Leaking Petcock

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Tobz

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I picked up an '81 XS and having an issue with the petcock. It's leaking from the back side of the body where the spacer and diaphram for the vacuum line are. I put in a new gasket kit and have the spacer in (I believe) the correct way. Yet the fuel still seeps through and drips down the fuel line when the valve is in the 'run' postion. If I put it on either 'res' or 'prime', it pours out even more. I'm almost ready the throw in the towel and weld up the holes and install a traditional fuel shut-off petcock, but I really want to get this bike on the road and I have limited funds. Any input would be great.
 
Welcome to the forum. All I can say is if your gasket is new and for the correct bike( sohc model not the dohc model) is to make sure the mating surfaces are flat and clean.
 
Funny. Same thing was happening to me (started leaking when the engine was off and it was on the 'on' position, and leaked even more on PRI and RES).

Took it apart and it turns out I had a small tear in the diaphragm, close to the center pin/washer. I'll have to order a rebuild kit, but in the meantime, I folded up some rubber (old bike inner tube) to take the place of the spring behind the diaphragm, keeping the vacuum valve closed. I then put a small bolt in the vacuum line to the left carb boot. Now it functions like a regular on/off petcock: just switch it to PRI to get fuel, and switch it either to ON or RES and it'll shut off.

Here's a pic of the rubber.
 

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When mine was leaking, I bought 2 rebuild kits, one from ebay, one from mikes. Neither of them worked. Others have had more success. For me it just added an extra $20 when I finally ended up throwing in the towel and getting a traditional petcock from partsnmore.com. They have a petcock that fits our bolt holes so no need to weld them closed. In all, it was like $45 i think. You will need to figure out if the bolt spacing on the tank is 42, 44, or 46 mm though. Mine is an 82 SOHC and it was 46.
 
I have to say, all of you guys have been a huge help and have given me hope to get this thing running. I really appreciate it. I hope to get some pics up here soon. Been working on a homemade cafe seat and a few other mods to make it stand out a little. Thanks everyone.
 
That double up method, my tank has been off the bike for 9 months now, and it still isnt leaking. (Had it running for 5 minutes, before shutting it down, and stripped a bolt on the stator housing(last hurdle to get it running))
 
The guy I bought it from said it was leaking when he was working on it, so when I pulled the petcock apart, I thought he had assembled it correctly. Turns out that the spring was on the wrong side of the diaphram and also that the diaphram was junk. Once I had the two peices of the diaphram on both sides of the spacer, the vent hole on the spacer facing the right way and the spring on the right side, it worked perfectly. But after I write this, I'll go out to the garage and see a huge puddle of fuel on the ground. Because that's just my luck....
 
Still not leaking fuel, but can't get the bike to fire. It has spark, fuel is getting to the carbs and it popped on carb clean. But it won't fire and run. Had the carbs rebuilt and I trust the shop that did the work. Unfortunately, the battery died and I need to charge it and give it another go. Just wondering if anyone has experienced the same issue.
 
Good charge on the battery and a little ether and it lives. Need to adjust the idle up a little and I think it's all good. Thanks, everyone.
 

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