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Engine Flooding

PostAuthor: jamesderek » Fri Oct 11, 2019 11:52 am

Hello everyone,
Need help I've been working on my 81 XV750 for over a year and I'm out of ideas. Replaced the idler gear, starter motor, battery and also installed the voltage stabilizer. After all these parts were installed the bike cranks much better but can't get it to idle. About a week ago it started for a minute or so and then died. Since then I ordered new float needles and installed them and it continues to flood. Have spark but after a couple cranks they come out black and wet. Any Idea or suggestion would be great! Thank you!

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Re: Engine Flooding

PostAuthor: Flyingdog » Fri Oct 11, 2019 12:18 pm

:VTF:

Boy..sorry to say, that could be number of things why it won't idle. From air intake to electrical to (and most likely) carbs.
First off, about the flooding..where is it flooding?... sure sounds like the float height is wrong. There's really only one way a carb floods..by way of fuel getting past the float needle/seat and the fuel just keeps pouring into the bowls. Float set to high, floats rubbing on the float bowls, float's pivot pin corroded, can cause float needle not stop the flow. Cuz, there again, float height not right. Possible the needle gets hung up on the seat. I've had this happen once when I had the float height off. Hit a bump..float pin hangs open...fuel pouring out of exhaust, while the bike was running. Even the little wire hanger can cause the needle not to close off the fuel. Have you checked the other internals of the carbs? Rebuilt them, other than floats & float needles, all jets (air and fuel) clean (specially the pilot). Pilot system controls idle, so that very important. Can also check vacuum piston diaphragm. No thin spots, rips? Emulsion tubes in good shape..all holes clean/clear/no ovaling of the end that goes into the venturi?
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Re: Engine Flooding

PostAuthor: extremeodd » Fri Oct 11, 2019 2:54 pm

:yup:
Was the bike ever running during your ownership? You mention working on it over the last year but not if it was running beforehand. If it was running, how well did it run? If it ran bad, what kind of symptoms did it have?

Apologies for the 20 questions, just trying to get a better picture of what is going on here. As Flyingdog said, it could be any number of issues but it's probably the carb and probably something to do with the float.

When it started for a min, was it firing on both cylinders or just one? Was the choke on or off? When your cranking, do you get some pops at all or does it just crank?

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Re: Engine Flooding

PostAuthor: jamesderek » Fri Oct 11, 2019 3:29 pm

Flyingdog wrote::VTF:

Boy..sorry to say, that could be number of things why it won't idle. From air intake to electrical to (and most likely) carbs.
First off, about the flooding..where is it flooding?... sure sounds like the float height is wrong. There's really only one way a carb floods..by way of fuel getting past the float needle/seat and the fuel just keeps pouring into the bowls. Float set to high, floats rubbing on the float bowls, float's pivot pin corroded, can cause float needle not stop the flow. Cuz, there again, float height not right. Possible the needle gets hung up on the seat. I've had this happen once when I had the float height off. Hit a bump..float pin hangs open...fuel pouring out of exhaust, while the bike was running. Even the little wire hanger can cause the needle not to close off the fuel. Have you checked the other internals of the carbs? Rebuilt them, other than floats & float needles, all jets (air and fuel) clean (specially the pilot). Pilot system controls idle, so that very important. Can also check vacuum piston diaphragm. No thin spots, rips? Emulsion tubes in good shape..all holes clean/clear/no ovaling of the end that goes into the venturi?


Thanks for the info! The engine is flooding, I’ve see wet sparks every time I try to start it and a couple times saw fuel coming out of the exhaust. I did open the carbs and did check the jets and diaphragm and they were clean with no damage. I was thinking about the float height as well but figured I’d ask you guys first before I started playing around with that as I’ve never done that before. Also I saw some black smoke come out of the exhaust yesterday if that helps.

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Re: Engine Flooding

PostAuthor: jamesderek » Fri Oct 11, 2019 3:43 pm

extremeodd wrote::yup:
Was the bike ever running during your ownership? You mention working on it over the last year but not if it was running beforehand. If it was running, how well did it run? If it ran bad, what kind of symptoms did it have?

