2010 GL1800 Cobra XL Aux Fuel Tank Filling

[Yogisan]

I just recently had an aux fuel tank installed. Since then I have been having a problem getting a complete fillup. The gauge indicates full until I ride a few miles and it drops down one or two gauge markers. I suspected a vent tube issue but I took off the seat and the vent tube is routed properly and doesn't show any signs of being kinked. I've tried the slow fill, wait, then top off process but either that doesn't appear to work or I'm not doing it correctly. Can anyone with a aux tank give me some help. P.S. I have a thorough understanding of the theory of how the aux tank is supposed to work. I just need help on the practical side, getting it to work.

[CobraXL]

Could it be that your main tank float was somehow moved/adjusted when the aux tank was installed?

If you are slow-filling then wait a minute or two before hanging up the gas pump and see what the fuel level does.

If you see it staying at the top--not going down after you quit pumping--then you've got an issue with the gas gauge on your trike. If the fuel level goes down then the aux tank is still filling.

My aux tank always fills nicely as long as I don't put the gas in too quickly--in fact the slower the better.

[Yogisan]

Could it be that your main tank float was somehow moved/adjusted when the aux tank was installed?

If you are slow-filling then wait a minute or two before hanging up the gas pump and see what the fuel level does.

If you see it staying at the top--not going down after you quit pumping--then you've got an issue with the gas gauge on your trike. If the fuel level goes down then the aux tank is still filling.

My aux tank always fills nicely as long as I don't put the gas in too quickly--in fact the slower the better.

I haven't pulled the metering assembly to check it yet. The last time I filled it the guage indicated the tanks were full, even after waiting a few minutes. The pump auto shutoff wouldn't let me put any more fuel in. I started driving and watched the guage gradually drop two marks then settle down during the first couple of miles. I'd like to do a drive-until-it's-empty ride to see how far a fillup will get me but, until I figure out this issue I can't do that.

I guess pulling the metering assembly is the next step.

[Papa Zook]

I haven't pulled the metering assembly to check it yet. The last time I filled it the guage indicated the tanks were full, even after waiting a few minutes. The pump auto shutoff wouldn't let me put any more fuel in. I started driving and watched the guage gradually drop two marks then settle down during the first couple of miles. I'd like to do a drive-until-it's-empty ride to see how far a fillup will get me but, until I figure out this issue I can't do that.

I guess pulling the metering assembly is the next step.

Hold on before you do that... I think I might know whats up but let me ask the expert and get back with you.

[Yogisan]

Hold on before you do that... I think I might know whats up but let me ask the expert and get back with you.

Ok. I'll put my sledge hammer back in the tool box. Lol.

[GPz1100]

have you looked with a flashlight at fluid level to see if it did indeed drop?

[California Sidecar]

We recommend that while filling the bike you put the fuel nozzle on the first, slowest notch so that it fills slow. This will allow the aux. tank to vent.

Please give me a call if you need more assistance. 1-800-824-1523 Will

[Yogisan]

We recommend that while filling the bike you put the fuel nozzle on the first, slowest notch so that it fills slow. This will allow the aux. tank to vent.

Please give me a call if you need more assistance. 1-800-824-1523 Will

I tried that and I still had the same issue. A few days ago I filled it from a little below half tank on the gauge. I tried filling it like I do with with my Lehman Jackal with an aux tank. I used my fingers on the pump handle to make the flow slower than the first notch flow. The gauge went up to the fill mark just about the same time the pump shut off. I waited a couple of minutes and the gauge didn't change and the tank wouldn't take any more gas.

I drove a couple of miles and the gauge didn't change. At about 10 miles it dropped a little and for the rest of the 180 miles the needle drop was relatively normal. I noticed it would go down if I was going uphill and up if I was going downhill, which is what should happen. When I got home the gauge read 1 1/2 marks above the empty mark. Number wise that's 28 miles per mark, which is not necessarily the mpg.

I'll use the same fillup routine when I gas up again and, if it fills up the same way, I'll calculate the mpg using the actual gallons to fill up.

[Yogisan]

have you looked with a flashlight at fluid level to see if it did indeed drop?

No, I didn't. Good idea though. Maybe I will next time it happens.

[Yogisan]

Since my last fillup I drove the trike to the point where the reserve light stayed on full time @ 230 miles. Did my version of "slow fill" (use fingers to hold the pump trigger for a flow less than first notch). It took 7.5 gal to fill the tank, and the guage to to the "F+" mark. That's about 30.7 mpg and that's driving under various load and speed conditions. So, it looks like the problem was my filling technique and everything else is working correctly. Thanks for all the inputs. They helped me figure it out.