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Old 04-09-2012, 10:02 PM
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Help with Carbs

Guys, I need some help with the setup of the carbs following cleaning. I initially cleaned them in a Pinesol solution and everything cleaned up just fine and shiny. I documented the position of the pilot jets and left the idle master adjuster knob alone. Upon reassembly, the bike started and idled like a champ, but a problem still persisted between 2000 and 3000 RPM. I had already replaced the voltage rectifier, so I surmised that I still had a clogged jet, as above 3500, she ran just fine. So I took the carbs off again and this time had a local vintage motorcycle restorer clean the carbs with the Yamaha carb cleaner. He said he could sync them also. Upon picking up the carbs, he said that he had run the master idle adjuster knob in and out. Upon reassembly to the motorcycle, I learned the throttle cable holder off of #3 got bent, so off came the carbs for a 3rd time. I was convinced that I had messed up the syncing, so I set out to sync them by the bread wrapper twist tie method. All went well, except, the procedure says to return the master idle adjustment knob back to its original position. I don't know where that was now. I attempted to sync the cards with the master idle adjustment at eight turn out from its fully tightened position. I got the bike started, but it ran poorly and I sooted up the plugs really good. My question - how many turns out should the master idle adjustment knobs be backed out when syncing the carbs. There is another method shown where the butterfly covers 1/2 of the three jets - again - how many turns would the master idle adjustment knob need to be turned out when syncing using this method. Lastly, on a perfect carb setup, with all the carbs synced and the master idle adjustment set perfectly, how much of a gap would exist between the butterfly's edge and the carb's throat?

Sorry for the long epistle, and thanks for getting this far with it. Bike is a std 78E model. Any responses will be welcome.

CK
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Old 04-09-2012, 10:35 PM
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DiverRay DiverRay is offline
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First off, you cannot sync the carbs via bread tie method. It is only a STARTING POINT for a sync. You can use a VERY FINE wire, or a #60 drill, to make sure all four butterfly's are the same space off the carb body. I would then turn the mixture screws all the way down VERY LIGHTLY!!!, and then back 1.5 turns. The idle screw should be about 1 turn past touching the stop.
Once the bike will idle, you WILL NEED a vacuum device of some type to sync the carbs. The shop will probably charge about $150 to $250 to do this, or you can by a tool for $75 to $125 and do it your self. If you search the maintenance section, you will find instructions on how to properly sync a set of carbs. The neat part is this works with two, three, or eight carbs, so after the three hours it will probably take for the first time, it will be easy. Do NOT forget to have a box fan, or some type of fan to blow air over the engine as you run it. the air cooled engines CAN overheat QUICKLY without air flow.
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Old 04-10-2012, 01:03 AM
crazy steve crazy steve is offline
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You can build a lo-buck sync gauge set up; look here: http://www.xs11.com/forum/showthread.php?t=986

Ray is correct; without a vacuum gauge set (either the home-made one or a commercially-built set), you'll never get the carbs set correctly....
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Old 04-10-2012, 01:25 AM
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Check the wires...

So, I had the exact same issue between 2-3k rpm. In fact, mine would stall if you were to slow on the gas. I cleaned the carbs only to have the same issue. Pulled the timing cover and checked the pick up coil wires and they were indeed broke. Fixed them, runs like a champ. Lots of info on here on checking those pesky wires..
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Old 04-10-2012, 05:13 AM
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Asking for a number of turns on this type of stuff is pointless because it really doesn't matter.

As stated, bread tie bench sync is just a base so that you can usually get the bike started. I set my by the butterfly covering the hole method. Then set the idle needles to 2.5 turns out.

Once you get the bike started and warmed up you need to adjust the master idle knob to set your idle to roughly 1100. Then you need to do a true vacuum sync and idle mix adjustment.
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Old 04-10-2012, 06:32 PM
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Thanks everyone for the input. I do plan on syncing the carburetors after the initial pre-syncing, but to even pre-sync, I feel that I still need to know where the master idle adjustment needs to be set first - that is, how many turns out. I noticed that as you turn it clockwise, its opening up the carb's butterflys. The master idle adjuster turns out about 11 turns, so I was thinking you would want to pre-sync the carbs at a position 5 1/2 turns out so there would be adjustment either way from there. So if I did pre-sync the carbs with the master idle adjustment knob turned 5 1/2 turn out, what would be the ideal gap between the bottom edge of the butterfly and the carb's throat that I would want to see? Would it be the diameter of a tie-wrap wire or be resting over one of the holes?

In regard to the broken wire possibility, I'm discounting that because all was well and good before I let the bike sit up for about three months - which wasn't a good move in hindsight considering the ethanol gas that was in the carbs at the time.

Thanks again for your help as I'm out of ideas.




CK
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Old 04-10-2012, 06:49 PM
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You want little to no gap at all on the butterflies. If you had it set half way open your rpms would be pretty high.

Again I say, there is no magic number, every bike is different and once it starts you just need to get the idle at about 1100.
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1978 XS1100E
K&N Filter
#45 pilot Jet, #137.5 Main Jet
OEM Exhaust
ATK Fork Brace
LED Dash lights
Ammeter, Oil Pressure, Oil Temp, and Volt Meters

Green Monster Coils
SS Brake Lines
Vision 550 Auto Tensioner

In any moment of decision the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing.

Theodore Roosevelt
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  #8  
Old 04-10-2012, 09:52 PM
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Thanks Nathan, I'll give it another try tomorrow and see where I get
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