Engine Problems (Not running on all cylinders???)

[Mgriz]

***Bike Description***
'79 GS1000E w/ 600miles on freshly rebuilt engine.
K&N pods
Dynojet Kit
Yoshimura cams and exhaust
Dyna coils and electronic ignition
Brand new boots, orings, wires, plugs, etc.


So I went on a great ride to T.W.O. in Northern Georgia. Its about 50miles of highway and then the fun starts... Anyway, the bike ran well while getting there (highway cruising @ about 80mph) and on the curvy country roads.

But about 5mins after getting back on the highway while cruising at 80 the power would cut in and out. I stopped at the closest turn off to see if anything was obviously wrong with it, but everything appeared fine. When I started it back up it was obviously not running right and it could barely move while I limped it to the nearest gas station. My buddy who was riding behind me said the exhaust smelt heavily of gasoline.

At the gas station I checked all the obvious things, it is certainly getting fuel and all the electrical connections (wired directly to the battery through a relay) for the coils and plugs are fine. I tried brand new plugs and it ran the same, sounds like its missing and has no power at all. I took the pods off the carbs when I give it throttle fuel sprays out of the carbs??? Any idea what would cause it to all of a sudden die when just cruising on the highway?

Any help would be greatly appreciated, as of now it sits behind a gas station 50 or so miles away. Hopefully I can get a truck and go get it tomorrow... Thanks again.

 

[Thomas Kenny]

You might have a stuck float needle or float. Seems unlikely, but it appears you are getting too much gas. How did your plugs look that you pulled???

 

[Mgriz]

3 of the plugs looked rich (which I expected b/c I have the large jets in) and had a slight shininess to them. One looked as if it was rich but was recently lean, everything was sooty black except for the electrode, which was grayish white.

Oh and it did seam like it was sucking gas way too fast. With the tank off and the line (about 8in of tube) filled it would empty the line in like 10seconds when I ran it.... which seams way too fast. You think one float being stuck open would make that much of a difference in power?

 

[Guest]

Is the fuel shooting out of all carbs? Sound like a low battery or a weak spark.

Did you cock the cam chain tensioner correctly so you didn't slip a tooth on the cams?

You don't have the petcock on prime do you?

 

[49er]

What colour were your plugs straight after your engine rebuild?
Check your carbs. Your plug colours and their shinny appearance indicate over rich mixtures. Like you suspect, your main jets are probably to big. I don't think that a float would suddenly stick while riding the bike.
Check the screws on your float bowls, in case one bowl has come loose. When you fitted the main jets, are you sure that you tightend them properly. If not, one may have unscrewed and dropped into the bowl.
If this has happened, you would have seen heaps of black smoke and the motor would have laboured above idle like you said it did.

 

[Mgriz]

Is the fuel shooting out of all carbs? Sound like a low battery or a weak spark.

Did you cock the cam chain tensioner correctly so you didn't slip a tooth on the cams?

You don't have the petcock on prime do you?

Its not shooting out in liquid form, is more of a mist that blows out of each carb. It very well could be weak spark but the battery seamed OK. And in the past it has run just fine w/ a dead battery (after I push stated it...)

I did correctly set up the tensioner, I was very careful about that. Besides when I was up in the mountains I rode it hard w/o problems. Then after maybe 5 miles of just putting around (under 5K rpm) it all of a sudden started intermitenly loosing power, then after I stopped all the power was gone.

The petcock was on run (I have a manual petcock now)

 

[Mgriz]

What colour were your plugs straight after your engine rebuild?
Check your carbs. Your plug colours and their shinny appearance indicate over rich mixtures. Like you suspect, your main jets are probably to big. I don't think that a float would suddenly stick while riding the bike.
Check the screws on your float bowls, in case one bowl has come loose. When you fitted the main jets, are you sure that you tightend them properly. If not, one may have unscrewed and dropped into the bowl.
If this has happened, you would have seen heaps of black smoke and the motor would have laboured above idle like you said it did.

The plugs were black right after my rebuild, I've been putting off really tuning the carbs b/c its been running strong and at least it wasn't lean.

I can't be sure I correctly tightend the main jets but I know that there was not any black smoke when the power was cutting out or thereafter.

Thanks for everyone who has responded, hopefully I'll be able to figure this out. This bike sure has been a handfull since I purchased it... Any other ideas?

 

[Billy Ricks]

Float level is critical to mixture. Check that and go to some leaner mains and see if things get better.

 

[BadBillyB]

If you are using slotted cam sprockets, the cam gears may have slipped....BadBillyB

 

[nabrams]

The bike was running strong for a while and then suddenly went south. So the basic tuning (jet sizes, float height, pods, etc.) was reasonable to begin with. Now, most plugs are really rich. Therefore, that points to the following in the order of the most likely problem:
1. Ignition problem: Did you visually verify spark on all cylinders, with the current plugs?
2. Too much fuel flow (or too little air) for one or more carbs: The usual suspects - leaking floats, main jet came loose, obstructed air filter/pod, etc.
3. Blown head gasket: This would affect one or more cylinders and would lead to greatly decreased performance because of low compression.

I think it's unlikely that it's a valve adjustment issue because the problem was so sudden.

 

[Mgriz]

If you are using slotted cam sprockets, the cam gears may have slipped....BadBillyB

-The cam gears aren't slotted, so at least thats out...

