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#2 cylinder not firing

  • Thread starter Thread starter Blastroiz
  • Start date Start date
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Blastroiz

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I have a 1981 gs750l I bought back in September. It ran from the get go but pretty rough only firing on cylinders 1,2, and 4 originally. The original owner told me it would need a carb clean, and new spark plugs. So I did a solid cleaning following the wonderful resources on this site and tested and replaced the spark plugs and coils. Boom number 3 cylinder starts firing but now cylinder 2 keeps flooding, like fuel leaking from the exhaust port and everything. I've taken the carbs on and off and everything looks good so I moved on to compression. The engine was covered in oil all over the mid section of cylinders 2 and 3 so I took apart the top and all the way down to the base gasket and replaced all of them. Fired the badboy up today and it started right up within 5 or 6 cranks and same problem with cylinder 2.
I'm getting pretty frustrated here and could use a second opinion on where to go from here. Tomorrow I'll probably check for spark again swap plug wires for 2 and 3 to see if the same problem persist and if it does dive back I to the carbs I guess. Any ideas?
 
I haven't. Where can I check that. I was originally thinking I had my pilot screw to rich but that doesn't seem to matter even if it's all the way closed. Thanks for the quick response
 
You'd probably call it the petcock. I'm not sure what type your model has, but first check should be 'has it been left in the 'prime' position?'
 
Ya I cleaned and check the vaccum seal on that. Looks good. Got a mouthful of fuel checking the seals also. Lol. carb bowls fill up in prime and work properly in on.
 
Ok, so if it hasn't been left on prime, and isn't leaking in other positions it should be good. Is your number 2 cylinder only flooding when you try to run the bike?
 
Yup. Everything is ok untill the bike is started. And then everything runs just fun except cylinder 2 doesn't fire off. Just floods with fuel and leaks out if the exhaust
 
I guess the next step is to check the ignition, like you suggested. See if you can find a bad plug, or plug cap, or HT lead.
 
I'll be checking into that tomorrow. I hope it's something dumb I just overlooked or a lead came loose messing with everything. I'll update when I find something out. Thanks
 
Good luck! One last thing - just check your oil hasn't been contaminated with gasoline.
 
sounds like the carb float needle isn't sealing.

It's hard to get at the carb on the bike, but if you can jam a piece of clear vinyl tube into the bowl's drain screw, you can check if the fuel level is way above where it should be.

To get a piece of vinyl hose to "thread in"(because it doesn't come in the correct size), heat it til it's stretchy...until it makes a "neck". Cut the "neck" where the size fits tight.
 
Last edited:
Blastroiz said:
Ya I cleaned and check the vaccum seal on that. Looks good. Got a mouthful of fuel checking the seals also. Lol. carb bowls fill up in prime and work properly in on.
Click to expand...

You need to check on the vacuum line from the petcock to #2. Pull it off the petcock and put a bolt in it to plug the line. Turn the petcock to Prime and run the motor, see if it clears up #2

But, check your oil for gas before anything else
 
Welp, I just spend my evening out there messing with it. Deff have spark at #2. Pulled the carbs and everything looks as it should be. Measured all floats and they are all within the 22mm range and sealing. Even checked the diaphragm thoroughly with a flashlights for leaks everything looks good.
I like what your saying BIG T and will check that soon as I get home from work tomorrow. Makes sense since the vacuum line literally goes to the cylinder I'm having problems with.
Also there's no fuel in the oil it just goes right in and out of the exhaust when it's running.
 
It was the vacuum line running like a champ now. Just try and keep me quarantined now HAHAHA.
Thanks for the help though to all that replied that was really driving me insane.
 
Nope, vacuum line not the problem, the petcock is the problem. All the line does is suck vacuum, the petcock is letting the fuel into the vacuum line. Just my opinion.
 
put on new petcock, thats seems to be the suggestion, on bike cliffs,
 
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