Author Topic: Does unscrewing/rescrewing the fuel mixture screws on the carbs unsync them?  (Read 201 times)

Offline BikerBoy

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Ive read messing with the fuel mixture screws under the carbs doesnt unsync the carbs, but I feel like it should.  Anyone know?

Offline themonkeyman89

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Carb synchronization refers to syncing the throttle blades and balancing idle vacuum, and generally doesn't mean air/fuel mixture screws. That said, the idle mixture screws generally end up being set pretty similar to each other, unless something is wrong with the motor.

Offline BikerBoy

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Carb synchronization refers to syncing the throttle blades and balancing idle vacuum, and generally doesn't mean air/fuel mixture screws. That said, the idle mixture screws generally end up being set pretty similar to each other, unless something is wrong with the motor.
Cool, thanks for sharing.  :cheers:

I wonder if my left float is stuck or faulty, when I was removing my carbs today there was 3.5 capfulls of gas in the left cylinder, only 1 capfull in the right cylinder. Maybe this is because its on the sidestand so the gas is tilted to the left, but I dont think there a way for gas to move from right to left cylinder. Im still getting a little gas in my airbox, not a lot, but sometimes there will be a 4 or 5 inch puddle under my airbox drain hose. But its pretty consistent that it will leak sometimes..

Offline Kilted1

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I wonder if my left float is stuck or faulty, when I was removing my carbs today there was 3.5 capfulls of gas in the left cylinder, only 1 capfull in the right cylinder. Maybe this is because its on the sidestand so the gas is tilted to the left, but I dont think there a way for gas to move from right to left cylinder. Im still getting a little gas in my airbox, not a lot, but sometimes there will be a 4 or 5 inch puddle under my airbox drain hose. But its pretty consistent that it will leak sometimes..

You could have a stuck or mal-adjusted float.  Or simply a worn out, leaky needle valve.  It's typical to get more out of the left carb drain when it's on the side stand.  Especially if you do that one first.  (If it's on the center stand you'll get more fuel on whichever side you do first because it's going to drain the supply tube as well.)  But to have fuel overflowing into the airbox and onto the ground means you don't only have a leaky float valve, you also have a leaking petcock.  It may not be much but over time even a slow drip adds up.

The sync adjustment is on the throttle shaft between the carbs, right next to where the cable attaches.  Not related to your issue.  It's basically just a trim adjustment between the left and right throttle plates as Monkeyman said.  Twiddling with the pilot jets won't bother your sync.

Good luck!   :cheers:

Offline BikerBoy

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I wonder if my left float is stuck or faulty, when I was removing my carbs today there was 3.5 capfulls of gas in the left cylinder, only 1 capfull in the right cylinder. Maybe this is because its on the sidestand so the gas is tilted to the left, but I dont think there a way for gas to move from right to left cylinder. Im still getting a little gas in my airbox, not a lot, but sometimes there will be a 4 or 5 inch puddle under my airbox drain hose. But its pretty consistent that it will leak sometimes..

You could have a stuck or mal-adjusted float.  Or simply a worn out, leaky needle valve.  It's typical to get more out of the left carb drain when it's on the side stand.  Especially if you do that one first.  (If it's on the center stand you'll get more fuel on whichever side you do first because it's going to drain the supply tube as well.)  But to have fuel overflowing into the airbox and onto the ground means you don't only have a leaky float valve, you also have a leaking petcock.  It may not be much but over time even a slow drip adds up.

The sync adjustment is on the throttle shaft between the carbs, right next to where the cable attaches.  Not related to your issue.  It's basically just a trim adjustment between the left and right throttle plates as Monkeyman said.  Twiddling with the pilot jets won't bother your sync.

Good luck!   :cheers:
I cleaned the carbs with pine sol and put back in a K&N air filter in the stock airbox, as well as 20s and 137.5 jets instead of 17.5 and 130. After that, the bike starts up really smoothly, and sounds good since the carbs were just synced really well. However I still have a small bit of gas leaking out, especially if it was just running, not much but sometimes 5 or 10 drops from the airbox then it stops. The rubber on the needle valve was still good, as well as the diaphragms.

I dont know how you know if the floats "stick", but they seemed to go on and off the needle very smoothly on its side. (I'd probably get a lot more gas coming out if theyre were truly stuck) Also I made sure the vacuum lines are all hooked up the way theyre supposed to be.

So youre saying the petcock might be an issue, like if the diaphragm is leaking, then fuel will keep going to the carb even when its shut off? Could this be the problem even if my floats are fine? Right now I think its something other than the vacuum lines or carb thats an issue, because Ive been there multiple times and am pretty certain thats not it. Thanks
« Last Edit: June 05, 2019, 10:53:00 PM by BikerBoy »

Offline BikerBoy

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I wonder if my left float is stuck or faulty, when I was removing my carbs today there was 3.5 capfulls of gas in the left cylinder, only 1 capfull in the right cylinder. Maybe this is because its on the sidestand so the gas is tilted to the left, but I dont think there a way for gas to move from right to left cylinder. Im still getting a little gas in my airbox, not a lot, but sometimes there will be a 4 or 5 inch puddle under my airbox drain hose. But its pretty consistent that it will leak sometimes..

You could have a stuck or mal-adjusted float.  Or simply a worn out, leaky needle valve.  It's typical to get more out of the left carb drain when it's on the side stand.  Especially if you do that one first.  (If it's on the center stand you'll get more fuel on whichever side you do first because it's going to drain the supply tube as well.)  But to have fuel overflowing into the airbox and onto the ground means you don't only have a leaky float valve, you also have a leaking petcock.  It may not be much but over time even a slow drip adds up.

The sync adjustment is on the throttle shaft between the carbs, right next to where the cable attaches.  Not related to your issue.  It's basically just a trim adjustment between the left and right throttle plates as Monkeyman said.  Twiddling with the pilot jets won't bother your sync.

Good luck!   :cheers:
Looks like you were right, I replaced the petcock with an ebay one and it solved my leaking airbox issue. Thanks!  :D