Gs500 problems...won't start

[cmat1120]

I just bought some new spark plugs so I'll try those first and if they don't help I'll move onto the electronics.

One thing I'm good with is electronics (I am planning on adding a fingerprint scanner based ignition system ). I can definitely test all of the things you suggested. I'll be back with my results.

I actually just looked on ebay and a much newer bike's wiring harness isn't too expensive. The wiring and connections all over my bike are not that great so I wouldn't mind just replacing the whole thing or at least most of it. How new of a bike's wiring harness is compatible with mine? Or how hard would it be to make one compatible?(I am happy to cut and solder wires)

[solac3]

That's how I have always done it.  In fact, I just did it the other day to help out a GS rider who brought his carbs down from Salt Lake City. 

I am that GS rider! Even with the worst math skills and spilling fuel on myself Kerry was able to help me in no time! I think that the idea of keeping things as "Stock" as possible helped me a lot also, so before I go buying new after market parts I would try and get the stock ones, and go from there.

[Kerry: Edited to change "Kenny" to "Kerry".   ]

[Kerry]

How new of a bike's wiring harness is compatible with mine?

Hmmm ... good question.

I believe yours is a pre-'01 model, right?  Mid-90's?  You should be pretty safe with anything up through 2000.  After that it might get a little dicey, but I wouldn't know for sure ... no personal experience with that.

But!  I have a spare wiring harness around here (somewhere) that someone sent me years ago.  Can't remember why I wanted one now; maybe because of those corroded connectors?  Unfortunately, I'm running out of time to be of much help until Saturday evening ... I have to get ready for an overnighter with my Boy Scout troop at 4:00 on Friday.  (As it is, I'll have to take a little time off work tomorrow to get everything done in time.  )

Hang in there!

[cmat1120]

It's a 1990 actually. I'd like to just modify an 09 harness if I can(newer wiring and connectors), but that might be a bit unrealistic. I'll see if there are any fresh looking older ones on ebay.

[cmat1120]

Using the appropriate resistance range on the meter, measure the resistance between a Black/Blue connection and a Brown connection.  Then test between Black/Blue and Green/White.  Both measurements should be between 250 ohms and 420 ohms.  If either of them measures higher than that (or "Infinite") you may need to make your way toward the signal generators one connection at a time until you find the "culprit" wire or connection.  (Hopefully the coils themselves are good!)

I've been "bitten" myself by some corroded connectors in this circuit.  My bike wouldn't start, and I was getting a nice-sized spark, but yellow instead of blue.  Fixing the "at fault" connections got me going again.

I tested those connections and got 2.03k ohms as the resistance for both connections. Could you help me with where in relation to the bike the next place to check is? I can't figure out from the wiring diagram.

[Kerry]

Using the appropriate resistance range on the meter, measure the resistance between a Black/Blue connection and a Brown connection.  Then test between Black/Blue and Green/White.  Both measurements should be between 250 ohms and 420 ohms.  If either of them measures higher than that (or "Infinite") you may need to make your way toward the signal generators one connection at a time until you find the "culprit" wire or connection.  (Hopefully the coils themselves are good!)

I tested those connections and got 2.03k ohms as the resistance for both connections. Could you help me with where in relation to the bike the next place to check is? I can't figure out from the wiring diagram.

From memory, the 4-wire connector (for "Step 2") is under or behind the "black box" that controls the ignition timing.  The best way to find it is to follow the Back/blue and Brown and Green/white wires away from the "black box" and toward the front of the bike until you encounter the 4-wire connector.  All of this is on the left side of the bike, but after leaving the 4-wire connector the wires cross over to the signal (or "pulse") coils behind the right side engine cover.

At each connector, you should be able to measure the resistance for a given wire through the connector by touching the meter probes to the metal crimps where the wires enter on both sides of the connector.  You should get a reading REALLY close to zero for each such measurement.  If you get a fairly high reading, pull the connector apart and check for corrosion, etc.

[cmat1120]

Ok, so I think I understand, but just to clarify. Now that I know there's something wrong with the resistance I want to check the same wire between each set of connectors to try and find the location of the unusual resistance, right? Or should I only check at the connector itself? I'll probably just check both since it takes a couple seconds, but since you are "directing" me here I want to make sure I'm giving you results for exactly what you're asking me to do. Also thank you very much for all this help!

[Kerry]

You could say that we're taking a top-down approach.  We start out by testing the entire "round trip" circuit.  If the overall reading is OK, there is no need to do further checks.  If the resistance is too high, we shorten the length of the circuit we're testing until the reading looks good.  At that point, we know the problem is somewhere "above" the measurement points.

The problem could be a broken wire, but that's not as likely as a dirty or corroded connection.

My original experience with this circuit came as a result of a "newbie" move on my part.  I needed to clean some corrosion from the battery terminals but I was so new at wrenching that I didn't want to disconnect the battery and remove it from the bike.  So I sprayed some "battery cleaner" on the terminals with the battery in-place.

