Quote from: DomIdeally I don't want to mount the tank again, but let me understand you correctly; you are saying to clamp off the ON hose, run the temp tank to the RES hose, switch the frame petcock to RES, clamp the vaccuum hose and see what happens?

Well, no.  I meant to "run the temp tank straight to the carbs".  The idea is to bypass the frame-mounted petcock altogether.  I described it assuming that the fuel tank was reinstalled ... sorry.

Quote from: DomThen, if any bubbling happens, I know that the carb is somehow creating back pressure, which I have no idea of how to remedy.

Yeah ... likewise!

Quote from: DomBTW my floats are dead on the gasket...well, at least the meniscus is...will that suffice..is a mm or so +/- ok?

If 1.0mm +/- is OK for the float needle it should be OK for the float.  :dunno:

Quote from: DomKerry, please theorize, I insist.

By "theorize", I just meant that I wanted to start with what I "know" and work towards the evidence you're seeing.  Let's see, what are all of the possible ways that bubbles could be made to appear at that point in the system?

1) By some kind of back pressure, like you said.

2) By bubbles forming right out of the fuel.  I don't even know if this is possible; all I have to go on is the cavitation effect from boat propellers.   [/list:u]For now let's say we ignore possibility #2, K?    All right, so we assume that actual air is being forced back into the fuel supply tube.  Where could it be coming from?

A) Directly from the lower T-connector between the carbs, because of a bad seal.  Possible diagnostic/fix - apply a thick layer of Vaseline or something there and see if a hole forms when the bike is running?  :dunno: (BTW, there are actually 3 connection points ... don't overlook one!)

B) From the float bowls via the float needle seats.  Hmmm, interesting possibility.  But how could it happen?
i) One or both needle valve/valve seat combos could have some dirt in between them which prevents a good seal when the valve is closed.  This

shouldn't matter at the throttle position you're testing with though.  Having the valve open is a GOOD thing, right?  To let more fuel in?  Still....

ii) "Excess" atmospheric pressure on the fuel in the float bowls.  The way I've pieced things together in my head, atmospheric pressure (from the hose attached to the upper T-connector between the carbs) PUSHES fuel up through the jets - when a vacuum is created by the intake air rushing over them.  Make sense?  Now, I'm not real clear on how the vacuum behaves at different throttle positions.  I understand that opening the throttle allows more air through the carbs, which pulls (uh, PUSHES) more fuel up through the jets.  But I'm not sure what the "vacuum curve" looks like along the range of throttle positions.[/list:u]
So OK, no conclusions yet.  But hey - I've got to get to bed!  Maybe something I've theorized will trigger an idea for you.

Meanwhile, I noticed a couple things in your photos:

* The large-diameter hose that once connected the valve cover to the airbox seems to be open to the air.  I don't know if this would have any direct effect on this back pressure situation, but I have always heard that you should install a one-way (PCV?) valve there.

* The hose that normally attaches to the upper T-connection between the carbs seems to be missing.  That hose supposedly draped over the airbox and ended between it and the battery box so it would have a fairly "smooth" supply of air, without major fluctuations in pressure.  With your K&Ns gobbling all the air in the immediate region ... maybe there is an unwanted pressure differential?  :dunno:[/list:u]One last idea: In an open system, the pressure measured at a given point in a fluid is a function of its depth at that point, right?  (Not the

volume of fluid above that point, just the depth.)  So as the fuel level in the tank gets lower and lower, the pressure behind the fuel entering the carbs decreases.  What I'm getting at is this:  If the hose attached to your coolant return tank is long enough, see what happens to the bubbles at the T-connector as you raise and lower the tank.  I'd be interested in your results.

I'd also be interested to know if you even HAVE an "open system".  Does the cap on that return tank allow any air in?  You may want to leave it open a crack....

You got bubbles with the test tank on ... OK the lower petcock is messed up ... bubbles there is indicative of some fuel flow screw up...
Cool.
Srinath.

No bubbles with the temp tank direct to the carbs, in fact the bike idled great, and revved awesome all the way to 10k, no flat spots or hesitation anywhere.  Once the needle hits 4,200 I can really see the needle gain momentum.   The bike was lurching so hard when I gave it full throttle that I thought it was going to hop right of the stand......and go nowhere...... cuz it was in neutral...  :lol:

So what do you think?  Bad frame petcock?  You think I should run the ON hose from the tank straight to the carbs?

Think I should put her back together and take her fer a spin?  I would hate to actually put a little resistance under the tires and have her poop out again...I think I would have to have a little tantrum.

