Bizarre running problem returns

Symptoms: Coughing and sputtering, won't hold an idle, dies without throttle.

Duration: lasts about 10-12 miles then gradually goes away, no sputtering, idles as normal.

Occurs: After gas light has come on and the bike is filled up.

Attempted cures: 1st instance, Plug wires changed to NGK, 2nd instance, Chevron Techron fuel system cleaner, 3rd instance, 99% isopropyl alcohol additive (dry gas).

After each "cure" the bike ran well until it needed gas...

Sounds possibly like vapor lock...have you checked all tubes are properly connected to canister and related vents, or plugged if a canisterectomy has been performed?

PJPR01 wrote:

Sounds possibly like vapor lock...have you checked all tubes are properly connected to canister and related vents, or plugged if a canisterectomy has been performed?

Bike has less than 6K miles and the canister is in place. I was thinking about the tip-over valve...

Could be, one way to eliminate vapor lock as a candidate here would be to fill up, close the tank, ride a bit while it's having difficulty, stop, open the tank and listen for a "whoosh" sound. If the problem goes away, you'll know it's vapor lock. I'm not that familiar with the tip over valve symptoms if it's misbehaving...

I completely agree regarding the tank venting issue -- it can screw with your fuel pressure and cause weird problems, and (as much as I hate to say it) it's truly best to ditch this particular setup in most cases. The tank should simply vent to atmosphere, and the throttle body ports can be plugged (or the hose that runs between them can be plugged at the tee).

Be somewhat careful releasing the cap when the bike is hot, as under some circumstances it's possible for a significant amount of pressure to build in the tank, enough to shoot a geyser of fuel 10+ feet into the air (I wouldn't have believed it until I experienced it myself ).

The tip over/rollover valve is actually located within the fuel cap assembly. The orange/blue unit is a low cracking pressure bi-directional check valve, that allows the fuel tank itself to become a storage reservoir for fuel vapors (up to the designated pressure relief point) while also allowing the tank to evacuate without creating a significant vacuum (and potentially sucking itself flat).

So, I should lose the charcoal canister and the weird valve?

YES!
a cannisterectomy should be in your future

>So, I should lose the charcoal canister and the weird valve?

Absolutely! And just to clarify my above "geyser of fuel" comment, this won't be of any potential concern so long as the tank is properly venting.

Do a search for canister. there should be a detailed removal procedure.

Certainly removing it will do no harm.

Thanks for your support. I will get to it.

Canister removed, TBs linked. I left the blue valve in place as it is easy to get to if I want to get rid of it. Two clear hoses were loose. The airbox has two hoses attached, black one top right and clear one (capped) bottom right so I secured those two. I don't know where the second one attaches. Forum member Udizit (in an ancient thread) opines that it is a transmission breather.  If so, where does it go?

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There are 2 large black ones attached to the front forward facing section of the airbox:
1. One upper left corner whose hose then wraps around the metal frame of the stepper motor and plugs into a t-section at the bottom
2. One upper right corner that connects to the hose that runs along the right hand side frame towards the front of the bike.


The 2 clear plastic ones:
1.  Attaches to the middle of the bottom of the front of the airbox
2.  The second one on the left hand side of the airbox, (not the bottom) but at the bottom of the side of the "V" of the airbox...so it attaches sideways.

not sure what you are describing with the blue valve, but if this is the the  flaky blue and orange check valve, it needs to go. The whole intent of the cannisterectomy is to let the fuel tank vent directly to atmosphere

Thanks to PJPRO and Chris W for their responses. I left that valve in place to see if the problem continues. One variable at a time!

The two clear hoses with plugs are the airbox drains and it is vital that they be installed and plugged otherwise they allow the ingress of dirt to the airbox and thence the throttlebodies. This will damage the throttlebodies in a remarkably short period of time if not rectified.

Pete Roper wrote:

The two clear hoses with plugs are the airbox drains and it is vital that they be installed and plugged otherwise they allow the ingress of dirt to the airbox and thence the throttlebodies. This will damage the throttlebodies in a remarkably short period of time if not rectified.

Aye aye Captain! Installed and plugged.

Put the bike back together sans canister, rolled on down to the gas station and filled it to the brim. The bike started and ran on a short jaunt so I decided to take it on an errand.

I bought another guitar on FB marketplace, so sensibly, I took the GRiSO instead of one of our fleet of four-wheel vehicles.

Bike ran fine on the 60-mile R/T but watch this space for future complaints.

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Good to hear it's running and all put back together!

Is that a Gibson on a GRiSO or a GRiSO on a Gibson?

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Washburn BT-2, Washburn is the family name so I stick with that brand.