Why did my bike die on the highway??

[rgierer]

I vote for petcock. On my first 1100G I had similar experience to what you have described. Petcock replaced and it NEVER happened again.

[hikermikem]

Thanks Robin,

I have replaced the petcock with a brandy-new one (OEM from Suzuki) previously. The old one, which I believe was the original, didn't work at all.

On an editorial note, I'm not sure why anyone would design such a lousy fuel shut-off system. What the heck's wrong with a basic shut-off valve??

[txironhead]

Because if you forget to turn your gas off every time you kill the bike, you risk oil contamination at the least, hydrolocked engine and major parts breaking at the worst. A lot of us are a bit.......what's that word......oh, yeah, forgetful.

[hikermikem]

Thanks all again for the suggestions:


- I don't have an inline fuel filter.
- running new fuel & vac lines & petcock.
- Disassembled & cleaned the gas cap assy a couple of weeks ago. Is there any way to check it's venting properly? It appears to be operational, but can't really tell.


Yeah Lee, I remember your complaint about the timing plate curves. I chose the GS1000 one because it's the same as the GS550 one for the same year ('79). Its marks are 6 degrees more retarded than ours (17 & 37, vs: 11 & 31), with the same 20 degree movement at basicly the same RPM's. I figured I would just initially install it 6 degrees "ahead" and fine tune from there.

I don't plan on switching over until the ignitor dies (the one from my parts bike bench tested dead). I know it's just a matter of time & I'll be ready to fix it when it happens - the advancer I bought from e-bay only cost me $10.

Going to do the plug chop thing today - I'll let you all know how it works out.

Regards

Well, I did some of the stuff I'd planned on, not all the stuff. I did have an epiphany today though... I remembered I'd removed the carb vent tube lines to troubleshoot somethin' long ago - never put them back; I re-attached them & trimmed my fuel and vac lines back as well, they were left purposely long to facilitate raising the fuel tank to improve carb accessability.

But first, I pulled the plugs out as-she-sat, just to see what 1/2 throttle looked like. They were all very good - nice tan color all, which didn't happen before the new coils I might add.

Checked the charging system, it was within spec at 2K & 5K limits per the stator papers checklist.

Warmed her up, then dropped the idle to 1K, and used the mixture screws to fine tune each cylinder. This time, I could ACTUALLY hear & feel the subtle idle differences in cyl as I slowly found the max point with each screw, using the highest RPM process - then returning idle to 1K to re-check each cyl several times.

It's true what everyone here alludes to - there are some adjustments you just can not make until you're absolutely positive lots of other things are NOT the problem. Carb adjustments fall into this bucket, as do electrical component replacements.

Anyway, cyl #3 was way out of whack & now my duck purrs (?) nicely and holds a strong idle at 1100. Starts right up every time (even hot) too.

Never touched the jets or needles, completely stock pipes & airbox.

At this point I'm done with the tinkering, ready for the riding part. I can say this, the bike was driven today under similar conditions as Friday's death march, and no problems arose. No 18-wheeler passes this time either however, just sustained highway speed for approx 15 mi with zero issues.

In the end, I think her recent highway death was mainly attributed to two things: poor mixture screw adjustment & improper carb venting, resultant from not using the vent tubes at each carb's vent port.

I'll probabally do at least one more plug chop to satisfy my OC side, but it should confirm the "tune" I hope.

Thanks to all - (sorry for this) but it's time to get the flock out of here.

Mike

[txironhead]

The vents could very well have caused the "mystery death" syndrome. High-speed wind over the vent tubes causes a siphoning effect and wreaks havok with the carbs, something that was probably intensified by the higher speed and wind shear effect from the semi.

Glad to hear the duck's a-quackin' again.

[Jagir]

tank is clean?

[KEITH KRAUSE]

Glad to hear it passed its test. I hope it stays happy.
If it was related to float bowl venting, I've always preached here to remove the vent lines if you run pods, but keep the lines on if you have a stock intake.
I can't say from your description just how abruptly the bike stalled, but vent lines issues (always poor fuel flow) aren't usually that abrupt but more like starting to run out of gas, hesitation, or like hitting a head on wind gust. Still possible though.
Mixture screw adjustment is very important but has an effect depending on the throttle position you were at during the stall. Your model at general highway speeds, would be operating on the jet needle with some pilot circuit (mixture screws) overlap. The way excessively rich mixture screw adjustment could cause a sudden stall would be if the mixture was too rich and you fouled the plugs. But since you were at least partly off the pilot circuit (operating on the jet needles) it seems that overly rich mixture screw adjustments and any problems, would have been MUCH more obvious at minimal throttle openings where you're riding almost completely on the pilot circuit. Also, if the mixture was too rich and fouled the plugs, then it shouldn't re-start after several minutes because the plugs would still be fouled from soot and they can't clean themselves off that easy. So it's possible, but I think the mixture screws weren't the cause of the stall.
You did say the fuel and vacuum lines were originally left longer than necessary though. That can cause problems. Kinks don't allow good vacuum to the petcock and fuel can slow to a trickle from either hose being kinked.

[hikermikem]

Thanks Keith,

OK, I'll add one more contributor to the "highway death" issue, supplementing the vent tubes & mixture screw "fault" causes.

Excessively long fuel & vac lines.

Although they were never "kinked" (I checked repeatably), they were each aprox. 12"-14" long or so before I trimmed them to their proper size of approx. half that length. They were always clamped at both ends, but perhaps they simply could not perform as they should being that long. It was A LOT easier to adjust the carbs that way however, as the tank was just resting on its mounting bolts - just had to "lever" it up from the back & rest it on a calibrated shim device (otherwise known as a wood shingle trimed to an exacting length). Reach in, pull plugs, adjust carbs and drop it back down again. I ran it that way for many weeks with NO problems. However, no highway jaunts either.

Anyway, as we all know, fixing these bikes often seems to involve resolving many little issues, and occasionally some large ones. In the end you never really know which fix produced that biggest bang for the buck.

Next "upgrade" will be the oil cooler install from the parts bike I have, but that can wait for now.

Keep smilin'

Mike