1982 GS450T T Losing half power during ride - coil issue?

[Guest]

I apologize...I've searched the forums & couldn't find the same issue....so a new post it is.

I was gonna do a long backstory, but I figured I'd just cut to the chase:

My bike was running good...not great...but good. Had a stumble at 4k RPM, but I could take in on an 80 mile freeway ride & it would hang in there fine.

I'm in San Diego...it's been colder/wet the last few months, so wasn't riding much....did start the bike up every weekend or so....to keep things loose.

About a month or so ago I took the bike out for a ride....it was running as usual....when I got about 4 miles out & it felt like it lost half it's power. It stumbled, kicked and jerked....then the next thing I know I had to keep the throttle pretty much wide open to maintain any speed.

At full throttle, I was maxed out at 4k RPM's....and top speed was only about 40/50mph. I limped back home....pretty much throttle wide open....and then I would get an occassional BURST of power. Like I said, it was kicking and jerking...half power...then full power...then back to half power (mainly half power).

It essentially feels like it's running on one cylinder.


First I thought it was a fuel thing....maybe with all the sitting around, a passage in one of the carbs got blocked/partially blocked....occassionally letting some extra fuel by which bumped the power back up....I don't know.

I'm not an expert with carbs.....I took them off...cleaned them, but not a full rebuild....dialed them in best I could.....Nothing seemed stuck or clogged.

Took the bike back out (the weekend).....ran great....got farther....then it happens again.......Back to the half power, throttle pegged, 4k RPM max, 50mph max.....with the occassional 'kick' of power. Limped back home.

Alright, maybe it's the spark. I get home....it's barely idling....I pull the left hand plug and....nothing. Has no effect. Hmmm, ok....maybe it's not getting spark. I put the left plug back....still no effect...I pull the RIGHT side, and it dies.

Now I think it's the LEFT side isn't firing...or is intermittant (because of the occassional power 'kick') . I start it up....see if I get any spark or hear any clicking at the LEFT plug....sounds like sparking. Honestly, as of right now, I forget what I did next....but I decided to pull the plugs.

I pull the plugs & I find that they're slightly different....one plug is an NGK B8ES.....the other one is an NGK-R BR9ES. I look it up...the BR9 is not for my bike & has a less hot spark. I think maybe the less hot spark is allowing the plug to foul, and the firing is sporadic. Nevertheless, I buy 2 new spark plugs and install them.


After instaling the new plugs, the bike seems to be running great....I take it out for a run.....about 12-15 miles.....the problem seems to have been solved.


YESTERDAY, I take the bike out....thinking it's all good.....it's ripping along....powerful, just kicking butt. I get out about 20-15 miles....zipping along WHEN....the dreaded stumble, then feeling of half power....full throttle is getting me 4k RPM & only about 40/50MPH. The problem is back.

It literally feels like it's only running on one cylinder. I again got the occassional burst of power....herky jerky....but for the most part for the 25 miles I limped back home, it was full throttle to maintain 50mph max.


I get back....it's barely idling at the house....I pull the LEFT spark plug wire, it dies. At the end of the day, the plug wire seems to have spark on & off.....SEEMS.

I check the coils resistance...they both seem to be within spec....4 ohms on the primaries....25k on the secondaries. They're both getting just shy of 12VDC on one terminal....6.5/7VDC on the other terminal. The manual says that the resistance between the two lead connections of the Signal Generating unit (brown & green wire) should read between 60-80 ohms....I'm reading 136 ohms.

I'm kind of at a loss for the moment......Because it's intermittant, I'm not sure what's what. So I guess I had a few main questions:

1) Anyone have a situation like this....lose half power, max RPM 4k at full throttle? Fits & starts? Anything like this?

2) Is this the behavior of a coil that is going bad? If the resistance measurments read good, could it still be flakey?

3) The spark plug boots.....just holding them I can feel them tingling in my hand while it's running....both sides....Am I losing spark because they're old? Should I get new boots?

4) The RIGHT side coil had the orange/white wire to the positive terminal....the LEFT side (suspect side) had the orange/white wire to the NEGATIVE terminal. The Orange/White wires are shared...shouldn't they both go to the positive terminal on BOTH coils?

5) I guess lastly, does any GS guru's live in San Diego...ha! I'm stumped.


Like I said, yesterday for 25 miles the thing was ripping along...full power....then bang, limping on half power. I'm convinced that one of the cylinders is not getting power...I think it's spark related, but maybe it's still a fuel/carb thing.


