needle for midrange?
Thank you for all the information. I am up the curve on the V65 sabre, but this is a new curve. I didn't buy this bike to work on, want to do some traveling with the wife.

Here are some pictures (I hope, not sure how this works).....
Threw in the V65 pic for fun.....just sold it yesterday.

Techman said:

Gentlemen, thanks for your wisdom. I will take the fuel shutoff valve out. I will plug the vacuum line (and inspect it). I am getting a 3/4" inch spark at idle, I am leaning to the carbs as the problem....it has gotten worse with seafoam. I guess I am taking the carbs off to get to the reality of the situation. I will checkout the water hose and casting situation while I'm in there. Probably change that stuff out. Im at 33K miles. I may do that idle jet #40 mod too, depending on whats in it. I was wanting to do all this in the fall, but here we are. I need this fixed pronto because I am short of cars and need this to get to work.
I am liking how this bike rides.....it does seem like I have a hard time consistently getting a clean shift from first to second gear. Should I be concerned about that?

Click to expand...

was there evidence of fuel in the vacuum line to the fuel shut off? Was the hose soft or gas soaked?

Didn't notice mention of this: The ST has no "choke", those circuits are fuel enricheners, pulling the lever pulls a plunger in each carb which adds fuel, rather than cutting air. Important to note, those plungers may be binding, especially if the the carbs have ever been separated. Easy to get it wrong upon reassembly.

BTW, I have a set of ST carbs, been completely gone thru but never reinstalled. Since I no longer have an ST, probably need to post them up For Sale, along with 3 panniers, both L and R back and a L 01, all complete with stickers. I'll get some pics poSTed soon.

Techman said:

OK. I was just going by what you said in your extensive rebuild article (thank you for it, by the way).....

http://www.st-riders.net/index.php?topic=10249.0

With what you are saying now, do you still recommend 1 shim on the needle for midrange?
Thank you for all the information. I am up the curve on the V65 sabre, but this is a new curve. I didn't buy this bike to work on, want to do some traveling with the wife.

Click to expand...

The shims are already there(they should be anyways) from the factory. Leave them in there. I have found in the past that they measure inconsistently. They are supposed to be .020" from the factory, but usually measure a little under. I always buy the .020" shims from PJ Motorsports, for exact consistency.

In the article, as stated, it is a generalized guide to help those along with giving their carbs a good cleaning and inspection. Everyone's individual "set-up" and jetting will differ, pending performance mod's, emission controls, riding style and the geographical location in which they ride in. Example: My personal jetting, riding style and location (Northern NY, one hour away from the Canadian border), will differ from someone else who is in, say, Missouri...

Your asking for a clean running bike, with a little extra umph, for two up touring. Make sure your ignition system is perfect, put in the #40's, tune to your area, and enjoy the bike for what it is.

OK, 10-4, thanks for the info Afrymoyer. That is what I will do. I was tempted to use the new spray seafoam to clean the idle circuits out (as I don't think that would trash the diaphrams), but I'm going to be a good boy and do it right so I don't have to do it again.
I had the same thought as you, George and checked that linkage.....
No evidence of fuel in vacuum line. Going to take that valve out to avoid future problems.

Techman said:

I am up the curve on the V65 sabre

Click to expand...

One of my very favorite bikes. I wish I'd kept mine. It might have prevented me from getting an ST though. But if not they're near perfect stablemates.

The V65 Sabre is nearly a naked ST but with an extra gear and a GPI. Mine was silver/blue. Gorgeous bike.

afrymoyer said:

Personally, I don't care for the K&N filter. While it lets in a little more air (and leans out an already lean running emission engine), it also lets in more grit. The carbs I've done in the past that have had a K&N, all had a lot of grit down in the plenum. One bike was a rally rider, with a ton of miles. The additional grit allowed into the system, wore out the plastic diphragm slides. Pick your poison....

Click to expand...

I believe Adam has a top notch tech reputation on this forum and this quote from his experiences with K & N air filters should be reserved for re-publication every time the air filter discussion comes up, which is not quite as often as oil filters.