running backfires, now no spark

[81GS850]

hello everyone, I have read through countless pages and cannot find the help I need so figured Id post, very new to bikes, I recently purchased a 1981 suzuki gs850g the guy I bought it from showed me it running and fired up no problem I have started it 2-3 times and now I am pretty confident theres no spark, I have had the plugs out alot recently cleaning and sanding as my father said it would help them. yesterday it was trying and today nothing I pulled a plug and held it against block with no signs of spark when start button depressed, I think the wiring harness has been screwed around with but it was still running since then.?? sorry if this is posted in wrong part but hopefully im not, I just need help as Im becoming very discouraged( my mechanic said fowled plugs could be causing it but I think its something else could I have knocked something off when disconnecting spark plug caps? please help Thank you all hohpefully we can figure this out.

[cowboyup3371]

Welcome to the forum. What kind of voltage do you have at the battery? Are your fuses good (do not just look at them visually, use a test light as they can break under the caps)? What voltage do you have at the coils? Are you sure the plug wires are on the right cylinders (left coil feeds 1 and 4, right coil feeds 2 and 3)

[allojohn]

I don't mean to demean you but have you checked the kill switch - right handlebar.

[tom203]

I don't mean to demean you but have you checked the kill switch - right handlebar.

This happens to me regularly on my dirt bike-kick away and nothing! But he (81GS850) did imply that his starter was working, so he must know this. Anyways, he needs to tell us whether after some cranking, his plugs are actually wet like his mechanic was thinking or dry cuz he's not using the "choke". Or maybe it needs some priming from petcock. Might be hard to see spark in bright sun

[81GS850]

plugs are wet and did visual inspection of fuses they all look fine but will check and replace maybe replace anyway, not the kill switch as its on run, I havent checked my battery as I know it could need replacing but grandfather and father say its fine I have to charge it up before I try bike or it loses its power but it was firing with this battery no problem just a few days ago, yesterday it started for like half a minute and today nothing(I had all the plugs out cleaned and dried and caps are all to proper plugs)
, plugs are wet but even when dried and no carbon i get nothing. Will starter and everything else engage if it was a fuse? ill have to check coils as im leaning towards that or me knocking something loose although was very careful when cleaning plugs , I am using the choke btw,

[cowboyup3371]

Check those fuses...saying this from the experience of fiddling with mine for 8 hours before checking them and fixing it instantly.

[allojohn]

This happens to me regularly on my dirt bike-kick away and nothing! But he (81GS850) did imply that his starter was working, so he must know this. Anyways, he needs to tell us whether after some cranking, his plugs are actually wet like his mechanic was thinking or dry cuz he's not using the "choke". Or maybe it needs some priming from petcock. Might be hard to see spark in bright sun

The first new bike I bought ('76 GT380) I sat on the dealers lot kicking and kicking - nothing, dead. I had the salesman with me and he didn't know what was wrong. After 10 mins of frustration I spotted the kill switch. I will never forget it again.

[tom203]

It never hurts to just replace fuses (switch ignition with headlight fuse), but no, it shouldn't even crank if the ignition fuse was bad- famous last words! Wet plugs after cranking means you got gas, now we need spark. You didn't leave petcock on "PR" spot for a few days did you? (this would be too much gas). This must be an ignition problem. As cowboyup said, doublecheck the plug wires going to correct plug- easy thing to mix up.

[tom203]

The first new bike I bought ('76 GT380) I sat on the dealers lot kicking and kicking - nothing, dead. I had the salesman with me and he didn't know what was wrong. After 10 mins of frustration I spotted the kill switch. I will never forget it again.

In my youth, I would remember to check, but now my brain seems to be elsewhere! Street bikes are easier (electric start) and I don't even use my kill switch much.

[81GS850]

nope never left on pri, as a matter of fact never used it,what is the yellow wire that runs of starter relay I beleive it is located on left of bike under side cover? Mine has been hacked into impretty sure and now has a section of light blue wire attached with male connector on end it was running with it connected to yellow wire. and I cant get it to stay together now could this be sorce of issue and cause nopower to coils thus no power to plugs?? immm trying everything listed above and then if nothing may have to get someone who knows more then myself. I hate to just give up and sell it because I can't figure it out grrr, well ill get bak to you guys and letcha know my findings

[koolaid_kid]

You need to work backwards from the plugs. Are the coils getting 12V (nominal)? Is the ignitor sending signal to the coils? Is the signal generator sending signals to the ignitor?
Look here for how to do these tests: http://members.dslextreme.com/users/...dd-n-ends.html

[tom203]

nope never left on pri, as a matter of fact never used it,what is the yellow wire that runs of starter relay I beleive it is located on left of bike under side cover? Mine has been hacked into impretty sure and now has a section of light blue wire attached with male connector on end it was running with it connected to yellow wire. and I cant get it to stay together now could this be sorce of issue and cause nopower to coils thus no power to plugs?? .....

No, it just would not crank, but the light blue wire is strange. The starter relay is fed by starter button, which is fed by kill switch. I made some anti theft devices on some vehicles that killed power to coils, but you did say that it ran a few times. You need to remove gas tank and check voltages at coils- orange/white is + 12 volts (to good ground) when ignition and kill switch is on. Do this first, cuz it tells alot.

[koolaid_kid]

nope never left on pri, as a matter of fact never used it,what is the yellow wire that runs of starter relay I beleive it is located on left of bike under side cover? Mine has been hacked into impretty sure and now has a section of light blue wire attached with male connector on end it was running with it connected to yellow wire. and I cant get it to stay together now could this be sorce of issue and cause nopower to coils thus no power to plugs?? immm trying everything listed above and then if nothing may have to get someone who knows more then myself. I hate to just give up and sell it because I can't figure it out grrr, well ill get bak to you guys and letcha know my findings

If it is a thin wire (usually 18 gauge) and has a spade connector on it, that wire is what activates the starter relay. You need to check it to verify it is supplying 12V when you press the starter button.

[81GS850]

i know this may seem a stupid question to pose now but with a combination of flooding and low battery could all this be from battery?, when plugs removed very very strong gas smell and only slight residue but thats without even trying to crank it?? could my spark plugs have become sorta waterlogged inside or something performing all electrical tests this weekend but its just driving me nuts in the meantime.

[rustybronco]

Yes, your spark plugs could be gasoline fouled. Replace them and charge up your battery.