Joshua in Indianapolis writes:
"I'm in need of a carb sync tool and am leaning toward the TwinMax - I thought I saw somewhere that you use one. Could you quickly walk me through the synch process on a Royal? Do you synch the carbs in a particular order? Do I need anything other than the TwinMax to do it? I don't have a tach and I keep reading that I might need one. Bear in mind money is tight - can a good carb sync happen without a tach?"
Well, first off, the TwinMax is kinda hard to find, so here's where you need to look:
TWINMAX Electronic differential depression gauge
$89.95 plus $5.75 S&H.
As far as the tach goes, it's pretty hard to "hear" the engine speed, and the idle will change everytime you tweak a carb. I don't know as I'd want to try it without one, but your call. The one I use has an inductive pickup - all you have to do is clamp it on the spark plug wire just above the boot on #1 to get a reading. Here's the source:
Digital Multimeter ATD5540
Item no: 25084
Price: $64.99
I also just picked up a SYNCHROMETER, not to be confused with a SYCHRONIZER like the TwinMax. The synchrometer fits into the carb throat and measures intake vacuum. Set the PMS (screw) on number one to 3½ turns, take a reading, then adjust each carb to match. No specific order, but here you really would need a tach - it's important to reset the idle to 900 RPM as needed to get proper readings. I got mine from the following source:
DELUXE CARBURETOR SYNCHROMETER
Code: BP7034-11X
Price: $35.99
You'll also need a phillips screwdriver with a very long handle. Should be able to pick one up at your local auto store. The one I use is maybe 18" long and really takes the work out of it. You also need a good flashlight to find the adjuster screws. I've got one of those LED headlights that is pretty slick for the job, and also real handy for camping, blackouts and scaring the crap outa the neighbors.
LET'S DO THIS THING!
Before you do anything, do you really need to resynch? It's usually not a problem unless you've torn down or rebuilt the carbs. That said, first thing I do is pull the plugs and replace them if necessary. Make sure you're working in a well ventilated area - 80 cubic inches can kick out a lot of exhaust. It takes a bit to do the job, and you'll probably have the radiator fan kick on a few times during the process. Scared the crap outa me first time it happened with my head in the motor, doncha know. Assuming you went out and got the recommended tools, your PMS caps are drilled out so you can adjust the screws, and that your throttle cables are properly adjusted, the procedure is as follows:
ADJUST THE INTAKE VACUUM
- Fire that sucker up, and make sure the ol' girl is up to operating temperature.
- Pull the gas tank and whatever passes for an airbox on the bike. This is a good time to check for problems that would affect performance. Good fuel flow from the petcock? The throats should be minty fresh and the slides should rebound smoothly all the way to the barrel stops when compressed. Needles can pop out of their seats - put a finger on each one (easy does it, friend) and see if you can wiggle it any. If you find a loose one, see if you can twist it till it pops back into the seat. You'll need to tear the carb down if that doesn't work. Doesn't happen often, but it's pretty frustrating to try synching the carbs if this happens.
- Hook up a fuel supply. I put the tank on a table next to the bike and run a long hose to the fuel inlet. You'll also need to remove the speedo and reset switch and hook these up temporarily on top of the motor. A coupla pieces of duct tape across the frame tubes makes a handy resting place. Don't forget to clamp the extended fuel line when you remove it later - you'd be unpleasantly surprised by the amount of gas that is contained in a coupla extra feet of fuel line. Another good tip, try not to trip over the line when working on the bike, as nasty things can happen if you attempt to walk thru, not around the line.
- Set your idle to the recommended 900 RPM, then place the synchrometer FIRMLY in the #1 barrel (back left carb). You'll need to hold it tight in the carb throat while doing the adjustment. Tweak the primary mixture screw (PMS) to obtain the maximum reading on the gauge. Make a note of this - this is your base reference number for all the carbs.
- Move the gauge to #2 (front left carb). Adjust the PMS to match the vacuum to your base reference reading. Readjust your idle if needed, then move to #3 (front right carb), and finally #4 (rear right carb).
- Replace the airbox (you did clean the filters and blowby, didn't ya?). You don't need the gas tank off to do the rest of the adjustments, so go ahead and put that back on. Good idea to cap the ends of the extended gas line to keep any stray crap from wandering into the hose and screw things up next time you use it.
SYNCHRONIZE THE CARBS
I'll assume you're familiar with a standard carb synch, so I won't bore you with the details. If you need more information, there's a good article posted on the following site:
http://www.venturers.org/NextGenTech/V2tech.html
- Follow the directions included with the TwinMax to calibrate the gauge.
- Remove the nipple caps on the intake manifolds for the left bank of carbs. Attach the TwinMax hoses to cylinders 1 and 2, then tweak the adjuster screw so the gauge needle zeros out in the center of the meter. The adjuster screw is located on the left side between the carbs, but you'll need to reach in with the long phillips from the right side. Blip the throttle a coupla times - the meter should settle back on zero when idling.
- Remove the TwinMax hoses, reinstall the nipple caps, then reset the idle.
- Remove the nipple caps on the right bank, and repeat the steps used to synch the left bank of carbs. There are two adjuster screws on the right side of the carb cluster. Reach in with the phillips from the left side of the bike and turn the rear screw to adjust the right bank.
- Remove the TwinMax hoses, reinstall the nipple caps, then reset the idle.
- Remove the nipple caps from both front manifolds and attach the TwinMax hoses. Reach in from the left side of the bike and turn the front adjuster screw on the right side of the carb cluster to synch the left and right banks. Blip the throttle a coupla times - the meter should settle back on zero when idling.
- Remove the TwinMax hoses, reinstall the nipple caps, then reset the idle.
TEST DRIVE
Hit the road and put on some miles. Enjoy the scenery, listen to the motor, and roll that power on ...