Vacum fuel petcck modification? Anyone?

[racerdave]

All new rebuild kits didn't help. There is a small trickle of fuel when motor is off. I can't see any reason for the oring/seat to leak with a magnifing glass. Years ago when I had a Kawi Concours there were mods to convert the petcock to only use the prime position for full flow with on and reserve being plugged with JB Weld maybe?. I never did it but many said it worked great. Anyone done a similiair mod to the 650's vacum petcock? I'm not concerned with not having a reserve.

 

[5twins]

The only way I know of involves using 2, a right- and left-handed versions that came on '78-'79 models. You switch some parts between the 2 .....

http://650wiki.org/index.php/5.02.1_Vac_Petcock_Conversion

 

[Pure-Pork]

On my 2 78's, I went with 2 manual fuel petcocks from mikesxs and used block-off plates to eliminate the right side petcocks. Of Course now they are currently out of stock. But it sure made it simpler.

 

[racerdave]

Yeah those petcocks from Mikes have been out out stock since June. That's why I bought rebuild ktst for my vacum petcocks.

 

[racerdave]

5twins, thats the type of conversion I was looking for. Thanks!!

 

[xjwmx]

I rebuilt my vac using parts from z1enterprises.com I think it's called. I used only the diaphragm from the kit. The first time I put it together it leaked. I took it apart and did it again and the second time I reused the sealing o-ring from the original diaphragm and was careful to hold it all in such a way that the spring could seat the o-ring squarely and maximally as I pushed it all together.

Seems to be good as new now for the last couple of months. The supplied o-ring was a hair smaller than the original. Not sure if that was the problem with the first rebuild attempt. The reason it needed rebuilding was the diaphragm developed a hole causing gas to pour out a little vent near the gas line connection. Was able to do an emergency plugging of that hole and ride over 200 mi, before rebuilding it.

 

[xjwmx]

Another thing you can do if it's just leaking out the fuel outlet is put an inline on/off valve in the line. O'Reily's has a nice one in their lawnmower dept. You could use that until Mike's is back in stock on what you wanted originally.

 

[racerdave]

XJ, like these? Bought 2 from Napa for a temporary repair, that will probably end up permanent if they hold up to ethanol.

 

[xjwmx]

^That looks like what I saw. I'd try the rebuild again myself. There's an Ace hw store here with a good selection of o-rings. I'd get one a hair bigger than what I was using and see how it goes.

If you used the valve you'd have to have the petcock in a certain condtion anyway - it would have to not leak out the side like mine was and it would have to keep flowing gas via the vacuum. You could always run it on prime of course, but you wouldn't have a reserve.

Or you could gut it and put a gasket where the diaphragm was, then use the inline to turn it off. You'd still get reserve from that.

 

[650Skull]

Here are some diagrams and Text that may help

 

[xjwmx]

^Is there any text somewhere that goes with that? I haven't seen that one before.

Here's something else that might be useful:

http://www.xs650.com/forum/showthread.php?t=7818&page=2

Incidentally, the reason I elected to fix my vacuum petcock rather than replace it was I was reading complaints about the replacement. Things like brittle metal, or unfamiliar and strange reserve level, which I guess you change if you wanted to. Honestly, if you think about it, I think a manual petcock might be as likely to break down as a vacuum one. A manual one certainly gets turned a lot more than a vacuum one, for one thing.

 

[weekendrider]

XSJohn did it.

http://www.650rider.com/index.php?n...storder=asc&highlight=convert+petcock&start=0

 

[xjwmx]

XSJohn did it.

http://www.650rider.com/index.php?n...storder=asc&highlight=convert+petcock&start=0

We have two ways of converting it to manual now.

 

[weekendrider]

Here is the same fix as in the Aussie site, an easy to follow write up with pics.
http://www.xs750e.com/page25.htm

 

[xjwmx]

^He talks about gas leaking into the vacuum line. To do that, I think there would have to be holes in both diaphragms and a leaky o-ring. On mine, if there's a hole in the front diaphragm, gas leaks out of a vent in the petcock, so you'd know something was up in advance. If there's a hole in both diaphragms the valve wouldn't open, so that gas couldn't get into the vacuum line.

Also on mine, if there's a leak through the carb it comes out through one of the air jets into the air box rather than into the carb throat. Not sure why. I don't think it's lower than the throat.

 

[bdholsin]

...Also on mine, if there's a leak through the carb it comes out through one of the air jets into the air box rather than into the carb throat. Not sure why. I don't think it's lower than the throat.

I've had the EXACT same issue. It was the float height setting. Took me sever attempts (5 I think) to get it just right. That included draining the fuel tank, carb removal and setting the float height with a measuring device. It was extremely touchy (on my right hand carb).

 

[bdholsin]

I've also gone so far as to add a home made gasket between the petcock and the tank for an additional seal. My o-ring was looking a little flat and wasn't quite doing the job. Fuel leaking down the petcock completely went away.

Maybe the OP is experiencing an air leak (one that is ever so small) between the tank and petcock. Just throwing it out there.

 

[xjwmx]

I've had the EXACT same issue.

On mine it was a leaky float valve. Another time was in winter and I think some things got some moisture in them and actually froze open. The thing though was it runs into the air box instead of into the cylinder. I'm glad of that.