1980 GS550E maiden ride, stalls no spark

[jasper]

K - need some help here.

I bought a 1980 GS550 that ran ok, except when it got hot it bogged nd stalled.

I joined this forum, read the mega welcome and promptly dipped the carbs, replaced the o-rings (intake boots too) gapped all the valves to 0.003 (they were really tight before that) and checked that the petcock flowed when vacuum was applied (using hand held vacuum pump).

Today I went for my maiden ride.

Besides some trouble getting the idle to drop back down, it ran ok (but not great) until it got hot when it started bogging and stalling. First time it stalled I got it started again, but it finally stalled for good and would not restart an hour ago.

I verified fuel flow through the petcock. Then I pulled a spark plug boot, stuck a screwdriver in and brought it a couple mm from the cylinder fin and again from the top of the plug. No spark at all.

So I'm guessing it's electrical since the carbs are fresh and I have fuel flow and that it ran before it stalled and I didn't even look at the elex during this little rebuild session of mine.

I want to check the voltage to the coils...can someone point me to the procedure. I will do the coil relay mod, but as has been advised, it's better to fix the root problem first.

Since there's no spark at all is there a chance that it's simply a fuse?

Thanks guys.

[cowboyup3371]

How many turns out are your mixture screws? If the idle isn't coming back down very well then you have some sort of vacuum leak some place. Have you gone through the stator papers and checked all of your connections as well?

[jasper]

Thanks Cowboy.

I agree I might have a vacuum leak, but I installed all new o-rings including the intake boots. I know my airbox seals are just crap, and the boots onto the carb inlets are no good either. That's where I'll look once the bike is running again.

The mixture sscrews are 2-3/4 turns out in answer to your question..

I'm not *so* concerned about the idle speed issue right now though...my spark is the priority.

Stator papers ....back to Bass Cliffs site I assume?

[cowboyup3371]

Did you seal the air box?

Cliff's site as well as the "In The Garage" section on the forum main page. You have a multimeter I assume?

[jasper]

I did not seal the airbox...I will get to that. My problem is spark at the moment. Unless you think the airbox seal is somehow causing the stall and non start? Seems unilkely to me. I could see this causing rough running or goofy idle, but my problem is that it won't run at all and I don't see a spark.

I read the stator paper, but it apears to concern the charging system. My battery has enough juice to crank the engine long and hard, so I'm assuming for the moment that the charging system is ok and that my battery is providing enough voltage.

I do indeed have a multi meter, and I will be applying it to my motor bike just as soon as my good buddy brings his pickup truck so we can get the bike from where I left it parked at the side of the road.

The question is, given my symptoms, what shall I test first?

Reading so far, I realize I tested for spark on #1 and #4, which fire off the same coil. I also know that a coil was replaced on this bike before I got it....

My first order of business will be to test the coils I think. The service manual gives me some resistances across the big and small windings, but I think the power to the coils is often flaky with these bikes???

What I'm looking for is a bit of guidance on where to start, what to check.

Cheers.

[jasper]

OK update...

Got the bike inside and did a more fullsome test for spark.

Pulled #4 plug, touched the -ve electrode to the head, cranked it and got what I would consider a weak spark. Very small and orange.

Pulled the #3 wire, did the same thing and got the same weak-ass spark.

I noted that the #4 plug was dry and tan coloured. OK about four hours after it last ran, but it wasn't black or wet at all.

So the good news is my ignitor isn't fried. Bad news is that I can't really rule out a lack of fuel flow.

I don't have the bike at my place unfortunately, so can't work tonight on it anymore.

Tomorrow I will check the voltage at the coils, pick up the coil relay mod parts and try to get that done. I'd like to rebuild my petcock too but the bike ran long enough for me to believe that fuel is flowing, plus I did check it for operation with a vacuum pump *and* I saw fuel in the see through fuel filter.

Did I mention the bike looks like it was parked outside it's whole life?

I must check and clean every single connection including the ground too.

[cowboyup3371]

Two things...you may not want to rebuild the petcock as many have had subsequent issues. Two, do a search on here about external fuel filters - they are more trouble than they are worth as they will actually restrict fuel. The filter in your petcock is all you really need.

