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1979 GS750L. All carbs (VM, Mikuni 26mm) have been dipped 24 hours, blown out, sprayed out and properly cleaned. New O-Rings all around. The floats are all set at 25.5mm (high spec for a 79). Slides have been synched (using the Morgan carbtune). Airbox has been sealed (one side is with weather stripping, one side is with the original rubber gasket, which is in pretty good condition). Airbox boots are nice and pliable, intake boots are nice and pliable, no cracks or weirdness on either. All valves are in spec (lowest clearance is about .05mm, highest is .10mm). Gas gets into the carbs no problem. Tank is clean. Petcock holds vacuum.
I'm sure you guys will let me know if I've missed anything, but suffice to say, I think I've taken care of everything this side of the pistons.
So here's the deal: I'm getting a real rough idle, with some pretty severe hesitation up to about 1/8th throttle (like, it doesn't kill the bike...but the bike kind of goes "hmmm, oh throttle?" for a half second, then picks up and goes real fast).
I think it's the #4 carburetor.
If I let the thing idle for a few minutes, the #1 - #3 pipes will burn my hand (something severe, truth be told), but I could grab on to the #4 pipe and it's just enough to keep my hand warm on a mild evening in the shop.
The odd bit is: I go out and ride it and it has no problem with 70, 80, 90mph. So long as i have the throttle pulled way far back, she just wants to go. As soon as I let up: "sputter sputter sputter".
I checked the plug, and I'm getting a nice, strong spark out of it. Tweaking the air and fuel mixture screw on the #4 carb has no noticeable affect. I can screw them all the way in and it runs. I can unscrew them 4-5 complete turns and get the same result.
The last bit of fun: I'm getting fuel seeping out around the plug. My thought is that the #4 carb is running way too rich and the gas isn't burning off, but I don't know what the deal is here.
Backstory re: Carb #4. This carb body is not the body that came with the bike. It's a replacement that I had to pick up because the original's fuel screw hole stripped out. It is basically the same carb, but differs from the other 3 in a few different ways:
#1 The pilot screws screw in much further than on the other 3 carbs. If I lightly seat then unscrew 2 turns, the screw heads sit right about where the screws would sit turned all the way in on the other carbs.
#II At the point where the needle valve enters the needle jet (hawt...)—on the other three carbs there is a small divet or washer or something that extends from the hole about 2mm. There is no such thing on the #4 carb body. This—coupled with the above—leads me to believe that the carb body is a slightly different model than mine.
C) There is some significant pitting in some places on this carb (particularly around inside the roof of the carb bowl area ). It kind of looks like a luffa in some places.
Erm...if that made any sense and anybody has any ideas, please respond. I'm getting ready to just buy a new bike and swear off carburetors forever....
I'm sure you guys will let me know if I've missed anything, but suffice to say, I think I've taken care of everything this side of the pistons.
So here's the deal: I'm getting a real rough idle, with some pretty severe hesitation up to about 1/8th throttle (like, it doesn't kill the bike...but the bike kind of goes "hmmm, oh throttle?" for a half second, then picks up and goes real fast).
I think it's the #4 carburetor.
If I let the thing idle for a few minutes, the #1 - #3 pipes will burn my hand (something severe, truth be told), but I could grab on to the #4 pipe and it's just enough to keep my hand warm on a mild evening in the shop.
The odd bit is: I go out and ride it and it has no problem with 70, 80, 90mph. So long as i have the throttle pulled way far back, she just wants to go. As soon as I let up: "sputter sputter sputter".
I checked the plug, and I'm getting a nice, strong spark out of it. Tweaking the air and fuel mixture screw on the #4 carb has no noticeable affect. I can screw them all the way in and it runs. I can unscrew them 4-5 complete turns and get the same result.
The last bit of fun: I'm getting fuel seeping out around the plug. My thought is that the #4 carb is running way too rich and the gas isn't burning off, but I don't know what the deal is here.
Backstory re: Carb #4. This carb body is not the body that came with the bike. It's a replacement that I had to pick up because the original's fuel screw hole stripped out. It is basically the same carb, but differs from the other 3 in a few different ways:
#1 The pilot screws screw in much further than on the other 3 carbs. If I lightly seat then unscrew 2 turns, the screw heads sit right about where the screws would sit turned all the way in on the other carbs.
#II At the point where the needle valve enters the needle jet (hawt...)—on the other three carbs there is a small divet or washer or something that extends from the hole about 2mm. There is no such thing on the #4 carb body. This—coupled with the above—leads me to believe that the carb body is a slightly different model than mine.
C) There is some significant pitting in some places on this carb (particularly around inside the roof of the carb bowl area ). It kind of looks like a luffa in some places.
Erm...if that made any sense and anybody has any ideas, please respond. I'm getting ready to just buy a new bike and swear off carburetors forever....
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