Anyone know the correct O ring sizes for a 1981 XS650 Petcock?

EvenmoreXS

1981 XS650
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My petcock is leaking and causing an annoying vacuum leak. I will be replacing the petcock with a new manual type in the very near future, but in the mean time Id like to replace a few of the O rings if I can. May solve the whole problem.

::::: Does anyone know the sizes of the O rings so I can call around and find them before I take my petcock off and drive all over creation trying to eyeball match em up.

Bike is an 81 model
 
I can't picture how the o-rings could create a vacuum leak. I have some used rings and I can measure them when I get back to the crib. Which one is the problem? z1enterprises.com has a rebuild kit that I used and that is holding.
 
If the leak is on the back side going to the vacuum tubing and then the motor(possible oil dilution) it is probably the diaphgram.
In the tech section 650skull has reposted some rememdies. Turning the vacuum type into a manual
If weeping on the front side around the selector lever it is probably the 4 hole manifold washer. Sometimes these can be turn around and reused( the little lips on the individual holes are too worn). This can also happen if you have the front off and don't get the wavy washer line up right catching it under the faceplate.
 
Thanks, specific sizes of the rings in the kit would help. I will remove, clean, and replace the petcock later tonight and see how it goes.
 
The thing to do is measure them yourself when you have them out, since you're planning to take it apart and clean it up. But I doubt they're causing a vacuum leak, like I said.
 
Gary, haven't seen that before. Thanks for posting.
The post by the moderator was interesting.
Best parts to use are available only through Yamaha.
Not to say o-rings couldn't be located at the hardware store.
 
I'm asking the author for his permission to post it here in tech.
I thinking that would be a good thing?
 
O rings may not be causing a vacuum leak, but it is leaking, and this is the only spot that is leaking, and vacuum is used through this petcock to pull from the tank, and Ive checked for all other vacuum leaks. The thing thats weird is that its been running and idleing great for several weeks now. Yesteday my petcock started leaking and was still leaking this morning when I rode to work. Idle raises when stopped, just like a vacuum leak.....choking helps some. It ONLY does this at the same time as when the petcock leaks. Yea, they could be related. Ive notice this before,,,,,same thing..,,, only when petcock appears to be leaking. If gas can get out, one has to assume air can get in. May not be the o rings though.

Again, I will be replacing it with a manual next week most likely, unless I can repair it. Thanks everyone. I will let you know how it goes.

Thanks for the link Gary.
 
It ONLY does this at the same time as when the petcock leaks. Yea, they could be related.

Are you leaking gas out as well as thinking you have a vacuum leak there? The rise in idle could be due to the level in the bowls dropping. There's a vent in the gray wafer that will leak if if the inner diaphragm has a hole in it. Otherwise the petcock will not leak visibly to the outside (unless something is terribly loose). Clarify.
 
Yes. It is leaking and acting as if it has a vacuum leak. Havnt syncd carbs yet but the left is lean and the right is rich. I know its not good , but it isnt causing my leak either. If I can fix the leak I can move on to the next thing. Appears to be leaking more that one place. Could be the diaphram.
 
The drain that can leak gas that I spoke of looks like a hole in side of the gray wafer between the two halves. Mine was oriented right beside where the gas line attaches. If it's leaking from there the diaphragm has a hole.

As somebody said I think, you can turn parts over and use the other side to try and get more mileage out of them if it's something else. I think it's covered in the tech section.

If you still think the issue is vacuum and a petcock leak, cap off the vacuum at the intake and run it with the petcock turned to prime and see what happens.
 
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