PC800 Carb Synchronizing, the 11-step way. By Clay Leihy.
Okay, I'm no mechanic, but I'll give it a shot.
1. Get the service manual. Really, get one, it's really worth it. Now read page 3-6.
2. Warm the bike up to normal operating temperature. (Go for a ride!) Then park her on the
centerstand.
3. Pop off the air ducts, then remove the side covers, after removing the screws.
4. Remove the center covers, left first. If you worry about the "bosses" like
me, you can reach up under the fairing and push them out from the grommets. Then remove
the top shelter (two screws up front, one on each side).
5. Hang your synchronizer from the handlebar. Piece of string or bailing wire works
perfectly. (I use the left side, doesn't interfere with the throttle that way.)
6. On the left side, you'll find a hose that attaches to the fuel auto valve. On the carb
end it goes onto a little metal ell-shaped pipe. Pull that end off. On the right side,
there is a similar little pipe with a rubber cap on it. Remove the cap and put it in a
safe place, like the fairing pocket. These have little spring clamps that can be
difficult, I use a needlenose pliers to get them off and on.
7. Attach one synchronizer hose to the left carb fitting and one on the right. Just push
them on.
8. Next, you'll want to apply some vacuum to the fuel auto valve hose and clamp it. Mighty
Vac is good for this, but human lungs also work as well. Clamp it with a hemostat or small
vise-grip, not tight enough to damage the hose.
9. Start her up, carefully! Don't give much throttle and be easy on it if you must. The
mercury can be sucked right out of the synchronizer and into your engine. This is
especially likely when RELEASING the throttle, so when you open it go slow, and when you
release it go VERY slow.
10. Now look down the hole in the middle of the air cleaner. Use a flashlight. You'll see
a philips screw head in there. Take your 8-inch screwdriver and use it to turn that screw.
Don't push on it, or you'll open the throttle, just turn it while looking at the
synchronizer. You want two of the tubes to come up to the same level. (The other two, of
course, are not connected.) I was surprised at this point because without even looking at
the tubes, I could hear the engine smooth out when they came into synch.
11. Slowly, bring it up to about 3000rpm, and adjust if necessary. Then S-L-O-W-L-Y bring
the throttle back. Check it again at idle. The level doesn't matter, just that the two
cylinders are the same. If you can't get them even at idle and at speed, you probably have
something else wrong.
EXTRA NOTES: The difference in smoothness and power really struck me. I think in a pinch
you could probably do this without the gauge. I had to set my idle down a bit afterwards,
and the off-idle performance increase catches me by surprise every now and then. (Now
zooming out at green lights, instead of staggering.) If you do snap the throttle and suck
the mercury into the engine, don't panic, it doesn't hurt the bike. Just take the
synchronizer off, put the bike back together, and go for a ride to flush the stuff out.
Then get some more mercury. Also, I've heard that the important part is to get them real
even at 3K, even if they're a little off at idle. Remember to put everything back
together, including the little rubber cap that goes on the right side.
That's it. Now you can synch with every oil change and be it top tune. The synchronizer
thing is pretty cool - I used to do my old CB400F by eyeballing the throtle slides while
opening and closing, adjusting till they all looked even. Having the toxic mercury around
makes me a little nervous, I may look into getting the electronic TwinMax synchronizer.
Riding smooth in West Jersey,
Clay Leihy
1989 PC800 "White Silk" aka "Sea Biscuit"
1987 VW Quantum GL5 "Der Wagen"
(No synching needed, Bosch fuel
injection. Now to figure out a way to retrofit that to the bike . . . )
http://go.to/pc800