#2 and #4 not firing after rejet

[KEITH KRAUSE]

Yes, the plug colors are a good indicator. In your case, the problem is the blackened plug. It's very close to fouling out. The causes of a black plug are either a rich mixture, excessive vacuum drawing more fuel (as compared to the other cylinders), a weak spark, or combination of these.
You can always try a new, gapped plug, but it's not likely to be a bad plug.
I still tend to think the coil is good but think it should be tested to be sure. Also, coil terminal connections should be checked/cleaned with a wire brush before testing. The battery must be fully charged before testing too.
If OK, then I'd focus on why the rich mixture or excessive vacuum.
Since you're gone all week, I'll let this go for now. Later this week I'll post everything I can think of that relates to your problem. You can look at it and we'll eliminate things if need be 'til we find the problem.
The vacuum synch/adjuster at #4 concerns me a lot. So does the fact the replacement carb body may still have a difference we're not aware of. It could be interesting trying to synch if it's not operating as it should. One way or another, the synch has to be done at #4, at least closely.

 

[KEITH KRAUSE]

The other interesting thing is #4 seems to have gone from no fuel (the throttle plates weren't even wet) to possibly too much fuel (the black plug).
But a previously blocked pilot circuit and a second problem, such as incorrect vacuum or weak spark, would explain this. We'll see.

 

[J_C]

OK I Removed the new carb body and replaced it with the JB Welded carb body. Took all parts from one and put them in the other, remeasured float height, installed.

Started up. 1,2, and 3 got hot while on choke, 4 did not. Once choke was released, #4 began to slowly heat up (Heat from block most likely). 1/4 throttle was applied and #4 instantly heated up, with lots of popping. Removed pods from 1 and 4 to have a visual comparison. Somewhere around 1/3 throttle the cylinders began to raise. They appeared to be raising on cue with each other.

My plan at this point is to do the following:
1. Wait for new exhaust; Install
2. Retest. If problem exists, next step.
2. Rejet all carbs to tested and proven settings achieved by chef
4. Retest. If problem exists, next step.
5. Replace all jets and choke assembly with spares.
6. Retest. If problem exists, next step.
7. Cry.

 

[KEITH KRAUSE]

Just a quick reply to let you know I'm still watching this.
Been busy all week/OT at work and today I'm going riding (not trying to rub it in) and then I have Fathers Day activities to go to, so I won't have time to reply today if you're working on it and need help.
I re-read this entire thread and it's a bit of a head scratcher. Possible vacuum, fuel, or air problems, or even a combination.
Obviously, the problem is just #4 now. #1 was once a problem too but it appears that extra cleaning or re-assembly or ? has solved its problem. I'm not positive, but it seems #4 is a LITTLE better than at the beginning, because it's at least popping and trying. This could be due to you opening the throttle more than during earlier tests, so I'm not sure. It also could be because of extra cleaning, etc.
The black plug at #4 only is bugging me though. That would suggest too much fuel (you say the spark is good). But your earlier tests showed a LACK of fuel entering the cylinder. Heck, the throttle plate wasn't even wet. But I'll stick with where we're at now.
By design of this carb, it draws fuel from the pilot circuit at closed/idle. At this time, you have no combustion. But as you open the throttle to 1/4 and then 1/3, you're getting well into the jet needle circuit. Now it's popping and combustion is improving. Hmmm.
So what's happening here, besides transitioning from the pilot circuit to the needle? Under "normal" conditions (all parts in good condition/correctly adjusted), we're introducing more mixture, both air and fuel into the cylinder. We're also increasing the vacuum. One, or a combination of these things isn't enough or happening at closed/idle position.
First and most common thing (considering what you day has been checked) would be a clogged carb passage somewhere. I say this because you haven't used high pressure air to help you clean the carbs. I have to say you MUST use high pressure, a good 150 or close to clean carbs after spraying/dipping. So that's a possibility.
Any chance you can take the carb someplace and blow it out with high pressure?
I have to go now but we'll check in later.
Quick thought... what exactly is wrong/damaged with the #4 synch adjuster? Does it "visually" hold its synch when you compare plate adjustment with the others after testing on the bike?
Following your EXACT starting procedures as before and using closed throttle/allowing it to idle, what happens if you place your palm over #4 intake and completely seal it off for several moments? Any change at all?? What if you let in just a little air by moving your palm a little? Any change?
Talk to you later.

 

[J_C]

Keith, I appreciate your time whenever I can get it You're not superman you know!

The thing about the pilot being clogged... I know it's possible... but is it likely that after a carb dip (without compressed air) a carb body could have a plugged pilot passage leading to exactly the same symptoms as the other carb body with plugged passages? I was thinking that it might be one of the individual parts since the same parts were used on both bodies and both bodies exhibited the same symptoms. I can still find somewhere with compressed air... At what PSI does a gas station air pump put out air?

When I put the JBWeld body in I did bench synch it using very wire gauge from a stripped trash bag tie. It was actually already perfect from a bench synch perspective, which kind of makes sense since it ran before and I didn't have to adjust 1,2, or 3 when I put on the unbroken carb body in.

we're introducing more mixture, both air and fuel into the cylinder. We're also increasing the vacuum. One, or a combination of these things isn't enough or happening at closed/idle position.

