Re: Flooding GS750
Re: Flooding GS750
zentar said:
Should I rebuild the petcock anyway even though in the ON position it only flows gas if there is a vacume?It does seem to be working properly.
Remember that there are two common problems caused by a faulty petcock. You have to consider and test for both problems:
1. As you suggest, the petcock can flow fuel without a vacuum.
2. The vacuum diaphram itself can be torn.
A torn vacuum diaphram allows fuel to be pulled into the engine
through the vacuum hose when the engine creates vacuum. This causes
rough running because the cylinder with the vacuum take-off runs too rich (raw, unatomized fuel).
The other symptom
is a slow leak of fuel through that vacuum line when the engine is off. This is usually marked by a slowly growing puddle of fuel under the bike as it sits overnight. In my case, the fuel flowed from the drain hose from the airbox. Fuel can also find its way into the cylinder and then past the rings into the crankcase.
Here is how to test for both problems:
1. With the engine off and the petcock in the "run (on?)" position, pull the fuel line. Does fuel flow from the petcock? Let stand a long time when checking. There should be
no flow. Repeat this test with the petcock in the "res" position if present.
Now move the selector to prime. *** Warning - Expect Fuel to Flow! *** Fuel should flow on "pri". Then, turn to "run (on?)" to stop the flow.
2. Leave the fuel line off. Pull the vacuum line off at the engine, not the petcock end. With the petcock on "run (on?)" or "res", apply vacuum to the vacuum line (by mouth should work *** don't inhale or swallow fuel that may be present in the line***). While vacuum is applied fuel should flow, and should stop entirely just as soon as you stop applying vacuum.
You should have found no gas in the vacuum line. If you got a mouthful of gas while applying vacuum, you can be certain your petcock is bad.
If no problem was apparent after this testing, I would thoroughly pinch off that vacuum line (it must be connected or you'll have a terrible lean condition on cylinder two) and try running the bike on "pri". If it runs better, suspect that petcock.
Ron and others are correct in stating that you have to deal with any rust/dirt condition in your tank/lines/carbs first. And, if you have a laundry list of problems going on, you're going to have a hard time diagnosing the problems yourself. Do the best job you can, eliminating the potential problems one at a time. 1. Rust/dirt 2. Install Inline Fuel Filter 3. Petcock 4. Rubber Intake Boots 5. Fine points inside the carbs. Good luck.
Is there anything I got wrong here, guys?