I have a 2005 GS500F that I've been rebuilding, but it's my first vehicle with a carburetor. I already cleaned it out completely, but did not replace anything but some o-rings because everything else looked fine. However, one of the current problems I'm also fixing is that there is no vacuum for the fuel. So to see if I cleaned out the carb correctly, I tried running it on prime. It ran, but the carb was overfilling and gas was continuously coming out of the overflow tube until I turned the valve back to on (instead of prime). I was wondering if since it overfills on prime, will it overflow on "on" also? I have conflicting thoughts about this. One being that once I repair the vacuum issue, the vacuum will solve whatever problem the overfill has. On the other hand, prime shouldn't overflow continuously (and doesn't use the vacuum), and that could mean that the pins or something are bad and actually need replacing (even though visually they look fine and the rubber is not dried up at all).
Prime is gravity fed, so I was thinking that, since the gas tank is higher than the overflow tube, it's also possible that it's overflowing in prime due to simple physics.
Also, when I reassembled the carb, I put the jets back in the way I found them, and that was threaded all the way in. I've read some things that mentioned adjusting the jets. Can these jets cause overflow issues? If so, what can I reference to correctly adjust them?
Since I'm here, I'll also ask this. With my vacuum issue, the carb will not pull fuel from the tank. I diagnosed it by bypassing some parts, referencing the electrical diagram, and the ignitor ended up being what seems to be the problem (when bypassed I got a vacuum to the carb, and thus the solenoid functioned, which was one of my concerns). I ordered a used ignitor today, but I was wondering if this was a common malfunction of the ignitor?
I look forward to getting some help on this. Thanks a lot!
One of two things...either the float height is improperly set OR the needle valves/seats are worn out.
I would question why you're not getting a vacuum.
From my diagnostics so far, the igniter isn't sending the signal to operate the solenoid, which allows the vacuumed air to pass through to the carbs. I have that on order now.
As for the float height, the only adjustable thing I saw was the screw that holds the axis of rotation down. So how do you adjust the float height? I'm pretty positive it's not a wear issue, so I'd like to try the float thing first.
I just realized.... the floats can be inserted upside down if done by a first time carb rebuilder without common sense... I'm gonna check it out after classes tomorrow. I remember that the floats are flat on one side and cone shaped on the other. Thanks for getting my train of thought on track!
Quote from: mcg2000 on April 11, 2012, 08:34:00 PM
I just realized.... the floats can be inserted upside down if done by a first time carb rebuilder without common sense... I'm gonna check it out after classes tomorrow. I remember that the floats are flat on one side and cone shaped on the other. Thanks for getting my train of thought on track!
No problem! Good luck!
So the floats cannot be inserted upside down. However, I finally figured out that the tabs on the floats can be adjusted, and doing so seals the pins correctly. The down side of my carburetor success is now the engine has it's turn in showing it's negatives, and it burns and leaks oil like crazy. Looks like piston rings, oil pan, and oil filter cap. I've never torn an engine down before, but I understand how they work, so this will be interesting.
These engines are cake to tear down. I had to replace the crank and a rod. I got mine in a laundry basket, in pieces. reassembled without manual, etc. you'll be good to go
Dang, I already ordered a manual! Good thing it was cheap. Thanks for reassurance. That means this will be a good first engine for me to work on. Not that I want to keep doing it, but since I do my own work, it's inevitable.
Am I the only one having a hard time understanding what's going on here?
The entire fuel system has nothing to do with anything electrical. No ignitor, solenoid, etc will affect fuel flow. Search around here and on the wiki and make sure you understand how the petcocks work. There are simple tests to check the vacuum of your petcock.
Have you done a compression test to confirm it's piston rings? The oil pan leak is probably just a gasket, but the oil filter cap has an o ring under it. Could be ripped, pinched, or missing. Before you touch the 3 acorn nuts around it, search the term "oil filter studs".
Quote from: Big Rich on April 14, 2012, 02:19:26 PM
Am I the only one having a hard time understanding what's going on here?
The entire fuel system has nothing to do with anything electrical. No ignitor, solenoid, etc will affect fuel flow. Search around here and on the wiki and make sure you understand how the petcocks work. There are simple tests to check the vacuum of your petcock.
Have you done a compression test to confirm it's piston rings? The oil pan leak is probably just a gasket, but the oil filter cap has an o ring under it. Could be ripped, pinched, or missing. Before you touch the 3 acorn nuts around it, search the term "oil filter studs".
I must disagree. Check out the parts diagram of the petcock for my year/model I posted below. There is no vacuum to it directly. However, the vacuum will pull the gas from the carburetor, and thus, by physics, will pull gas from the petcock. But you said there is no electrical control of fuel flow, so I must ask, how would the system know when to put in more gas when you twist the throttle? There's a throttle sensor on the side of the carburetor (#57 of second image, solenoid is #47), which in turn sends a signal to the solenoid, which in turn allows more or less of the vacuum through. The igniter's sole purpose in fuel flow is to complete the solenoids circuit when starting the bike, as the solenoid's ground is what's controlled through the igniter. Thus, if I'm not getting gas to the engine during starting, then it's either the solenoid or the igniter. See my other post on help confirming a solenoid or igniter issue (though I think we have it resolved).
As for the engine components, I've decided to go ahead and do a complete top end rebuild (also the oil pan gasket). It will be sold to somebody, and I'd rather not have something else stark leaking a couple months later. Better safe than sorry.
(http://i1146.photobucket.com/albums/o540/mm_mcg2000/Petcock.jpg)
(http://i1146.photobucket.com/albums/o540/mm_mcg2000/carb.jpg)
Alright, after reading this and another post, I went out ot check the petcock. Turns out you're right. There's a vacuum line that runs straight to the petcock from the constant vacuum line. No solenoid controls it. Did I mention? Crap!
I already bought replacement parts.... I guess for my first carburetor repair it could've been worse. Now to see if I can just resell these extra parts!
I'm going to take apart the petcock right now and see what's seized up. Thanks for posting this Big Rich... and for the other post Adidas.