I suppose the only way to test this is with the mercury sticks to at least eliminate vacuum... I put together my mercury sticks but will have to wait until I'm back next weekend to try them.

There is nothing wrong with the synch adjuster. The cracked part is actually the neck of the air screw. When the adle adjust plate it pushed with a finger all appear to rise together.


I actually did the hand trick over the vacuum yestrday. I #1 as well to have a comparison. #1 the idle increased (makes sense, right now 1,2 and 3 are running lean as seen by the only slightly gray plugs) but I don't remember what happeened with #4, other than both 1 and 4 spitting gas back at my hand if I held it there too long. I will try it again before I leave for Father's day festivities.

 

[J_C]

Discovery at the hands of stupidity?

Discovery at the hands of stupidity?

So I went out to do the test. Today I didn't notice any difference in either 1 or 4 when blocking the carb with my palm, other than it almost swallowing my hand. I did get coated with a nice covering of fuel though \\/

However, I did note this. When I put the carbs on today, I forgot to screw in the screw that connects #4 to the choke rod. When I started the bike, 1,2 and 3 heated up.... Amazingly enough, #4 began to heat up (slowly) for about a minute then it got hot. This is all at idle.

This may further point to a really rich mixture? When choked its too rich to fire? Dont know... I'm running out too, but one more point to note. Afterwards it seemed to be accelerating with much less popping... usually taking place on deceleration when I suddenly chop the throttle.

 

[KEITH KRAUSE]

Hi. I can see you're skeptical about two cleaned carb bodies still having clogged pilot circuit bypass ports or ? I'm not outright saying your cleaning job is poor, but if you read all the posts I have that started with "I cleaned the carbs really good" and ended with " I thought the carbs were clean", you'd be amazed. Many people can't believe how careful you have to be depending on the carbs condition. Some carb cleaners actually ADD their own gummy film if allowed to evaporate on the parts. The fact that you didn't use high pressure to blow out the passages just makes me think there's the possibility of clogged passages. I may be wrong, but I can't rule out the possibility. To me, there's nothing at all odd about two identical carbs having the same cleaning problem. If both carbs sat and fuel was allowed to varnish up the fuel or air passages, why wouldn't they both show the same problem? I guess I just have my way of doing things and I can't consider the carbs being cleaned right without high pressure. I can be wrong though, just like anyone.
I know you're putting a lot of thought into fixing this problem and I'm trying to think too when I have the time. That's why I keep pointing to how these carbs are designed to operate and your test results.
It still appears #4 cylinder won't run while depending on the pilot circuit for fuel (closed throttle/idle). There DOES seem to be a little improvement but the bike still responds much better when you transition from the pilot to the needle. We can look at it as a clogged pilot circuit lacking fuel, or, we can look at it as a clogged pilot circuit lacking air. By the way, since you seem to be sure the bench synch is good and I now believe there's no problem with the synching screw, I'm gonna toss out vacuum as a cause, at least for now and to simplify. So we're just considering fuel and air. The cylinder runs much worse while on the pilot, improves on the needle, but still doesn't run right. The richening effect of the choke seems to make #4 worse, while the other cylinders handle the choke as designed.
The black plug tells us it's rich, but that can be either too much fuel or too little air in the mixture.
Too much fuel could be the float level, leaking float valve/damaged or missing valve o-ring/weak valve spring/sticking float/punctured float (you should see fuel overflowing), wrong size, type, or "drilled" pilot jets, damaged passages from incorrect cleaning with wire or ?, worn jet needle or needle jet, jet needle raised higher than others because of incorrect re-assembly, clogged holes in the needle jet (bleed pipe as some call it) leading to poor atomization of fuel.
Too little air could be a clogged pilot air jet or primary air jet, wrong size PA jets, clogged needle jet holes.
The choke could cause a problem by opening sooner than the others or not seating/sealing all the way. But it appears to me the choke is operating right, at least opening and closing right. The jet inside the starter tube could be damaged or even missing, though that would be the work of a butcher.
So there's lots of possibilities.
I suppose you can try swapping some parts and see if the problem follows. That can be time consuming but it sometimes works.
I know if it was my bike I'd first try high pressure cleaning after some spraying. If no joy, then maybe the parts swapping will help.
I've got a little more on my mind but I have to get up at 5:00. So I'll continue later if needed.
You're not alone with it. Have patience.

 

[KEITH KRAUSE]

Just bumping this up.
If you still need help, just ask. If you fixed it, let us know the fix so we can help someone else down the road.

 

[J_C]

Sorry for not replying... it's just that I haven't been home yet to work on it so I don't yet have a status update...


Just for piece of mind... what is the correct method to measure float height.... I must have read 5 different ways of doing it in my research.

 

[KEITH KRAUSE]

Sorry for not replying... it's just that I haven't been home yet to work on it so I don't yet have a status update...


Just for piece of mind... what is the correct method to measure float height.... I must have read 5 different ways of doing it in my research.

Nothing to be sorry about. Just letting you know we're around.
I think one of the reasons a member "disappears" is because he thinks he's asked too many questions or something. Just didn't want you to be one of them.
The factory says to place the carbs upside down. Remove the bowl gaskets. Allow the float to just contact the float valve. The pic shows the float fully resting on the valve. If the valves pins/springs sag a lot under the float weight, that will compromise your measurement. There are different opinions on how to counter the spring sag.
To measure, I use verniers. Measure from the bowl surface (where the gasket was) to the top part of the float body. The exact point is where the curved float body meets the small step up part for the float arm. Hope I explained that right.
Of course, the factory manual assumes the float valves have good springs and there are no other problems.
Spring sag is very common and even new rebuild kits may have valves that compress when new. The better quality genuine Suzuki valves are expensive so many owners don't buy them and take their chances with the cheaper valves and the problem of trying to get an accurate adjustment made. But I've seen many genuine Suzuki valves compress just a bit too. Luckily, many models state that you have a range to set the floats within. I always set them in the middle of this range and it's usually close enough to allow for SOME sag and adjusting error and still be within the range.
Some sites say to carefully measure float height by tilting the carb bank almost straight up and down on one end and slowly tilt the carbs so the floats just rest on their valves. Seems hard to measure that way to me and I've never tried it.
If you have very still fingers, you can try letting the float just contact the valve and while keeping the weight from pressing the spring down further, take a measurement. This float measurement stuff can get involved if you're anal about it.
Maybe I'm just a good guesser, but I can generally tell when a spring is too weak and the valve should be replaced. I always buy the Suzuki valves unless I'm rebuilding for someone and they insist on the cheaper valves. I then just follow the factory procedure. I let the float rest gently on the spring and if it sags a LITTLE, so be it. Take my measurement and set them right in the middle. Never had a problem. But some models have a narrow range. Some bikes with mods can benefit by setting the floats a little richer, but I don't do that with stock bikes.
I don't have a factory float adjustment for your specific model, but I do have the measurement for the '80 GS1000 with the same carbs (BS34SS).
It says 22.4 +/- 1.0 mm (0.88 +/-0.04".) I know many non-factory manuals (Clymers, Haynes...) may show different settings and people get confused on what's right. Hope this helps.

 

[J_C]

Keith, thank you very much for the clarification... but what's this spring you're speaking of? Is the spring INSIDE the needle valve?

I think that's one of the only parts I exchanged when I rebuilt them... maybe I should try one of the other needle valves I have laying around while I'm at it....

 

[KEITH KRAUSE]

Keith, thank you very much for the clarification... but what's this spring you're speaking of? Is the spring INSIDE the needle valve?

I think that's one of the only parts I exchanged when I rebuilt them... maybe I should try one of the other needle valves I have laying around while I'm at it....

I once installed TWO brand new valves that were part of a cheaper kit (I warned the carbs owner about buying them) and they leaked badly when I leak tested them. That's not the first time I had supposedly good valves cause a problem either. New doesn't always mean good. I'm not saying your valves are doing this, just sharing experience. A weak valve will obviously richen that carbs mixture.
The float needle valve has a small spring inside that the pin pushes on. They get weak over time. Hard to say exactly when the springs weaken enough to reach the point of replacement.
If you can GENTLY push the pin in (no more than 1/2 way), slowly release it until it's out as far as it will go by itself, and STILL be able to pull out some remaining spring, then it's too weak for sure. Do this test with your fingernail only, because your finger can sometimes "stick" to the pin, helping it to push out and give you a false test of any slack. Another way is to just try wiggling the pin up and down. If you can feel/see any slack, the spring is too weak. But you can have zero slack and still have a weak spring that allows the float to compress it too much. Like I said before, it can be hard to know when the valve spring has had it.
On the other end, the needle point can get a groove worn into it. At some point, the groove will deepen enough so the valve can't seal. This usually causes fuel to overflow out the bowl dump line but not always. Sometimes it just causes a high fuel level in the bowl. The needle valve and its seat wear in as a unit, so don't mix them up.
If you do try a different valve (and hopefully its original seat) you should re-check the float level.

By the way, do you plan to try swapping any parts to see if the problem at #4 follows?
Just be absolutely positive you've cleaned and checked/adjusted everything else before swapping parts.

 

[J_C]

I finally got the opportunity last weekend to work on the bike but I didn't quite get to the carbs. I'm thinking at this point that I'm going to temporarily put this on hold.... It got me to a level of frusteration that I think I need to take a break from them and do something else (I wasn't having fun on the bike anymore, and that is NOT good.)

Keith, would it be ok with you if I revive this thread in a month or two while I proceed with some of the other items I need to get off my list?

 

[KEITH KRAUSE]

Keith, would it be ok with you if I revive this thread in a month or two while I proceed with some of the other items I need to get off my list?

No! We must fix it now! I'm not getting any younger you know. :lol:
Hey. I'm just here to try to help. You do what you gotta do.
You're not alone with the frustration. Many of us have gone crazy trying to fix a problem.