1980 GS 450 BOGGING, LOSING POWER, MAKING LOW RUMBLE and STALLING

[Guest]

My 1980 Suzuki GS 450 is losing power AGAIN! It makes this low rumble, loses power, bogs down. Then suddenly it will regain throttle just to lose it again.

Second time this summer it happened. First time it was 3rd gear when it would happen.

This time it happens when shifting into 6th and going fast. Now its only a matter of time till it don't run at all like before.

First time it happened I took it to the shop. The guy cleaned everything and said he could not id problem. He did fix the right exhaust that was not firing or getting hot, not emitting gasses. But I think I did that goofing around with the spark plugs trying to diagnose the problem before contacting him. But when he gave it back it ran.

He thought it might be moisture, so I switched gas and used seafoam. Actually I was using it, seafoam, before I took it to him.

But I remember when the problem started the first time.

I let the bike warm up, and took it out and gunned it immediately,trying to get up to speed on hi way....... and then the problems started.

Guy says bike is cold blooded....but I give it long enough to warm up...but it still takes miles for full capability.

If I go too hard before then could that be the cause of problems? Or could it be the result on riding over bumpy construction patch road?

Because this time when the bog started I was on this street in my town that is all patched up from construction. And when I went over the bumps I heard the engine bog a bit.....and now a few weeks later the thing is bogging like the first time.


Bike is NOT STOCK. Airbox has been taken out, and Kawasaki front forks.


Here is a photo

[Nessism]

When was your last valve adjustment?

Were the carbs rejetted for the pod air filters?

[pete]

Those symptoms sounds similar to what was happening to me when the right cylinder Dynatek module was failing.

Loss of power, sounds completely different, and stalled at idle purely due to it running on one cylinder instead of two. Took me ages to fault find it and I only found it because the module finally failed altogether and I couldn't get spark on the right cylinder at all.

So, it could be spark plugs, spark plug lead, spark plug cap on the end of the lead, coil, ignitor, or simply an electrical connection to the coil or ignitor.

Actually you say it's a 1980... points or electronic ignition? If it's points then it could be the points themselves or the condensor on one coil too...

When it happens, is one spark plug wet indicating unburnt fuel? Is one pipe warm or cool rather than hot?

[William P. Guff]

Thanks for the help

Those symptoms sounds similar to what was happening to me when the right cylinder Dynatek module was failing.

Loss of power, sounds completely different, and stalled at idle purely due to it running on one cylinder instead of two. Took me ages to fault find it and I only found it because the module finally failed altogether and I couldn't get spark on the right cylinder at all.

So, it could be spark plugs, spark plug lead, spark plug cap on the end of the lead, coil, ignitor, or simply an electrical connection to the coil or ignitor.

Actually you say it's a 1980... points or electronic ignition? If it's points then it could be the points themselves or the condensor on one coil too...

When it happens, is one spark plug wet indicating unburnt fuel? Is one pipe warm or cool rather than hot?

It's a push button start. So I guess its electric. If you cant tell, im not exactly a mechanic.

But earlier in the summer, the first time it did this, it was the right pipe that wasn't getting hot. The mechanic fixed this, but said he could not ID the source of the loss of power, loud deep rumble, bogging, and stalling.

He cleaned the carbs and tank, I think, and all was fine. Rode for weeks, about 400 miles or so .Then one day after a regular warm up, I got on the hi way and tried to get up to 40-50 mph fast, cuz I was in a hurry. But this bike is notorious for deciding it doesn't want to pick up speed until much later.

But when the bike finally gets hot it runs great. And It makes you feel unstoppable at times.

So I'm just thinking my impatience may be causing this. And perhaps my bike simply needs a much longer warm up period before really pushing it. But still I would like to know exactly what the problem is.

Also I felt problems after going over about a half mile of bumpy patched road. So I'm not sure what was affected. But I'm convinced that made a major contribution to the problem.

I'll check the pipes today though to see if that cylinder problem has returned. I never thought to check it as I usually just park it and call the mechanic.

Thanks for the help, though. I really appreciate it.

[William P. Guff]

When was your last valve adjustment?

Were the carbs rejetted for the pod air filters?

The mech I take it to gives it a full tune up over the winter. When the problem happened the first time he told me all the basic tune up stuff had been done. He is the one who put on new air filters and such.

I did ask him roughly the same question, and he suggested that the work shouldn't need re done because he did a thorough tune up. I'll ask him again though. Thanks!

[lemonshindig]

The mech I take it to gives it a full tune up over the winter. When the problem happened the first time he told me all the basic tune up stuff had been done. He is the one who put on new air filters and such.

I did ask him roughly the same question, and he suggested that the work shouldn't need re done because he did a thorough tune up. I'll ask him again though. Thanks!

Well his definition of "basic tune up stuff" might be different than ours. Ask if the valves have been adjusted, and if the carbs were rejetted for the pod filters. Ask about these two items specifically, because he may or may not be including them when he says "basic tune up."

If the valves WERE adjusted last winter, and the carbs were correctly jetted at that time, then neither of those is your issue now.

Could be a vacuum leak.

[pete]

When I asked about electronic ignition, I'm referring to how it generates the sparks rather than how it starts.

If it's electronic ignition, then under the left side cover on the plate with all the other components like your starter relay, main fuse, and regulator/rectifier there will also be a black box which is the ignitor.

If you don't have this, then instead under the timing cover (which is the round cover with the Suzuki emblem on it on the right side of the engine) you will see a set of points.

