Are my carburetors the problem?

[Art708]

 My '98 Standard cranks up fine, idles well, runs through the gears well up to a point...then it starts missing..hesitating...not like it's misfiring but acting up. It will cruise on the highway effortlessly at 75-80 but if I open the throttle wide it just bogs and VERY slowly increases speed. If I ease on the throttle it will accelerate faster. I've never messed with a valk's carbs but I think someone needs to.
Does this sound to y'all like the proper place to start?  Thanks in advance....

                   Art

[DFragn]

It's possible there's a pinhole or small tear in one of the needle diaphragms. It's unusual, but I've seen it happen to a friends Valk with similar symptoms.

You might want to inspect them one by one with a bright back-light. Easy to get at, they're just under the primary carb covers.
Go easy they are delicate.

[Daniel Meyer]

Also check your petcock function and vent hose.

[Art708]

Petcock seems to be working fine....shuts off securely, reserve works. I'll check the vent tomorrow. Diaphragms can be accessed by removing the tops of the carbs, right?

[Larry]

Was going to mention the vent line too and yes the chrome carb "caps" are correct as DFragn mentioned. Good luck.

[DFragn]

Petcock seems to be working fine....shuts off securely, reserve works. I'll check the vent tomorrow. Diaphragms can be accessed by removing the tops of the carbs, right?

Yep, gentle on the screws. The chrome cover conceals the functional cover. Hold the covers in place as you remove the screws. The real cover contains the diaphragm/needle spring too. Not a lot of tension/push but don't damage it. Use one of the cover screws threaded into the center of the diaphragm to lift it and the needle out. Careful, the diaphragm may stick at the edges. Note how they're in there to replace properly and don't jab the needle when reinserting the diaphragm unit.

[Art708]

 Thanks a lot. If the vent check doesn't fix it then I'll check out the carb diaphragms. Wanna come over and supervise? Thanks again for taking time to help..

                    Art

[Mr.BubblesVRCCDS0008]

I'ld open the tank cap with a spare key and run her down the road to make sure it's not a vent problem.

[Wildman]

Check the main fuel line for kinks.

[98valk]

that is the symptons of a lean condition. at those speeds and rpm, and no air box or jetting mods, then I would check, needle diaphragms as stated, air filter has a large hole in it or it is the intake manifolds leaking at the o-rings or the carb to manifold connectors.

[Daniel Meyer]

Petcock seems to be working fine....shuts off securely, reserve works. I'll check the vent tomorrow. Diaphragms can be accessed by removing the tops of the carbs, right?

Pull a vacuum on the line to it and make sure it holds...

[3W-lonerider]

mine done the same identical thing a few years back when the diaphram in the petcock went bad..could get enough vacuum to keep fuel flowing on a regular basis but not enough fuel for wot.. i'd seriously dismantle the petcock and check that vacuum diaphram for a hole or slice.

[MP]

Do what Daniel suggests.  Take the vac line off #6, pull a vac with your mouth, stick your tongue on it.  Like a kid with a soda straw.  It should hold vacuum.  If not, diaphram is bad.

MP

[Art708]

Petcock seems to be working fine....shuts off securely, reserve works. I'll check the vent tomorrow. Diaphragms can be accessed by removing the tops of the carbs, right?

Pull a vacuum on the line to it and make sure it holds...

    Do I pull the vacuum with the petcock open or closed?  If it's open will that let a cylinder flood like a hydrolock? It'll be easy enough to hook up my MityVac and pull a small vacuum but I want to make sure to do it properly.

[98valk]

Petcock seems to be working fine....shuts off securely, reserve works. I'll check the vent tomorrow. Diaphragms can be accessed by removing the tops of the carbs, right?

Pull a vacuum on the line to it and make sure it holds...

    Do I pull the vacuum with the petcock open or closed?  If it's open will that let a cylinder flood like a hydrolock? It'll be easy enough to hook up my MityVac and pull a small vacuum but I want to make sure to do it properly.

the bowl floats will keep the needle and seat closed preventing a flooding condition. However do it with the petcock closed, ie double valve protection.
search my handle for petcock rebuilds and using a snubber in the vacuum line and the cause of hydro lock on the GL1500 goldwings when they first came out, honda's fix, and why on our bikes could be the same problem, the bowl vent hose. search also my post about seafoam and its ingredients and how they can cause hydro lock.

[FLATSIX]

In witch cuontry do you live Art?

Is it the USA-model or another Valkmodel that you have.

If it is an Australian or Europe model of Valk then I know that your problem is the vent-restrictorfoam on top of your airbox and I can help you - had the same problem last year.

US-models don't have that problem as their air is not restricted in the airbox.

[Art708]

In witch cuontry do you live Art?

Is it the USA-model or another Valkmodel that you have.

If it is an Australian or Europe model of Valk then I know that your problem is the vent-restrictorfoam on top of your airbox and I can help you - had the same problem last year.

US-models don't have that problem as their air is not restricted in the airbox.

   USA, all the way.   

[Art708]

 So this morning I opened the gas cap and took off at a great rate of speed. The bike ran pretty well up to 7K. Then after breakfast I left the tank cap locked and it still ran pretty well. I dunno...guess I'll just have to keep watch and the next time it happens I'll pop the tank cap and see if it clears up. Thanks for all the input guys....

                             Art

[Ricky-D]

So this morning I opened the gas cap and took off at a great rate of speed. The bike ran pretty well up to 7K. Then after breakfast I left the tank cap locked and it still ran pretty well. I dunno...guess I'll just have to keep watch and the next time it happens I'll pop the tank cap and see if it clears up. Thanks for all the input guys....

                             Art

If what you do makes it good then the problem is a pinched vent line from the tank.

Usually happens when replacing the tank improperly.

***

[MP]

Carry a black wire tie.  Then, if it happens, stick it in the fuel opening, and close the cap.  That will allow venting thru the cap.  If that cures it, it is vent for sure.

MP