Running problems

[gregvhen]

My bike will start up when i take out the air filter and spray carb cleaner in the box, but then itll just rev for a seond then die.  the floats are right, the jets are clean, the slider move fine, tired the petcock in all 3 positions, gas is good. cant figure out whats goin wrong.  even if there was a problem with the float height though, just the fuel in the bowls should be enough to run it for at least 2 minuetes.

[The Buddha]

High float can get gas in the chamber as a liquid and kill the spark by wetting out the plug.
Cool.
Buddha.

[elementguy053]

The gs500 has what's called a Constant Velocity Carburetor. What this means: I have no freaking clue!
But I do know that in order to function correctly it has to have laminar flow (all air flowing without turbulence in one direction) into the carbs. When you remove the air filter you may be causing turbulent flow and causing the carbs to malfunction. It won't damage them, but it will keep the bike from running. You'll notice the bike won't run without the airbox either.
-Max

[The Buddha]

Elementguy ... you should prolly stic to the elements.

However I have to look into whether the reynolds number for a carb is typically below 2000 or over 3000.
With My luck, it will be 2500 ...

Anyway constant velocity carb is one where the air flow through the venturi - where the needle is is the measurement point for the velocity and air velocity there is constant no matter the rpm.

Is it always the case ... is it ... is it ... can anyone tell me ?

I doubt he's gone from laminar flow to turbulent flow and doubt it even matters.

The jets and in this case mains and needle are what matters feed in fuel into that vacuum. OK man I have to find out if it is laminar or turbulent @ this point. I'll be back after visiting my favorite corner of the world ...

Cool.
Buddha.

[elementguy053]

I"m no motorhead, I heard it from a mechanic on youtube, so i can't source it anywhere and i'm not about to take off the airbox again to test it, but greg seems to be in a position to try it out.  See if your bike runs without the airbox on. Any better explanation for what might be going on?

edit:
Just kidding I found it.
Relevant information begins at about 9:30. See? I wasn't talking out of my ass! 
http://www.youtube.com/watch?v=4azg3hIl9oI

[The Buddha]

I actually could not find laminar or turbulent flow, dont matter though.
Oh, yea at low velocities its not constant velocity, that's why the pilot and the air screws are ahead of the venturi.
I cant see the video @ work, have to at home.
Though plenty of people pull off their air box ... makes little difference.
Cool.
Buddha.

[cboling]

Greg: Okay, now that the sci-fi babble is over, here are some "simple" methods to figure out what's going on. I've been through the same thing in the past few months and although there is a ton of information here (some good, some not good including some of my not so good) here is what I have found to help.

First - Clean the carbs (which you stated you have done.)
Second - Set the float height (which you stated is correct)
Third - Make sure fuel is getting to the carbs. (If it's in the float bowls, it is at least getting there, right?)
Fourth - Make sure you have spark. (Pull a plug place the cable on the plug and run the ignition. Spark at the plug?)
Fifth - Install the carbs and do not install the choke cable or the throttle.
Sixth - place a temp gas line to the carbs to make sure you have fuel.

Now, place your palm over the open face of the left carb. When you try to start it, does the carb feel like it is "sucking" pretty hard against your hand? If so, you should also feel your palm get wet. (I know, it sounds bad in all kinds of ways but, really.) You might even get it to fire off slightly.

Now place your palm over the right carb face and feel for the same suction. Gas on your palm? Did it act like it was going to start?

If you don't feel enough suction, turn the idle screw (big thumb screw at the bottom) until you can see it just touching the throttle lever. A couple of quarter to half turns then repeat the 2 steps above. Any better? If you can get it to sort of run doing that, you had a problem with the engine NOT sucking enough fuel into the carbs to get the engine to turn over. Simply remove the carbs. Make sure to clean them really really well. Make sure you clean all the little tiny holes and passages with a bread bag wire or similar. Keep in mind, no air box or filter will add more air and can cause more air to get in than fuel which may keep the bike from continuing to run.

Another thing about the carb cleaner (which you already know I am sure) is that you are only introducing enough "fuel" which is going to burn very quickly and likely at a high rpm. Hence, short run time.

