I'm synching my carbs with a u-tube manometer made of a plastic U-tube filled with auto trans fluid with one end connected to each carb nipple.  (It measures the vacuum difference between carbs).  I can get them to sync at idle -- 1200 rpm.  However, as soon as I rev the motor, one cylinder has more vacuum than the other -- when the throttle is let go, the situation reverses itself.  Also, one cylinder's reading seems to fluctuate a bit more than the other.  Is this a burnt/leaky valve?  I see no evidence of vacuum leaks.  Valve clearances are in spec (actually right intake is a bit loose, but that shouldn't hurt anything).  Plugs both look good and the same.  Carb slides move freely.  RPM takes a while to drop back to idle from cruise when the throttle is let go.  There's also a hesitation at 5-6k RPM.

Jetting is 145 main/#40 pilot with 2 1/2 turns out on the pilot screws.  Exhaust is aftermarket Yosh can with K&N lunchbox air filter.

Before I bought the bike, it was running VERY rich on the right due to a broken float needle tip and a butchered pilot jet on the right carb.  The right plug, when I initially pulled it, was literally completely coated with ash.  I'm wondering if carbon could actually be holding the right intake valve a bit open, which also might be causing it not to seat correctly.  Or maybe the left valves are burnt, since the jetting on the left carb was stock, so the left cyl was running lean with the Yoshi and K&N.

Haven't done a leakdown test yet.  HAVE run the bike at 8k RPM on a 20-mile stretch of expressway -- "Italian tuneup".  This seems to have improved things quite a bit, but not 100%.  What would be the best way to decarbonize the engine w/o pulling the heads.

Thanks,
-b.

seafoam it ?

my first guess was valve clearances, but you've already stated they were proper.

i like the italian tuneup deal, think i'll try that tonight. 

Quote from: ohgood on June 16, 2007, 05:42:45 PM
seafoam it ?

my first guess was valve clearances, but you've already stated they were proper.

Can I hook a hose up to the carb sync nipple and have the motor suck up water/seafoam/whatever via the nipple?

-b.

I had an auto shop teacher swear by auto trans fluid for decarboning the valves (hot engine required). You could try it... just use a small quantity. you could try in the synch ports, but I would just yank the lunchbox off, run it at part throttle, and have the engine "lick" it off the spoon. If it still smokes after 10 minutes of running at 3k, italian tuneup again.

btw, you're supposed to sync the carbs at 3k rpm, not at idle. there's not enough airflow to make the adjustment worth it at idle.

and, i personally just sync my carbs on the bench til the clearances feel right.