Fuel spilling from intake

[jonathacvb]

I apologize in advance if this has been previously answered. I know there is a ton of talk about carb issue/fuel leaks/sticky floats and so on but I cannot seem to solve this issue..

The context:

Bike was running, but roughly (sputtering, coughing, backfiring). The previous owner claimed to have rebuilt the carbs and had them checked by a mechanic (questionable, but for now Ill take his word for it). So I started taking a few things apart and ended up 1. Cleaning inside fuel tank 2. inspecting and cleaning both petcocks 3. inspecting and cleaning air intake box. 4. with carb on the bench I opened up the top of #4 and for the sake of curiosity I only briefly pulled out the spring, diaphragm, and slide to inspect it (appears to have been rebuilt).

I put everything back together, being sure to put it all back where it belongs. I fired it up no problem when I noticed fuel dumping out of the intake. After further diagnosis I realized that when engine is off and I set EITHER petcock to PRI, ON, or RES it will leak fuel out the intake.

To me, this rules out that I mixed something up with carb #4 since it leaks if I only have LEFT petcock open. Perhaps I'm wrong about this.

The other thing I am questioning is if I hooked all the hoses up correctly. I have compared my work to the diagram many times now and the only thing I am a little unsure of is the hose going from the 'octy' to the 'engine vacuum supply' (I believe this location is nipple on the boot between carb #2 and the motor. Please correct me if I am wrong, In the photo I don't have this attached, but it was previously). Also there is a hose that runs from the lower part of the motor to a nipple located on the front of carb #2. Perhaps I have something mixed here.

All feedback is appreciated

[oldyam80sg]

Most people havre elminated the Octy on their bikes as they can be problematic, and me I didn't like all those hoses. The carbs if fuel pours out of intake,take a screwdriver and hit the top of the carbs. The floats and float needles can stick if dirty or if they rub on the carb gasket. Rapping on the carb might free them.

[jonathacvb]

Ok so after opening up Carb#4 again, she stopped leaking fuel.... I suppose the needle must'a stuck or something?

Anyway. The big question I have now is... Looking at the posted picture. The two lines on the left most side of the photo.. are they running each to the right location? I have a bad feeling I have it wrong but I cannot seem to find a thread to answer this

[cajun31]

I apologize in advance if this has been previously answered. I know there is a ton of talk about carb issue/fuel leaks/sticky floats and so on but I cannot seem to solve this issue..

The context:

Bike was running, but roughly (sputtering, coughing, backfiring). The previous owner claimed to have rebuilt the carbs and had them checked by a mechanic (questionable, but for now Ill take his word for it). So I started taking a few things apart and ended up 1. Cleaning inside fuel tank 2. inspecting and cleaning both petcocks 3. inspecting and cleaning air intake box. 4. with carb on the bench I opened up the top of #4 and for the sake of curiosity I only briefly pulled out the spring, diaphragm, and slide to inspect it (appears to have been rebuilt).

I put everything back together, being sure to put it all back where it belongs. I fired it up no problem when I noticed fuel dumping out of the intake. After further diagnosis I realized that when engine is off and I set EITHER petcock to PRI, ON, or RES it will leak fuel out the intake.

To me, this rules out that I mixed something up with carb #4 since it leaks if I only have LEFT petcock open. Perhaps I'm wrong about this.

The other thing I am questioning is if I hooked all the hoses up correctly. I have compared my work to the diagram many times now and the only thing I am a little unsure of is the hose going from the 'octy' to the 'engine vacuum supply' (I believe this location is nipple on the boot between carb #2 and the motor. Please correct me if I am wrong, In the photo I don't have this attached, but it was previously). Also there is a hose that runs from the lower part of the motor to a nipple located on the front of carb #2. Perhaps I have something mixed here.

All feedback is appreciated

Ok... to answer your question the longer hose from the vacuum advance goes to the number 2 carb nipple. The hose from the octy goes the the number 2 manifold nipple.

Didn't take long for someone to chime in and suggest that the Octy is eliminated by most folks. I am not one of those people. If working properly it serves as a safety feature to stop the flow of gas so I am a proponent of rebuilding it. There are kits available for the octy and petcocks. I would suggest that because the bike is new to you that you need to inspect and rebuild the octy, petcocks and the carbs. Take nothing for granted. You will have better peace of mind doing everything yourself.

How long had the bike sat up before you bought it? What kind of gas was used? Ethanol is not very friendly when it comes to carbs. Even small lengths of time can mess up the carbs. If it is all you an get then get used to the idea of running the carbs dry before any time storing. I do my best to buy non ethanol gas and I still am in the habit of letting the bike run until it stops on it's own after shutting the petcocks off.

