I GIVE UP!! Figure this out if you dare!

[Planecrazy]

Thanks yet again! I'll check the vacuum line too (assuming the gas cap passes the upcoming test). It's pouring here in the Chicago area so it may be a few days before we get a chance to test it. In the meantime, I'm replacing the clutch on my 1100G.

Regards,
Steve 8)

[Anonymous]

bogging

Had the same thing happen to my xs11 but it turned out to bad coils when hot they broken down and the spark be came to weak to fire the mixture, thats how I got a cherry xs 11 for $500 bucks, the shop that had it replaced every thing on it electric except the coils cause they checked good when cold but when heated up they started to fail, if it is a vent issue you should here the tank suck air when you pop the cap. did you replace the condensers?? cause they will do the same exact thing, does this bike have a ballest resistor in the system you may want to check that if it does, just my 2 cents worth

[Planecrazy]

no condensors ... electronic ignition -- brand new throughout, because I thought (as you did) that the coils or wires were overheating ... thanks anyway!

Steve 8)

[MikeW665]

When I read the thread the first thing that came to my mind is vapor lock. In 1982 Honda made a change in their Accord where they put the intake manifold over the exhaust manifold so on hot days you could drive the car, but when you parked it and then tried to drive it a few minutes later it would missfire all over the place. If you opened the hood and looked at the sight glass on the carb you could actually see the fuel bubbling in the carb. I don't know if this helps but I thought I'd throw it out there. BTW I devised a timer and extra fan so that when my brother stopped the car all he'd have to do is push a button on the dash and the aux fan would run for 15 minutes and keep the carb from over heating, then shut off so as not to drain the battery.

[Anonymous]

I have a 1980 GS550L like you and have run into the exact same problem many a time. I'd have to pull it off the road and let it cool down for at least 15 minutes, then it'd go like there was nothing wrong. For the longest time, I couldn't figure out the problem for the life of me. Even now, I'm not totally sure I've fixed it, but I haven't had a problem in quite a while, even on longer hot rides.

I found that the problem with my bike was actually a pinch in the fuel line. When I first started having the problem, people told me to check that, but it was fed through the engine nicely, so I swore that wasn't the problem. Then I switched gas lines (ended up with one that was slightly more flexible) and ran into the problem again. After much frustration, I noticed that the heat from the engine had caused the tubing to fold over, totally pinching off the gas. I had to shorten the tubing significantly so that it doesn't have a chance to bend, and haven't had the problem since. My assumption is that I was having the same problem with the original tubing, but that was strong enough to "undo" itself once it cooled down and then let gas flow nicely.

Anyway, try to check the gas line just when it dies to see if it's pinched or folded at all, and make sure the routing is really good (I had thought mine was). Good luck!

--Tyler

[Anonymous]

I found that the problem with my bike was actually a pinch in the fuel line.

I think the gas line pinching may be a symptom causted by inadequate venting of the fuel tank. You may want to check it out anyway. One way to verify the tank venting is to take a ride with the cap loose (near empty tank). If you don't have any problems then - it's probably the venting.

[Planecrazy]

I will make a note to have my buddy check the fuel line as well (if the gas cap venting test doesn't pan out). Actually, Tyler, it's funny you left me this note because I just got finished leaving you the fuel vent tip in YOUR thread! LOL!

Steve 8)

[Anonymous]

Another thing that can happen is that the needle shut-off valve into the carby can be slightly clogged or bent and when it heats up it jams shut, when it cools down it is loose enough for the spring pressure to open it.

This happened to my GS1000G a year or so ago, caused a few hours of mechanic's time trying to find what was showing up as the hot-coil symptom.

Kim

[Planecrazy]

I would tend to doubt that this is my problem, only because I've had the problem almost the entire 15 years I've owned the bike, and the carbs have been rebuilt several times during that period...

Steve 8)

[nert]

[In both instances, it happened much more easily in hot weather (because pressure builds up much more quickly on a hot day). ]

That doesn't fit with the moral of the story!. Heat by your statement makes more pressure more rapidly. Pressurizing the fuel. It sounds like everyone is suggesting vacuum, or a negative pressure restricting the fuel. Hot weather may be affecting something else?[/quote]

[jimcor]

The problem is the petcock. Non-rebuildable 69 bucks about 8 years ago. I had the identical problem with my '80 550L.

[Planecrazy]

[In both instances, it happened much more easily in hot weather (because pressure builds up much more quickly on a hot day). ]

That doesn't fit with the moral of the story!. Heat by your statement makes more pressure more rapidly. Pressurizing the fuel. It sounds like everyone is suggesting vacuum, or a negative pressure restricting the fuel. Hot weather may be affecting something else?

[/quote]

The reason they're all suggesting vacuum (and why it makes sense) is that the engine at high rpms (on the highway) is drawing fuel into the engine faster than it's expanding in the tank as vapor. Normally the fuel vent would allow air to enter the tank and fill the void, but if the vent is clogged because the old material is expanding in the heat, a vacuum would be created in the tank that would starve the engine of fuel flow.

We haven't had a chance to test this theory yet, because it's been storming here for days now, but as soon as we get a chance we'll let you all know what we find... I sent Jimcor a reply to a PM addressing the petcock suggestion. I'll keep it in mind, but I think a bad petcock would be bad regardless of temperature ... mine works fine when it's cold out.

Regards,
Steve 8)

[nert]

I understand the fuel starvation theory. I have no opinion on the cause of this GS problem. More information needs to be obtained, more tests performed.
I am pointing out that an individual replied and offered the argument of heat/hot day makes the situation worse because excessive/accelerated pressure build up in the fuel tank more rapidly on a hot day.
The prevailing thought through out the messages was fuel starvation.
May be it is the cause, maybe its not.
I am just pointing out that, positive pressure in the tank won't make a fuel starvation situation worse and IS NOT a valid argument to support the theory of fuel starvation on a hot day. Just the contrary!!!

[Planecrazy]

I understand the fuel starvation theory. I have no opinion on the cause of this GS problem. More information needs to be obtained, more tests performed.
I am pointing out that an individual replied and offered the argument of heat/hot day makes the situation worse because excessive/accelerated pressure build up in the fuel tank more rapidly on a hot day.
The prevailing thought through out the messages was fuel starvation.
May be it is the cause, maybe its not.
I am just pointing out that, positive pressure in the tank won't make a fuel starvation situation worse and IS NOT a valid argument to support the theory of fuel starvation on a hot day. Just the contrary!!!

Sorry Nert, when I read your post it looked like you were the one talking about a buildup in pressure because you didn't attribute the prior quote to anyone else (Chuckycheese) and I didn't remember seeing it. I went back and re-read his quote ... looks like he was describing a vacuum situation everywhere except in that one sentence, so I think maybe he meant to imply something other than how it came out just then ... anyway, thanks for the input!

Steve 8)

[Planecrazy]

Hi All,

Well, finally, we had a chance (and good weather) to reproduce the problem and check the gas cap for proper venting! Turns out that the fuel vent is NOT the problem, as the bike still refused to run properly after lifting the cap (and there was no telltale whoosh).

I'm now leaning toward a suspect petcock, based on some of the prior posts. Looks like I'll be ordering a Pingel this week and we'll see if that doesn't solve our problem. At least when I sell this bike (soon) I'll be able to say that almost every known Suzuki GS issue has been addressed with proper replacement parts... Damn this is frustrating!!

Steve