[jasper]

Thanks for that advice. I actually believe the petcock is ok, but maybe just maybe the vacuum to it is intermittent.

As I understand it the failure mode is a torn diaphragm and this leads to it not closing properly. That isn't my problem.

External filter wise. The hose from the carbs has a clear plastic capsule with a steel frit inside. I assumed this was standard GS equipment...is it not? Maybe removing this filter would help me troubleshoot.

I don't recall the drawings of the petcocks I have seen showing an internal filter though...maybe I shoudl look again but more closely.

On the topic of petcocks (here in the elec forum) mine has two positions only. RES and ON. I see that some petcocks have a PRIME position. Which is more common?

Thanks

[cowboyup3371]

I don't know if yours is the dreaded 1980 petcock I've read about so I'll let someone else speak up about it.

But the long tube that slides into your tank is the filter. That external filter IS NOT OEM equipment and put there because someone just "thought" they needed it. You won't hurt much if you remove it.

[jasper]

Yes of course - the long wire mesh tube that goes up in to the tank would be a filter wouldn't it.

I'll remove the fritted external filter. It may well be impeding the flow of fuel.

Good tip, thanks.

Any idea what the diameter of that fuel line is? I'll have to either union the two short line together or replace them with one long line.

Back to spark.....I have the bits for the coil relay mod in hand now also. I will make my measurement tonight before and after I make the mod and post the data and performance afterwards.

[jasper]

OK Cowboy - looks like it's just you and me.

First thing I did was check the voltage across the battery. 12.8 V
Than I checked at the coils 12.6 V and 12.2 V. I did not take the time to install the relay mod because of this.

Then I cleaned as many of the grounds I could get to. I got all of them except the big ones because they were not accessible. Namely, the one on the crankcase under the carbs and the one that grounds the ignitor by where the back fender meets the frame.

Checked my spark and it still looks weak weak weak.

I then removed the in line fuel filter, replaced it with piece of brass barbed at either end. I also checked the petcock with a hand help vacuum pump. It flows with no problem at all.

I primed the carb bowls with my hand pump..because my petcock only has two positions..and started the bike but it barely idled and would not take any throttle at all.

I'm sure I have fuel flow, and I'm thinking it's spark...but I've been wrong before. I'm expecting to see a nice bright blue snappy spark when I remove the plug and ground the negative electrode. Am I expecting too much?

I checked the primary coil resistance - 4 and 5 ohms for each coil. I could not figure out how to test the secondary coil resistance though (pardon my ignorance). I tried testing from one of the high tension leads to ground and got nothing. Am I doing this right?

The ignitor is really hard to get to. Would a bad ground or other fault cause a weak spark, or no spark?

So, I'm a bit stumped I'm afraid. Any words of wisdom?

[cowboyup3371]

You measured the 12.8v while the key was off? What was it when the key was on? While cranking? Do a search on here for the ignitor and how to test it. Lots of people have had issues with them but I can't tell you how to test for it since I'm still a newbie at electrical stuff.

[Steve]

OK, I'll chime in, too.

As I understand it the failure mode is a torn diaphragm and this leads to it not closing properly. That isn't my problem.

That is one failure mode, but not all of them.

Actually a torn diaphragm would prevent it from opening, as there is a spring that pushes it closed.
A torn diaphragm can also allow fuel to bypass the shut-off mechanism and dump fuel down the vacuum tube into the #2 intake tube.

External filter wise. The hose from the carbs has a clear plastic capsule with a steel frit inside. I assumed this was standard GS equipment...is it not? Maybe removing this filter would help me troubleshoot.

As Cowboy has already mentioned, it is NOT standard equipment.

The basic problem with most external filters is that guys will just go to Auto Zone or Wal-Mart and grab one that is designed for a car. Cars have fuel pumps that will push the gas through a rather restrictive filter element, our only "pump" is gravity. The only way to add gravitational "pressure" is to raise the tank. If you really do insist on having an external filter, get one designed for a lawn tractor, most of them are also gravity-fed.

On the topic of petcocks (here in the elec forum) mine has two positions only. RES and ON. I see that some petcocks have a PRIME position. Which is more common?

Thankfully, the ones with a PRIme position are in the majority. In fact, they ALL have a PRIme function.
In fact, some are missing the REServe function, fortunately that is reserved for some of the '80 models.
Oh, you have an '80, don't you?

