Fuel Petcock ID

Nelson

XS650 Enthusiast
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Kennewick, WA
I am using a gas tank from an unknown year XS650. The tank I had was and still is pretty ratty. The single petcock on this tank is different than the dual petcocks on the original tank. when looking at the valve control lever it is marked PRI on the right, ON on the bottom and RES on the left. There is no OFF position. In addition to the single fuel outlet there is a an additional smaller fuel outlet. What is this second outlet for? can I just block it off and only use the main (larger) fuel outlet to feed the carbs?
The mounting is different than the original tank so I can't just use one of the single outlet petcocks from the original tank. The newer tanks petcock has mounting screws that appear to be 46 mm on center. The old tanks petcocks have mounting screws that appear to be 42 mm on center.

On a slightly different note, what can I use to clean up the petcock. Can I use carb cleaner or is there a better way to clean it up. I am really eager to get this taken care of as it is the last thing I need to do to get this 15 year long project bike back on the road. Thanks for any help you can give.
 
I am using a gas tank from an unknown year XS650. The tank I had was and still is pretty ratty. The single petcock on this tank is different than the dual petcocks on the original tank. when looking at the valve control lever it is marked PRI on the right, ON on the bottom and RES on the left. There is no OFF position. In addition to the single fuel outlet there is a an additional smaller fuel outlet. What is this second outlet for? can I just block it off and only use the main (larger) fuel outlet to feed the carbs?
The mounting is different than the original tank so I can't just use one of the single outlet petcocks from the original tank. The newer tanks petcock has mounting screws that appear to be 46 mm on center. The old tanks petcocks have mounting screws that appear to be 42 mm on center.

On a slightly different note, what can I use to clean up the petcock. Can I use carb cleaner or is there a better way to clean it up. I am really eager to get this taken care of as it is the last thing I need to do to get this 15 year long project bike back on the road. Thanks for any help you can give.
So, the petcock you have is from a newer model. The second outlet is for the vacuum hose from the intake rubber to connect to. The petcock will flow fuel when the engine is running. The vacuum hose opens a diaphragm in the petcock. If you move the lever to PRI position the fuel will flow without the engine running. The RES position is for reserve like other petcocks. Hope this helps.
 
So, the petcock you have is from a newer model. The second outlet is for the vacuum hose from the intake rubber to connect to. The petcock will flow fuel when the engine is running. The vacuum hose opens a diaphragm in the petcock. If you move the lever to PRI position the fuel will flow without the engine running. The RES position is for reserve like other petcocks. Hope this helps.
Thanks, I appreciate the info. It sounds like I can simply block off the vacuum outlet and go ahead and use it.
 
Thanks, I appreciate the info. It sounds like I can simply block off the vacuum outlet and go ahead and use it.
As far as I know, when you're in PRI (prime), it passes fuel until it's gone. In other words, no reserve.

Just something to keep in mind.
 
Thanks, I appreciate the info. It sounds like I can simply block off the vacuum outlet and go ahead and use it.
Yes you can just run on the PRI position, However, the Pri position will eliminate the reserve amount of fuel and use the whole tank. The vacuum hose connected to the petcock allows you to have a regular tank of fuel and a reserve tank.
 
Thanks. Based on your response I checked Mikes XS and sure enough they had one with the correct screw spacing. It’s now on order.
Before you use it I would suggest you take it apart and check for any roughness on the castings. especially the inside of the selector handle that seals against the rubber disk. One I just took apart on a new to me bike had a rather rough surface. Rubbing it on some 600 grit wet or dry paper (wet on a flat surface) had it nice and smooth, a quick session on the buffing wheel to polish, remove any sharp corners and done.
 
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Nelson, what year is your XS? Which carbs?
I always say the bike is a 77 but I am only sure the frame is. Over the years it has been thru a lot including a replacement engine, which as I recall is from a 75 XS650B. The carbs are also of indeterminate origin but are BS38's. The tank is apparently from a 78 or later model as that is what the petcock I ordered is listed for. The Velorex 562 Sidecar mounted to the bike is an 81 or 82. I originally had it mounted to a Yamaha SR500 for a couple of years before I picked up the XS650D and switched the Velorex over to the larger bike where it has remained ever since. The bike has recently been modified as follows:
1- Leading link front end by Dauntless Cycles
2- 15" car wheels laced to all 3 hubs
3- Dual disks on front wheel (from Yamaha 750)
4- Crank turned 83 degrees, Cam shaft cut and welded to match, PAMCO ignition to match
5- High output alternator
6- Haiden Tuning Big Fin 750cc cylinder block
7- Hughs Handbuilt 2 into one exhaust out the left side of the bike

My wife and I took this outfit on our honeymoon to West Edmonton, Alberta from our home in WA state in 89. Once I have the bike running and fully tested we are hoping to retrace that trip next summer. Also, since it is narrower than our Harley Sidecar outfit, it will fit on our trailer so we can also pull it behind our RV as our 'dingy' or 'toad' as RVers refer to their towed vehicles.
 
2 into 1 left side for the sidecar ?
Yes. I had it go out the left side to keep the exhaust noise as far from the Monkey as possible. Also there are two lower mounts for the sidecar on the right which makes it harder to find mounting points etc with the exhaust on the right side getting in the way so it just makes mounting the sidecar easier. Sidecar is mounted on the right side of the bike in the U.S. and other countries that drive on the right. In countries like England the sidecar is mounted on the left.
 
Before you use it I would suggest you take it apart and check for any roughness on the castings. especially the inside of the selector handle that seals against the rubber disk. One I just took apart on a new to me bike had a rather rough surface. Rubbing it on some 600 grit wet or dry paper (wet on a flat surface) had it nice and smooth, a quick session on the buffing wheel to polish, remove any sharp corners and done.
I have the one with the vacuum outlet and I have the two from the original tank. I will take them apart to see how they work then clean them up and reassemble. Always good to have trading material in stock 😊
 
IMG_7335.jpeg

Seems like you have a functional twin petcock Standard tank ? Was wondering considering the sidecar, monkey, 750 bbl,
2 into 1 , goin the distance ! 😎
You being a local can have this set of 79 vacuum petcocks if they help you. They are very near great !
(Meadow Springs Golf neighborhood)
 
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Seems like you have a functional twin petcock Standard tank ? Was wondering considering the sidecar, monkey, 750 bbl,
2 into 1 , goin the distance ! 😎
You being a local can have this set of 79 vacuum petcocks if they help you. They are very near great !
(Meadow Springs Golf neighborhood)
Thanks for the offer but I have already ordered a new petcock.
 
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