I think these carbs are having an ignition problem ....

[MPittma100]

Float Level

Was thinking to shoot for the bottom of the washer next go around. I read about the "running level" test and can't see any way to do that on this bike. It's hard enough sealing off the tubing for bench testing; I can't imagine trying to manipulate the lines without them being pulled loose and soaking down the motor with fuel. Makes me wish I had a lathe. Could center drill a drain bolt and epoxy a nipple on it to attach the tubing. Or maybe someone has already made something similar and I just haven't seen it.

The float levels should definitely be checked on the bench before installing onto the bike. If you have not already done so, spend the money and get the Mikuni float valves. A side-by-side installed comparison of the 2 different valves will amaze you as to how much difference there is.

Once they are correct, you will have an XS1100 that runs like a champ. And you will get some really good MPG.

[Barbarosa]

Yup.......still a bit high(dang K&L parts) fuel level needs to be at center of lock washer. Do that, set idle mixtures(lean-drop method) and THEN sync, go ride with the permanent grin.

Put in new plugs and tuned in the carbs again with bench level bowl level even with top of washer/bottom of lip. Starting at 1 ½ the mix screw had some effect at around ½ turn out and seemed to do better closed off completely. Started easy, held idle well, and revved better this time with crisper throttle response. no hanging idle. Didn’t ride it because it still carbon fouled the plugs. Rather than tinker with a half a mm to hit the center of a washer, I lowered the float level to 3mm below the lip trying to force a lean condition and had similar results, carbon fouling, after initial tuning. It seems to me that even the dastardly K&L valves would respond to that. Sure has me stumped how too much fuel is still getting through. The airbox is off and it has 2 to 4 aftermarket exhaust with stock jetting in the carbs. If this thing wasn't so pretty and pull so smooth when it runs ......

[mack]

K&l

The reason we despise K&L is because it is not a brand name. It is only a packaging company. Sometimes the product will be from Taiwan, check republic, china or worse. They buy in bulk and then package what ever they got. There is no production standard. Mikuni on the other hand will only put the square in the square if it meets their standard.

[Barbarosa]

K&L or whatever name valve shouldn't make a difference if the fuel shuts off at the bowl level they are bench set for. They shut off the fuel at the bottom of the lip and the plugs carboned up They shut off the fuel at 3mm from the bottom lip and the plugs still indicated a rich condition when in theory it should be lean. The history of this bike is running good when parked, but improperly stored for 2+ years. I'm beginning to wonder if it wasn't starting to peter out and the PO got tired of cleaning plugs and just put it up. Putting the carbs back to bottom of the lip and starting from scratch 1 more time.

[motoman]

Put in new plugs and tuned in the carbs again with bench level bowl level even with top of washer/bottom of lip. Starting at 1 ½ the mix screw had some effect at around ½ turn out and seemed to do better closed off completely. Started easy, held idle well, and revved better this time with crisper throttle response. no hanging idle. Didn’t ride it because it still carbon fouled the plugs. Rather than tinker with a half a mm to hit the center of a washer, I lowered the float level to 3mm below the lip trying to force a lean condition and had similar results, carbon fouling, after initial tuning. It seems to me that even the dastardly K&L valves would respond to that. Sure has me stumped how too much fuel is still getting through. The airbox is off and it has 2 to 4 aftermarket exhaust with stock jetting in the carbs. If this thing wasn't so pretty and pull so smooth when it runs ......

Fuel level in bowl dictates majority of running rich or lean.......that half a millimeter to high IS still the 'running rich issue'. Also, fuel levels being too low, say 6-7mm WILL also cause a rich running issue. Think of it this way as carbs work same way........fill a glass of water to the top, insert a straw and blowing across top of straw will draw fuel out at a constant rate.
Now fill glass half full and perform same thing. Harder blowing(venturi velocity) is obviously needed, with result of water coming to top and out of straw, but at a way to fast a rate in order to keep flow going.....same result from carbs......