Just hang that little tank from the mirror and you are ready to go! :lol:

I guess you would have to stop for gas more frequently.

I can't remember: did you test riding, just leaving the frame-mounted petcock on PRIme?  That won't hurt anything; it will just tell you whether there is a problem with the vacuum-actuated "ON" setting (or just maybe with the "ON" hose or in-tank intake).

If it runs great from the reservoir tank to the carbs, I'd be tempted to cut to the quick, and run the fuel from either tube on the real tank straight to the lower T of the carbs.  If the bike runs great, then you know the problem is with the frame mounted petcock, hoses or vacuum system.  If it runs poorly, then maybe there's a problem with the tank-mounted petcock (like it's not quite open all the way).

I think I'll run hoses to dual side mounted 5 gal. jerry cans and drive all the way from here to mexico nonstop.  Catheter and colostomy bag, I.V., the works.  If my calculations are correct Ill only have to stop to fuel up once.

I don't remember if I tried riding on PRI but it doesn't matter because my floats were wacked anyway.

Rebuild petcock?  Swap it out?  Nix it all together?

Yea rebuild it ... that srileo dude ... chased his problems for weeks, even sent me his carbs and I jetted them to where it was flawless ... and his bike still crapped out 30 miles form his house ... turns out ... big gaping hole in petcock... he fixed it and its not come back in 5-6K whatever miles.
Cool.
Srinath.

Quote from: Rema1000If it runs great from the reservoir tank to the carbs, I'd be tempted to cut to the quick, and run the fuel from either tube on the real tank straight to the lower T of the carbs.  If the bike runs great, then you know the problem is with the frame mounted petcock, hoses or vacuum system.

(Emphasis added)

Just make sure that if you use the ON tube (for testing) that you have a couple gallons or more in the tank.  And if you DO decide to toss or bypass the ON/RES/PRI petcock and run straight from the tank to the carbs, choose your tank outlet carefully.

• If you use the ON outlet and cap the RES outlet you'll hit the REServe level after about 3 gallons and have no way to use the last gallon or so.
• If you use the RES outlet and cap the ON outlet, you'll have to be careful not to run the tank dry and strand yourself who-knows-where.

If you wanted to be adventurous you could try a setup like this, which would use both outlets and preserve your switch-to-REServe capability:
    ______________
   |               \
    \     FUEL       \
      \     TANK       \
        \ ______________|
                 R  O
                 E  N
                 S  |        T-Connector
                 |  \-------  <--+-->  --------- To lower T-Connector
                 |               |                  between carbs
                 |               v
                 |
                 |               |
                 \-------+-------/
                         |
                    Aux. Petcock


Here's a sample T-connector for joining the RES and ON hoses (from the Chaparral catalog):



It looks like you have already found a source for simple auxiliary petcocks. 

Sweet solution, Kerry

Should I put the #40 pilots back on, the ones with the eight holes, now that everything is running right or will they definitely make it run too rich?  They are the only pilots that anyone around here carries.  I mean, a #40 Mikuni pilot is a #40 mikuni pilot, right?  Maybe just redesigned.  Or does the new design make it run to rich...

If I can't use those #40s does anyone have any they want to sell?

If you are putting pilots with side holes put in 37.5 ... yea the stock GS size ... those holes make it flow just ~ 1 size higher ... no holes = 40... 40 holes are too much ... they are = 42.5 no holes...  :x
I have been stuck with the same shiity dilema ... I ended up yanking them off my bike and putting it in srileo's and I tried the bleed (holes) in mine and it works about 37.5 = 40.
Cool.
Srinath.

Thanks

So does that mean that on new models that the stock pilot size is one lower than 37.5 or does Suzuki still use the pilots without holes?

Don't forget - the '01+ carbs are totally different than the older models.  They have a pilot jet, a mid-main and a main ... none of which are the same size as the older ones.  I think they're even from a different "series":

Quote from: DomThanks

So does that mean that on new models that the stock pilot size is one lower than 37.5 or does Suzuki still use the pilots without holes?

Yea what Kerry said...
Nothing from a 01+ translates to an 89-00. You need 40 non bleed - aka no holes, or 37.5 bleed - with holes.
The 01+ has 17.5 funky ass pilots and they rejet with a 20, do not try that ... its a different number, they are set differently in the carbs making it work differently and they have mid mains... nothing copies over. Heck the whole carb body is 1mm bigger ID...
Cool.
Srinath.