Really stumped on this one - running really badly

[RainMaker]

I am helping with a 1500 that was running great (the last bike BigBF worked on) and then one week later after running fine, it is now barely able to run while on full choke.  It will make it to 2000 rpm at full open throttle and dies if the choke is turned off.  Thought it might be fuel starved so put a new cover set on the petcock.  Made sure that the vacuum opened it.  Replaced the vacuum line from cylinder 6 just to be safe.  No change. Thought it might be bad gas so dumped the tank and refilled with fresh clean no-ethanol fuel with no change. Seafoam - no change.

Now wondering if the plugs were fouled by what might have been bad gas or the fuel filter in the tank is somehow clogged (no rust I can see in the tank, but...). 

Looking for other ideas.

RainMaker

[gordonv]

Fuel delivery or vacuum?

You've already replaced the vacuum to the petcock.

Anything else done to the bike since BigBF?

I had fuel delivery, vacuum to petcock. Run but unable to accelerate. I had a lose of power at passing speed and WOT, which seems fine now that I replaced all the vacuum hoses and caps.

Added fuel filter, any tampering with the fuel line, maybe a desmog or?

[WintrSol]

I'd start by draining the carbs into a clear container, preferably not glass, but chemical resistant, like a paint mixing cup. Just to see what, and how much, comes out.

[The emperor has no clothes]

I'd start by draining the carbs into a clear container, preferably not glass, but chemical resistant, like a paint mixing cup. Just to see what, and how much, comes out.

I’m curious as to why not a glass container ?

[John Schmidt]

If you have a Mity Vac here's a good method to clear debris out of the bowls. Attach the MV to the drain tube that comes out below the bike, then pump up some vacuum on that line. Next, open a single carb drain screw...once done draining that carb be sure to close the screw. The vacuum creates a good amount of disturbance inside the bowl as it drains out, causing any loose debris to be stirred up and sucked out.

Repeat on a single carb at a time, be sure to close the drain screw each time before moving to the next carb. If there's debris in any of the bowls, this usually will bring it out. If it doesn't help, what you're describing sounds like plugged slow jets or the passages associated with them. Time to pull and clean.

[ckahler]

Remove the tank and connect a fuel bottle directly to the carburetor fuel hose. Also plug the vacuum hose. This will confirm or rule out fuel delivery.

[98valk]

I am helping with a 1500 that was running great (the last bike BigBF worked on) and then one week later after running fine, it is now barely able to run while on full choke.  It will make it to 2000 rpm at full open throttle and dies if the choke is turned off.  Thought it might be fuel starved so put a new cover set on the petcock.  Made sure that the vacuum opened it.  Replaced the vacuum line from cylinder 6 just to be safe.  No change. Thought it might be bad gas so dumped the tank and refilled with fresh clean no-ethanol fuel with no change. Seafoam - no change.

Now wondering if the plugs were fouled by what might have been bad gas or the fuel filter in the tank is somehow clogged (no rust I can see in the tank, but...). 

Looking for other ideas.

RainMaker

" it is now barely able to run while on full choke.  It will make it to 2000 rpm at full open throttle and dies if the choke is turned off. "

 That can be an indication pilot jet/s are clogged. do u use sta-bil in every tank?
Or
plug/s have failed. check ohms of each one, or plug cables connections are bad plug end or coil end. 
Or
Did u use too much dielectric grease in the plug caps? dielectric grease is silicone which does not transmit electricity.

[Jims99]

Good advice above. Definitely sounds like clogged jets. I’m interested to hear what comes out if you drain bowls.

[Pluggy]

Did u use too much dielectric grease in the plug caps? dielectric grease is silicone which does not transmit electricity.
[/quote]

Should not be a problem.  Mating the terminal to the spark plug moves excess dielectric grease out of the area of electrical contact and into the boot.  Once out of the way in the boot, the grease is of no harm or benefit.  Too much grease is wasteful, but should not affect the quality of the connection.

[98valk]

Did u use too much dielectric grease in the plug caps? dielectric grease is silicone which does not transmit electricity.

Should not be a problem.  Mating the terminal to the spark plug moves excess dielectric grease out of the area of electrical contact and into the boot.  Once out of the way in the boot, the grease is of no harm or benefit.  Too much grease is wasteful, but should not affect the quality of the connection.
[/quote]

I've see too much to be a problem esp., during higher rpms in vehicles. OP stated will not go over 2k rpms.
 ZERO dielectric grease should be on the spark plug end connection, that is what I was trying to convey.

[Pluggy]

Did u use too much dielectric grease in the plug caps? dielectric grease is silicone which does not transmit electricity.

Should not be a problem.  Mating the terminal to the spark plug moves excess dielectric grease out of the area of electrical contact and into the boot.  Once out of the way in the boot, the grease is of no harm or benefit.  Too much grease is wasteful, but should not affect the quality of the connection.

I've see too much to be a problem esp., during higher rpms in vehicles. OP stated will not go over 2k rpms.
 ZERO dielectric grease should be on the spark plug end connection, that is what I was trying to convey.
[/quote]

Hello Mr. 98,

Putting dielectric grease on spark plug contact points is not something I would do.  But, some guys do it every time with no problems.  A tight fitting connector slides on with a "snowplow" action that cleans the surfaces for good metal-to-metal contact.  This self-cleaning action is probably why so many guys can stick grease in there and ride trouble-free.