[motoman]

Keep in mind also, not a lot of room left for fuel volume with float taking up a lot of that space.
What that amounts to associated with these side-draft Mikuni carbs is 1mm of float change equals 3mm of fuel level change. With that, fuel levels ARE critical pertaining to initial fuel/air flow. Kinda makes those settings critical and a PITA.........but 'it is what it is'.

[TopCatGr58]

Hey there Barbarosa,

You mentioned K&L floats/seats, but you haven't mentioned what JETS you have???

IF K&L floats/seats...then a kit may have been used, and may have also used K&L jets? As Brant/Motoman stated, the K&L are not calibrated the same as Genuine Mikuni, and are also known for excessively RICH condition!! Their metering holes are much larger than OEM type. So....when you pull the carbs, pull the pilot jets and check them for the double square/diamond pattern/brand marking of Mikuni. If you don't see it, then you don't have Mikuni jets, and you'll need to get them before doing any other adjusting, otherwise, you'll be chasing your tail!

T.C.

[Barbarosa]

Sorry for any confusion. First post about this bike was 5/23/16. Jets are mikuni and are stock size. If float level is the problem I have reached the limits of my ability. Have been set at even with top of lip, bottom of lip, and 3mm below lip. Just finished tuning with level set at middle of lip and still carbon fouling. I understand about finicky carbs, but when the levels are within the width of surface tension lines of being even and set from the top to past the bottom of the lip, it just doesn't make sense for 1 of the positions not to work. Not disagreeing with any advice or shared experience of this group. I think it's more about convincing myself I don't need further experimentation. Will be checking voltages while it's running next. Everything checked good on the bench and at connections with key on, but might be different under a load.

[Barbarosa]

I think these carbs are having an ignition problem ....

This is a continuing saga and I hope it's ok to repost the same problem on multiple threads. Had plenty of carb help now looking for ignition specs I can’t find. Hoping some of the electrical folks will see this and respond. 1980 SG carbon fouls plugs while riding and then during initial tuning after carb adjust/install. Reasonably certain that the carbs are right so I'm moving back to checking voltage. Bench tested all ignition components beforehand as good according to multimeter, but not with bike running. Battery reads 14.5v at 5k rpm. Key off battery 12.2v, on 11.9v. At TCI gray 11.1v, orange 11.1v. (Others at 6.1v and 11.1v.) With the engine running there is 7.5v at gray/orange and it fluctuates quite a bit from 4v all the way to 0 at times on both. Checked several times to ensure contact and accuracy.
I have traced the voltage drop to the stator. With it unplugged the system does not lose voltage when the key is switched on. I remember reading somewhere that the coils need 9v from the TCI to fire properly. Has anyone encountered similar conditions of low/fluctuating voltage from the TCI and found the cause of it. Hope this is the gremlin I have been chasing and someone out there can help me get it whooped.

[motoman]

Well, first off, you need to specify whether bike is either 78-79, 80, or 81-XJ. Three options there related to both primary or secondary ignition.

[Schming]

Reread . . .

Well, first off, you need to specify whether bike is either 78-79, 80, or 81-XJ. Three options there related to both primary or secondary ignition.

. . . the fourth sentence

[Barbarosa]

1980 SG, in the third sentence lol. I'm not real swift in this form of communication, but I believe you have responded several times to my posts on this fix. Thanks to all for helping me get this far. Was leaning toward ignition when I started posting on 5/23 and have come back around to it with the TCI voltage readings to the coils. The condition I suspect is causing the plugs to carbon foul is weak spark. The voltage from the TCI to the coils drops from 11.2v to 7v when started, fluctuates from 7v to 4v, and even drops to 0 at times. My questions are what can cause the voltage from the TCI to fluctuate like that, and how much voltage is required for proper firing of the coils? Grounds are good and the voltage drop that happens when key is switched on comes from the stator. I know this because it doesn't happen when the 2 wire plug is disconnected. Took the lid off TCI and no noticeable damage is evident. Any Black Box gurus to the rescue?

