petcock leaking issue help

i am working on an 86 vf500f for my buddy i have a problem with the petcock (i searched and couldn't find an answer) when looking at it mounted (looking at the selector switch) there is a small port that comes off the side points to the right that is leaking gas. it only leaks when the petcock is on or reserve when off it doesn't leak. is there a line that's supposed to go there? or is it a vent and i have to rebuild the petcock? i have the gas line hooked up (left side) and the vacuum hooked up (back side pointing down) but i have no line for the other port. the bike wont run i just cleaned the carbs and did a bench sync it will turn over all day with maybe a slight hint to start but wont really try it wouldn't run before i started working on it (reason i have it lol) i can post a pic if necessary i gotta get this thing running asap please help!

 

Please post a photo when you have a chance.

It sounds like the vacuum controlled fuel shut-off safety feature has been modified.

 

here is the pic. from what the owner has told me this bike has never been modified or messed with i found no evidence of tampering anywhere he said this leak is why he quit riding it 2 years ago it started leaking and wouldn't run

 

The 'leaking port' is an atomspheric vent for the vacuum diaphragm.

As a next step, remove the petcock and inspect the diaphragm. You'll be able to easily tell if this has been modified (i.e. cut). When this is cut you need to close off the vent and vacuum port by connecting the two ports with a hose or sealing these off with J-B Weld (or a similar product).

Or another way to check, if this has been modified, does gas flow when you have the petcock set to 'on' or 'reserve'?

I don't have a schematic for the '86 but here is one for the '84/'85:



And a good reference for what you should find inside a petcock that hasn't been modified:

 

thanks for the help one of the rubbers is bad inside it now i gotta find a rebuild kit the bad one is #2 in the above pics

 

Your local Honda dealer should be able to help or if in a pinch check our Service Honda here in the States or David Silver Spares in the UK. Both are great sources for hard to find parts.

Glad this was of help and let us know when you are up and running. Always good to have another 500 out on the open road.

 

I think I may still have an 86 VF500 Petcock kit.

If needed, PM me.

 

Invisible. I think it may be time for you to make a guide post (likely to be a sticky) with all of your great photos, parts descriptions, etc., etc. Your work and attention to detail has helped out a lot of folks and it would be a shame to keep it all scattered amongst dozens of posts.

Great job as usual!

 

Thanks Michael. It is a work in progress for sure. It does seem like a few items (valve lash, valve springs, cams and followers, petcocks and spark units) are the usual suspects that keep these bikes in the hanger bay or sadly send them to the boneyard. I could definitely see a digital guide being developed here on VFRworld to help keep these great bikes up and running.

This said, it seems like the biggest caveat to owning the 500 right now is finding a proven source for the valve springs. Hopefully this will get dialed in, in the near future.

 

Hi all,

I have a similar problem. I'm getting gas flow on all settings. The Off setting is slower, but I still get fuel flow. It's flooding the carbs, overflowing and filling a cylinder (and has probably gone to the oil as well but I have not checked yet). My set up is gravity fed (no pump) but the petcock has not been modified. I opened it up last night and all the parts are there, without holes in the diaphram. Is this a case of the riveted section of the valve failing, requiring a new petcock all together? Or does this sucker need a vaccum line applied to it to get the fuel to shut off? I don't think it is the latter because I am not sure how the engine would apply vac when it's not running...

 

Even if the petcock is always allowing fuel flow, the carbs should not overflow, it is probably a hanging float/float needle problem.

 

OK, I'll get into the carbs and see which one(s) is stuck. Would love to verify if the valve is shot though. Has anyone ever taken off the two rivets and check on the shutoff valve in there? I get about 1/2 the flow rate on off as I do on Reserve or on, but would love to be able to shut the flow off completely...

 

More info can be found here:

http://vfrworld.com/forums/1st-2nd-generation-1983-1989/29702-petcock-leaking.html#post250039

 

Good info. Thank you all. I pulled the carbs and cleaned them up. The floats now all look good and the pins all slid easily. Im hoping it was just something that was catching and keeping the float/pin from sealing and leaking into the chamber. I have to tell you though, im still not "getting" how the vacuum works on the petcock. As I mentioned I am a gravity system, with no pump. The petcock has failed in the sealed/riveted part as I get flow now matter what setting its on (its slower on off, but still flows 50%). My question is... with no pump on it should I be hooking a vacuum up to the petcock or is it fine as is? I had it apart and I see the rubber bit(part #2 and c above) that looks like it might have to get sucked away from the valve to get fuel to flow out of the valve, but I have no suction on mine and it's flowing fine (tested into a gas can). I don't have either of vacuum nipples capped and get no leaks there either. It seems like basically the entire spring loaded vac diaphram is just sitting alongside the valve doing nothing. Is that possible?