Persistent flat spot off idle

jackleberry wrote:

Mean Green Z28 wrote: I am very new to this but one passage/opening I found clogged on my carbs was the pilot bypass orifices near the throttle blade. Idle was fine and mid/top range was fine, the off idle fueling was f'd up, and it turned out that these tiny little orifices were clogged.

they're shown here as transfer ports

www.xs650.com/forum/showpost.php?s=2464b...7&p=4464&postcount=2

That's possible. I know the pilot jets themselves are clean because I've had them out many times. I've blasted that entire circuit with carb cleaner many times and seen it exit via those holes. How did you know yours were clogged and how did you unclog them?

bountyhunter wrote: You might try draining the bowls and reinstalling the bowl screws then filling the carbs with Gumout liquid or some equally strong carb cleaner and let sit for a week. If internals have oxidized gas gumming them up, that should clear it.

LarryC wrote: When no amount of jetting cures a problem it's a good indication the fuel level is not correct.

mopguy wrote: Maybe you need a new throttle cable or it needs to be lubricated so it slides freely all the way to the bottom?

Nessism wrote: If the passages are plugged it's extremely difficult to clear them by trying to force spray though. That's why you should soak the carb body in carb dip followed by a water rinse. Use the spray after to verify the passages are open.

Mean Green Z28 wrote:

jackleberry wrote:

Mean Green Z28 wrote: I am very new to this but one passage/opening I found clogged on my carbs was the pilot bypass orifices near the throttle blade. Idle was fine and mid/top range was fine, the off idle fueling was f'd up, and it turned out that these tiny little orifices were clogged.

they're shown here as transfer ports

www.xs650.com/forum/showpost.php?s=2464b...7&p=4464&postcount=2

That's possible. I know the pilot jets themselves are clean because I've had them out many times. I've blasted that entire circuit with carb cleaner many times and seen it exit via those holes. How did you know yours were clogged and how did you unclog them?

just a lot of head scratching until I found the diagram that showed those two bypasses. Didn't even know they were there. When I first sprayed, I saw nothing come out, but I kept spraying lightly from the bore side to soak it and also using a strand of wire to poke the holes. Then wrapped a bunch of electrical tape around the carb cleaner nozzle and poked it up into the pilot jet tube from the bottom and kept praying and blocking off any other holes that the spray would come through (may have sprayed my face a few times, ha), until I saw a nice stream come through those openings. It was a pain in the ass and my skin dried out like crazy 'cos of all the solvent on my hands! hahaha

Nessism wrote: Back to basics. Here is a link to a Mikuni BS CV carb rebuild tutorial. Bust down the carbs and soak each one in carb dip to be sure all the various passages are open. Replace all the O-rings. Verify fuel level is correct using the clear tube method. If the weight of the float depresses the float needles replace the needles. Look at each jet and make sure the numbers match the factory manual for your bike. If someone put aftermarket carb kits in your carbs that may be your problem right there. Most common carb kits are full of inferior junky jets that may or may not match your originals. Big red flag there if that's the case... zeus.mtsac.edu/~cliff/storage/gs/Mikuni_...Rebuild_Tutorial.pdf

jackleberry wrote: [Have already done this with Seafoam.