The bike was running strong for a while and then suddenly went south. So the basic tuning (jet sizes, float height, pods, etc.) was reasonable to begin with. Now, most plugs are really rich. Therefore, that points to the following in the order of the most likely problem:
1. Ignition problem: Did you visually verify spark on all cylinders, with the current plugs?
2. Too much fuel flow (or too little air) for one or more carbs: The usual suspects - leaking floats, main jet came loose, obstructed air filter/pod, etc.
3. Blown head gasket: This would affect one or more cylinders and would lead to greatly decreased performance because of low compression.

I think it's unlikely that it's a valve adjustment issue because the problem was so sudden.

1. I did not verify spark to each cylinder, that'll be the first thing I check when I get the bike back home. I need to go through the electrical system. If I have the coils wired directly to the battery, what else would effect the intensity of spark?

2. Thats where Im hoping the problem is, would make the least amount of work for me to fix it... so Im crossing my fingers.

3. I hope not, Ill check the compression...

Thanks again for everyones help.

 

[Guest]

I'm experiencing the same problem with my '81 750L. It's been very rare in the past but has become far more frequent in the past month. It's now happening on every other ride. It'll run strongly for anywhere from 5 minutes to 3 hours and then suddenly act as though it's only running on 3 cylinders. WOT barely keeps you moving at 50MPH. This weekend, my friend said riding behind me made his eyes water. For whatever reason it suddenly starts running pig rich.

It was totally stock when I bought it. So far I've replaced the ignition system (Dyna S pickup & new Dyna coils), spark plugs, floats and inlet valves to no avail. #1 & 2 plugs look a little rich when it's running well and are saturated with fuel when it's bad. #3 and 4 always look perfect. All 4 plugs fire properly at all times so short of a jumped timing chain (which then jumps back?) it has to be something in the fuel system. I'm running out of things to rebuild / replace though.

I feel your pain--it's hard to believe how such a simple setup can be so frustrating.

 

[Beef]

It is funny cause it seems like this is a common problem with GS period... I am working out the same type of issues with my 80 750

I am so suprised no one knows what causes this if the problem is so common

 

[Guest]

Have you guys had any luck with your bikes? I took the lazy approach and bought another set of CV carbs. I'll hopefully have time to drop them in this weekend.

As it sits, the engine won't even fire up now. Ignition and fuel delivery (to the carbs at least) are fine and it's not dumping fuel into the cylinders with the petcock on prime. So much for an easy fix. :evil:

 

[Mgriz]

Have you guys had any luck with your bikes? I took the lazy approach and bought another set of CV carbs. I'll hopefully have time to drop them in this weekend.

As it sits, the engine won't even fire up now. Ignition and fuel delivery (to the carbs at least) are fine and it's not dumping fuel into the cylinders with the petcock on prime. So much for an easy fix. :evil:

No luck yet, I was lucky enough to be able to get the bike back home before I had to fly out to CT. I just got back so I have not had a chance to poke around anymore. When I do I will post what I find in this thread, thanks for everyones assistance so far.

 

[Mgriz]

So I finally mustered up enough motivation to figure out what the problem was... Now i'm just very confused so any help would be appreciated.

Upon further inspection I found that cylinders 1 & 4 were not firing but 3 & 2 were. I checked the coil and its fine, cam timing is good, but my dyna-s was not firing the 1-4 coil correctly or at all... I checked with a multimeter and I'm getting battery voltage to the coil all the time no matter where the magnet is wrt to the 1-4 module. I also checked the 2-3 coil and it appears that the switch module on the dyna-s is working correctly. I'm not really sure whats going on to make one switch work but the other stay open. The dyna-s instructions say that it could be a bad ground on the timing plate or the module is not getting power. But since one is working perfectly the ground must be fine and they both get power from the same source/wire... Any ideas, I suppose the module could be bad but I wasn't able to find any stories of this happening to other people and its only been on the bike for roughly 700 miles. Thanks for any help you can give me.

 

[Guest]

I remember a thread by earlfor saying he had this problem with a dyna-s. He had to send it back and they fixed it. Send him a PM and he'll be happy to fill you in. I'm working on a pretty fouled memory.

 

[Mgriz]

Thanks guys, it was the Dyna-S. Luckily I had an extra dyna-s laying around that the previous owner pulled off a junkyard bike. I threw that on, set the timing and it started right up... Not that I hold anything against the dyna-s but it is kind of ironic that a component I put on the bike to make it more reliable with less maintenance actually stranded me miles from home.

 

[Mgriz]

So I finally got around to moving the bike since putting the old (but working) dyna-s in it. Been busy with a new job and house purchase. Anyway, I got about 2miles down the road and I'm assuming the same thing happened. Lost almost all power, so I limped it back to the apartment and I'll be trailering it to my new home... My questions are

1) What would cause two Dyna-s switches to fail?

2) The battery is kind of weak but that should be effecting this, right? I'm assuming that again its only running on two cylinders b/c one of the magnetic switches is malfunctioning.

I'm loosing my patience with this bike as its starting to look like its never going to be back running at full steam... Any help would be appreciated

 

[49er]

So I finally got around to moving the bike since putting the old (but working) dyna-s in it. Been busy with a new job and house purchase. Anyway, I got about 2miles down the road and I'm assuming the same thing happened. Lost almost all power, so I limped it back to the apartment and I'll be trailering it to my new home... My questions are

1) What would cause two Dyna-s switches to fail?

2) The battery is kind of weak but that should be effecting this, right? I'm assuming that again its only running on two cylinders b/c one of the magnetic switches is malfunctioning.

I'm loosing my patience with this bike as its starting to look like its never going to be back running at full steam... Any help would be appreciated

You could determine if it is the Dyna S by reverting back to the points set up as a trial. That's assuming that you still have them and want to bother re-fitting them.