PLEASE HELP:Spark Plugs arent firing

[gtzuki750]

Alright this is my first post, so please excuse any forum fopaux. I recently bought a 1977 gs 750 , when I bought the bike it started and everything worked well for a motorcycle sitting outside for 2 years. once I had it home first thing I did was strip the bike of all exterior plastics, seat everything so that I could get to the carbs and clean them as well as have direct acess to wiring harness, well long story short a week later I finnaly finish cleaning everything and rewired everthing as well (kinda) I go to try and start the bike and all I get is, FIRST some popping periodicaly as it turns, then I stop , SECOND I pull the plugs and check my fuse, fuse is fine but pulgs are pretty chared up. so THRID go I just take spark plug caps and plug together and turn motor to see if I get any spark and NADA. then genius grandfather says stick a screwdriver in there and see if it make a connection with the block (thank god.... Not really) nothing happened... so I have come to find help, im absolutely lost I checked everything with voltage meter to see if it was getting juice, im lost, ignition coil? bad plugs? bad plug caps? bad wiring ?.. I just wanna ride

[simon kuether]

Let's work through this one step at a time .

With the plugs out but they're in the plug caps and touching the head , and there's no spark , correct ?

Welcome by the way .
The guru's will get you going old mate .

Cheers , Simon .

[tom203]

Of course you "just want to ride" but seeing how you just bought a 37 yearold bike, you have to be realistic. Lots of maintenace is likely overdue- this must be done for your safety.
When you check for spark at a plug, make sure that the companion plug (note that each ignition coil has two plug wires) is connected to its plug (and grounded) or you won't get good spark at plug.
Here's a link to view;

http://members.dslextreme.com/users/storagecliff/images/electrical_odd-n-ends.html#A17

your bike likely has points ignition- if you back up on that link, there's tons of info including checking the contact points.

[gtzuki750]

Let's work through this one step at a time .

With the plugs out but they're in the plug caps and touching the head , and there's no spark , correct ?

Welcome by the way .
The guru's will get you going old mate .

Cheers , Simon


-simon thanks a bunch , I took all 4 plugs out , then got wire #1 connects to cylinder #1 and put the plug and cap on and clamped it to the head.


Of course you "just want to ride" but seeing how you just bought a 37 yearold bike, you have to be realistic. Lots of maintenace is likely overdue- this must be done for your safety.
When you check for spark at a plug, make sure that the companion plug (note that each ignition coil has two plug wires) is connected to its plug (and grounded) or you won't get good spark at plug.
Here's a link to view;
http://members.dslextreme.com/users/...-ends.html#A17

your bike likely has points ignition- if you back up on that link, there's tons of info including checking the contact points.

- tom I didnt try doing cylinder 1 and 4 at the same time, but now I will!. I read through the article (don't test me on it) and im almost positive its a plug issue but from what I got out of the article is I can just pop off the ignition cables and test that with an ohm meter? then go from there and see what is and isn't getting or giving power?

[Nessism]

Service manual download here...http://members.dslextreme.com/users/bikecliff/

Maybe something went wrong during your "rewiring" job? You are going to have to trace down wires until you find the problem.

And please don't just stop at that. You bike needs a valve adjust, charging system wiring clean up, brake system clean up, etc, before it's safe to put on the road.

[greg78gs750]

um, don't take this the wrong way, please, but, might i suggest you sell the gs and spend a bit more to get a newer bike that will need less work? from the tone of your post i am not sure you have the patience/will to get this bike working. just one opinion, not trying to be a d!**, but if you "just wanna ride", this will get you there much, much faster. cliff will be along with a mega-welcome, lots of info for you there, sounds like you could use it.

greg

[gtzuki750]

hahaha, no offense taken one bit greg. the only reason im "impatient" because I see the potential , im not getting rid of the bike at least not anytime soon and I definitely plan on invest some serious time and money into... considering I already have in the past 3 weeks. since my post a little less than I week ago I still haven't figured out the plug issue, I have studied the wiring diagram in my manual and scoured the wiring harness with electrical cleaner& volt meter for anything and everything I could find, I.E exposed wiring, bad connections the whole thing. low and behold as I was searching i found on my garage floor a ground cable, undoubtedly from when i took the battery out and the remaining wiring under the seat. so as of right now im clueless , but ill just have to go back through the diagram and see what im missing.

side note: i recently bought float bowl gaskets (everything else looked good), front and rear caliper rebuild kits (i was told they were fairly simple) my goal right now is to just get the bike in working order not necessarily road worthy... just working

[gtzuki750]

good news! I found the problem the source of the problem, for what ever reason I didn't check the wiring inside of this little rubber booty and low and behold lies my issue. a couple of the female and male adapter wire covers were all eroded and melted together, now that is probably a problem in of itself. but I tested brand new plugs like Simon said and they sparked. so as of right now (hopefully) obstacle one is out of the way and now onto why there melted together in the first place.

[Steve]

The reason they were melted together is because there was a bit of corrosion in them. Corrosion is resistance. Resistance is HEAT.

Nessism mentioned earlier, I will mention it again, you need to clean ALL connections in the harness.

You mentioned in the first post in this thread that the bike had been sitting for two years. That is two years that you know of. How long was it REALLY sitting? Unless you really KNOW the person that sold the bike and really, really trust them, don't believe a word they said about how good the bike is.

.

[greg78gs750]

my experience has been that even if you DO trust them, DO NOT trust the work they have done on what is now your motorcycle. nice work getting some kinks worked out, keep heeding the advice given here, esp. about electrics.

greg