And hoses are all routed properly...  she just dies if the petcock is set to on.. like it's out of gas...


this is with a new petcock.. so what gives?

Quote from: se7enty7she just dies if the petcock is set to on.. like it's out of gas...

Um, IS it out of gas?  If you can see the "hump" on the bottom of the tank then it's getting into "iffy" territory:




I'm a little confused.  Your thread title says "won't run in prime" but your post basically says "won't run in the ON position".  :dunno:

eeekkk... should say will ONLY run in prime... sorry.. and yep it has plenty of gas..

O, I C.

You say it's a brand new petcock?  If so, then there's not much reason to open it up and check the diaphragm for holes, etc.  The only thing I can think of is a poor vacuum hose and/or connection from the petcock to the carb, especially if it dies in the RES position as well.

If it runs fine in RES then I would check the ON hose from the tank to the petcock, and maybe even pull the tank-mounted petcock and make sure the filter screen is clean.  :dunno:

Quote from: KerryO, I C.

You say it's a brand new petcock?  If so, then there's not much reason to open it up and check the diaphragm for holes, etc.  The only thing I can think of is a poor vacuum hose and/or connection from the petcock to the carb, especially if it dies in the RES position as well.

If it runs fine in RES then I would check the ON hose from the tank to the petcock, and maybe even pull the tank-mounted petcock and make sure the filter screen is clean.  :dunno:

well it's not brand new... I don't think.. looked new though

plus I took apart my old petcock and it looked fine.. no breaks in the diaphragm... I checked the hoses and they are hooked up properly (according to your diagram.. )

I'm sure the vacuum hose is hooked up correctly.  What I'm wondering is if the hose itself has any "discontinuities" or chewed-up ends or something.

Here's an idea: Try submerging the vacuum hose in a bowl of water.  Put your thumb over one end, and blow in the other end.  See if you get any bubbles -- like testing a bicycle inner tube for leaks.

Most of the evidence points to a vacuum problem.  (Although you didn't say how the system acts on the petcock's REServe setting, so no decision there yet.)

Before you're through, you may need to run the ON hose straight from the tank to the lower T-connector between the carbs.  OR ... switch the hoses at the fuel tank and see if the bike will still run on PRIme.  If neither of those work then forget about vacuum problems until you find out what's blocking the ON hose.

hmm.. doesn't run in reserve either... im going to start replacing hoses and whatnot.  I've got an 89 so they probably need replaced anyway..

I suggest you try clear vinyl hose from Home depot.  It's the exact same stuff they'll charge you 10x as much for at the bike shop.  It lets you see the bubbles right away.  What is happening most likely is that bubbles are forming in the hose the goes to the bottom T fitting on the carb...  I have the same issue... I havn't sorted it out yet because I am on vacation but I will probably do what Kerry suggested.  Check out my rejetting thread: http://www.gstwins.com/forum/viewtopic.php?t=13637&start=40

Quote from: DomI suggest you try clear vinyl hose from Home depot.  It's the exact same stuff they'll charge you 10x as much for at the bike shop.  It lets you see the bubbles right away.  What is happening most likely is that bubbles are forming in the hose the goes to the bottom T fitting on the carb...  I have the same issue... I havn't sorted it out yet because I am on vacation but I will probably do what Kerry suggested.  Check out my rejetting thread: http://www.gstwins.com/forum/viewtopic.php?t=13637&start=40

yes I went to home depot today.... is that vinyl hose okay for fuel though?

OK where is your vacuum hose connected to in the carb, ... that might be where the problem is.
Cool.
Srinath.

Quote from: seshadri_srinathOK where is your vacuum hose connected to in the carb, ... that might be where the problem is.
Cool.
Srinath.

which vacuum hose? keep in mind I have a cali bike... although I removed the charcoal canister and junk... but it wouldn't run in prime even before that.....


I need to install those DJ carbs I bought... along with the K&N, muffler, advancer, etc...


need to buy plug wires first though... I broke one of mine where it goes into the boot.... still runs though..

Ok carbs have a vacuum fitting, CA or not ... the left carb has a fitting that is ~1/2 way down on the front part and its facing the right carb... vacuum line goes there and to the vacuum part of petcock ... charcoal cannister crap is different, the front bottom T fitting goes to that, and isn't needed...
Cool.
Srinath.