1980 Yamaha xs400 Fuel Petcock Leaking

Is the tank on the bike? Is the petcock switched to on? Is gas leaking when the bike is off? Is the gas coming from a small hole in the nylon piece sandwiched between two petcock halves?
 
Thanks for your response. No the tank is off the bike. I purchased a new petcock rebuild kit. On the diafram there is two gaskets. Looks as though they were designed to stay together. I dont have a gasket for the bottom half of the petcock housing. Should I tear one of those gaskest off of the diafram and use it on the bottom half of the petcock?
 
No I did Not. What is the nylon square? I have a square plastic peice that the diaphram sits in, but this new kit has 2 rubber gaskets on it
 
Nylon or plastic piece about an 1 1/4" square, thread one of the diaphragms through the hole in the middle of it, making it a total unit, diaphragms plus plastic piece.
 
okay I see how it works. I will give it a try and let you know.

Thanks Buddy You Are The greatest
 
Okay my man. Replaced fuel petcock no leaks Thanks. Heres my next problem, my bike cranks by will not start. What could cause that. Battery is fully charged. Fuel tank has plenty of gas. Please Help me

Thanks
 
Did you set the petcock to "prime" to start it?

If gas is getting to the carbs, do you have spark? Pull a plug out and rest it against the head and see if it sparks. If you have spark, spray some carb cleaner down the carb throat (filters off) whule cranking with the throttle open. If it fires, but will not keep running, the issue is fuel.

Has this bike sat for any length of time? If so, the carbs need a good cleaning....a real cleaning, not pouring something in the gas tank. Plenty of threads here on how to do that.

Good luck!
 
Yes gas is getting to the carbs. Yes I have spark on both spark plugs. I sprayed some starting fluid in the air filter housing and it starts for a second and then cuts off. It has a pop when running. Yes the bike has set for a long while.

Thanks
 
Well then, looks like it's time for the carbs to come off for a good cleaning. I look at carb cleaning like a new mother looks at nursing- bonding time.
 
I have taken the carb off and begin cleaning. What is a good cleaning solution you would recommend?
 
Okay I have cleaned the carb real good and put it back on the bike. Bike still just turns over and no start. What could be causing that. Any idea

Thanks
 
Hello My Buddy

I am turning the throttle and leaving the choke in and then I pull it halfway out while cranking and then all the way out just to see if it will start. Bike still cranks but no start. Question: Can I start it with the air filters off, or do they have to be on?

Thanks
 
You can start it with the filters off. They just need to be on to do adjustments. Unfortunately, sounds like you still have clogged passages. I use Berryman's carb cleaner. When everything is clean, you should be able to see the carb cleaner shoot out the idle mixture hole and the 3 holes over the throttle butterfly. You should be able to get flow of carb cleaner both when spraying in the air jet at the carb inlet and when spraying it through the idle jet passage with the idle jet removed. Make sure the idle jet is 100% clean.

Good luck!
 
Thanks for the advice. I tooked the carb back off and remove all the jets nd everthing. I took the carb to my yamaha dealer, and they are going to soak it in their solvent for me. Thanks Ill let you know how it turns out.

Thanks Again
 

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