Hi writing about issues with bike running. Talked with someone who thought maybe the diaphragm was bad on my petcock. Just curious if anyone is familiar with this problem, and how they diagnosed and fixed it. Thank you and hve a great day!
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petcock bad?
- Thread starter zonk39
- Start date
Onetype
XS400 Addict
When I was having problems with mine it wouldn't flow fuel very well, even after taking it apart and cleaning it. I could tell because my in-line filter wasn't filling up, bike would die on me while running etc. I ended up ditching it for a manual, you can find repair kits here as well as the manual petcock. I know quite a few of us on here are running the manual one.
http://www.partsnmore.com/parts/yamaha/xs400/?filters[fitting]=custom
http://www.partsnmore.com/parts/yamaha/xs400/?filters[fitting]=custom
Thanks for the input. Do you have a pic of the manual one you are talking about? How much are they and where do you get them. Also, my neighbor worked on the bike. All that runs from petcock to carb is a solid black tube. Is that OK? Thanks again and have a great day.
Onetype
XS400 Addict
The link I provided will take you there. Check under the carb section, its the universal petcock. You need the right plate though so you will have to measure the bolt holes on the bottom of your tank once you take the petcock off. That is assuming you want to to go that route. With the manual you have to manually turn it to on/off everytime you ride. Its around $50 for the petcock and the plate.
The vacuum petcock you have now should have a line going to the carb boot. Thats what starts the flow once the bike is started and it has vacuum. IMO its a neat design but if there is a chance to simplify things I always will. What exactly is the problem with the current one?
The vacuum petcock you have now should have a line going to the carb boot. Thats what starts the flow once the bike is started and it has vacuum. IMO its a neat design but if there is a chance to simplify things I always will. What exactly is the problem with the current one?
Does your petcock have a PRI (prime) setting? ON/RES require vacuum from the engine turning over to open the diaphragm, but PRI does not. Leave PRI for a few seconds and open the float bowl drain plugs slightly to check for fuel.
If it works on PRI, but not on ON/RES your petcock vacuum line is probably cracked or leaking.
If it doesn't work on any setting try cleaning the gas cap to make sure it is venting properly.
Cut the fuel line from the tank to the carbs and insert a fuel filter; this will also allow you to see fuel flowing.
Failing all of that pull the carbs off and pull the float needle seats off; there may be a screen below them that can get clogged.
We need to know if fuel is actually getting to the carbs and on which petcock settings.
Finally, list your year/model in your posts. Some of these details vary by year.
If it works on PRI, but not on ON/RES your petcock vacuum line is probably cracked or leaking.
If it doesn't work on any setting try cleaning the gas cap to make sure it is venting properly.
Cut the fuel line from the tank to the carbs and insert a fuel filter; this will also allow you to see fuel flowing.
Failing all of that pull the carbs off and pull the float needle seats off; there may be a screen below them that can get clogged.
We need to know if fuel is actually getting to the carbs and on which petcock settings.
Finally, list your year/model in your posts. Some of these details vary by year.
Thanks for the input. Turns out I found a small crack in the vacuum line hooked up to the petcock under the tank and to the other carb. Don't know if that would cause a problem or not.
cutlass400
XS400 Member
there are cheap rebuild kits on ebay and it's not hard to do if it's old just rebuild probably needs it anyway
billymac
XS400 Member
Just bought a street tracker xs400h, built by Doil Williams. Beautiful, but it won't run; petcock suspected after many other checks. This thing is a Rube Goldberg nightmare. Whatever happened to on/off/reserve? Any suggestions? Please help this old dawg, this thing is going to drive me to my grave.
billymac
XS400 Member
Mine is an '81 xs400H; who designed these fool petcocks? Whatever happened to on/off/res? Would like to ditch whole stock system and go to the above-mentioned type. At age 72, I still can remember when to turn the tap on and off - screw this primary/run system, without even a clearly defined OFF setting. Help, please, this thing is going to drive this poor old Irishman to an early grave. Thank you, me friends.
Welcome to the forum. Can you post a picture of what is driving you crazy?
My bike is all original and it came with FUEL/RES/PRI/ON. If there are no leaks in the vacuum line it flows on all 3 settings. It always flows on PRI. Some have written on here about having to clean detritus out of little tubes. Have you tried that and it still doesn't flow?
billymac
XS400 Member
Thank you, Lou. No, I have not gotten into the tank yet. But if I have to do that, I would rather just replace everything having to do with the petcock than to try this and then try that. Some have told me to go OEM, and others say to buy a simpler system with on/off/reserve. Even at my advanced age of 72, I can still remember when to turn taps on and off. Unfortunately, I have not been able to locate either an OEM or a generic replacement. Suggestions most welcome. Incidentally, I just bought this bike; it is a beautifully built Doil Williams Street Tracker; looks like an old Kenny Roberts bike. Have not been able to get it to start, although have been at it since Monday. Strange, my Nortons, Triumphs, Ducati's, and even an old Ariel all start easily. Help, please. Again, thank you. Billy
This is what I use on my modded bike. http://www.mikesxs.net/product/20-0019.html
Attachments
billymac
XS400 Member
BC; thank you. I am just not that great a mechanic. My bike is a 1981 xs400h street tracker. I would just rather replace the petcock; much easier for this old dawg. But, I can't find an OEM or a generic replacement anywhere. Any suggestions. This is one instance of money being no object; within reason. Again, thank you. Billy
Billy, if we are going to get along, you have got to stop the advanced age talk. Even though I am a good decade behind you, I am not amused by the aging process. My Dad at 92 would still have been able to ride his '37 Royal Enfield (if Hitler hadn't stolen it) and that is what you and I need to believe will happen for us and how we need to think
Me neither - especially if we are dealing with those little copper pipes with the lightning in them. But I have not been shy about taking simple things apart in case there is simply some foreign substance stuck in them. Even if you can't see something, blow on it anyway just in case your dim old eyes are missing it.
If the petcock is the cause of it not starting then you wouldn't be getting any gas flow - even on PRI. If only on PRI, then something is stuck in there.
And if there is flow, then the starting problem is down-line from the petcock so you need to troubleshoot the carbs or one of those copper pipes with the lightning.
Anyway, you have 20 years to get it fixed, that's the main thing.
This is what I found,I took the petcok off the tank completely ntheres a screen attached that goes into the tank.It was completely clogged with old gas that had varnished up.I cleaned it with carb spray.Maybe you have a grandson who can help you?Taking the petcok apart and cleaning them isnt that big of a deal.You can buy kits to or whole assemblies from the Old bike barn and MikesXs.They also sell repair kits pretty cheap.Good luck keep us posted.
Drewcifer
1976 XS 360 Maniac
Yeah, Billy you're with friends here for sure. You might find a kid around town who'll help you take down the petcock and give it a once over.
