leaky petcock?

[fiddlesticks]

We've tried everthing to get one of the bikes to stop blowing black smoke. Carb rebuild, turned carb screws mostly in. Capped the yikes, cleaned all connections , checked battery and even swaped tci's. Gave her an airbox upgrade in case she couldnt breath. Still runs way too rich and after warming up rpm starts to climb after giving her some gas.
We start thinking petcock. Bring the tank over to the other v (whick also has the yikes capped and the new airbox) Stick her on ?and run the bike for a bout 20 min. Sure enough she starts to stumble and when you give her some throttle she goes wacky and the rpm starts to climb until you kill the switch. No smoke though? what do ya think? Is the petcock the thing im missing?

[kiawrench]

sounds like the problem is in that there  pet-thingie !!
  from what you describe, it sounds as if the petcock is allowing full free flow at all times when running .
  this can be trash inside the petcock , bad discs, or missing parts.
  
    drain the tank in question, carefully remove the petcock ,then take it apart over a clean, dry white or tan towel(in case of dropping gas/parts-towels make it easier to locate them ) i buy detailers towels just for fuel system takedowns and after use just wash them out.

    once apart ,use the photos in parts guide or service manual to verify you have all the parts, and the condition of each. sometimes it is just a flake of rust that offsets the thing and creates all this trouble .if you decide a rebuild is needed, the kits are on e-bay ,buy now  listings,,, not too expensive .

[fiddlesticks]

Thanks kia

Its the only thing I could think of we havent checked yet so I threw it out there to see if anyone agreed. I wasnt even sure if it was possible for that to be the problem. Im going to take that there pet thingy apart and check her tomorow.

Fiddlesticks

[louthepou]

Even with a petcock that lets the fuel just whiz by (as if stuck in the "prime" position all the time), the needles in the float bowls should stop the fuel flow, right?

In any case, it's a good thing giving the petcock an overall once in a while. Did dozens of them, send me an e-mail if help needed.

By the way, did you recieve the YICS?

Cheers

Louis

[Paul_Jungnitsch]

Is it possible for a bad petcock to leak fuel into the vacume line?

[louthepou]

I love your hypothesis Paul. If technically possible (would need to open a petcock to figure out), it would cause an extra-rich mixture indeed...

Lou

[QBS]

Disconnect and plug the petcock vacume line.  Put petcock on prime and see what changes.

[fiddlesticks]

Lou - yep I got the yikes. We put a different tank on the V in question today. Still smokes like a chimney. Im thinking tomorow its time to swap the coils. I'll post results.

Fiddle Faddle

[fiddlesticks]

Well I'll be damned she is leaking. Im now glad I havent gotten around to touching the coils yet anyway. If it aint broke dont fix her. The gas is actually finding a way into the vacuum line. When we pulled that line off today it was dripping with gas. Not sure exactly how its getting in there yet but we'll figure that out once we take her apart.

Fiddle