'80 XS1100 MS leaking float valves(?)

[gtem]

Reviving this thread. I have the '80 Midnight Special in my possession to get running and riding. The carbs that I've had on the bench for months were ready to go. Threw them on the bike, and man they are just *DUMPING* fuel like crazy on all four cylinders, immediately floods the cylinders out. I have no idea what's going on, but will be digging in. Where I had left off was I had installed new OEM float valves with o-rings, carbs do not leak when on the bench, tho I will be retesting this now. 117.5 mains, 42.5 pilots, idle mixture turned out just 1.5 turns, float level set to 23.5mm. One thing that sort of stood out to me is the travel of the choke lever seems pretty long compared to the '80 carbs that I have on my '78, another thing I will be taking a closer look at. Is a mis-adjustment where the choke plungers are opening farther than they should even possible? There's only so many places so great a quantity of fuel could be coming from, at this point I'm convinced it's not related to the pilot circuit.

[Radioguylogs]

What are your fuel T's like? (The T-shaped tubes where the fuel hose connects to the carbs). Those dry out and shrink when not in use. It takes several hours for them to swell back up after they are re-exposed to gas.

You might have sticky float(s)s that can be fixed with a rap on the fuel bowl with a screwdriver handle.

[gtem]

What are your fuel T's like? (The T-shaped tubes where the fuel hose connects to the carbs). Those dry out and shrink when not in use. It takes several hours for them to swell back up after they are re-exposed to gas.

You might have sticky float(s)s that can be fixed with a rap on the fuel bowl with a screwdriver handle.

There are no external fuel leaks, and the float valves are brand new OEM. Like I said, there are no more fuel leaks from overflowing bowls when bench testing. I appreciate your input but please read the thread.

[cajun31]

Reviving this thread. I have the '80 Midnight Special in my possession to get running and riding. The carbs that I've had on the bench for months were ready to go. Threw them on the bike, and man they are just *DUMPING* fuel like crazy on all four cylinders, immediately floods the cylinders out. I have no idea what's going on, but will be digging in. Where I had left off was I had installed new OEM float valves with o-rings, carbs do not leak when on the bench, tho I will be retesting this now. 117.5 mains, 42.5 pilots, idle mixture turned out just 1.5 turns, float level set to 23.5mm. One thing that sort of stood out to me is the travel of the choke lever seems pretty long compared to the '80 carbs that I have on my '78, another thing I will be taking a closer look at. Is a mis-adjustment where the choke plungers are opening farther than they should even possible? There's only so many places so great a quantity of fuel could be coming from, at this point I'm convinced it's not related to the pilot circuit.

I know it can be frustrating. Need a bit more information to help diagnose. You stated that one of the carbs has a bad float bowl post but is still ok operationally? What all did you do in terms of cleaning the carbs? I mean every detail? The reason I ask is because if the float pins were not removed and checked, they could be a source of your problem. Do you still have the OCTY or not. If so was it rebuilt checked and the petcocks as well. The OCTY if working correctly stops the flow of fuel when the bike is shut off. When the bike is flooding the way you described it really can only be the float area. The float bowl gaskets could be too wide and are interfering with the floats as the rise and fall, getting hung up. Sounds like you have checked and double checked the needles and seats so would think those are ok. Those pins on the floats can become warped if someone got too rough with them or crud could have formed on them or the tunnels on the floats where they go through. I always take all those apart and check them for straightness and lightly sand them with emery cloth. I also take a small drill bit about the same size as the pins and, by hand, twist them in and out of the float pin tunnels with carb cleaner to make sure they are clear. I then put everything back together and check for operational smoothness to ensure the floats are not binding. Sounds like you have done the floats at various different heights. The only question I have, and based on the heights you have already experimented with is not really a factor other then possible fuel starvation when running, is was the gasket removed when setting the float heights? Jet sizes are not a factor when diagnosing flooding carbs, however is a concern when you get everything right and eliminate the flooding. The 117.5 mains are too large if you are dealing with the later carbs that came on that bike. OEM were 110 on 1 and 4 and 112 on 2 and 3. They came that way from Yamaha. The two inner carbs were jetted slightly larger with the thinking they would run a bit richer thus running a bit cooler. I have run 110 across all 4 with no problems. I just mention that now because you will be running rich on all four carbs if those are not changed.

