Why did my bike die on the highway??

[hikermikem]

My "85 GS550L has recently come back to life!! I've done & checked all the things I've learned & read about here: complete carb overhaul, air leaks fixed, electrical fixes, new coils, new intake o-rings, new petcock, new fuel & vac lines, cleaned gas cap, no tank rust, etc...

My little duck is now running great!!!

However, I just "blasted" down the freeway, and it died while accelerating past an 18 wheeler (approx. 75mph). I had electrical power(based on the gages/idiot lights working), but the engine was dead.

Yes, there was plenty of fresh gas in the tank. This has not happened on regular roads, even at comparable speeds.

I pulled over and waited a couple of minutes (I opened the gas cap in an attempt to "hear" if the venting was bad - nada), it started right up & off I went. No more suicides as of yet, but I'm leary of getting on the freeway again.

Any ideas as to why it died like that?? All opinions/suggestions appreciated.

Thanks Mike.

[MelodicMetalGod]

I'm not an expert, but without greater details and addressing the "sudden death" of the engine at speed, I would explore either fuel delivery/starvation issues and elctrical failure issues. Obviously, since you rode away after a few minutes, the issue is intermittant. Given that it hasn't happened to you anywhere but on the highway, heat may play a role in the issue(s).

The first specific issue that comes to mind for me with these bikes is the notorious electrical system and the fact that heat can cause temporary failure.

Here's a post from Keith Krause, one the many good troubleshooters on this forum, regarding heat exacerbated electrical issues:

A low battery is a common cause of this. It may start OK cold, but heat increases resistance. Fully charge the battery and top off water, check when completely warmed up for correct voltage. If it's getting old and losing its charge, replace.
If not battery related, and not knowing the overall state of tune, I might try adjusting the mixture screws on your CV carbs. It's quick and easy and you just keep a record of any adjustments and you can put them back to where they were if you want. With warming up, your mixture will richen somewhat. Leaning the screws may help. Generally, these screws should be adjusted using the "highest rpm method". I'd try that next because it's easy to do, may be the cure, and if not, you can put things back easily and go to the next thing. If your screws are still factory capped, then adjustment shouldn't be needed, however, dirt or old fuel/varnish build up can accumulate in the air jet/pilot circuit passages and cause your problem.
If not battery/carb related, another cause can be a dirty starter. The commutator can get dirty or worn and the brushes can wear out or make poor contact too. Heat worsens a starter problem.
Could be other things too. Even a dirty air filter can cause this, which I meant to mention earlier.

Here's the whole thread...look for more like it: http://www.thegsresources.com/_forum...ht=heat+issues

Best of luck!

[hikermikem]

Thank you for responding - I have a lot of respect for the knowledge floating around in this forum. I was wondering if anyone may have had a similar issue in the past with their bike.

I've posted numerous questions regarding this bike in the past couple of months & the reason it runs at all is directly related to the advice/guidance I've received here.

Let's face it, these bikes are OLD & some of their components (i.e., electrical) are not the most reliable from a design point of view.

As a friend of mine is fond of saying, "it is what it is." Indeed.

mike

[BassCliff]

Mr. hikermikem,

I don't know if this applies to your bike.

My friend's bike would die, for no reason, while he's going down the road. Then it would "bump start" a second later and keep going. It turned out that he has an "idiot" switch on the kick stand (side stand) and when it got jarred just enough (going over a little bump) it would kill the motor. For now he uses a bungee cord to keep the side stand up in place until he can either fix it or defeat it.

Or it could be some other "idiot" switch on your bike and passing the truck was just coincidence.

Thank you for your indulgence,

BassCliff

[LeeGS550E]

Ya know, I had the same problem with my 550 when I was still in the test/tune phases. Running it flat out for a considerable amount of time (5 miles at 6k give or take) would cause it to die on me, then after sitting for a bit, I could finally get it to crank up and if I revved on it real hard, it would get going. The problem went away with more tuning on the jetting. I was too rich at WOT and too lean in the midrange. Here's some thoughts:

-Jetting's not right and at WOT or close to that you're fouling plugs?
-Like others have said, fuel starvation. Check your petcock and hoses.
-Also like others have said, heat is causing an electrical problem to crop up. How's the resistance on your coils? Have you cleaned all of the connections?