Are you ABSOLUTELY sure of your two positions? You have the "dreaded '80 petcock". As I recall, it takes a screwdriver to change positions. Your two positions (and I don't remember which is which) are RUN and PRIme, you don't have a REServe.

Any idea what the diameter of that fuel line is? I'll have to either union the two short line together or replace them with one long line.

OEM fuel line is 7mm. You will be hard-pressed to find proper fuel line on the shelf of any store. Even bike shops will likely sell you either 1/4" (6.25mm) or 5/16" (8mm) and it will likely be thicker, reinforced hose for a car. ORDERING the proper hose is the best way. By the way, if you order it from any of the online sites, it looks a bit expensive, but you get about 6 feet of it in the package.

I primed the carb bowls with my hand pump..because my petcock only has two positions. ...

Please check something for me. If you do, indeed, have the "dreaded '80 petcock", it's easy to check which functions you have. As I mentioned, I don't know which position is which, but put a hose on the output of the petcock so will empty into a safe container, and connect the vacuum fitting to your hand pump. Apply a little vacuum, so that fuel flows. Remove the vacuum, see if fuel flow stops. If it does, that is your RUN position. Move the petcock to the other position, apply vacuum to start fuel flow. Remove the vacuum. Does fuel keep flowing? If so, that is your PRIme function. The '80 petcock requires a brief application of vaccum to start the flow, but it will keep flowing until it is turned back to RUN. If the fuel flow does stop, you do, indeed, have a REServe on your petcock.

I could not figure out how to test the secondary coil resistance though (pardon my ignorance). I tried testing from one of the high tension leads to ground and got nothing. Am I doing this right?

No.

Don't you have a manual for your bike? ALL of the manuals have the procedure for checking the secondary resistance.
It's really very simple. Pull the wires off the spark plugs. Measure from the inside of the cap for #1 to the same point on #4. Do this again for 2 & 3. You should be seeing about 30k ohms.

.

[jasper]

Awesome, thanks for kicking in Steve. I need all the help I can get, although I figured out much of what you suggest last night on my own.

Petcock: I set the valve to RUN and applied a bit of vacuum with my hand pump. Fuel flowed easily into my metal pot and kept flowing until I broke the vacuum and then it stopped.

I did not test the RES position since I was happy enough with the behaviour of the valve in the RUN position. I note here that the valve is clearly labelled RES and not PRI so if it's actually a priming petcock then Suzuki was playing some dirty tricks back in 1980.

I took out the in-line filter and replaced it with a brass union - that red herring is now cooked and eaten. Lastly, I used my hand pump to prime the float bowls so I'm sure the carbs had fuel in them when I tried to start it last night.

Coils: I downloaded the service manual from BassCliff and noted all of the tests and expected readings. I didn't get around to most of them though - that's for the next day, but the service manual was not clear on how to test the secondary coil.

Since my post last night I have learned that it should indeed be measured across the two leads (1,4 and 2,3) and I will do that soon too. I also now know to check the resistance of the caps, and to cut a 1/4 inch from the end of the leads, and to check the voltage across the battery during cranking, although the battery is new and there is no indication whatosever that it is not charging so I'm not holding my breath that this is my problem.

SO, I have a weak spark, and I feel like that's my problem, but others on this board have suggested that any spark is good enough...I don't agree but if I am wrong (been known to happen) and spark isn't my problem then WTF is wrong.

Review: When I got the bike it ran ok until it got warm and then it bogged itself dead.

I totally stripped and dipped the carbs, installed new o-rings and bench synched them according to SOP. The carbs looked ok when I had them apart - there was no real bad crud or blockage evident.

I checked the valves, they were all tight, so I installed thinner shims and felt them all to 0.003"

Then I started it up and it ran ok until it got warm and then bogged itself dead.

I kind of have to rule out a fuel problem don't I?

Lastly - I could not reach the main ground wire and the ground wire at the ignitor. I want to address these two before I can rule out a bad ground but they each require significant disassembly (carbs off for the one and rear wheel off for the other). What's up with the goofy grouding on these bikes anyway?

Oh well, time, sweat and skinned knuckles. Riding would be better.