Bonneville America Forums Forums Technical Forums Performance Mods Carbs balanced - Plugs read opposites

Here's my dilema. My left side has been showing black soot on the plugs which is showing a rich condition. The right plug is whitish grey - Lean. The carbs were balanced (yes I switched the hoses and it read the same) and the air/fuel screws set to 3 turns out. I have 155 mains, 45 pilots, 1 shim on a stock needle, freak and bubs exhaust. Any thoughts on what may be causing the two side to be completley opposite?

Could be a vacuum leak on one of the carb/intake ports or the intake rubbers.

That sounded like a logical place to start so I torn the bike apart and removed the carbs. I checked the floats, intake rubbers (which are on the correct way), and vaccuum plugs and everything looks good. I put it all back together and rebalanced the carbs again. I took her out for a short 2-3 mile run and check the plugs again. Same problem. I held a smoking cigar all around the carbs and cannnot see any leaks. I am frustrated and baffled. I also checked the hidden fuel filter and it was ok too. Any more suggestions before I give up and take it into a shop? Is it possible the right side is sucking more air in because the filter is too exposed? I have a freak on and all of the cheese graders and plastic parts are off so the filters are 100% exposed. Any help or insight is much appreciated. Thanks

-Josh

could be a plug, coil, or a wire. If you have an ohm meter, ohm out the wires and see if they are close to each other.

When was the last time you cleaned your air filters? A clogged filter will act like a choke and cause a rich condition.

Josh
The carbs will vary quite a bit actually and balancing them only adjust the actual moment they open together. It sorta just syncs them, but does not really effect anything else.

It sounds like you need to adjust your pilot setting a bit.
But first you need to be sure that your mains and then your needles are set for optimum operation. A dyno is the best way, but you can do it by the seat of your opants and get it really close if you follow the destructions to the letter. Refer to the Mikuni Tuning manual for the proper procedure, be sure to actually use the tape and marks to get it right. Start with the mains at WOT then the needles/shims and then do the pilot adjustment.

Pilot screw adjustment:
Start the bike with one side plug wire pulled with idle about 1100-12oo rpm. Adjust the side running pilot screw in until it starts to stumble, then back it out until it starts to rev a bit higher. Set it in the middle of these two points. Shut down bike and then do the same with the other side and then the carbs will be tuned the same at idle.

Pat or any other carb Guru: I have the same similar problem ,I know one cyl.is burning richer than the other. I've read some posts somewhere that one could balance F/A (pilot screws) that way(Like Pat described) The feedback wasn't good for that post or something about stressing the other cylinder with the other coil wire off.At this point I could care less about their views I'll tell you what if it has your endorsement I'm going to do that too!You've had more hands on,then I'll ever have.Already Mercury balanced the carbs,Had a little trouble trying to get them dead nuts in fact I couldn't.I switched lines over 6 times.One was always up 1/8" over the other. I tried right,I tried Left and back around. Was trying to be careful,a little fearful of that mercury ,it started getting hot,blued my pipes a bit, the RPM"s crept up on me during the procedure ,caught me unaware(close-2800) I was trying to watch both instruments,Had panic attack;was waiting for mercury to come flying out of exhaust,promptly took it down to a safe level ,anyway I'm working on getting it Dyno'd , not so easy to find around these parts ,For people(Business) that of which are willing to 'run'-dyno a Triumph that is, they claim different connection? However, if you say doing what is described above(pilot screws) is going to get me closer to the ballpark, then great! My settings are as follows:

Carbs vary from one to the next. it is possible to get matched pairs, but your bike would likely cost as much as a Tourglide if they did match them because it is strictly a trial and error test that takes a lot of time and effort.

Idle jet turn counting is only a quick way to get to a good starting point where the engine will run well enough to fine tune the mixture.

With the engine warmed up fully, start on one side and adjust the mixture for best idle speed.

Any time the idle speed gets much over 1100 RPM, adjust the idle speed control to get it back to just below 1000. If you let the idle speed get too high, it will start pulling fuel from the transition jets and that will confuse your adjustment. When you have optimized the idle speed, in hot weather, richen the mixture 1/8 to 1/4 turn so the engine will run a little cooler.

Once that cylinder is done, readjust the idle speed and do the same on the other cylinder.

Follow up by rechecking the balance and adjust as needed.

If you have added a balance hose between the manifolds, be sure to remove it and cap the fittings before you try to adjust the idle mixture or you will end up with your head hurting.

I re-edited my post above. I still pull the coil wire to plug for each adjustment, correct.will I need to balance-sync the carbs again since I made the F/A Tweek? ....Note;what causes RPM -Tach to advance in such a way like that after manual Idle speed Adjustment, The Igniter unit advancing ? (Brain)

I've just read this thread from a while back which I hope will explain why one plug was a bit more sooty than the other. Also the last time I rode her, she didn't idle the best either, so that when taking off from a standstill I had to be careful not to give too much of a handfull cos she would die on me.

I've had my bike over a year now and for some reason I've never heard about doing one cylinder at a time when adjusting pilot screws. Anyway, there's hope yet I'll get her to run just right.

Anyway, I was just wondering has anyone else adjusted their pilots like this and found it gave them the best results. Just interested that's all cos I won't be able to do my bike until the weekend

It may be a bandaid, but I had the same scenario and put a balance tube in and now they are both nice and clean (left side set 1/4 turn less than right, based on decel popping).

I want to ask- when you pull your plugs, what was the last throttle position? What I'm getting at is if you ran 10 miles at 1/4 throttle on suburban neighborhood roads to get home and then pulled the plugs, you're looking at your mix at a specific part of the fuel delivery system (refer back to Pat's post on plug chops).

Bryan, funny you should say that cos I only did the balance tube arrangement just before I took her for a ride and then looked at the plugs.

Anyway, I do think this doing one carby at a time thing makes a lot of sense when adjusting the pilot jets, it's just that I haven't heard of it before. It also may explain why that when I syncro the carbs and swap over the tubes, they then show they aren't syncronised at all, and btw it's always been like that.

So what I'm saying is, I probably always needed to have both pilots adjusted seperately to avoid the gruesome threesome continuing ie

poor idling/take off from start prob,

different plug colour prob and

inability to synchronise the little fu**ers.

BTw, FYI, the ride I had before I pulled the plugs was just after I had put in 150 jets, freak etc, as well as put in new shims, chain, sprockets blah blah blah and because of this she got a bit of a wristful And yes, I do love the freak or should I say the new pods and how much more grunt my bike has now