I know you've been tinkering with the jetting on this bike. How did that finally end up?

[hikermikem]

Mr. Basscliff ,

Thanks for your thoughts. Actually, the PO had already sniped the wires feeding the side stand switch, so I guess that wouldn't be it!! I'll look for another idiot switch somewhere, but I don't think there is one.


Lee,

I never did tinker with the jetting like I had proposed before. You may also recall that I was going to put Dynatek 5 ohm coils on, but you convinced me that the 3 ohm were better suited (especially since I was also planning on upgrading to a Dyna S ignition too). Soooo.... I returned the 5 ohm ones I bought from Jeff at Z1 (he really is a super nice & very knowledgeable guy), and bought 3 ohm ones.

I also picked up a '79 GS1000 mechanical timing advance plate on e-bay (same OEM advancer as on a '79 GS550L) to be ready for the Dyna S when it shows up. I traded Jeff the 5 ohm coils back for a Dyna S, as I felt bad that I had to buy the 3 ohms coils from a a competitor because he was out of stock.

Anyway, as soon as I put the new coils on & reinstalled the "patched" stock 4-2 exhaust pipes, the bike took off like a rocket!! (You may have heard the loud cheers coming from CT last weekend).

Haven't really had a chance to do plug chops & tune it with the mixture screws, but it seemed to run very well with the screws set approx. 2 turns out or so.

I was very satisfied that I finally fixed the "problem" (coils), but when I took it on the highway it died after a couple of miles (as I stated in the beginning of this thread).

So now plug chops are in order I suppose, but I've read here something about setting the mixtures screws using the "high RPM method". What is that method?? I'm not familiar with it, so a bit of "site searching" is up next. Actually, I'm pretty happy I figured out what WOT meant all by myself (wide-open-throttle?)

I also seem to recall your 550 is running stock 95 & 105 jets? This one is stock with 90 & 97.5 jets. Seems odd that identical engines are jetted so different.

I did buy a crap load of jets & have 2 each of the following: 90, 92.5, 95, 97.5, 100, 102.5, 105, as well as lots of #4 SS washers to shim needle jets if I want to really go crazy!! (I think not).

I plan on playing with the "duck" this weekend & will of course report back the results. I believe I will be installing an oil cooler from my parts bike too. Suggestions are, as always, very welcome.

Mike

[hikermikem]

Forgot to ask - where did the dinosaur come from??

Just curious.

[earlfor]

I had exactly that problem when I first got my 750. Bike ran fine always, except when I spent more than a minute at high throttle settings and it would just die out. Pull over, wait a few minutes and it would be fine. The problem turned out to be the aftermarket inline fuel filter the previous owner had installed in the fuel line between the petcock and carbs. The filter was not capable of flowing enough fuel for full throttle requirements of the engine. At partial throttle, it was fine. Open the throttle, run out of gas. LOL I did away with that little sucker.

Earl

[txironhead]

You may want to look into getting a Colortune. It's a prismatic thing that allows adjustment of the bike according to the "color" of the spark. Do a search for colortune and you'll find links on where to buy, how to use and rave reviews. Probably have to order it from Europe, along with the proper adapter, but well worth the money from what I hear.

You might get lucky and find one on Ebay that's the proper size.

[LeeGS550E]

I don't think you should really question your jetting if you're running a solid stock exhaust and your airbox is well sealed with a stock or close to stock air filter. It sounds like you have fixed a major problem with the coils, and I'm glad about that. I didn't want you to go half-cocked into the dyna-s install because its kind of a pain to get it to work on the late 550's, and I'm still not convinced its a good idea since the advance curves are so different on the earlier models that we steal the mech. advance from. Don't do it until your ignitor goes bad and you're looking at dropping $125 on ebay for a used replacement. My 550 ran ok with the Dyna S, but I think it would have eventually been a limiting factor.

