Yamaha 80 Carb Sync

Dora~Jean · Posted: Sun Apr 22, 2007 9:46 pm Post subject: Yamaha 80 Carb Sync

This weekend I got into sync'ing the carbs (4) on my twins. First I looked up the vacuum gauge and manifold fittings (set of 4) in the Service Manual. Called up nearest Yamaha service center, they quoted a whopping $692 for this simple set. Just item #1:

Hmmm, thought about 1-2 seconds, decided to make my own set. Took me about an hour and a half to make all 4 fittings after getting the items at the hardware store. The factory fittings have connections that self seal when disconnected, I was just fast with the caps!

See photos of my 'homemade' set starting here.

Checked port engine first, set at recommended 900 rpms, then again at a faster idle, 1100 rpms. All within the 'wide spec' of +/- 50mm Hg (+/- 2" Hg), these measured within about 1" Hg, now they're within 1/4" Hg. Starboard engine's #1, 2 cylinders were off by 2" Hg, they're now within 1/4" Hg. Won't matter much in performance for the amount I changed them but good peace of mind they've been looked at!

Dora~Jean · Posted: Mon Apr 23, 2007 2:36 am Post subject:

Forgot to add that I'd be happy to describe how I made the fittings and materials, and how to do the actually synchronization. There are many ways to make a similar part, I just picked the first one that seemed the simplest to me.