97 R1100RT sputtering when tank low

[leaton10]

I am the proud new owner of a 97 R11RT and love it.
I have had airheads and K bikes in the past, but find this one my new
favorite.
As is always the case, I am learning about it and tweaking things, since
I'm a bit of a fanatic about making things work correctly.
An engineer by trade, it drives me nuts to have something not work correctly.

Anyway, the problem:
The bike runs well, except for the slight surging at slower RPM's that seems to
be common on these bikes (I will look into that soon).
However, when the gas level gets to around 3 ticks on the info display it will
start really surging, and will then turn into a complete bucking bronco. I
have had to pull over in the emergency lane 3 times when this happened,
as the bike will continue to run, but very slow, like it's running out of gas.
I make it to a gas station, fill up and it's fine.

I thought maybe the gas gauge is incorrect, but looked in the manual and it
says the bike will hold over 7 gallons and when it's low, I should get a
'low fuel' light on the center display. This has not happened and I filled it up
to brimming with around 5 1/2 gallons.

Could it be that it just needs a new fuel filter. I would change it as a quick
guess, but found out it is not the quick job like on an airhead, that it requires
removal and draining of the gas tank.

Thanks in advance

Larry

[BC1100S]

Considering that the issue seems to be centred around fuel and fuel levels, I think you're going to end up inside your gas tank sooner rather than later.

I'd get a good schematic of the routing and connection of all hoses and ensure that all is as it should be inside the tank. Replace filter while you're at it. Be prepared to replace a hose or two. Use good clamps.

Others with more knowledge will chime in soon.

[Bmandiego]

Sounds like the filter and hoses to me.
Get the pump and hoses looked at inside the tank.

[JimMoore]

That's a little odd. Is there a vaccuum when you open the tank during one of these events?

[Roger 04 RT]

Although I just got through changing the pump, filter and all the internal and external hoses due to leaks and age, I think Jim is onto something. It sounds like the evap canister or its purge hosing is clogged. With a full tank the weight of the fuel is opposing the vacuum that's eventually building at lower fuel levels.

I'd either check and see if the evap canister is clogged or cracking open the tank lid when this happens and seeing if you have a tank vacuum.

You could also just pull the electrical connection to the evap purgemvalvemon the left side beneath the seat.

[BC1100S]

To add to the above great ideas, here's another step in diagnosing the problem.

When you start to experience the problem, pull over and open the gas cap. See if you hear a momentary vacuum sucking sound. Leave the cap open for a few seconds before closing it and restarting the bike. You will have equalised the pressure inside and outside the tank. If the problem has disappeared, you're a step closer to the problem.

[leaton10]

Thanks folks. I will follow up on your suggestions and let you know the
results.

[jfremder]

Sounds like the filter and hoses to me.
Get the pump and hoses looked at inside the tank.

My guess too. Look for cracks in the hoses on the bulkhead plate, especially the 'U' shaped one.

[PGlaves]

I'd be pretty sure:

1. The bike still has the charcoal canister
2. The canister is clogged
3. The tank isn't venting.
4. The vacuum in the tank is slowing fuel flow

As soon as it starts open the tank. If this cures it in a few seconds you know you have a vent problem.

[leaton10]

Well - I got the parts and spent over 3 hours today siphoning out the tank,
pulling the side panels off, taking the tank off, etc.
I replaced the fuel filter, filter screen and the horseshoe shaped hose.
The bike has 44 K miles and I could tell since the clamps were factory type
that this had never been done before. The screen was really dirty,
and the reason I replaced the U hose is it seemed the factory clamp had
loosened on the pump end. Seems to run better,
but I'll have to run out another tank of gas to see if it solves the problem.

Thanks for all the suggestions. If this doesn't do it, next, I will explore venting
and carbon canister.
Got my fingers crossed though.