Question about 1982 Yamaha XS 400
Your bike has a vacuum operated fuel petcock....so there is a vacuum line from intake that acts on a diaphram in the petcock to open the fuel supply up upon startup. I suspect the diaphram is leaking so when it lifts the diaphram to admit fuel to carbs, the vacuum is drawing raw fuel down the vacuum line flooding the intake.
Have a container handy, remove the vacuum line from petcock...check for fuel leakage....now manually open the petcock by setting it to the PRI for "prime" position...you will likely see fuel leaking out vacuum port.
Kits to rebuild the petcock are readily available.
Posted on Mar 22, 2011
First check to see if the oil level in your crankcase is too high. If
you have a vacuum petcock malfunction (hole in the diaphragm) or if the
fuel petcock is left in the prime position and a float needle sticks,
then you get you get gas running into the cylinders, past the rings, and
into the oil.
When you start your motorcycle the oil/gas mixture has no place to go, the crankcase is too full, and the mixture exits through the crankcase breather into the air box where it will ruin a paper air filter. Always turn your fuel petcocks off when not driving. If the petcock diaphragms are bad rebuild the petcock with K&L rebuild kits or replace the fuel petcocks with new ones. If the float needles in the carburetors are bad or sticking, take the carburetors apart, clean them, and replace any worn or damaged parts You will have to change your gasoline saturated oil for it will no longer properly lubricate your motor.Just a note: in 1983 brand new Honda's would fill there engines in gas. All the components were clean and new. This can happen to any machine in any condition at any time. When not riding always turn off the fuel vales never leave them in the prime position.
Posted on Mar 22, 2011
Save hours of searching online or wasting money on unnecessary repairs by talking to a 6YA Expert who can help you resolve this issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
Here's a link to this great service
Posted on Jan 02, 2017
Tips for a great answer:
Mar 01, 2015 | Craftsman Snow Blower / Snowblower Bottom...
Sep 07, 2014 | Motorcycles
Feb 19, 2013 | Honda Motorcycles
Jun 08, 2012 | Motorcycles
Aug 12, 2011 | 1982 Yamaha XJ 650
Jun 03, 2011 | 2004 kawasaki ZRX 1200 R
Sep 07, 2010 | 1981 Yamaha XJ 650
Aug 29, 2009 | 1994 kawasaki ZZR 400
May 26, 2009 | 2004 Yamaha YZ 450 F
Jun 19, 2018 | Motorcycles
393 people viewed this question
Usually answered in minutes!
Step 2: Please assign your manual to a product: