1 dead cylinder and 1 weak cyclinder, can't determine why

[Valkyrie0002]

In an earlier post I mentioned pulling the carbs for a cleaning because I let the bike sit several months without treating the fuel and the left side jets were plugged.  Wasn't much gunk in the bowls or on the floats- just discolored.  After the tear down and cleaning the left side still wasn't running right even though the jets were clean.  

I pulled the carbs again last weekend and opened the left side carbs, checked the jets- still clear and then sprayed cleaner thru the slow jet passages and had a good spray come out thru the small openings by the throttle valve.  I sprayed thru the pilot openings, they are clear.  I did find some crud in #6 pilot screw.  Pilot screws passages are clear at least from the screw and into the throttle body.

I thought all was good now so reassembled and test ride.  #4 runs great now but #6 is still partially plugged at idle and #2 is dead cold at idle.  After a 30 minute ride the RPMs at idle increased a lot so I turned it down.  

There is a noticeable stumble at 2k - 2.5k rpm.  I have a heavy dose of techron and been running it at 2,000 -2,500 rpm with WOT in that range and above to try and clean them out but it was not improving.

Yesterday I took the tops off #2, #6, removed slides and pilot screws and drained the bowls, removed the intakes and plugged them.  Sprayed cleaner into pilots again, sprayed thru air passages for slide.  Everything seems clear.  

Carb bowls have fuel, jets are clear and small passages are clear.  I checked for spark a while back and that's fine.  Intakes from airbox are all open.  What am I missing here?

[Ricky-D]

I feel the first thing to do would be to run a compression test on all the cylinders.

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[sunrisor]

 I would pull the spark plugs and look at their condition.  How they are burning may lead you to a specific cylinder.  i.e. lean, normal, rich, etc.  Make sure the ignition timing is set correctly.

Did you change the timing belt recently?
How long has it been since you replaced the coils?  I know this one, I have a '97 that I've owned since new, and she doesn't have the umph that it used to, I'm pretty sure the coils are a contributing factor.

Checking compression is a good idea but these are some of things I would try first.

[Valkyrie0002]

I know which cylinders are the problem.  #2 is cold and #6 is just warm at idle.

Bike has about 5,200 miles on it.  Not bad coils or bad rings/ valves.  Have not changed timing belt or messed with the timing.

#2 plug had some carbon on it and I cleaned and swapped it a while ago.  I could swap those 2 plugs to the right bank and see if that changes anything.

Bike ran fine until I let it sit 6 months without stabilized gas.  That's when the issues started.

[9Ball]

Are you getting fuel to the #2 carb?

What’s the condition of your petcock?  Check petcock vacuum operation if OEM still installed.

[Valkyrie0002]

Fuel flow to carbs is not the problem.  I run it at 60 mph no problem.  All carb bowls are full. 

[9Ball]

Fuel flow to carbs is not the problem.  I run it at 60 mph no problem.  All carb bowls are full. 

Perhaps not enough vacuum at idle but plenty at 60 mph....was just a thought.

[Ricky-D]

If you don't think it's the carburetors, it wouldn't hurt to run some gasoline additive thru it for a few tanks full. js

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[Valkyrie0002]

Been running heavy doses of B12 and then techron since I got it running early June.  Gotta be 200+ miles on it by now.

Pretty sure its still the carbs because on the 2nd cleaning of the left bank #4 opened up and is running great now.  I took the same steps on all 3 even # carbs so I was really disappointed they all didn't clear up.

Slides move freely and the needles have been cleaned of scale buildup.

On the 2nd cleaning is when I found the junk in #6 pilot screw but its clear to the throttle body and slow jets are clear to the throttle body. 

Its amazing to me how well these engines can run on just 3 or 4 cylinders.

[gordonv]

Pretty sure its still the carbs because on the 2nd cleaning of the left bank #4 opened up and is running great now.  I took the same steps on all 3 even # carbs so I was really disappointed they all didn't clear up.

I take it that if the cleaner can not go through the opening, then it won't clean it out. More drastic methods will be required. Physical or an ultrasonic bath.

[Valkyrie0002]

Cleaner passes through the jet, pilot and orifices.  Thats why I can't figure out what else I need to do.   

[Harryc]

First check for spark at the (2) dead cylinders. If spark is present, remove the plug/s from the (2) non-working cylinders and squirt some fuel in there (not a lot, maybe a teaspoon full). Replace the plugs and start it up. Do those cylinders now fire? If you can get the bad cylinders to fire by adding fuel directly, you have a fuel delivery problem still...aka carb issues. If it's difficult to tell if they are firing, remove all spark plug wires except those (2) . You should be able to detect a difference by playing with what cylinders you leave the wires on and what the result is. Difficult to explain, but you'll get it.  It could be as subtle as those (2) pop or backfire when fuel is added but do not without (even if the engine does not start), or you can hear the engine trying to start with and without fuel added. Or maybe with all (6) wires connected the engine sounds different when you start it with fuel added directly to the (2) bad cylinders.