Apologies for the 20 questions, just trying to get a better picture of what is going on here. As Flyingdog said, it could be any number of issues but it's probably the carb and probably something to do with the float.

When it started for a min, was it firing on both cylinders or just one? Was the choke on or off? When your cranking, do you get some pops at all or does it just crank?


Had it running good once took it once up and down my block but after that had no luck. When I occasionally got it to idle I got a lot of back fire and would die when I gave it throttle. Both cylinders did fire when I got it started the other day without the choke. Yesterday when I tried it I just got black smoke and saw some fire coming out the exhaust for a second.

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Re: Engine Flooding

PostAuthor: Flyingdog » Sat Oct 12, 2019 3:11 am

jamesderek wrote: Also I saw some black smoke come out of the exhaust yesterday if that helps.


That's going to be lotta "what ifs", till ya get it pinned down. Black exhaust (as with backfires) usually signs of overly rich A/F ratio. But what/why? Touching on a few...choke plunger stuck open, someone changed jetting (throttling), pilot circuit outta whack (idle), intake blocked, weak spark (have you checked all primary coil connections, secondary wiring/cap, the coil-itself... resistance?), etc etc..are some. JMO..I'd set the float level to specs..then check level by way of "clear tube" method while bike is running (hopefully you can keep it running long enough to check level). You can get it close while on the bench too, with the tube method. Just not as accurate. Guess, you could try to lock your carbs in a vice or make-shift stand. Trying to get the carbs same angle as if mounted on the bike. Attach the tube, open the drain/screw, hold tube in place, squirt fuel into carb and see where the level/against the float bowl ends up. 2-3mm below float bowl/carb seam. Be waay general, but at this point, there's gotta be a starting point. Always sounds worse than it is to do.

Oh yea..was going to mention..probly wouldn't hurt to check to see if petcocks (in the "on" position) are stopping the fuel flow when bike is off. Nother one of those often overlooked gems, that'll sneak up on ya.
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Re: Engine Flooding

PostAuthor: jamesderek » Wed Oct 16, 2019 9:03 pm

Flyingdog wrote:
jamesderek wrote: Also I saw some black smoke come out of the exhaust yesterday if that helps.


That's going to be lotta "what ifs", till ya get it pinned down. Black exhaust (as with backfires) usually signs of overly rich A/F ratio. But what/why? Touching on a few...choke plunger stuck open, someone changed jetting (throttling), pilot circuit outta whack (idle), intake blocked, weak spark (have you checked all primary coil connections, secondary wiring/cap, the coil-itself... resistance?), etc etc..are some. JMO..I'd set the float level to specs..then check level by way of "clear tube" method while bike is running (hopefully you can keep it running long enough to check level). You can get it close while on the bench too, with the tube method. Just not as accurate. Guess, you could try to lock your carbs in a vice or make-shift stand. Trying to get the carbs same angle as if mounted on the bike. Attach the tube, open the drain/screw, hold tube in place, squirt fuel into carb and see where the level/against the float bowl ends up. 2-3mm below float bowl/carb seam. Be waay general, but at this point, there's gotta be a starting point. Always sounds worse than it is to do.

Oh yea..was going to mention..probly wouldn't hurt to check to see if petcocks (in the "on" position) are stopping the fuel flow when bike is off. Nother one of those often overlooked gems, that'll sneak up on ya.


Ok so I had some time to take a look at the carbs and noticed my floats were way off. I tried to get them as even as possible and tried again and I got it to run for a bit while giving it throttle. While cranking and the short time that it was running I noticed white smoke this time. Wasn't able to check the float level while running cause it wasn't running long enough but was able to get them both even they are a bit under where they are supposed to be. Going to try to upload a picture hopefully it works and gives you guys a better idea. But thanks again. Really appreciate all this help!

https://imgur.com/a/00jLgja

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