Excess cleaner dripped onto the 4-wire connector (situated under the negative battery terminal, now that I think about it) with the following result:




Of course, when I tried to measure the resistance through the connector, I got a very high (or "infinite") reading on at least one wire.  Try as I might, I could not pull the connector apart, so I ended up cutting it out of the circuit altogether and replacing it with 4 separate connectors (the pink ones in the photo below):



(Fair warning!  The pink connectors worked fine for many thousands of miles, but the recent problem I had with the bike not starting was traced back to one - or more - of them.  Either the crimp was starting to fail, or there was a little too much "oxide" on the aluminum connector itself.  I replaced one of the connectors and cleaned the others, and my ignition problems are solved again ... for now.)

[cmat1120]

Alright so I may have done this wrong the first time. That connector that you posted the pics of...if i measure the resistance n the left side(towards front of the bike) of it I get about 350 ohms. the right side(towards back of the bike) is where I get the 2k ohms. Where should I measure next? I know theres a bunch of connections in the headlamp and thats the only place I know of where there are connections following the wires in the direction of the high resistance...

[cmat1120]

wait wait wait wait. I might have been really stupid. should I keep the connection together and just check the resistance through the back of the plug? If I do that I get about 300 ohms which would mean that the resistance is fine.

Also heres a pic of the spark plugs. I am getting a new battery later today and I will replace the spark plugs when I have the battery.

[Kerry]

Yep, that's the idea! 

But I was a little "stupid" too,; I neglected to mention that the measurements for these circuits should be taken with the 3-wire connector pulled apart.  That isolates the signal generator coil circuits from the "black box" and other circuitry.

[cmat1120]

Ok, but since the left side of the connector is measuring the correct resistance I'm ok? Or does it sound like I still have an issue? Looking at those spark plugs now they look pretty bad, but I don't know what it takes to make a spark plug not work anymore.

Also I noticed that that black and blue wire goes all the way back to the connector for the left controls on the handlebars...is that normal? I'm trying to find a full wiring diagram, but even in a manual I have I can't find it.

[Kerry]

Ok, but since the left side of the connector is measuring the correct resistance I'm ok? Or does it sound like I still have an issue?

That depends on whether the 3-wire connector has been pulled apart.  If not, then the current from your ohmmeter might be taking a "path of least resistance" through the "black box" or another part of the circuit.

With the 3-wire connector pulled apart, if you get the right measurements between the 2 pairs of wires, you're done.  If not, you need to trace down until you find the part of the circuit with the too-high resistance.

I'm trying to find a full wiring diagram, but even in a manual I have I can't find it.

Try one of these:

• http://bbburma.net/Scans/Haynes_WiringDiagram_US_90-96.jpg
• http://bbburma.net/Scans/Haynes_WiringDiagram_US_97.jpg

[cmat1120]

Ok, I think im having trouble finding where you say to start. I think I've been measuring where you marked as the second step. what does that first 3 wire connection look like and where is it? maybe my wiring harness has been hacked up or something, but I can't find it.

Nevermind, nevermind, nevermind lol. I found that three wire connector(the white one that was right in front of me lol). Measured the resistance there and I got 363 ohms for both connections.

[Kerry]

I found that three wire connector(the white one that was right in front of me lol). Measured the resistance there and I got 363 ohms for both connections.

Cool.  Sorry for the long detour, but at least you've eliminated another possibility. 

[cmat1120]

So I tested the new spark plugs and battery and no change... I'm absolutely out of ideas at this point . Plus it turns out my mustang's engine is pretty messed up(shop said an engine replacement is probably my best bet  ) so now I really need to get this bike running soon lol.

[Snake2715]

Kerry also suggested the coils.. I know you got sidetracked on the connector.. were the coils tested from the bottom of page 2? know they spark.. but not sure if you tested them.


This bike was starting and not staying running.. now its not starting..

Has compression test been done?



I will be honest when it gets down to testing wires, etc It can be a little over my head so I am throwing ideas out to see if anything sticks.

[cmat1120]

no compression tests...I'm guessing I'd have to take it to a shop to get that done? and I haven't tested the coils. If someone could help with how to test them or direct me to a source that tells me how I can test them tomorrow morning. The new plugs do spark nice big blue sparks now though. One of the problems I have is no way of getting it to a shop(no truck or trailer or even a vehicle to pull a trailer). At this point I'm ready to test just about anything(I have sooo much free time lol) so if anyone has any idea or anything I can test or try please tell me.

[BockinBboy]

A lot of auto sales stores allow you to rent a compression tester... Autozone around me does, probably Advanced Auto too, and I'm sure there are others.  You just need to make sure it has the correct sized fitting for our engines (not sure which that is off the top of my head).

- Bboy

[cmat1120]

So i just went ahead and bought one. Here are the compression results: right dry: 90, left dry: 80, right wet: 140, left wet: 80. I honestly don't know what this means other than its probably gonna get expensive lol. Does anyone know where to go from here? Also what are the correct numbers for compression?