FathomYourFears Posted May 14, 2010 Share Posted May 14, 2010 I have a 1981 XS400 special. As you may know, the petcock is a vacuum-fed when in the on position and when in the prime position it dumps fuel into the carbs through gravity. My question is: when it is set to reserve, is it still vacuum-fed? or does it switch to gravity fed like prime position? Thank You. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted May 14, 2010 Moderator Share Posted May 14, 2010 reserve is vacuum operated Link to comment Share on other sites More sharing options...
FathomYourFears Posted May 14, 2010 Author Share Posted May 14, 2010 Arrggg. Thanks. This means I need a petcock rebuild kit. I was washing my bike today and I noticed my oil in the sight-glass went up above the glass. So I went to drain it and it smelt horribly of gasoline. How difficult is the rebuild? Any good place to get the kit? Thank You. Link to comment Share on other sites More sharing options...
duaneage Posted May 14, 2010 Share Posted May 14, 2010 Arrggg. Thanks. This means I need a petcock rebuild kit. I was washing my bike today and I noticed my oil in the sight-glass went up above the glass. So I went to drain it and it smelt horribly of gasoline. How difficult is the rebuild? Any good place to get the kit? Thank You. I replaced the little o ring on the valve inside mine and it stopped leaking. Bought a bag for a dollar at Lowes. that was a year ago and it still doesn't leak. Link to comment Share on other sites More sharing options...
Runningdog Posted May 14, 2010 Share Posted May 14, 2010 I got my kit from Keyster.....easy job to refurbish the petcock, only about 7 parts to worry about.... Link to comment Share on other sites More sharing options...
HoughMade Posted May 14, 2010 Share Posted May 14, 2010 To be clear, the fuel is never drawn by vacuum. The vacuum only turns the flow on and off and the fuel is fed by gravity. Rather than rebuild the petcock, I put on an adapter plate and manual petcock. Link to comment Share on other sites More sharing options...
FathomYourFears Posted May 15, 2010 Author Share Posted May 15, 2010 To be clear, the fuel is never drawn by vacuum. The vacuum only turns the flow on and off and the fuel is fed by gravity. Rather than rebuild the petcock, I put on an adapter plate and manual petcock. You got rid of the stock one and put a different petcock in? Or did you put a manual one in-line? Link to comment Share on other sites More sharing options...
HoughMade Posted May 15, 2010 Share Posted May 15, 2010 You got rid of the stock one and put a different petcock in? Or did you put a manual one in-line? I replaced the entire petcock. Here is a pic of the finished product: I got the adapter plate and petcock here. Notice that I had to notch the lever because otherwise it would not go full to the reserve position, but that was no big deal. https://www.partsnmore.com/cat_index.php?model=xs400&category=carb Link to comment Share on other sites More sharing options...
FathomYourFears Posted May 24, 2010 Author Share Posted May 24, 2010 UPDATE: I refurbished the petcock. I replaced all the part and reassembled. When in the "ON" position, my petcock drips. Is this normal? Link to comment Share on other sites More sharing options...
Moderator drewpy Posted May 25, 2010 Moderator Share Posted May 25, 2010 UPDATE: I refurbished the petcock. I replaced all the part and reassembled. When in the "ON" position, my petcock drips. Is this normal? no, it should only pass petrol in the prime position Link to comment Share on other sites More sharing options...
FathomYourFears Posted May 25, 2010 Author Share Posted May 25, 2010 no, it should only pass petrol in the prime position Unfortunetly gas/petrol still passes through. Any ideas on what the problem is? Link to comment Share on other sites More sharing options...
Moderator drewpy Posted May 25, 2010 Moderator Share Posted May 25, 2010 recheck the seals are sealing, i think i had to do mine as i got the parts wrong way! Link to comment Share on other sites More sharing options...
exess4 Posted May 29, 2010 Share Posted May 29, 2010 I have a 1981 XS400 special. As you may know, the petcock is a vacuum-fed when in the on position and when in the prime position it dumps fuel into the carbs through gravity. My question is: when it is set to reserve, is it still vacuum-fed? or does it switch to gravity fed like prime position? Thank You. You have an '81 but this just in. RECALL - "Petcock may be defective" http://www.motorcyclistonline.com/motorcycle_recalls/49/1978/yamaha/xs400/18539.html Link to comment Share on other sites More sharing options...
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