reserve at 1/2 tank?

[Don R]

It's an 81 GS1100EX with a new K&L petcock. For the second time it went on reserve at half tank on the gauge, and took only 2.5 gallons to re-fill. Does that sound right? It took 5 gallons of evaporust to clean the tank so I have a pretty good idea of what it holds.

Edit, it also started missing a little while on reserve. I cleaned and dried that tank until the cows came home but it is what it is.

 

[Rob S.]

Definitely does not sound right. I'll go as far as stating that it is definitely NOT right. But the answer, or at least a mighty big clue, is in your post: new petcock. Sounds like it was screwed in too far.
I also was surprised to hear it only holds 5 gallons total, but that's a horse of a different color. Show us pics of Cycle World's Bike of the Year, the bike that beat the Kaw GPz at the dragstrip (and everywhere else).

 

[rphillips]

Most reg. model big GS's hold right at 5 gal. with near 1 gal. on res. The "G" models hold about a gal. more "L" models about a gal. less, but most have nearly a gal on res....

 

[Don R]

This one has the two bolts holding it on. Pretty difficult to screw it in too far or cut down the stand pipe since it's inside the screen. I'm not crazy about no off position either. There may be a Pingel in my future. Speaking of that I think it's still set to reserve. I'd better go turn it to on.

 

[rphillips]

Can't imagine anything but tube on that K&L is too long for some reason... Guessing you never owned or rode it with orig. pet cock....The "80" models had "NO" RES... Mine got appx. 40 mpg. Learn to use trip meter, when got to 120 mi. knew appx. 1 gal. or 40 mi. till empty. Not good, but better than trusting the fuel gauge.

 

[Burque73]

Curious, Don R do you have an inline filter? If so that may not let enough gas flow and cause running issues.
In regards to fuel level, mine goes to reserve sooner than it used to according to the gauge, but not the trip meter. I always thought I bent the float arm trying to siphon gas out or just over time the sending unit lost it's calibration. 850 G, stock petcock, 55k on the clock.

 

[Don R]

Thanks for the good advice, I already removed the inline filter and got a new fuel line, (I had that issue a couple times on old cb750's. I tried the old petcock until it flooded the crankcase with gas, then bought the K&L. My trip odometer just started working finally, it zeroed out but didn't turn the numbers for a while. I tried pushing the reset while riding and it started working. Being an old Honda 750 guy, I'm used to watching the odometer. My wife still re-sets the trip odometer on her car. Bike habits stick with you.
The air/fuel meter says it is way rich but it went about a hundred miles on the 2.5 gallons.

 

[Don R]

I did add a set of K&N oval filters since the picture was taken. The wet concrete is from me wet sanding the clutch cover, it was pretty gnarly looking.

 

[rphillips]

Well, It's just me & many will disagree, but I've never had problems rebuilding orig. pet cocks. A few yrs. back my 2005 B12 leaked the fuel into the crankcase, over the winter. I just took it apart and cleaned the seat and plunger thing and stretched the spring a little & it's been fine ever since.

 

[Don R]

I can't disagree with success but my experience was different. That said, mine sat for 10 years with bad gas and rust in it.

 

[Don R]

I'm wondering if a petcock inspection is needed, I cleaned the rust from the tank with vinegar and then evaporust. I flushed it with water and then e 85 to get the water out and blew it dry with a leaf blower before rinsing with 2 stroke gas. All of that said, I'm wondering if there is something building up on the petcock screen.

 

[rphillips]

I'd expect an inspection to see if tubes in new and old are the same. you can hold them up to light & see through them, through the filter. The same filter covers both the "ON" and "RES" openings, if it was clogged half way up, when it quits getting gas through "ON", when you switch to "RES", you'd still not get gas... Just can't come up with another cause of your problem.... Gas comes through opening appx. 2" above bottom of tank till fuel level is below this opening, switch to "RES" and lower opening is opened to let the bottom 2" of fuel in tank flow through... Like said same filter covers both openings.

 

[Don R]

I'd agree with your assessment, I got an unexpected paycheck so I ordered a set of 36 Mikunis, a set of K&N's and a push pull throttle. I'll check the gas tank while it's apart. I'll start by draining into a 5 gallon gas can to see how low it will drain. I can barely turn the handle on the petcock without pliers, I'll try to ease that up a little too.

 

[rphillips]

Yep, mine is hard to turn also. I like your plan with the gas can. Please keep us informed... Also thinking the 36's and K&N's still won't let you keep up with the newer 600cc bikes... Crazy ain't it?

 

[Rob S.]

...I got an unexpected paycheck so I ordered a set of 36 Mikunis, a set of K&N's and a push pull throttle...

I like a man who has his priorities straight!

The petcock on my '82 11E is extremely hard to turn to reserve.

 

[Don R]

I tested the petcock today, I put the fuel line in a gas can and pulled a vacuum on the petcock with a hand pump. It drained down to where I assume is correct (about 4 gallons) and when put on reserve it drained most of the remaining fuel. This leaves me with no idea why it started missing at 1/2 tank twice in a row.

 

[Don R]

Update, the issue hasn't returned, I've ridden it down pretty low a couple times and experienced no missing. On one trip I did make it to a proper reserve level, if I recall correctly it took a tad over 3.5 gallons to re-fill it. I did the RS36 carburetor swap and got a new set of K&N filters.