Bikes runs but front left cylinder is not firing

[1986vmonster]

I got my bike up and running finally but it ran rather rough and I felt the exhaust and the front left is dead cold. Did a compression test and it started at 90 psi and finished at 150 psi so I assume the issue is not mechanical.

The plug was not wet and looked clean. I swapped over the plug wire from the right front cylinder and then it only ran on the rear 2 cylinders.

I soaked the front left carb with carb cleaner yet it did not heat the exhaust up even slightly when I ran it again. I might add that my Vboost has been deleted completely. Must be an aftermarket set up or something. Its the way I recieved it from the previous owner that seized the original engine. I have not seen many around like this. It has cobra pipes, Stage 7 w/ K&N filters.

Whats the best route to figure out if the coil is bad or if the carburetor is not putting fuel in that cylinder??:ummm:

So close yet so far.... Again. Calling it a day I am smoked out.

 

[Traumahawk]

Its probably time for a shotgun (a particular method of cleaning the carbs).

It is very easy for the gas that we have with Ethanol to clog up jets.

Here is a site that will walk you thru step by step.

http://vmax.lvlhead.com/tips/shotgun.htm

Its very easy to do.

 

[bazwell]

Tests :

Use an external plug to check the spark.
Block off the vacuum line connected to number 2 cylinder.
Swap number 2 and 4 coils and see if the problem moves to number 4.
Swap the 2 wire connectors going to no 2 and 4 coils and see if the problem moves again.

Post up what you found.
IMO with vboost always open, even if no2 carby is fudged, you should be getting some fuel from no 1 carby and therefore some heat. Maybe not at idle, but some heat at revs.

 

[1986vmonster]

Its probably time for a shotgun (a particular method of cleaning the carbs).

It is very easy for the gas that we have with Ethanol to clog up jets.

Here is a site that will walk you thru step by step.

http://vmax.lvlhead.com/tips/shotgun.htm

Its very easy to do.

Well, I read the description in the "shotgun website" and that is exactly the condition I am suffering from. I have heard of the shotgun method but this really nails it with ease.

Thank you for the reply and the helpful link. Will try this first thing tomorrow and hopefully get my 4th cylinder and a proper idle. Very stoked!

Hopefully it is the carburetor and not a bad coil or worse. I figure with some proper spark it would have made some heat on the exhaust just from scavenging from the opposing cylinder but who knows. The plug was not wet so I can picture the carb being the culprit.

Cheers!:snow:

 

[MaxMidnight]

I swapped over the plug wire from the right front cylinder and then it only ran on the rear 2 cylinders.

Did you physically swap the lead from one coil to the other which would suggest a fault with the lead or plug cap OR just swap the leads over from left to right but on the original coils - won't fire as the timing will be wrong.

 

[1986vmonster]

I simply swapped the plug wires from front right to front left and the front left was still not firing. I did not swap out the leads as it would not be firing due to timing. Considered swapping the coil and test the leads but that a bit of work and I would rather give the shotgun method a chance before I go down that road.

If it were a ignition issue I believe that the spark plug would have been wet at least. I was working in my garage with the door open while it was snowing out to let fumes out so if the exhaust did warm up a bit it would have been cooled fairly rapidly. I did not ride the bike therefore the engine load was very low.

I just know that after a few minutes of running 3/4 manifolds were hot and 1 was cold enough to grab with bare hands. It ran on the choke but would always die if I took the choke off and it was running rather rich obviously. It would rev up and stay running w/ out choke if I kept giving it gas but it would not idle no matter how much I adjusted the idle screw.

Glad its assembled and at least running now. Although its a dog of a max.:damn angry:

 

[bazwell]

The more in depth description is sounding like your carbs might just need a balance!

 

[1986vmonster]

As of an hour ago I did the shotgun method of cleaning the left front carburetor. Used plenty of carb cleaner and compressed air. Cleaned the heck out of everything Again, the exhaust does not heat up and it still runs like dog sh*t. I cant say that my efforts made any improvement.

Drained plenty of fuel out of the float bowl so the left front carb is getting fuel. The other three cylinders are firing and the exhaust from those heats up.

Pulled the left front plug again and its not soaked in gas. No carbon on the tip so it does not look like its firing. Not to mention I removed it right after running and it was hardly warm.

I am giving it a break for a week or two. My dream to hear it idle smooth this weekend is being put to rest...

 

[one2dmax]

You may need to actually take apart the carb and clean the pilot jet. This is the most common reason for a carb to not work well. Another thing to look at is the carb sycn. Not sure if you said you tried that? More often then not the sync can be an issue too.

Sean

 

[D-Max2012]

Just something to look into..
Take your airbox off and look down the carb in question and compare it to the other 3. Notice if you can see a mini sprinkle of fuel being sucked in as you rev it up. all venturi's should look the same.. If you notice that the one in question is dry, then you know that carb is not getting fuel.
Also, "If you haven't done this already" take the plug out of the cold cylinder then reconnect the plug wire and ground the tip to the engine block. hit the starter for a few revolutions.. See if you're getting spark across the plugs gap.

