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1 and 2 not firing :s

  • Thread starter Thread starter Scoooter
  • Start date Start date
S

Scoooter

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Ok bike is 82 gs750T, I now have it completely together and the clutch issue is solved. I ran it today and it is sputtering and backfiring horribly. I started it got it to idle. Started pulling plug wires to check for spark. the cylinders on the right are getting plenty of fire, take 1 of them off and it dies. Left side, pulled #2 it doesnt change anything, the #1 makes a diff but its small, only decreases idle, doesnt kill engine. These are seperate coils so i am confused as to the problem, I have checked all my wires and all seem ok. The plug wires are numbered 1-4 so the cylinder on the far left if your sitting on the bike is #1 correct?? Thx guys and I won't bother you for awhile after this lol, Scott
 
To check for proper spark its better to pull each plug, ground it to the engine, crank the engine, and actually see the spark. One coil is for plugs 1-4, #1 is on the left side of the bike the other coil is for two and three. Another easy way to see if all cylinders are firing is to feel your exhaust pipes.

Backfiring and rough running could be a timing issue, or a carb issue as well.
 
I'll go check the order again on the plugwires. As far as starting I have to pushstart the bike, the starter is toast, new one be here next week.
 
The plugwires are in the correct order and 1 and 2 have a little fire, but not enough to run properly. All wires were rechecked for connectivity. Beats me
 
So anyone tell me why only half of both of my coils are producing the proper fire? I don't know what else to check
 
Everybody must be out of town for labor day! I'm don't know your bike very well, but coils as I understand it don't "half" work. You have no spark at all, or just weak spark on one and two?

There's lots of other things to check that would created the sputtering and backfiring you describe. How are your plug caps for example? Those can be checked for proper resistance. Screwed on good? Is your battery in good condition and well grounded? Bad or weak batteries can produce a lot of problems. Contacts clean etc? Coils can be checked for primary and secondary resistance (I don't know the specs for your bike).

Sputtering and backfiring can also be cause by carburetion problems. Are yours good and clean, properly adjusted?

Even a bad petcock assembly could cause the symptoms you describe. I think on your bike the vacuum line plugs into the #2 carb. If its sucking gas instead of creating vacuum, that could mess you up, giving you an overich mixture, especially on #2 and fouling your plugs, giving you a weak spark.

You could use new plugs and check for spark again. If your plugs have fouled sometimes they don't fire well after that.

There's a few ideas! Good luck.
 
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thx Mark, I have new plugs in the bike, just took apart the carbs and cleaned them day before yesterday while I finished reassembly of the bike. 1 and 2 have some spark, but not enough to make a difference when you pull the wires off, pull 3 or 4 off and it dies. I know coils don't go half bad, thats what has got me so irritated, I have spent a ton on this bike and I love riding it but I am thinking about finding another, this not riding is killing me, and it will be the end of riding season in Ky before to long. I have checked every wire on this thing and my battery is almost brand new and is fully charged. I went out after installing yet another set of plugs and tryed to push start it, it fired once and didnt start. I pushed it back into the garage and said heck with it. I would really hate to see this thing parted out on Ebay:cry: Oh btw I also just put a brand new petcock on it and the vacuum line is dry.
 
Sounds frustrating. But maybe it isn't as bad as you think. It will probably be a lot easier once you get the starter in there and you aren't trying to push start the thing!

You say you've put a lot of money into it. Has it run good in the past? What's the story? Maybe that might help in figuring out what the problem is.

Here's some more stuff. When you cleaned the carbs, did you make sure your float adjustments were correct? Air screw adjustments right? Are the carbs synched properly? I've had cylinders that didn't fire well when the synch was way off......and when I forgot to set my air screws.

If you can get it running do a plug check and tell us what your plugs look like (color etc.). That would help too.

Notice that I'm ignoring what you said about "parting it out on Ebay". We don't like that here. :-D
 
yea it ran like beast, I tore it down to check tranny because of a bad vibration, found a warped oil pump gear, changed it, motor looks like new inside. Plugs that I took out had a hint of white like its running lean, #1 plug was wet from not firing properly i suppose. bike is stock except a kerker 4 in 1 and k&n air filter.
 
O.K. I'm going to hazzard a "best guess here".

I think your problems are probably carb/intake related and not ignition problems. In general if you're running too lean due to intake leaks or aftermarket exhaust issues you'll get the backfiring/sputtering (ask me how I know). Stuck float or float adjustment way off, on #1 would lead to the wet plug/ not firing/sputtering.
 
I talked to a guy today that runs a repair shop and he has worked on tons of old bikes, he told me to buy a dyna s ignition and it would fix the problem. Who knows, guess I'll start comparing prices:-|
 
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