Do XS's run better with a full fuel tank?

[Upright]

It's probably just my imagination running away with me, but it seems like my XS runs better after a fuel stop. Anybody else?

[Snow]

You could actually have a fuel-delivery problem that is somewhat alleviated by the force of the gas's weight when you fill up your tank. How old are your fuel lines, when's the last time you cleaned your carbs including the little filters (if you have that style)?

[DEmily]

Hey Upright,

Another one from the KC area! Great! I actually have experienced that. I really never could determine if it was my imagination or what. After rebuilding the petcocks and cleanng the screens in the tank, I never really experienced again.

So where abouts in KC do you live? I have been trying to find someone else with an XS or XJ around here. Would like to here it running. I recently rebuilt one my brother gave me and am not sure if all the noises I am hearing are normal for this bike.

[Upright]

I should probably clarify a bit. It's not like the bike's running poorly prior to the fuel stop, it just seems to run smoother afterward.

Snow, I sincerely hope it's not a fuel delivery problem. I just got the bike back from Merriam Cycle for a complete fuel system overhaul....rebuilt petcocks and carb replacement. (PO evidently thought he improve the bike's performance with a Dremel tool. )

DEmily, I live in Overland Park and work in Shawnee. Whereabouts are you? What kind of noises are you wondering about? Mine has a "clatter" that I was concerned about, but Bob at Merriam Cycle said to not to worry.

[DEmily]

I live in Independence Mo. But work in Overland Park. The Clover Leaf Buildings off 63rd Metcalf.

I think the sound I am talking about may be the clattering you are talking about. I think it is just the primary chain.

[Dennyz]

I just got back from a trip on a '79 Special that would hardly run once my fuel got down to near reserve (light comes on). I found I had a dirty petcock on the right side. The petcock screen was plugged with debris and the reserve/prime port was partially blocked.

[TopCatGr58]

Hey there Upright,

Still could be reduction in fuel flow, for several other reasons, poor vacuum/lines going to petcocks not fully opening valves; clogged gas tank vent, so when getting down on fuel, vacuum buildup in tank preventing it from flowing as easily/quickly!"

Have you noticed this more with Intown driving, or highway? If intown, could be fuel in tank and carbs and engine getting very hot, but after fill up with nice cool gas in tank?? Or vapor lock in lines, are they very long and hanging down below level of carbs?
T.C.

Originally posted by Upright
I should probably clarify a bit. It's not like the bike's running poorly prior to the fuel stop, it just seems to run smoother afterward.

Snow, I sincerely hope it's not a fuel delivery problem. I just got the bike back from Merriam Cycle for a complete fuel system overhaul....rebuilt petcocks and carb replacement. (PO evidently thought he improve the bike's performance with a Dremel tool. )

[Upright]

I've noticed it mostly with in-town riding....but that's where I do most of my riding! I'll check those vacuum lines. Thanks!

[gaffer77]

hi just butting in on great thread im in england my vac hoses r all scrunched up ,put new ones on still kincked ,cant get em to sit without bending somewhere,my bike runs good,only seems to get to 110mls an hour tho and clatter i got that too thinking,shimms,camchain,but it dont sound terminal and its old so dont know whether to do everything and see or what .mine sounds from top left of engine more but then havnt tried to locate too much really just keeping fingers crossed,its not really a clatter or rattle its more like pinking but its not.... ,it doesnt seem bad under load no smoke no missfires as such it does stutter intermittently held at 3,000 revs constant or any revs constant but seems fine under load ,let the throttle off on the road it does cough now and again tho

[randy]

The Swamp Thing actually does run smoother and has better slow speed balance with a freshly topped up tank.

Not because i have a fuel delivery problem but i think it has a lot to do with the extra 40lbs in the center line. It also doesn't seem to vibrate quite as much.

And come to think of it, it runs a lot longer on a full tank.

Cheers,

Randy