With this problem, I think you need to continue searching for problems with your carbs and the WOT circuit. Try to head out on a backroad, run for a few miles at WOT, and then do a plug chop. I'm curious if you're not running out of fuel somehow, like everyone else has mentioned. How's your petcock and fuel lines? New I hope...

[SqDancerLynn1]

another thing to check would be the gas cap vent hole

[SPARKSS]

My "85 GS550L has recently come back to life!! I've done & checked all the things I've learned & read about here: complete carb overhaul, air leaks fixed, electrical fixes, new coils, new intake o-rings, new petcock, new fuel & vac lines, cleaned gas cap, no tank rust, etc...

My little duck is now running great!!!

However, I just "blasted" down the freeway, and it died while accelerating past an 18 wheeler (approx. 75mph). I had electrical power(based on the gages/idiot lights working), but the engine was dead.

Yes, there was plenty of fresh gas in the tank. This has not happened on regular roads, even at comparable speeds.

I pulled over and waited a couple of minutes (I opened the gas cap in an attempt to "hear" if the venting was bad - nada), it started right up & off I went. No more suicides as of yet, but I'm leary of getting on the freeway again.

Any ideas as to why it died like that?? All opinions/suggestions appreciated.

Thanks Mike.

Hi Mike. When it died, was it a clean shut off or did it lose power first and then quit? Was there any backfiring associated with this event? When you got pulled over and tried to restart, and I assume it wouldn't initially, did you try switching the tank to PRI?

Unless you have an intermittent problem (more likely electrical), then a possible common denominator to your problem is sustained high rpm on the freeway. One probability here are that it ran out of fuel temporarily. Though you checked for venting (good) it may have been a failure of the vacuum actuator in the petcock or a restriction in the fuel line (do you have a seperate inline filter?). This is the reason I asked about switching to PRI.

A second possibility is that your system voltage got up to an abnormal high level for a significant time (time is the key) while on the freeway, and this caused your electronic ignition to shut down......or even a related connection (probable coil primary) to start to burn (becomes high resistance). These are the reasons I asked about a clean shutdown and then any gradual (may have been fairly quick) loss of power or backfiring).

All of the above I've experienced over the years. Unless there's other parts of the history missing, I'd suggest testing system voltage at equivalent road rpm to see if it's gradually climing without regulation, and depending on what you find, checking for fuel restriction or seeing if you can duplicate the problem and check for a petcock problem by selecting PRI when it happens.

Don't overlook the kill switch for signs of becoming intermittent as it's often not used.......in conjunction with the voltage testing above.

[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

[SPARKSS]

Mike, a common method of checking for inlet restriction (venting or otherwise) is to tee in a vacuum gauge as close to the carb fuel manifold as possible (or further up if you're sure about the integrity of that part of the fuel line). What you're looking for is low vacuum and NOT increasing. On a system with a fuel pump (not most bikes) you'll typically see some vacuum here indicating the pump is doing it's job.....even here you don't want to see it climb. Make sense?

[hikermikem]

SparkSS - thanks for the input. I have an engine vac gage, perhaps that'll work if I decide to perform that test.

I also read your previous post & I'll keep those suggestions in mind as well. I wasn't driving when the bike when died on the highway (I was a hapless passenger), but it appeared to just cut out, & didn't seem to lose power gradually. It started right up after a couple of minutes of exchanging colorful adjectives with it though. The coils are BRAND NEW.

My gut tells me there's a fuel starvation issue here, & I'm REALLY tempted to up the stock jet sizes a size or two. Seems the 90 & 97.5 ones on it are quite small, when compared to other stock 550's I've researched in OEM manuals. As I've said before, this "L" model 550 is an odd little duck.

My first test will be of the charging system at different RPM's. I've printed off a copy of the Stator Papers (IV, me thinks) & will use that as a guide to determine the overall health. (Thanks for pointing me that way Keith)

I am playing with putting an oil cooler on as well (cannibalized from my parts bike) today after that. We'll see about that, not a priority at this point, but I have it - why not use it?

Then I'll adjust the mixture screws AGAIN, using that "highest RPM method," and then do some plug chops to see what's going on. To quote from Keith, "the plugs don't lie".

Enjoy your day!