I'm frustrated.....has anyone expienced this? I'm afraid to go too far because it's like it just comes out of nowhere. It does not inspire confidence.

Any help would be greatly appreciated.

[tom203]

Wow, long posting ! Sure sounds like you are running on one cylinder after a while, but why?
The orange/white wire should go to plus side on both coils- the ignitor "grounds" out the ignition coils-at least that's what it was designed to do, so I'm surprised it worked at all. You could have a bad ignitor that doesn't like getting hot causing left side not to fire. There was a recent poster that opened his ignitor up and found loose connection and resoldered with success.

[rogue1313]

Long post, I know....tried to whittle it down as much as possible...but kinda need the back story to get a feeling for what's going on.

Something getting hot....that's kind of where I'm at in my thinking as well....BUT, when it first started a month or so ago, I really only got 4 miles or so from the house before it started.

After changing the spark plugs a couple weeks ago....it ran normal for 12-15 miles worth of test runs......Then yesterday I got in 25/30 miles or more in, before it started.

I ordered a couple used coils....even though mine seem to test out ok, maybe it is when one gets hot? Guess I'll try an Igniter too.

I'm hoping someone else has experienced something like this....PLEASE let me know...any suggestions are welcome.

[davegs850]

good luck

Im not much of a mechanic but that sounds a lot like my ride home after cdi failed. Im sure these guys will help you sort it out

[rogue1313]

Dave-

Well, not that I'm glad you had to deal with it....but it's good to hear someone had a somewhat similar situation.

The first time it happened I wasn't sure what was going on....like I said in my post, I thought it was a gas/carb issue....but now I'm pretty confident that that's not the case.

It does seem like an electronic component that's getting flakey & on it's way out....but which one is it? CDI? Coil? 30+ year old wiring? I hate electrical problems....they're the worst.

But I think I'm on the right track. But again.....anyone who reads this and has experienced something similar, PLEASE let me know.


I should get the replacement parts this week....so I'll update more next weekend (hopefully). It sucks, I can ride it....it's just a 'when' situation riding around...I hate that....takes the fun out of it....worrying the whole time.

[tom203]

Rogue1313 said...."worrying the whole time"

Yes, you want the bike running well, so you can focus on the road. An ignition coil could heat up and behave erratically, but it's more likely in the electronics of the box-

[pete]

I hate to say it but that sounds *exactly* like what I found when my Dynatek was failing on the right module.

It would run great and then suddenly cut to one cylinder. At first it only did it while hot but then would come good for apparently no reason.

I had to ride all the way home on one cylinder one day... that was a shockingly painful trip home. Stopped to check the post box, and then it fired straight up on two cylinders.

I even went as far as re-wiring the mini harness I made to hook the Dynatek up and it seemed to fix it for a day or two then it happened again.

Finally the right module quit altogether and I was able to prove once and for all that was the issue. I bought a replacement and all is now good.

It sounds to me like you've covered everything else off so I suspect a dodgy ignitor is your enemy.

Oh, when checking the signal generator, green to black and brown to black should be 60 - 80 ohms. Green to brown will be 120 - 160 ohms as you're measuring across both the pickup coils like that.

Unfortunately the ignitor module on our 450's is potted so you can't easily pull the cover off and attempt to repair it, you need to "un pot" it first in acetone or something like that, and if you manage not to damage it further by doing this you might be able to figure what part of the circuit is kaput.

I used a heat gun to melt off the potting on mine and effectively destroyed too many of the components to even contemplate trying to repair it which is why I went down the Dynatek path instead.

[barnbiketom]

4) The RIGHT side coil had the orange/white wire to the positive terminal....the LEFT side (suspect side) had the orange/white wire to the NEGATIVE terminal. The Orange/White wires are shared...shouldn't they both go to the positive terminal on BOTH coils?

.

Fix this first.
The ignitor might not like that..

[pete]

Good pick up Tom, the ignitor won't like that at all! I missed that completely when reading through...

[barnbiketom]

I dunno if it makes a difference, but it sure doesn't hurt to have everything right!


i've had so many bikes come in, and so much stuff wrong, they had to have gone through 10 people to screw up so many different things on one bike!

I usually go through the obvious visually first, then a little logic based diagnosis will tell me what direction.

of course it's always MY BIKES hat throw me for a loop hahaha

[rogue1313]

Thanks for all the feedback....sorry for taking some time, I gotta set this up so I get an email when I get a response.