[9Ball]

thanks for the update email.  Sorry it’s still not running right.

Good luck and let us know if you get it resolved.

[JimBob]

Valk-02
Did you get 'er running correctly or do you still have 1 weak and 1 dead cylinder?

Thinking about it.... grasping at straws, really....
Did you unscrew the slow jets and check the emulsion tube section to see if the air holes in the side of the emulsion tubes are clear, or did you just shoot some carb cleaner through the jet?
(I don't know what the symptom of clogged emulsion tube 'side holes' would be, but hey, it's a straw to grasp!)

For what it's worth, the slow jet is a #35, which I take to mean the 'through-hole' in the jet is 0.35 mm diameter.
Converting to inches, it works out to .014 inch dia.
Years ago, I made a jet-cleaning tool for the enrichener jet on my dirt bike, by cutting one strand from a standard steel wire brush, soldering that strand to a 4" piece of 1/8" dia. brazing rod so the wire strand extends straight out the end of the brazing rod, then I used needle-nose pliers to 'dog-leg' the wire strand so that it is now roughly centered with the brazing rod. I use this tool to clear the 'enrichener' jet that is recessed down in a hole in the (Mikuni) carb bowl on my old Suzuki dirt bike.

I measured the wire-brush strand, and at least the wire brush strand that I have is .013 inch diameter, so it SHOULD (ha!) pass through the .014 dia slow jet as the wire is .001 smaller in diameter.
Cleaning the carbs on my 'new' project Valkyrie, I found that all the main jets were clear, but the main jet emulsion tubes were cruddy, and ALL SIX of the slow jets were blocked. Cleared the slow jets with the wire-brush-strand cleaning tool, cleared the side holes in the emulsion tubes on both the slow and main jets, did all the other usual carb-cleaning stuff, and the ol' girl fired right up.
 
I don't know if this helps, but I hope that it does.

[Valkyrie0002]

I haven't had a chance to work on it in a few weeks.  Jets and tube orifices are clear. 

[pancho]

I had the same type of problem with the idle not right, but the bike running perfect at 1500 RPM and above. I followed the same procedure as you removing the carb bank several times and cleaning and checking passages then syncing carbs and still not a perfect idle with intermittent popping on #4, 6 and almost dead 5. I was looking for the most power at idle speed for parking lot acrobatic maneuvering. I finally bought one of these thermometers so I could get an accurate look as the temperature was coming up on the headers and used that as a guide in adjusting the pilot screws. WHen I finally had the bike running right at idle, the adjustments were all over the board with some 2 out and one as much as 4 and 1/4 out. My narrow thinking had never let me imagine that, I had assumed they needed to be much closer to each other. I think I am going to look into an exhaust gas analyzer to fine tune and get a better look.

[Tfrank59]

First check for spark at the (2) dead cylinders. If spark is present, remove the plug/s from the (2) non-working cylinders and squirt some fuel in there (not a lot, maybe a teaspoon full). Replace the plugs and start it up. Do those cylinders now fire? If you can get the bad cylinders to fire by adding fuel directly, you have a fuel delivery problem still...aka carb issues. If it's difficult to tell if they are firing, remove all spark plug wires except those (2) . You should be able to detect a difference by playing with what cylinders you leave the wires on and what the result is. Difficult to explain, but you'll get it.  It could be as subtle as those (2) pop or backfire when fuel is added but do not without (even if the engine does not start), or you can hear the engine trying to start with and without fuel added. Or maybe with all (6) wires connected the engine sounds different when you start it with fuel added directly to the (2) bad cylinders.

+1.  You have to verify that you've got strong spark to those weak/dead cylinders, since you're confident they're getting fuel.  On another post, the problem he had with spark turned out to be loose wires going to the coils--apparently the first time we've gotten that report, but our bikes are getting old and plug wires don't last forever.  Just a thought.

[Valkyrie0002]

I checked for spark before I pulled the carbs the 2nd time.  The whole left bank was still dead after the first attempt at cleaning them.  I pulled the carbs the 2nd time and removed the pilots then hosed those passages well.  Cleaner was shooting out of the small orifices in the throttle body on all 6 carbs so I thought I was good to go.  Took it for a ride and the idle speed increased quite a bit and the bike started to run better which is when #4 came to life and #6 woke up some at idle.  #2 was still cold at idle and I think its dead at speed because I can feel a miss under heavy throttle.  Much better than it was after the 1st cleaning but still not 100%. 

[Tfrank59]

Okay thanks for the clarification. That certainly seems like a fuel delivery issue rather than weak Spark