Bs38 pilot question, high idle

[thrashin]

Hey all, I'm in the middle of tuning my 72 xs650. It has BS38 from a 76 I believe. It has the vm style pilots and vent tubes on the carb bodies, also has a single choke lever and the carbs are tied together at the bottom by a small piece of angle. I also have the small filter xs pods and the oem straight pipes with no mufflers.

Currently I have 135 mains and 30 pilots. The needle clip is in the 3 ring.adj screw is out 2.5 turns.

My problem is I went from an agressive popping engine with 25 pilots to a much better running engine with the 30's. But it seems like I neeed to go bigger?? It's no longer popping but even with the idlle screw all the way out it idles high. Do I need more pilot jet? I haven't really messed with the sync screw in between the carbs. Any ideas? Thanks

 

[gggGary]

Yup mess with the synch screw, ear, hand over pipes or gauge, and make sure you have enough slack in the throttle cable that the throttle arm can rest on the idle set screw.

 

[thrashin]

There is a tiny bit of slack in the cable. I did a bit of a bench sync before I mounted the carbs. I need to do a search on a proper sync while runing I guess.

 

[gggGary]

Check slack by pushing the arm against the screw. search manometer here for how to make an inexpensive home sync tool. Most BS38s have vacuum ports capped by screws if your manifolds don't have ports.

http://www.xs650.com/forum/showthread.php?t=25724&highlight=vacuum+port+bs38

 

[peanut]

sounds like too much air at idle causing a lean idle mixture.
I would guess that your butterfly valves are not shutting off the venturi properly which may be due to them not being centred when the carbs were rebuilt.

if you press down hard on the idle adjust end of the throttle shaft with your thumb (with your stop screw fully backed out ) and the idle drops then thats the culpret.

Heres a vid on how to centre them which might be helpful

 

[thrashin]

Got it whooped yall! Thanks for the help. They were just out of sync pretty good. Runs nice and smooth now.