Well, I'm waiting on some 'new' (used off of Ebay) coils & an ignitor (hopefully they're good).....Should have the parts by the end of the week, then we'll go from there.

I'm fairly confident I'm on the right track.....keep my fingers crossed. The hard part is that everything so far seems to measure OK, so it's hard to tell. And the problem seems to take a while to arise, so I don't think my mind will be completely eased unless I can pull off 50 miles with no issues......Guess I'll keep a spare coil on me

As far as the crossed wiring on the coil.....the guy I bought it from thought the bike had a charging issue, so I'm guess he fooled with it. I checked the output and all that, but never really looked closely at the coil wires.....Maybe being hooked up wrong finally took it's toll and killed it or the igniter?

Anyway, I hope I can sort it out.....I love this little bike....It's turned out to be way more fun than I anticipated. And after taking the time to dial in the carbs a little (not that I'm an expert), it was REALLY ripping along there last weekend...until the dreaded 25 mile limp on one slug back home. It's amazing how quickly the fun can be sucked out of it...and turned into 'just a few more miles, c'mon...'.

Thanks fellas....I'll keep ya posted on the results.....and still, any other suggestions are always appreciated.

[pete]

Cool... although if the PO suspects it had a charging issue, it probably does!

These beasts are notorious for it.

While you're waiting for the parts, you should be able to go through the stator papers in the garage section of the main GS Resources web page.

Do it and make sure your charging system is good.

I have a strong suspicion going by the number of faulty 450 ignitors that our dodgy charging systems are a big contributor to the failure rate.

[rogue1313]

I'm pretty confident the charging system is good (enough). The PO bought it as a project & never really took the time to clean it up & deal with loose connections. he said even with a new battery, after only a ride around the neighborhood, it would be dead the next day. Once I degreased everything, tightened connections, and added a few new wires....it worked fine for me.

I mean over the past 8 months I've owned it, it's never died on me....If it wasn't charging the battery, I would have been stranded on the side of the road a long time ago. Like I said, it did a couple 80 mile round trips without issue.

It doesn't charge like a beast....gets a little over 13VDC at the battery...but from what I understand, that's not all that uncommon....just the nature of the charging system.

I'm fairly certain it's just the spark is cutting out....so hopefully the 'new' parts will solve it. Got them in the mail today, so will give them a shot on Saturday & see what happens.

[pete]

Good luck, but do yourself a favour and still give the charging system a thorough going over.

Undercharging is one thing, but the killer for the ignitor is going to be overcharging when the R/R starts failing. I don't think they like 17 or 18 volts for an extended period of time...

Of course definitely get her running right first

[rogue1313]

***UPDATE***

Well, last weekend I did some more checking/troubleshooting:

+Static tests on the Rectifier seemed to reveal that it's doing OK; the diodes & resistance readings checked out

+compared my original Ignitor to the 'new' used one I bought...static testing (resistance readings) all seemed to match between the old & new. I know that that probably doesn't mean much, but at least they seemed to measure the same.....so I think the original one is OK.

+Re-checked the AC output for each of the three lines coming off the generator & they still seemed to be OK.....each line got up to just about 70VAC....not a powerhouse, but at least they all measured the same.....there wasn't a dead line or anything.

+Re-checked & tightened various electrical connections....made sure all the contacts are good & tight

+Decided to run a second GROUND WIRE from the Ignitor & the Rectifier....just to make sure everybody was getting a good ground

So with everything seeming to measure good & having all the connections secured, it was down to the suspect coil......The suspect coil still seemed to be within spec with regard to the static resistance checks, BUT not knowing where else to go with it, I decided to just replace the suspect coil with one of the 'new' used ones I got off Ebay.

All that being done, I took the little beast out for a 40+ mile ride last weekend....and didn't have any issues. Took it out again today for another 30 mile trip & still seems to be working fine.

So where does that leave things? I'm still holding my breath that one of the things I did fixed/helped.....guess only time will tell. Nothing really seemed to be out of whack with the measurements, so I'm really not sure where exactly the fault was, but so far so good (knock on wood).

I wish I had found a definite 'bad' part, but what can you do......I'll just keep riding & keep my fingers crossed.

Thanks for all the advice......I'll keep posting updates as I go along.......And again, if anyone comes across this post & has had a similar problem, or has an idea of what's going on.....more advice is always appreciated.

Thanks again everybody.