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Why'd he put a shut off valve in?
- Thread starter thielb
- Start date
ken56
XS400 Enthusiast
Maybe your bike has a faulty petcock and it was how he stopped the fuel flow when engine was not running or your PO did not understand the difference between the ON and PRIME positions and ran the bike in prime thinking that was the only way to deliver fuel to carbs.
Richmond
XS400 Enthusiast
My dad's old bike had a leaky petcock diaphram even after he rebuild it because the seat wasn't good so he threw one of those on there just so it wouldn't flood the carbs like Ken said.
thielb
maxim
Well my petcock was in the on position when I got the bike. I thought maybe the valve was to stop fuel flow when the bike was stored. So I stored the bike with it open for a week while I was at school to see what happened. Nothing seemed to be out of line when I got back. Bike started and ran fine and there were no leaks anywhere. How would I know if the petcock was damaged or not working properly?
I can't resist .... If the bike doesn't start and run fine ..... sorry
I don't actually know, but I assume that too much gas would flow down into the carbs and overfill them. Not sure if it would actually leak out.
One thing to check though which could be a hidden problem. If they overfill and leak internally instead of externally, then you could have gas in your oil. It wouldn't affect the bike starting and running (seemingly fine) but it could spell trouble in the long term if you run the engine. Better open the filler and smell inside - or siphon or drain some out to check.
The $2 shut-off is cheaper than fixing the petcock but it would seem to be risky if you ever forgot the shut-down routine.
I guess for me, the clue is when I want to take the fuel tank off, and the fuel doesn't stop dripping out. It should stop letting fuel out. Mine on the other hand, will drip at a high rate till I can re-connect it, or plug it, or clamp it with a vise grips or something. Smoke anyone????
thielb
maxim
Thanks Lou, sorry for talking out of my ass, should really think before I type 
I'll definitely have a sniff around the filler. When I disconnect that line to pop on a fuel filter, gas should stop leaking as stated my arfstrom correct? Same concept as if I was taking the tank off yea? That seems like the easiest way to detect a leak. I've read plenty of posts on here from guys warning about the severity of gas getting in the oil so I definitely want to get to the bottom of this. Thanks a ton for the help everyone!
I'll definitely have a sniff around the filler. When I disconnect that line to pop on a fuel filter, gas should stop leaking as stated my arfstrom correct? Same concept as if I was taking the tank off yea? That seems like the easiest way to detect a leak. I've read plenty of posts on here from guys warning about the severity of gas getting in the oil so I definitely want to get to the bottom of this. Thanks a ton for the help everyone!
MrStubb
XS400 Addict
I'd have to agree with most posts by saying you have a leaky petcock. I am thinking of the same mod for added insurance in case of a leak. My crank case did fill up from a leaky petcock and it may be a while before it's totally flushed out. On my LS2 I always close the valve a block before I shut it down and run the carbs dry. My carbs have always seemed to leak even with new needles.
just disconnect the line at the carb and open the tap, if fuel keeps dripping out, the petcock is leaking!
thielb
maxim
Will do, drewpy. Simple as that huh. If it is leaking, I really hope I can fix that one way or another so I can ditch the valve. Would be a bummer if I ever forgot to shut it and gas got where it wasn't supposed to. Thanks for the help!
probably not best Idea either.
thielb
maxim
Well CRAP! Finally got home tonight and was going to take the bike out for a spin but wanted to check the petcock/shut-off valve situation first. Pull of the line with the petcock at "on" and she damn near dumped the whole frickin tank on me 
. There is definitely some flow. Take a whiff at the oil cap and holy shit. So my POS petcock is garbage and now I need to change my oil STAT before I ride. Not a happy guy right now. So I know what kind of oil to use, I see plenty info on that all the time here. How about the petcock situation? Anyone have any recommendations? Obviously I can just keep using the shut-off valve but that's a pretty shitty way to fix the problem imho. Is there a petcock at mikesxs that fits the maxim?
. There is definitely some flow. Take a whiff at the oil cap and holy shit. So my POS petcock is garbage and now I need to change my oil STAT before I ride. Not a happy guy right now. So I know what kind of oil to use, I see plenty info on that all the time here. How about the petcock situation? Anyone have any recommendations? Obviously I can just keep using the shut-off valve but that's a pretty shitty way to fix the problem imho. Is there a petcock at mikesxs that fits the maxim?
MrStubb
XS400 Addict
Get Brave. Mine was easy to cobble together once I took it apart. Be very cautious with the diaframs they can be delicate. Also on mine there was a spring, needle and an o ring. There might be some transfer of material from the o ring to the valve seat. Thanks to that F#%$@*&^* ethanol fuel. You can find a new o ring to replace the original at most good hardware stores. The original has a certain profile but for the time being it will be fine. Make sure that you carefully clean the valve seat with out scratching it. I also pulled on my spring a little to add some more pressure on the valve when it closes. This might not be the best since it also may restrict fuel flow. Putting it back together was a bit of trouble for me holding the whole thing together as I installed the screws. You can test it with a couple pieces of vacuum line by drawing on the vacuum side with some fuel in the tank. fuel should flow with vacuum and stop as you stop drawing on the vac line. If you start to taste liquid fuel Stop immediately. Fuel isn't tasty and can give you dragon breath. If this happens order a rebuild kit since your diafram has been ruptured. (insert safe sex joke here). Good luck
thielb
maxim
So I'm still lookin around at petcock rebuild videos. Feeling a little more confident about it now. In the mean time, religiously using the shut-off valve. New oil is in now. How quick should I change the oil again? I know most people recommend pretty quick again after the first change following the contamination. Help?
MrStubb
XS400 Addict
I'd suggest the same. You want to get that gas out of your crank case as soon as possible. But you also don't want to waste a lot of time and money either. I think you could go a few hundred miles or possibly a couple weeks. I'm not really sure what the recommendation is for this. I also will have to do this as soon as I get mine up and running. I did drain the oil when I discovered this. But since it hasn't really run yet aside from trying after I got my carbs back on and petcock working. I don't think I'll have much of a problem. I've seen petcock kits on line for about $20.00 give or take and they have all that you'd need. Check Mikes XS and there's a place in Canada where I got my LS2 Carb kits from. Do some research I'm old and have C R S. (cant remember s$%&stuff)
thielb
maxim
Thanks a ton MrStubb, really appreciate the input. I'll probably do oil and filter in a couple hundred miles unless someone else has something better to suggest. I'll start searching for petcock kits
heres one off of youtube, I didn't have time to review it, but I think I will be double checking it sooner than later. Somewhere I think I posted a really good PDF, last year, or the year before. good luck Youtube allways give you a few extra's that pertain to the subject, just like this system.
