Engine Dying

[Anonymous]

Hopefully someone else has experienced this and can help out. My 77 GS550's engine will suddenly die while riding. More accurately, I can feel it begin to run poorly (bogging down, poor acceleration, etc), then at the next stop, it will just die. The only way to get it to fire back up is to use the choke, then turn the choke back off. At this point, it no longer wants to idle, and backfires. After sitting for a few minutes, it seems to be fine again. I'm at a loss, any ideas??

 

[earlfor]

Re: Engine Dying

Yep, its running out of fuel. The possibilities are: crud and silt in the fuel tank and the filter screen on the petcock clogging due to fuel draw. Faulty petcock diaphram. vacum line. Clogged inline fuel filter. Kinked fuel hose. Kinked vacum hose. leaking vacum hose.

Earl


[quote="73mtneer" After sitting for a few minutes, it seems to be fine again. I'm at a loss, any ideas??[/quote]

 

[Anonymous]

Ok, that makes sense. In my earlier post I neglected to mention that twice when it has done it, right after I acquired the bike, I thought that I was out of gas. Both of those times, I switched the petcock over to reserve and everything seemed fine. Today, despite having a nearly full tank of gas, I rode the remaining 4 or 5 miles to work on reserve with no further problems. Weird thing is, I had it out for about a 40 mile ride on Monday & it ran fine the entire time. Any suspicion as to why the problem seems to come and go with no pattern? The two incidents this afternoon (the 2nd being much more severe) mark the 4th time that it has happened in the short time that I have owned the bike.

Given this additional information, would you suspect a bad petcock? Should I just replace it or can they be rebuilt? As you might guess, I'm pretty new to motorcycling, this being my first bike. I bought an older bike 1. So I wouldn't cry if/when I dropped it & 2. So I could learn a little bit about working on bikes before moving on to a newer model. I guess I am getting my first taste of reason #2 here.

Thanks in advance for your help!

 

[redliner1973]

More than likely, your petcock is clogging up, it runs good on reserve because most of the crud is on the normal part of the screen due to the fact that thats where most of the gas flow has gone through during its lifetime. Some people say rebuild, I say replace, they are not that expensive, and I have heard mixed results rebuilding them. It would be wise, however, to add an inlie filter to your lines, to keep everything out of the carbs. Hope that helps....

 

[Anonymous]

If replacing, do you have any recommendations? I've read on here of trying everything from OEM to Pingle to parts scrounged from the local hardware store. What kind of cost should I expect in an aftermarket petcock?

Thanks!

 

[earlfor]

Oh there is a pattern. When youre just putting along slow and easy, the fuel flow is minimal and the silt is not pulled into the petcock screen blocking flow. Flow requirements are small, so even some blockage still allows sufficient fuel flow. More agressive throttling, climbing hills etc, anything requiring more fuel, pulls more sediment and blocks the screen just when you need an increase in fuel flow. Switching to reserve changes the fuel pickup point to a lower position inside the screen and usually will help the situation, but not always.

I would take off the tank, remove the petcock and check the screen to see how gunked up it really is and clean it. Adding an inline fuel filter will keep junk out of the carbs, but will do nothing for the blockage problem of fuel feeding from the tank. It may be sufficient to rinse out the tank with gas a few times to wash out any sediment. If you find chunks of rust or such though, just rinsing the tank will not be adequate and you could end up having to coat the inside of the tank. That fuel flows apparently correctly through the petcock, I would not just yet automatically replace it as I think there is a very good possibility that your only problem is sediment in the tank.

Earl

Weird thing is, I had it out for about a 40 mile ride on Monday & it ran fine the entire time. Any suspicion as to why the problem seems to come and go with no pattern?

 

[Anonymous]

New Information

New Information

Ok, here's another twist in my mysteriously dying engine. I started poking around the bike this morning and found that gas is draining through the overflow hose on the #1 carb. Not enough to puddle under the bike, mind you, but enough that the end of the hose is wet, as well as a 2-3 inch area where the hose was laying on the swingarm. This is after sitting for about 9.5 hours overnight.

Is this possibly related to the problem that I am having, or is it just normal drainage (I assume there is a normal rate of overflow or the hose wouldn't be there for it)?

 

[Anonymous]

Update:

When I left for work today, there was a very slow drip coming from that overflow hose on carb #1. This was at about 3:00 pm, and the bike had been parked since midnight last night. I switched the valve back to "on" from "reserve" to see if that would stop the flow.