On BassCliff's site there is a link to the Clymer manual and this lists specific tests to check the ignitor out.

Also, have you checked your charging system out properly? The ignitor on these is notorious for failing, and a dodgy charging system that is over charging will exacerbate this.

[pete]

But when the bike finally gets hot it runs great. And It makes you feel unstoppable at times.

So I'm just thinking my impatience may be causing this. And perhaps my bike simply needs a much longer warm up period before really pushing it. But still I would like to know exactly what the problem is.

Forgot to answer this...

I start mine on the choke and let it run while I put my gear on, then I close the choke, roll out the driveway and get going.

By the end of my street (about 50 metres) the bike's not hot but is warm enough to be running reasonably properly.

About another 400 metres and I'm turning onto the main road on the way to work and it's pretty much up to full speed ready to go.

Unless you're starting your bike and instantly on the highway, I don't think you're impatient as such...

It really needs another few minutes to get up to proper running temperature, but that's not going to give you any of these symptoms due to being too cold.

[William P. Guff]

Troubleshooting

Well I tried troubleshooting today. I started the bike on choke for a minute. Then went to half choke for another.

I touched the pipes and let it run till they both were hot to the touch. And both of the pipes were emitting hot exhaust.

I then rode it on a 5 block loop, and everything was fine. It was definitely warmed up.

I then took it out to the hi way in front of my place and began to bring it up to fast speed. And as soon as I got to 5th gear the deep BRUUUUGHHH, and loss of THROTTLE.

I kicked it back down in gear to 4-3 and throttle returned to normal. But that's only a temporary impeding of the inevitable. And only a brief return to normalcy.

I know for sure that shifting to 5th and 6th ,to go fast, starts the whole debacle.

But earlier in the summer it was in 3rd gear that the bike preferred pull this stunt.

Then, like before, suddenly it will go back to normal, like something is BLOCKING THROTTLE or gas flow. But it cant be throttle cable related. But it is not the fuel filter either because you could see if it was blocked.

And when it happens Ill have the throttle pulled the whole way back but barely move, with the deep BRRRUUUUUHH blaring.

But, again, throttle will suddenly go back to normal briefly. So obviously there is a blockage somewhere. Something related to fuel and throttle.

I don't think it to be electric because all electric systems work.

[William P. Guff]

Gs 1000s

When was your last valve adjustment?

Were the carbs rejetted for the pod air filters?

I looked at your photo bucket page and saw the GS 1000s. I recall reading an article about that bike in Cycle World last year. From what I remember they were supposed to be really rare bikes with only a few examples available going for 10K a piece.

And you have 2 of them?

Of course my memory of the article may be clouded. But I recognized the bike right away. You might want to check Cycle World from 2012-2013 and see if you can find the article.

[skreemer]

did you seal the vents for your gas tank?

[William P. Guff]

Bhhhhuuuurrrggghhh

did you seal the vents for your gas tank?

I'm not sure if they were or not. Ill ask my mechanic.

But honestly I thought this might be some problem that someone would have heard of by now on a 30+ year old bike.

I guess I'm spoiled by the rapid info attaining internet age, maybe im expecting too much. But surely I thought somebody might be able to recognize the specific low grumble sound that I was describing and be able to say "oh thats the such and such".

I appreciate the help though. Im not a mechanic. And as far as I am concerned being a mechanic is just as prestigious as being a doctor.

These are complicated machines. And I do have a Clymer manual. And when I opened it and saw all the stuff, I just wanted to close it and set it right back down on the table.

There was no way I was going to even try to fix the bike myself.

Although last year I did identify a regulator rectifier problem last year by looking at the internet and referencing the Clymer. I then promptly referred the matter to my mechanic, cuz I wasn't doing jack.

I couldn't even loose the one screw because it was so tight and rusted to the point of being fused.

But again how many things could cause that sound ,(BRRGGGHHHHUUH), and instant, but fleeting, loss of throttle?

[pete]

Hmmm your initial description of the symptoms definitely sounded like mine on one cylinder, but the further descriptions make it sound less like that now...

When it starts happening, have you tried popping your fuel cap off to see if that fixes it?

What Skreemer is saying is that if there is no vent for the fuel tank, as it starts using the fuel it needs to replace the volume with air. If that can't happen, then the fuel stops flowing because it essentially creates a vacuum that holds the fuel in the fuel tank, just like if you try to pour water out of a container that has no vent in it...

[tom203]

I see the Champion decal- what kind/brand of spark plugs are you running?

[Gorminrider]

But again how many things could cause that sound ,(BRRGGGHHHHUUH), and instant, but fleeting, loss of throttle?
lots of things can cause that. Lots and lots. I think the folks here doing a great job of blasting the birds out of the air, but somebody- you or your mechanic-has to start plucking them sooner or later.
Intermittent problems are hard to pinpoint, but your description sounds like something is sticking and then gearing down or hitting a bump loosens it...floatneedle,floats,vacuum slides, an electrical contact, a vapour lock at the tank...I bet your mechanic groans when you show up. What are you going to do? give him/her ideas? so Try to narrow the symptom down .Stop when it BRGHHS and have a real good look at the stuff you can handle. Try to make it consistently repeatable -trap the problem.Just wiggle one thing, one wire or tap the carbs only. don'tgeardown wiggle,tap,goose the throttle...just do one thing and see...and yes,another good one-swap the plugs. NGK are good.