1976 GL1000 Carb flooding when connected to cylinder

[Akifrend]

Dear Scott and every GL1000 rider.

I´m almost done with my GL1000 restoration after being sat for 9 years. I finally could go for a ride of 30 miles, the bike felt great but suddenly lost power and I had to go back home. The starter motor also failed (short circuit on the rotor), so I had to wait almost 5 months to fix the starter motor (Here in my country is not easy to get GL1000 spare parts).

Ok, fixed starter motor, charged battery, so I cranked the bike, it ignited in the second press of the starter switch, and kept idle excelent and accelerated terrific, I was happy as a child on his birthday. Then, it changed, idle got erratic and acceleration was poor, It remembered me the day I rode it and it failed, so I checked many things: sparks in all cylinders, static timing, fuel level, battery voltage, everything was ok. Tried to start it again, wasn´t as easy as the first time but it ran, in some seconds failed again, So I removed the air box cover and found the plenum full of gasoline !!!.

I cleaned all gasoline at the plenum and started the bike again, and saw how the gas came from the #2 carb like a river, it was mindblowing for me.

I removed the carbs, checked 21mm floats level (as Randakks method), checked floats and pivot pin condition, needle valve oring and the valve itself, checked plenum gasked and replaced carb to plenum oring. Mounted carbs on the bike again, it delayed to start running (I suppose it was filling the carb bowls) and started, idled excelent and accelerated really good, but in few second started the river in the plenum again from carb #2.

Removed carbs again, checked everything, found nothing wrong for my knowledge, installed them and same history.

So, I did as follows: Removed all carb manifolds (the curved pipe that connects carbs and cylinder heads) and found intake valve of cylinder 2 full of fuel (literally a pool of gas) so I cranked the engine with the manifolds disconnected to validate my hypotesys that the flooding was caused by a leak in any connection oring (plenum fuel circuit, or carb to plenum oring. For my surprise, there is no flood if the manifolds are disconnected, so it is not due to any leakage in the fuel circuit, I connected one by one carb to the cylinder head, no flood with carbs #1,3 and 4 connected (made test with kill switch in NO START position). Ok, so carb #2 is the problem, I said, then I connected carb 2 manifold, cranked for 4 seconds, removed #2 carb manifold and was full of liquid gas, a lot of liquid gas.

Sorry for the long story, just wanted to put You in context, and here is my question: Why I get flood when I connect the carb #2 to the cylinder head? If I disconnect again this manifold, flooding is not present, I connect the #2 manifold and flood appears again. I see the carb cylinder (vacuum cylinder) also full of gas, Is there any way to have fuel in air lines in that carb? If I close the tank petcock with the bike running or cranking there is no flood, there is also no flood if the petcock is in Reserve or On position with the bike turned off. I get flood only with the bike turned on or cranking and petcock in ON or Reserve positions, but if I disconnect carb #2 manifold from the head cylinder there is no flood.

What should I check in carb #2?

Thanks a lot for your patience, time and advice.

Jimmy.

[cfairweather]

Jimmy- I do a lot of the GL1000 carbs and know them well. There are several reasons that you can have fuel in the bottom of the plenum. The first and most likely is one or more of the float valves are not properly sealing. The second reason is the plenum seals may have failed. Finally, the floats may be sticking and causing the overflow. So replace the plenum seals while you have things apart and test them with a vacuum pump. I can provide more details about this if needed. If you used third party float valves, go back to the genuine Honda originals. You can usually clean up the originals and they will be fine. Use a Q-Tip and a drill with some Mothers metal polish. The hole and seat should shine when you are done. Also, clean/polish the float valve pin, especially the tip but also the sides to make sure it will slide smoothly. Get all of the polish out of there and basically make them look like new. Make sure the spring/shock absorber on the needle works perfectly. I use WD-40 to clean this item. Now take a good look at the floats. You may want to replace all of these because they only cost about $40.00 for new ones but if you use the originals, look at the part where the needle contacts the float. Look for a little dimple and you will probably see one on each float. This is a big deal because that little dimple will cause the float to stick. You must carefully polish out that dimple. The metal must be very smooth when you are done. Set the floats as you did before. While you are in there, verify all the jets holes are open. Run a guitar E-String through the tiny hole in the slow jet. After you install the float bowls, you should test the float valves before installing the carbs on the bike.
A great way to verify the float level and float valves is to connect four clear tubes to the drain holes. If you buy these tubes on EBay, they will cost you about $20.00 each so most people cannot justify buying them. Good news, you can make your own. Order some inexpensive M6 X .75mm zerk grease fittings and drill out the spring. The ball will easily come out once you remove the spring. Then drill out the hole with a 1/16" bit. See the picture below of the clear tubes i made. The float level should be at the lower edge of the rim as shown. If you see one go high, something is wrong and you must resolve it. This is the only way you can know for sure if the floats are set correctly. I use an electric fuel pump with 2-3 lbs of pressure to test mine, but you just use gravity and this will work fine.
https://drive.google.com/file/d/16ez1vw ... sp=sharing
https://drive.google.com/file/d/17IXnbJ ... sp=sharing

[Akifrend]

Hi Cfairweather, thanks a lot for your reply and tips, I have never heard about the clear tubes method to verify floats and valves, it´s a great idea, i´ll try that.

I checked everything you mentioned and used the original items (floats and valves) and everything looks normal for me, I´ll check today the dimple you mentioned anyway.

I´ll keep you posted. Thanks.

[Akifrend]

Just for the records, today I removed the carbs from the bike and connected a 5 foot hose to fuel input and filled with gas, started flooding, I did not use the transparent tubes method recommended by Cfairweather for time sake, I just removed the screw for all the carbs bowls, they were almost at the same level, carb #2 a bit higher tho (I guess at flooding level). I checked the float and needle in that carb, even kept floats with a rubber band in closed position and got no leak, needle valve is sealing. I notice that the tang (the metal of the floats where the needle is pressed against) had a curveish shape (floats were set at 21 mm as Randakks advices), so I adjusted at eye percent until carb #2 bowl level resulted to be the same as the other 3 carbs, Gravity fuel test was successful, no flooding, I installed the carbs on the bike and cranked it, it started but now needs a carb syncro, It is weird that when flooding it was steady, now this no flood it goes to 3000 rpm and idles slowly, I've seen this before on this bike, nothing that a syncro doesn't fix.

Thanks Cfairweather for your guidance, was really helpful.
Sorry for language mistakes, english is not my native language.
Cheers !!!