Posted May 14, 201014 yr 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.
May 14, 201014 yr Author 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.
May 14, 201014 yr 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.
May 14, 201014 yr I got my kit from Keyster.....easy job to refurbish the petcock, only about 7 parts to worry about....
May 14, 201014 yr 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.
May 15, 201014 yr Author 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?
May 15, 201014 yr 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
May 24, 201014 yr Author UPDATE: I refurbished the petcock. I replaced all the part and reassembled. When in the "ON" position, my petcock drips. Is this normal?
May 25, 201014 yr Moderator 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
May 25, 201014 yr Author no, it should only pass petrol in the prime position Unfortunetly gas/petrol still passes through. Any ideas on what the problem is?
May 25, 201014 yr Moderator recheck the seals are sealing, i think i had to do mine as i got the parts wrong way!
May 29, 201014 yr 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
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