Topic: Rebuild or Replace the petcock

[samfig]

Hey All,

I'm pretty sure my petcock has gone bad since there is a pretty regular puddle under the overflow tubes of the bike.  I've made sure to close the petcock and burn all the gas out before I put her away and there is still a small puddle after about a week.  Today, after not having ridden the bike in about 2 1/2 weeks I moved the bike and noticed that gas was coming from the air box as well.  It would seem to me that the petcock must be broken.  What do you all think?

Also, whats the usual thing to be done about this?  Do you rebuild something like this or just replace it?  I looked at buying a new one off of House of Honda parts for $42 but the shipping was an additional $17 on top of that

Any advice would be appreciated.

[martin99]

Even with a leaky petcock you shouldn't have a puddle under the overflow tubes. Sounds like one or more float needles are not seating correctly. Time for a good clean - petcock, lines and carbs - and perhaps an inline filter if the one in the tank is knackered.

[Muckinfuss]

What he said.  However....if the puddle occurs with the petcock closed....it just might be both the carbs and the petcock need a little refresh.

[samfig]

The carbs were cleaned and a float was changed this Spring ... so I'm guessing my culprit is the petcock.  I've searched a bit but haven't found any DIY instructions.  Can anyone help by posting a link?

[ekpent]

  Simply put if a petcock is working correctly it totally turns off the gas. Looking at your sig you have a 73 750 and rubber parts etc are cheap and easy to get to replace. Make sure you still have a viable filter screen also. Petcocks can get damaged beyond repair by folks cleaning tank with caustic cleaners like toilet bowl cleaner etc.  who do not remove them and plug the holes. Start with the petcock and move down from there 

PS-Make sure gas is not getting into your oil if you have a major leaker---- Not a good thing

[bjbuchanan]

Pull the petcock and snap a pic to see which model you are working with. There is a guy on ebay with an excellent DIY kit for the petcock that includes an OEM sealing gasket.

The sealing gasket with the holes behind the actual handle is what leaks. You can flip it around and see if it stops leaking. Often times it fixes it right up.

Link for the rebuild kit, this guy even includes qtips

http://www.ebay.com/itm/Honda-CB750-CB-750K-CB750K-500-CB550-petcock-rebuild-mount-kit-fuel-valve-/231333971757?pt=Motorcycles_Parts_Accessories&fits=Model%3ACB750&hash=item35dc94472d&vxp=mtr

His username is dgs38, he has different kits and different 'stages' of rebuild. Prices are nice and fast shipping.

[Stev-o]

With the petcock off, disconnect the fuel lines and slip a plastic Baggie over it, secure with wire or rubber band. Check it in a day or so, if you see gas, it's leaking (betting it is).

I've had bad luck rebuilding petcocks, I buy new now. 

[750cafe]

Buy a new petcock. Geogefix on Ebay sells many at good/fair prices. See if he has one for your application.

Eric

[Dunk]

Check your needles and seats as has been said.

For my 750 K1 I rebuilt the petcock as the kit was much cheaper than a new one. It's really quick and easy to clean and refresh it. I polished mine too and it looks like new. Unless new is same price or less I'd rebuild the original. Original parts always help maintain value as well as sometimes the same PN replacement may be slightly different... Learned that during my restore and had to search for NOS for a few items which can be tricky when the PN is the same or cross references to the new PN automagically.

[chewbacca5000]

The little fibre washers for the right hand petcock wear out and gas will keep dribbling even when the petcock is closed.  I ordered some thorough local parts store for $4 a piece.  Also got the rubber selector for another few bucks.  $12 to rebuild.

[samfig]

  Simply put if a petcock is working correctly it totally turns off the gas. Looking at your sig you have a 73 750 and rubber parts etc are cheap and easy to get to replace. Make sure you still have a viable filter screen also. Petcocks can get damaged beyond repair by folks cleaning tank with caustic cleaners like toilet bowl cleaner etc.  who do not remove them and plug the holes. Start with the petcock and move down from there 

PS-Make sure gas is not getting into your oil if you have a major leaker---- Not a good thing

My tank was kreemed at a shop and I'm unsure if they took out the petcock or not.  Also, how would gas get in to the oil?

[DH]

  Simply put if a petcock is working correctly it totally turns off the gas. Looking at your sig you have a 73 750 and rubber parts etc are cheap and easy to get to replace. Make sure you still have a viable filter screen also. Petcocks can get damaged beyond repair by folks cleaning tank with caustic cleaners like toilet bowl cleaner etc.  who do not remove them and plug the holes. Start with the petcock and move down from there 

PS-Make sure gas is not getting into your oil if you have a major leaker---- Not a good thing

My tank was kreemed at a shop and I'm unsure if they took out the petcock or not.  Also, how would gas get in to the oil?

If the carbs are overflowing fuel can sometimes go down the intake ports/through open valves/past pistons and into the crankcase, mixing with and contaminating the oil. Telltail sign is that oil level will show too high on dipstick, and thinned oil.

[samfig]

HOLY SMOKES!!  I actually just checked the oil after I was done riding and it was high.  I'd imagine that the best bet is to not ride and get the petcock fixed as well to change the oil. 
Do you guys think there is anything else I should do?

[samfig]

Is there something in particular i should be cleaning the petcock with?  Also, when I removed the petcock it seems that there was a white smear of something that was between the petcock and the tank.  Shouldnthere have been?  Am i suppose to put something on to help fill the gap / seal the petcock to the tank? 

[samfig]

Heres another.

[DH]

That oval shaped o ring is flattened out. Probably started leaking and someone tried to seal it with glue/sealer. Get a rebuild kit from dgs38 on ebay. around 30.00. or source parts individually as has been suggested.
I just did mine and it turned out good. The screws that mount the valve also have fiber washers (included in the kit) that can go bad and leak, allowing gas to get past the valve even though it is in the off position. kit comes with clear concise instructions too. Clean/smooth the area of the tank where the valve mounts.
Very fine sandpaper (also included in the kit) The white stuff may be the kreem treatment as well, dont know. Once the valve is fixed, find out why the carbs are overflowing. They shouldn't 

[samfig]

I did buy a kit from him and am just now getting to it. 

So do you recommend that I sand all the white stuff from the tanks and the petcock?  Should there be no putty like substance at all to create a gasket or sorts with tank?

[DH]

I did buy a kit from him and am just now getting to it. 

So do you recommend that I sand all the white stuff from the tanks and the petcock?  Should there be no putty like substance at all to create a gasket or sorts with tank?

The o ring alone should seal it, no additional sealer is required. Just make sure the tank surface is free of old sealer or paint etc. and it is absolutely clean and smooth.
The groove in the valve that holds the o ring should be free of any debris, old glue, etc. I can't remember if they say to use a little grease to hold the oring in the groove or not,  I'd just follow the directions to be safe tho. I've done a few of
these and so far so good. just my experience.