[TopCatGr58]

Hey Barbarosa,

Okay, the TCI routes the power to the spark plug coils thru the Ballast Resistor once the bike is running...but sends full power to them during starting...that's why you saw ~11.1 V at coils with Key on, but only 7 V or less when running. Check the harness connectors for the Ballast Resistor, clean, reconnect and recheck voltages. As has been stated in previous posts in your other thread.....and YES...it's better to keep discussing similar problems in the SAME THREAD....since the carbs and ignition are both related to getting it running properly, that way we can see ALL that you've done, tried, as well as what has been previously suggested, so we don't repeat stuff across several threads. I'll be merging this thread with your carb thread in a short bit.

The ALT doesn't generate much power at idle, and can actually DRAIN the battery if left idling for a while.....that's why you check the ALT's charging affect at 2,500 + rpm, and as you said, you have 14.5 V so it's working right. But yes, you're on the right path in that the OEM coils could possibly be running on too low of volts....but other places for power loss is the Emergency Stop switch, as well as the connectors at the TCI.

You took the cover off of the TCI....did you look closely at the SOLDER joints where the external connectors are soldered to the PCB? You can try resweating those contacts.
Also, have you pulled the plug caps and checked the wire for corrosion, if found, clip 1/4" at a time till clean copper, clean the cap screw and reinstall. Have you checked ALL of the charging harness connectors, cleaned??

T.C.

[3Phase]

Barbarosa,

Put the cover back on the TCI.

The ignition coil primary voltage may seem low but it's designed to be low. The '80SG uses a 1.5 Ohm ignition ballast resistor to drop the current/voltage for the ignition coil primary winding after the engine is started so it doesn't burn up the coils.

You'll only 'see' +12V on the ignition primaries with a meter when the engine is cranking and the Start circuit is working. The White/Red wire goes hot from the TCI and feeds a junction/splice in the harness with the coil primary Red/White wire.

For the Orange and Gray wires that come from the coil primary windings and go to the TCI, they get switched on and off just like the old points and condenser (Kettering) ignition systems. When you try to measure their voltage with a digital meter it will fluctuate because you're using the old-skool 'Tach' connection and the meter is basically taking snapshots of instantaneous voltages so it acts like an erratic digital tachometer. Use an analog meter and it will stop doing that.

Unless the bike's been seriously miswired or just plain shorted out then the stator doesn't do anything until the engine is running. A fully charged battery should hold 12.6V to 12.9V so recharge the battery or replace it if it won't hold a charge.

With the ignition switch on and the engine not running, the voltage regulator has the field coil pegged wide open to raise the system voltage and recharge the battery but because the engine is not running all it can do is drain the battery. Recharge or replace the battery and quit leaving the ignition switch on or you'll eventually kill the battery.

So, if the the voltage drop you're seeing at the battery happens when the ignition switch is on but the engine is not running then it's because your battery is over half dead and doesn't have the ability to maintain the system voltage while you take measurements. Recharge or replace the battery.


.

[Barbarosa]

Understand the switching and voltage drop to protect coils. Got the idea of how an analog tester is needed for actual readings too. Inspected and cleaned the ballast connections during search for voltage drop. Battery is currently coming back to full charge, pretty sure it is ok since it’s new. Fingers crossed. Drops the same amount of voltage when at 12.6v or 12.9v though.

Haven't figured out how to quote yet, but here's one:

With the ignition switch on and the engine not running, the voltage regulator has the *field coil* pegged wide open to raise the system voltage and recharge the battery *but* because the engine is not running all it can do is drain the battery. Recharge or replace the battery and quit leaving the ignition switch on or you'll eventually kill the battery.


Is the pegged field coil supposed to create a voltage drop? With the thing unplugged every place that should have 12v does. Plug it back in and everything loses a volt when the key is switched on. That’s what isn’t adding up for me. If a switch or connector was bad it seems there wouldn’t be 12v anywhere except directly from the battery. Voltage going to the TCI effects voltage coming out and if it’s too low the coils performance is affected. The TCI reading never went above 7v. Assuming that is the peak reading, is that enough to fire the coils properly? I read somewhere that 9v is the minimum and am wondering if I am beginning to hallucinate. Waiting to hear back from DaVinci on this too but appreciate any info that comes my way. Will start fresh in the morning with a hot battery and a smile on my face lol. Thanks again for the help