Here are rebuild kits for the octy and petcocks. Yamaha xs1100 petcock rebuild kit for sale | eBay. One thing ... replace the large o rings in the kit that are used for the petcocks on their base against the tank. They are generally too small in diameter and you need thicker ones to make a good seal against the tank.

The carb flooding could be due to several factors but the first thing you need to do is pull the carbs and take the float bowls off. As you are already aware, best to keep parts associated with each carb separated by each carb. Pull the float bowl gaskets off with each bowl and turn the carbs upside down and check the float heights. Especially on the on you suspect is flooding.

[Patrick1980]

Adding onto that I completely cleaned my carbs, got the float levels right and the carbs still flooded in one of them. I gave it a couple taps and it stopped. After having the carbs empty for a while sometimes the float will struggle to open from just the force of the gas so I always give it a few taps if I’m putting fuel in for the first time and there are no issues after the initial fill up.

[jonathacvb]

Ok... to answer your question the longer hose from the vacuum advance goes to the number 2 carb nipple. The hose from the octy goes the the number 2 manifold nipple.

Didn't take long for someone to chime in and suggest that the Octy is eliminated by most folks. I am not one of those people. If working properly it serves as a safety feature to stop the flow of gas so I am a proponent of rebuilding it. There are kits available for the octy and petcocks. I would suggest that because the bike is new to you that you need to inspect and rebuild the octy, petcocks and the carbs. Take nothing for granted. You will have better peace of mind doing everything yourself.

How long had the bike sat up before you bought it? What kind of gas was used? Ethanol is not very friendly when it comes to carbs. Even small lengths of time can mess up the carbs. If it is all you an get then get used to the idea of running the carbs dry before any time storing. I do my best to buy non ethanol gas and I still am in the habit of letting the bike run until it stops on it's own after shutting the petcocks off.

Here are rebuild kits for the octy and petcocks. Yamaha xs1100 petcock rebuild kit for sale | eBay. One thing ... replace the large o rings in the kit that are used for the petcocks on their base against the tank. They are generally too small in diameter and you need thicker ones to make a good seal against the tank.

The carb flooding could be due to several factors but the first thing you need to do is pull the carbs and take the float bowls off. As you are already aware, best to keep parts associated with each carb separated by each carb. Pull the float bowl gaskets off with each bowl and turn the carbs upside down and check the float heights. Especially on the on you suspect is flooding.

Thanks for the reply. I will likely go the route of rebuilding the octy. I completely dismantled, cleaned, instpected and re-assembled the petcocks. They seemed to be in good order. A previous owner had already cut and installed some extra gasket material to create the better seal.

The previous owner had not let the bike sit long as he was in the process of attempting to restore that. Fresh oil+filter, air filter, spark plugs, rebuilt carburetor etc. My guess is that prior to this it spent time sitting. I am unsure about the gas used and will look into getting non-ethonal fuel.

I am going to be looking into rebuilding the carb too. Just got to do a bunch of reading a head of time. Is anyone know where I purchase the appropriate service manual for the bike? My bike is the 1980 XS1100SG

[Radioguylogs]

https://www.ebay.com/itm/35473228435...0AAOSwqgBkQXOw

[LAB3]

https://www.ebay.com/itm/35473228435...0AAOSwqgBkQXOw

That's a darn good price for one of those!

[jonathacvb]

https://www.ebay.com/itm/35473228435...0AAOSwqgBkQXOw

Thanks! I would’ve bought it but it already got scooped 😩
I will keep looking

[cajun31]

Thanks! I would’ve bought it but it already got scooped 😩
I will keep looking

Until you can find a hard copy just download the manual from here : Ringler.us | My Bike

[jonathacvb]

Until you can find a hard copy just download the manual from here : Ringler.us | My Bike

Oh wow, thanks again!

Ok so my bike is, apparently a 1980 XS1100SG (3U9-000983). So how to I reliably consider the differences in my bike since that service manual is more specific to a different model?

[cajun31]

Oh wow, thanks again!

Ok so my bike is, apparently a 1980 XS1100SG (3U9-000983). So how to I reliably consider the differences in my bike since that service manual is more specific to a different model?

That page has an aftermarket manual that covers your bike. Also... many available on Ebay for your specific bike. yamaha xs1100 service manual for sale | eBay

[jonathacvb]

Got it. Sorry, I could've read further. I know I'm been a little over eager and could afford to slow down a bit

[Rasputin]

There are Factory service manuals right on this site for download.