Any speculation if this is at all related to my problem with the engine suddenly shutting down?

 

[argonsagas]

May I suggest you look back up the thread and read previous posts?

Skip the concerns about the petcock. You have every indication of a problem with fuel blockage. Sort that out first.

1-
Drain your gas tank with a hose. If at all possible, look for sediment in the container you put the gas in after waiting about 10 to 20 minutes.

2-
Take the tank off the bike, add a pint of gas and swish it around hard for twenty seconds, then turn the tank upside down and immediately dump the gas in a large, clean, container. Look for rust or bits of junk coming out with the gas.

If it looks like it's all or mostly rust, then you need the tank cleaned and re-lined, and it doesn't matter if there are other fuel problems, doing anything else is a waste of time if you don't do the tank.


The "drips" are there because you have the petcock set on PRIme and one or more of the needles/floats in your carbs is not fully seating. The rate of flow means nothing, as it could be because of limited fuel flow at the petcock, blocked lines, or because the float/needle settings are anywhere from poor to just- off- perfect. If the bike is on the sidestand, then the floats may, or may not, operate properly. Back to the tank.

If it proves to be the tank, and I suspect it will, my suggestion would be to get it professionally cleaned and relined. The cost is higher, but you want it done right, the first time.

After that, and before starting the engine even once, install an in-line filter.

 

[earlfor]

A drip crom the carb #1 overflow hose will result from the float needle not closing off the fuel flow into the bow. Either the float needle seat or the float needle is dirty. Probably both. This should not be happening and you need to fix this. While you have the carb off, you might also want to check the float level setting.
The valve should not weep fuel through regardless of the petcock setting. This problem has nothing to do with the engine shutting down.

Earl

Update:

When I left for work today, there was a very slow drip coming from that overflow hose on carb #1. This was at about 3:00 pm, and the bike had been parked since midnight last night. I switched the valve back to "on" from "reserve" to see if that would stop the flow.

Any speculation if this is at all related to my problem with the engine suddenly shutting down?

 

[Anonymous]

The "drips" are there because you have the petcock set on PRIme and one or more of the needles/floats in your carbs is not fully seating

I appreciate the advice, but as I stated, the petcock was in the reserve position, not prime.

I have read all of the previous posts, but am trying to narrow down the problems with the fuel system. So far it looks like I have both a carb problem and a blockage possibly resulting from sediment somewhere, or at the very least from the fact that this is a 25 year old bike & I have no idea what has been done to it previously.

The carbs were supposedly cleaned before I bought the bike about a month ago, but you know dealers. No telling how well they looked things over.

 

[argonsagas]

May we all please get together and find a way to push our dear friend into positive action.

Simple route, in order:

1 follow instructions above and find out if you have, or do not have, a problem with the tank.

2 if there is a problem with the tank....fix it.


3- if there is no problem with the tank, then there IS a problem with the petcock. There are two options A-fix it B-replace it

4- If you have fuel flow when the petcock is set to any position except PRIme, then there is a problem with the petcock. Same options as at 3-

5-Gas is leaking from the tubes while sitting overnight/ 9 hours. Ergo, there is a problem with the needle valves in the carbs. They are NOT supposed to leak. Fix them.


Report back, Grasshopper, when the above are completed, and we shall endeavour to address any further problems.
Best wishes.

 

[earlfor]

Well Ron, You can lead a horse to water...............

BTW, I have a vibration at about 4500/5000 rpm that shakes my mirrors and the bike chortles and backfires. It appears to be related to the chile I had for lunch. Ideas?

Earl

Report back, Grasshopper, when the above are completed, and we shall endeavour to address any further problems.
Best wishes.

 

[Bill + Karen]

Well Ron, You can lead a horse to water...............

BTW, I have a vibration at about 4500/5000 rpm that shakes my mirrors and the bike chortles and backfires. It appears to be related to the chile I had for lunch. Ideas?