Also keep in mind, you will have to push the choke slide in manually IF you can get the bike to run even slightly. Then you can operate the throttle plates by hand to give it extra fuel.

hope that helps and good luck, I nearly pulled all my hair out trying to get mine running. I still have an idle problem which I believe is related to a clog.

[gregvhen]

Greg: Okay, now that the sci-fi babble is over, here are some "simple" methods to figure out what's going on. I've been through the same thing in the past few months and although there is a ton of information here (some good, some not good including some of my not so good) here is what I have found to help.

First - Clean the carbs (which you stated you have done.)
Second - Set the float height (which you stated is correct)
Third - Make sure fuel is getting to the carbs. (If it's in the float bowls, it is at least getting there, right?)
Fourth - Make sure you have spark. (Pull a plug place the cable on the plug and run the ignition. Spark at the plug?)
Fifth - Install the carbs and do not install the choke cable or the throttle.
Sixth - place a temp gas line to the carbs to make sure you have fuel.

hope that helps and good luck, I nearly pulled all my hair out trying to get mine running. I still have an idle problem which I believe is related to a clog.

First - check 
second -  check
third - check 
fourth -  check
fifth - have to do that tommarow at school.
siixth - I already know i have fuel so check.

thanks for the had tips.  You know, why i was reading this, i was thinkin, i may have put the plastic washer on the needles on wrong. Do they go on top of the permanent metal wahser or underneath it?


My teacher just set the floats to what he thinks he links, regardless of the what the measrements are.  I'll see how it works tommarow.

and element guy, yea stick to skating. or the elements. youtube is not always a very viable source for mechanic knowledge.  and i already said it ran for a few seconds without the airbox. and alot of bikes run without airboxes. hell, my buddy and  have a kat 600 on a dune buggy were makin that has ran without anything on the carbs at all. (only in the shop, and not for long time of course. I am well aware of the threats that unfiltered air pose to an engine.)

[cboling]

I put the washer between the e-clip and the white plastic piece.

As for the float height, I finally found that while I have the carbs off, take the bowls off, use a metric ruler or metric dial caliper. Hold it upside down, measure from the highest edge of the float (white plastic) to the edge of the carb body. I found that mine set at 15mm, is dead on the gasket line. 14.6 may be better but that's a difficult measurement when all you have is mm marks. (not half mm marks.)

[gregvhen]

I checked today, and my needles and washers are correct, i looked in the manual. still doing the same vrooooooommm.....putt putt dead.   How many turns is everybodys idle on? start couting the moment it touches the metal peice that opens the carbs up.  Also the idle adjustment screw is behind some plugs i know that much, but is it on the side or the bottoms of the carbs?
One more thing, the step where you put your hand on it to see if it gets wet, well i know what you were getting at. when the choke is on, my teacher said i should literly see fuel coming out (towards me) from the two little holes on the bottom before the venturi, and going up into the venturi. Thus, if your hand is over the hole, then your hand will get wet. well i didnt see the fuel coming out and no hands got wet.  So what does that mean to you guys?

[gregvhen]

OK folks, today I decideded to go straight from the tank to the the carbs. thinking maybe the frame petcok aint good.  What do you know, she started up a couple times and ran when i pumped the throttle. Kept dying at low revs, but once i got it warm from running high revs i slowly let her down easy and she ilded just fine.  Im very happy now that itll run, but im hoping that once I put the petcock back on, it'll still run.

I cleaned out the petcock by 1 shooting air through it, then put it in the carb dip tank for 10 minites, then rinsing with water, and shotting air again.  I noticed though when i was flushing with water that when i turned it to the ON position, no water came out even when water went in both holes, and same goes for RES.  The only time i got anything to flow was in the PRI posistion. does anyone know why this would be?

[elementguy053]

There's a diaphragm that the vacuum line from the carb pulls on that opens fuel flow from on and reserve. Prime is for when your carbs are empty and the engine can't make the vacuum to pull the diaphragm and lets fuel flow through freely to fill the carbs.

[gregvhen]

There's a diaphragm that the vacuum line from the carb pulls on that opens fuel flow from on and reserve. Prime is for when your carbs are empty and the engine can't make the vacuum to pull the diaphragm and lets fuel flow through freely to fill the carbs.

Oh shoot, i completely forgot about that. Thanks so much for reminding me. It connets the petcock to one of the holes between the two carbs on the top right? like right above the fuel T?