Now with all that said, if it were me and I was doing the job, I would take those carbs back off the bike and I would go through them thoroughly. I mean complete dismantle, separating the carbs, keeping parts isolated per carb, and give them a good cleaning. I would also replace the shaft seals. Just what I do when rebuilding carbs and really pay off when tuning and synchronizing the carbs when you get to that step. Doing that will also allow you to see what is going on with the choke tubes and seats. The ends of those choke plungers and seats cand get crud on them, leaving them less then totally seated and sealed when closed and could be a source of your problem. I don't know what you have at your disposal or what the guy that owns the bike wants to spend but a 1 gallon can of Berryman's would allow you to soak each carb body and parts. Really does a great job and breaking down all that crud in the tunnels you can't see. Rinsing the carbs thoroughly then taking compressed air and blowing everything out lets you see and hear if you still have blockage. Again I don't know how you are set up so that may not be possible. Keep the conversation going as I am sure others will chime in as well.

[speedlimit85]

Mine is '80 and has rubber passage plugs. Without these plugs with the float bowl assembled and the needles set will dump out gas.

https://www.partzilla.com/product/ya...7a911be38f78bb

[gtem]

Hi speed, that was a thought I had as well, but I confirmed that these '80 carbs (just like the others I have on my 78 E) do not have the fuel feed crossover from the main jet to feed the pilot. Unless I'm misunderstanding where else the pilot jet could be getting fuel from, I've dealt with that plug before on BS34s on several Suzukis I've owned and there is always a drilled out passage from the main jet to the pilot to feed it.

[gtem]

Jim I did a thorough cleaning of the carbs by my own standards, not the whole shibang with taking them off the gangplate and replacing throttle shaft seals, but blowing out and clearing all the jets and passages, confirming good flow through the various circuits. I did end up taking all of the floats off to access and replace the float valves with OEM parts+ new o-rings, and leak tested them extensively on the bench. The one item I didn't get into here was the choke enrichment plungers, I only confirmed that there was a good feed through the hole in the fuel bowl. Looking externally they all seem to move freely and return to a fully closed position, but I'm planning on taking a closer look there.

[DEEBS11]

Another possibility are the needles not sitting down properly in the slides. This will also cause a rich condition.

[cajun31]

Jim I did a thorough cleaning of the carbs by my own standards, not the whole shibang with taking them off the gangplate and replacing throttle shaft seals, but blowing out and clearing all the jets and passages, confirming good flow through the various circuits. I did end up taking all of the floats off to access and replace the float valves with OEM parts+ new o-rings, and leak tested them extensively on the bench. The one item I didn't get into here was the choke enrichment plungers, I only confirmed that there was a good feed through the hole in the fuel bowl. Looking externally they all seem to move freely and return to a fully closed position, but I'm planning on taking a closer look there.

When you cleaned the carbs did you install new float needles. I thought I read that you did. The reason I ask is, and you are probably already aware of this, that the pin in the top on those needles sits on a spring that can allow the pin to compress a bit then expand as the float rides on it. If the are stuck in the compressed position and you set the float heights from there then you are not stopping the fuel flow quick enough and they can flood. Probably nothing but I thought I would mention it. Those choke plungers can't be completely removed and inspected unless you take the rack apart.

[gtem]

Another possibility are the needles not sitting down properly in the slides. This will also cause a rich condition.

Yes, as I learned with my '78 with '80 carbs in the other thread! I will definitely check, the neat thing is that I now have two sets of these '80 carbs to compare side by side.

[gtem]

When you cleaned the carbs did you install new float needles. I thought I read that you did. The reason I ask is, and you are probably already aware of this, that the pin in the top on those needles sits on a spring that can allow the pin to compress a bit then expand as the float rides on it. If the are stuck in the compressed position and you set the float heights from there then you are not stopping the fuel flow quick enough and they can flood. Probably nothing but I thought I would mention it. Those choke plungers can't be completely removed and inspected unless you take the rack apart.

Yep I got full sets of float valve seats/needles, OEM Yamaha, with new o-rings for the seats. Floats have been checked and rechecked for proper height and not hanging up. No issues with overflow when tested on the bench, I even checked with low pressure compressed air to confirm that the new float valves don't let a few PSI's worth of air by.

[gtem]

One more question for the crowd: is this the *Correct* style of pilot jet for the 1980 BS34s?
Yamaha part number: 4G0-14142-42-A0
Some google image searches show it has having solid walls with no bleed holes along the sides at all, I need to check and see what the ones I bought from partshark for my '78 E (that's running '80 carbs as well) have.

[DEEBS11]

Looks like no bleed holes.

[DEEBS11]

However, when examining a photo of a cheap Chinese kit....well well well. Lookee here.

[DEEBS11]

Here is another Chinese kit. No holes.