May I suggest some sort of cork or stopper as your exhaust may be flowing a little to freely. 8O If you don't restrict the flow somehow, you may have to rejet (or are you already jetting?) :lol: Safe Riding, Bill

 

[earlfor]

LMAO

Earl



May I suggest some sort of cork or stopper as your exhaust may be flowing a little to freely. If
you don't restrict the flow somehow, you may have to rejet (or are you already jetting?) Safe
Riding, Bill

 

[argonsagas]

[quote="May I suggest some sort of cork or stopper as your exhaust may be flowing a little to freely. 8O If you don't restrict the flow somehow, you may have to rejet (or are you already jetting?) :lol: Safe Riding, Bill

With Earl's history of parachute drops, let's hope he doesn't develop a jet stream :twisted:


If the luncheon chiles have not yet worn off, this is the season, at least in my area, for Highland festivals.....perhaps we could put you in a Scottish Caber dance.....but stay away from the Highland fling.

Oh' yes, the vibes.....have you considered a jazz group??

Alternatively, I would pull the carbs off and look at the butterflies ...no not the tummy ones, the carb ones (but bee really careful, especially after those chiles). I've had a similar problem and finally pulled them off a couple of days ago....#3 was out of synch and pulling too hard no matter what I did with the adjuster screws and synch tool.

Thought for sure it was a needle valve not setting properly, but with the carb bank sitting on the pad in front of me I could see #3 butterfly valve was just a bit off. I considered replacing the butterfly (I have a spare set of carbs) but instead opened all the screws. Backed off the idle screw until it was free from contact, then adjusted # 4 screw until 3 butterfly was closed.

Vibration is gone, and engine purrs nicely, but I have lost most of the power. Adjusting the choke setting at mid-range makes it pull better, but there simply is no top end at all. Definitely a mixture problem.

I just pulled out the air filter and its partly gone, so I have too much air. An OEM part was on back order for months, and a mechanic made one for me, a few months ago, but it has partly disentegrated.

Off to get the stuff right now. and will fake my own.

Good luck with yours.

 

[argonsagas]

Follow-up
The new filter material worked. (Not what I wanted, but it is better than nothing) Mixture now turned back to lean and got all the rpm's back. Smmooooth as kitten's purr at the low end, growwls at the upper.

No white horses nearby, but I heard there was a diesel Chevette that's new in town...also a shaft drive and about the same vintage as my GS. Gonna search it out and have me some serious competition.....

Earl: Hope you have the same luck.

 

[Anonymous]

Alright guys, I give! I bought a 5 gal gas can tonight and I'm gonna' pull the tank and drain it on Monday. Will any small inline fuel filter work for my purposes, or is there a specific one that I should get? Hopefully there's no rust in the tank and everything is just gunked up from the bike being 25 years old. Anyway, I'll do everything that you told me, including cleaning up the fuel valve.

About the carbs, I'm a little leery of tearing them apart, will a cleaning spray solve the problem or should I take it all apart and dip them? I have the Clymer manual for the bike, but I haven't had time to read through the carb section yet.

Thanks again for all of your help!

 

[argonsagas]

Alright guys, I give!

About the carbs, I'm a little leery of tearing them apart, will a cleaning spray solve the problem or should I take it all apart and dip them? I have the Clymer manual for the bike, but I haven't had time to read through the carb section yet.

Thanks again for all of your help!

So, you're a little Leery, are ye? Apologies to ye, lad. How could I have missed the Irish brogue??


First....the tank.....get a large clean container, such as a plastic tub, and have it ready for when you swish the tank. I do understand the confusion you face, but you don't have to look swish in the Irish manner, you only need to swirl a pint of gas around the tank before you dump it in the container.


If the dumped gas has a lot of rust, you may have your problem fully identified.
If it is rust-free (and who charges for rust anyway?? I am sure it is free in most areas) then you have a petcock problem.

 

[earlfor]

Well Ron, oddly, I did. Spent the day retuning the carbs to a little richer setup. (I seem to get a bit more power, its smoother, and it revs nicer) Anyway, was out for a test ride on the interstate, checking out the "roll on" at 85 mph or so and had noticed the unusual vibration was still there around 60. Well, turns out it was a baffle in the right muffler that had worked loose and at a particular rpm and resonance, it vibrated. 85 mph apparently was enough to blow it completely loose and heh heh heh...no more vibration. Oh yeah, I'm happy with the carbs now. Priscilla thinks she's an 1150 now instead of a 750. I figure my gas milage will drop about 5 mpg, but I dont care. She runs faster and cooler now.

Earl

[quote="argonsagas"

Earl: Hope you have the same luck. [/quote]