Pluggy

[RonW]

dielectric grease that gets snowplowed out of the way is of use. It keeps the non-contact portion from oxidizing together with the rest of the over-grease. For the contact area itself there should be no layer of dielectric grease. It's vital to push/pull the parts back and forth a thousand to scrape the grease away from the contact area. Dielectric grease on the start button isn't a problem since the grease gets snowplowed off to the sides. 

[98valk]

"Can Too Much Dielectric Grease Cause a Misfire?"

""Yes, it can! Improper use can lead to a misfire in your vehicle.

Dielectric Grease is non-conductive, meaning it does not conduct electricity. It can prevent arcing and corrosion by keeping elements out of the spark plug boot and making transition and movement easier.  

When you add the dielectric grease to the spark plug boot, you need to use it sparingly, as using too much can cause a misfire. Inside of the spark plug wire, you need to prevent adding too much into the terminal when adding it, as the grease can prevent the spark from traveling properly through the wire.
old and new spark plugs with car engine and dielectric grease""

https://gearslap.com/what-is-dielectric-grease/

[WintrSol]

I'll often use red grease instead of silicone grease, but it doesn't change how I apply it. Just a wipe around the lip of the boot, and maybe on the 'shoulder' of the plug itself (below the upper flat area), both to make it easier on/off, but improve the seal and life of the rubber boot. Too much red grease may increase likelihood of arcing, if it gets near the contacts (don't know, but it is vegetable based), which is another reason I use the bare minimum of either.

But, back to the possible fuel issue: any results on what was in the carbs?

[Rams]

Remove the tank and connect a fuel bottle directly to the carburetor fuel hose. Also plug the vacuum hose. This will confirm or rule out fuel delivery.

Watched Joe Studebaker do this on one of my Valkyries, doing this determined that I did have a fuel delivery issue in the Petcock.   While that may not be the issue with this Valk, it will definitely eliminate a few possibilities.

Rams

[hubcapsc]

Pull an easy vacuum on a good petcock and it should flow like
gangbusters... like when six carburetors are sucking enough
gas to make your 800 pound bike go 95 miles an hour uphill.

-Mike

[WintrSol]

Pull an easy vacuum on a good petcock and it should flow like
gangbusters... like when six carburetors are sucking enough
gas to make your 800 pound bike go 95 miles an hour uphill.

-Mike

In practice, actual flow rates should be much lower than the petcock can provide. For example if your bike gets 20mpg at 95mph, the fuel demand is only a bit over 10 ounces per minute. Of course the maximum flow rate of the petcock itself has to be higher than that to make up for the restrictions, like the float valves, and the rate drops as the tank empties. Still, the apparent flow rate of an open petcock IS impressive when you just let it dump out, even from a half full tank.

[rug_burn]

Sounds like it's time to rebuild those 6 carbs.   Don't worry, by the time you get 'em all 6 done, you'll be an expert  (like most of us here...)

     
   

[Valkpilot]

I am helping with a 1500 that was running great (the last bike BigBF worked on) and then one week later after running fine, it is now barely able to run while on full choke.  It will make it to 2000 rpm at full open throttle and dies if the choke is turned off.  Thought it might be fuel starved so put a new cover set on the petcock.  Made sure that the vacuum opened it.  Replaced the vacuum line from cylinder 6 just to be safe.  No change. Thought it might be bad gas so dumped the tank and refilled with fresh clean no-ethanol fuel with no change. Seafoam - no change.

Now wondering if the plugs were fouled by what might have been bad gas or the fuel filter in the tank is somehow clogged (no rust I can see in the tank, but...). 

Looking for other ideas.

RainMaker

There's not an in-line fuel filter installed, is there?

[Timbo1]

There's not an in-line fuel filter installed, is there?

No there is no in-line fuel filter on OEM fuel lines, however there is a filter screen on the fuel pickup on the dongle in the tank.

[rug_burn]

Yes- When my bike sat and the gas went bad, it plugged up that filter sleeve pretty good.   Even now, a few years later, I think I gotta check it again, 'cause when it's on reserve, it starves out real bad running continuously at about  60, but will do 45 or so pretty well.   -  It's got a gunked up filter sleeve, the lower in the tank, the worse it gets.  I'm beginning to notice it even when it's low, but not on reserve.   Maybe some residual varnish or something.

[Willow]

...   -  It's got a gunked up filter sleeve, the lower in the tank, the worse it gets.  I'm beginning to notice it even when it's low, but not on reserve.   Maybe some residual varnish or something.   

You do know that can easily be cleaned or replaced?

[Valkpilot]

There's not an in-line fuel filter installed, is there?

No there is no in-line fuel filter on OEM fuel lines, however there is a filter screen on the fuel pickup on the dongle in the tank.

I'm aware.  However, some well-meaning folk (not Rainmaker, he knows better) install an aftermarket in-line filter which rarely works as intended.

The petcock filter/screen is a good 5 inches high and the main inlet from the tank to the petcock is an inch or so less than that.  With a full tank of fuel, it's possible, but hard to believe that that screen is so clogged that it would prevent sufficient flow.

The two most likely causes, at least in my experience, are faulty petcock operation or fouled jets.  I've had a newly rebuilt petcock not flow fuel because the diaphragm wrinkled when it was put in.  I'd start there before pulling the carbs apart.
 

[Jims99]

Any updates, curious on what you found.