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Old 06-27-2010, 07:31 PM   #16
Bigger Al
Still a stupid tire guy
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Joined: Oct 2004
Location: Auburn, CA
Oddometer: 7,980
Did you adjust the valves before trying to synch the carbs?


Of course, it would prolly make some difference if I read every post before replying myself.
"I'd rather wake up in the middle of nowhere than in any city on Earth."

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Old 06-28-2010, 12:05 AM   #17
Brevis illi vita est
Joined: Jun 2010
Oddometer: 4,611
Originally Posted by noz
hang on maybe it me with the setting of the mixture, and finding the sweet spot for it and not setting it for the sweet spot before setting the idle after that.

would this cause these irregularities?
If you are happy when you are done tuning but unhappy after a ride, then something changed. But what?

Bike at the same temp? Not properly warmed up will hurt as will overheated after a ride?

Wrong or worn plugs? If the plugs are partially fouling during tuning and then cleaning themselves during a ride the tune will change.

Valves dead on (including rocker end shaft play)? set them dead cold and check them again dead cold if the tune changed. You did torque the heads before setting the valves, right?

Air leak check? (you said you did, did you use ether?)

Tuning on the centerstand, right?

Throttle cables completely slack when setting up idle? (not 1/16", 1/8" +++). Throttle assembly free, lubed? If you have a splitter cable is it in good shape?

Personally I don't use a manamoter for balance. I had an old BMW wrench teach me to power balance and it worked well. I tried a Walus setup once and it just wouldn't cut it. The power balancing is faster and incredibly accurate---and you set it up for your most frequent cruising speed so you always are running in the sweet spot. On an airhead, especally as the miles pile on, the manifold vacuum corelates poorly with the power output. The left side usually has more compression. So you balance the thing for power, not vacuum. Makes for very smooth running. In addition it provides a couple of in process diagnostic moves that you can quickly repeat later if things aren't right.

Do your valves and timing. Warm it up with a ride (I don't do the ride but I have do measure temps and most people don't have that gear).

Slacken the throttle cables completely and fully back off the butterfly stop screw so both throttles are completely closed. lift up on the throttle lever and release to ensue the springs fully close those throttles. A PO may have fitted softer springs. Beware.

Set the butterfly stop screws to initial position per manual. You must know exactly when the screw touches down so you can start counting turns. Try a bit of cigarette paper as a feeler gauge if you have to. It's not dead critical though.

Set idle mixture screw to initial setting per manual. Don't tighten it in real hard---just till it's closed then back it out. It's got a good o-ring on it, right?

Start the bike and it should idle. If not you gotta problem. Diddle the idle mixture screw on one side until it runs best. Repeat on other side. Go back to first side and see if a little diddling makes better. Ditto the other side. Now the idle mixtures are set. If one screw position is vastly different than the other you gotta problem.

Shut it off and fit the shorting wires.

Start it, let idle a half minute then short one side with the insulated screwdriver. The running side should hit 2-3 times then die. For higher idle it should hit 3-4 times then die. Adjust the butterfly stop screw to get this.

Now short the other side and repeat. 2-3 hits then dies. Adjust the butterfly stop screw on the running side again. If the settings on the two screws are vastly different you gotta problem.

Now the idle mixture and speed are done. If you want a higher idle turn in both butterfly stop screws exactly the same amount---and it's a very tiny amount. Wait 30 secs. between adjustments for the motor to catch up. Never touch the throttle or throttle cables.

If you are new at it (hence low) watch your engine temp. Let it cool some or fire up the fans.

Remove the slack from the throttle cables. Take it to just barely peerceptable slack. Work the throttle at the handlebars a couple times to WFO and back and makes sure things are right (slightest slack) at the carbs.

Start it up again. Take it just off idle and then short one side, with the throttle ind it up to cruising rpm and lock the throttle so it does not move (throttle lock screw, this is where you use it).

Rapidly switch the shorting to the other side. Have both screwdrivers touched down on the shorting wires and just slide one forward to contact the head and the other back to break contact. helps to watch someone do it once. The rpm should not change. Go back and forth a time or two to identify the weak side. Shut it off and tighten the throttle cable on the weak side. Experience will reveal how much to try at a time.

Fire it up and repeat. Continue finding and correcting the weak side until there is no (as in none) change in rpm when you change from one side to the other. Tighten the cable lock nuts and you are done.

If one cable needed a whole lot of tightening to get it balanced, something may be funny. Keep it in mind.

If you ever un-short BOTH sides when you have it wound up to speed on one side only then the engine will run away---fast. So don't do that. Better to short both sides by accident and just kill it.

Now if you are unhappy the following day you put your shorting wires on and short one side at idle. Then try the other side. If the balance is way off then either the butterfly stop screws moved, you had some procedure error in the beginning, the butterfly aren't closing against their stops or the idle mixture got hosed (aside from a valve adjustment issue, etc.)

Check the mixture screws at idle. Diddle each one a little and see if a change is required to get one or the other side to idle best again. if they need readjustment there is something funny in your idle circuit. Try running some Seafoam to clean things and check the idle mixture screw o-ring, the tip of the idle mixture screw for ridges or being mashed or maybe even bent. Make sure the idle jet and whatnot is clean and seated. Make sure the carb bowls are clean and you aren't sucking crap (like water).

Beware the choke cover gasket. A common failure. Leaking diaphragms can also give you grief as can a worn needle/needle jet. See the Bing manual for Dx.

If you do use a manometer you introduce a change as soon as you are done---the manometer is no longer connected and you put the screws back to plug the holes in the carbs. Check the washers under those screws.
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