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I have a 1982 Spectra 750-N. I just bought the bike and I got it running right briefly. However, now sometimes it runs off 2 cylinders and then other times runs off of 4. It idles great and when I give it gas it acts as if it dosent want to run. It stutters and backfires. I looked over the wiring and found some pretty bad looking wire. Should I start with a wiring harness or something else? Any suggestions? I know the carbs are good. I just cant figure out why it is doing this. I just dont know much about the electrical side of things. Can someone please help?!?!?
 

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If it's flitting from 2 to 4 cylinders it does point to an electrical, probably ignition-coil or pickup-coil problem.

When it goes onto 2 cylinders try to work out if it's 1 and 4 or 2 and 3 which are failing by squirting water at the downpipes.

If you find out which pair (and therefore which coil) is dodgy, swap the coils round to double check, if the fault goes to the other pair of cylinders there's your answer.

if you've got a wiring-diagram try to isolate the ignition wiring ie Low-tension feeds to the ignition-coils plus feed wires from pickup-coils to the IC-Igniter and check for shorts/chafing/burning etc
 

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Not sure, this really sounds like a carb issue to me, at least partly. I can see an ignition problem dropping it back to 2 cylinders, but the stumbling when giving it gas issue really sounds like it's not getting enough gas. You say you know the carbs are fine. Did you work on them? If so, what did you do? Sometimes they need to be soaked overnight in good cleaner and then thoroughly blown out with compressed air to get all the crud out. Some of those passages are pretty small, and even though they look clean, they may still be obstructed.

Another thing to try is to check how strong the spark is. You will want to do this one at a time so as not to mix up the plug wires. Pull the spark plug out. Hook it back up to the high tension wire and set the other end somewhere on the metal part of the head so that it grounds. Then crank the engine over. If you have the other plugs connected, try to keep it from starting or shut it off quickly, but pay attention to the spark that jumps across the plug. It should be thick and bright blue. If it is yellowish or orange then you have a problem somewhere in your ignition system. Do this for all 4 plugs, and note which ones if any are weak. BTW, it helps to do this in a shady or dark area so as to be able to see the spark. They can be kinda hard to see in the daylight. :)
 

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Thanks. I found out it was 1and 4 cylinders that are not fireing. I also have an issue with he starter button, it will kill the bike but not start it, jumping the silonoid works but not something i like doing. One last thing for now "I hope" brake light. The rear running light works but nothing happens when hitting the hand or foot bake. I replaced the bulbs but still the same.
 

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Thanks. I found out it was 1and 4 cylinders that are not fireing. I also have an issue with he starter button, it will kill the bike but not start it, jumping the silonoid works but not something i like doing. One last thing for now "I hope" brake light. The rear running light works but nothing happens when hitting the hand or foot bake. I replaced the bulbs but still the same.
 

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i need help i dont know what year my zx7r is title said 1997 bought it as a 1997 but the vin has a p1 in it 1997 vin has p2 what do i have
 

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i need help i dont know what year my zx7r is title said 1997 bought it as a 1997 but the vin has a p1 in it 1997 vin has p2 what do i have
You have what is commonly called a "Thread Hijack". Clicking on the "Start New Thread" button at the top of the main page in this forum is the answer.
 

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Hook it back up to the high tension wire and set the other end somewhere on the metal part of the head
You should always use a spark tester to check for spark. They are cheap (under $10) and they make the job easier. Nine times out of ten you can get away with it, or the old screwdriver in the plug wire trick, but it is that tenth time... ouch. You end up with a shorted snubber/driver in the ignitor and maybe even some smoke!
 

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I have a 1982 Spectra 750-N. I just bought the bike and I got it running right briefly. However, now sometimes it runs off 2 cylinders and then other times runs off of 4. It idles great and when I give it gas it acts as if it dosent want to run. It stutters and backfires. I looked over the wiring and found some pretty bad looking wire. Should I start with a wiring harness or something else? Any suggestions? I know the carbs are good. I just cant figure out why it is doing this. I just dont know much about the electrical side of things. Can someone please help?!?!?
Hi Matt, There are a lot of things that can go wrong but...I was very frustrated with cylinders not firing, backfiring etc. The main cause was old leaking carb mounts (or manifolds, they are the rubber things that connect the carbs to the head). I guarrantee if your carb mounts are original, they leak. For sure. I fixed my problem by using Hondabond to seal the connection to the head but getting new ones from Z1 is a better idea. Try that, it will take care of an almost sure problem and if it does not fix it, it will make troubleshooting easier. Good Luck!
 
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