 

[jfeagins]

Just something to look into..
Take your airbox off and look down the carb in question and compare it to the other 3. Notice if you can see a mini sprinkle of fuel being sucked in as you rev it up. all venturi's should look the same.. If you notice that the one in question is dry, then you know that carb is not getting fuel.
Also, "If you haven't done this already" take the plug out of the cold cylinder then reconnect the plug wire and ground the tip to the engine block. hit the starter for a few revolutions.. See if you're getting spark across the plugs gap.

If you do this: WEAR SAFETY GLASSES. Wouldn't want an accidental backfire, or engine belch, blowing fuel directly back and into your eyes....

...had a Honda do that to me ONE time - lost a perfectly good set of contact lenses as I blindly screamed my way back into the house getting to running water to flush. (my bad, as my safety glasses were laying beside me when I done it, but forgot to put them back on after wiping away sweat that day):bang head::bang head::bang head:

 

[D-Max2012]

WEAR SAFETY GLASSES

Good point.. Safety 1st..

 

[1986vmonster]

Just something to look into..
Take your airbox off and look down the carb in question and compare it to the other 3. Notice if you can see a mini sprinkle of fuel being sucked in as you rev it up. all venturi's should look the same.. If you notice that the one in question is dry, then you know that carb is not getting fuel.
Also, "If you haven't done this already" take the plug out of the cold cylinder then reconnect the plug wire and ground the tip to the engine block. hit the starter for a few revolutions.. See if you're getting spark across the plugs gap.

I do not recall seeing any fuel spraying around in that carb but I did see that in the other three so something must be clogged in the carb. Did the shotgun method of cleaning it but that may have been inadequate. Need to do the spark plug gap test and then I will tear down the carb. I could play in gas all day if it were not for the dang fumes being trapped in my garage. Always have to run ventilation.

Oh well. Next weekend it will be time to crunch on the latest issue. Hopefully I will get some half ass warm weather. Working in the garage with fumes while it snow is a real bummer:bang head:

 

[Fire-medic]

I do not recall seeing any fuel spraying around in that carb but I did see that in the other three so something must be clogged in the carb. Did the shotgun method of cleaning it but that may have been inadequate. Need to do the spark plug gap test and then I will tear down the carb. I could play in gas all day if it were not for the dang fumes being trapped in my garage. Always have to run ventilation.

Oh well. Next weekend it will be time to crunch on the latest issue. Hopefully I will get some half ass warm weather. Working in the garage with fumes while it snow is a real bummer:bang head:

Especially if you have a gas heater, or a gas water heater in-there too. :confused2:

 

[D-Max2012]

I do not recall seeing any fuel spraying around in that carb but I did see that in the other three so something must be clogged in the carb.

There you go right there.. It's a great thing when you got 3 other carbs for comparison. Chances are, you've got some serious jet / passage blockage on that dry carb.
You might want to rule out total carb blockage by turning the float drain screw out on that suspect carb. Just to make sure you don't have a dry or low bowl volume. Might as well do the same test on the other working 3, for a comparison levels. Use a small beaker or clear glass cup. mark the levels of the good ones and compare it to the bad.

Just be careful not to smoke while doing this. You'll be working with raw gas.. And you don't want to be looking like Nicolas Cage in Ghost Rider :rofl_200:

I like to periodically drain each carb, just to get a comparison on how much fuel is in each one at rest.

 

[1986vmonster]

I drained the carb bowel when I did the shotgun method of clearing and it drained out plenty of fuel. Looked fairly clean. Nothing too crazy. I bet the pilot jet or something along the line is clogged up.

Looking forward to working on it this weekend. hope the weather improves but its frickin winter here in Colorado so what can ya do...

Quit smoking 4 years ago after I got super sick. Only have a furnace in my garage area and it does stink up the house so ventilation must be very adequate. Or my girlfriend and cats get a cheap buzz, puke and die...

Thank you for all the good advice. I will let you know what I find out. Perhaps document with picts.

 

[D-Max2012]

Good going brother.
Just remember this, gasoline fumes is the thing that burns,, not the liquid itself. So if those fumes are concentrated, you could unintentionally expand your garage, just a bit.. :rofl_200:

 

[1986vmonster]

Today I used dielectric grease on many of the connectors unplugged during the engine swap. Carb 4 still no gas but after I soaked the heck out of it with carb cleaner the 4th cylinder started singing with the rest as long I kept hosing it down. Exhaust manifolds were ALL hot. Guess its a carb issue after all.

Need to buy a carb soft rebuild kit and a carb synch kit. Cant wait to have a smooth idle.

 

[1986vmonster]

unk:Well I finally figured out what was wrong with my Vmax.

The cylinder that was not firing had a totally clogged carburetor. Float bowl was getting fuel but the jets leading from the bowl were completely clogged. :bang head:

I rebuilt all 4 carbs and now she runs like a wild dog with rabies. Fantastic!!!! All I need to do now is synch the carbs and she should really purr. Rock and roll!!!:clapping:

 

[Fire-medic]

"Roarr your ride!"

(Courtesy of our Rimouski rider)