Carb Synching 101

[donebysunday]

Thanks, I had my carbs checked for sync and they were spot on, once bike was fully warm or hot and choke off, the RPM's would slowly drop below 1000RPMs on idle and stall out, if I rotate throttle the throttle grip just a slight tad, and hold it there, the bike idles just fine.

Can the the throttle cable be adjusted near the the throttle grip near handle bars, where that chrome nut linkage meets the throttle grip? What is that nut for, to remove slack from cable?

Thanks,

d-1

Yes the nut at the throttle grip is to remove slack. It could be used to control idle but the cable gets pulled and slacked off by turning the bars and that will cause fluctuations in the opening of the butterflies and then change rpm.. The more positive adjustment is the turn screw at the carbs, then set the cable so it does not pull at the carbs and change rpm. when you turn the bars.

[dolphans1]

Yes the nut at the throttle grip is to remove slack. It could be used to control idle but the cable gets pulled and slacked off by turning the bars and that will cause fluctuations in the opening of the butterflies and then change rpm.. The more positive adjustment is the turn screw at the carbs, then set the cable so it does not pull at the carbs and change rpm. when you turn the bars.

Thanks for the update.

d-1

[LoHo]

Addendum:

As you work through this process and get the carbs closer together, feeling smug and confident, you might notice a pronounced rev in two carbs, which you will frantically try to compensate for by readjusting the synch you just made. Then either the bike will shut off or the other two will rev up. Dumbfounded, you will shut off the engine and curse the XS gods, just before you notice that your remote fuel tank has run dry.

[IanDMacDonald]

Addendum:

As you work through this process and get the carbs closer together, feeling smug and confident, you might notice a pronounced rev in two carbs, which you will frantically try to compensate for by readjusting the synch you just made. Then either the bike will shut off or the other two will rev up. Dumbfounded, you will shut off the engine and curse the XS gods, just before you notice that your remote fuel tank has run dry.

Lol, don't feel bad. I think my bike was running on two cylinders the other day as it was low on gas.

[Pat Kelly]

An OCD detail I add to my sync.
I noticed when syncing at idle, I get the carbs balanced. Twisting the throttle to raise the RPM would bring the carbs slightly out of sync.
I want my carbs synced under throttle, not idle.
I raise my RPM to just above idle (cruise control) and sync them there. They are slightly off at idle but perfect above idle.

[motoman]

An OCD detail I add to my sync.
I noticed when syncing at idle, I get the carbs balanced. Twisting the throttle to raise the RPM would bring the carbs slightly out of sync.
I want my carbs synced under throttle, not idle.
I raise my RPM to just above idle (cruise control) and sync them there. They are slightly off at idle but perfect above idle.

.

[DiverRay]

I check mine at about 3K to 4K when I'm "done" with the sync. IF they are off, I'll adjust to the higher RPM sync. I don't always bring it up perfectly, but get it close so it's still good at low RPM.