Petcock peeves

[stepaway]

I have a 600 Hornet from 2000. Working through some bits slowly to get it back on the road after 5 years in a friends uncles garage.

I wanted to replace the petcock filter. Glad I did as the old one was non existent when I removed the tap out of the tank. Carbs will be being stripped and rebuilt but while the petcock was off I removed the back off to check the diaphragm and squirted a bit of WD into the port and on/off switch as the lever was a bit sticky.

Anyway, changed the filter and now when the petcock is back in the tank there is a slow leak of fuel, seemingly from the adjuster knob rather than the diaphragm cover.

Any ideas on where the leak might be from? Have had a good look online but turning up little other stuff about this issue.

[stepaway]

Sorry, meant to add. The front cover is riveted in place, the diaphragm cover has 4 x screws.

Assume the only parts that can fail are the bits behind the diaphragm cover or am I missing something? New o ring fitted on the in tank filter too where the big nut locks it on to the tank. Are these in anyway sensitive to leaking?

[fred bloggs]

Yes. The leak is from the petcock. You'll have to buy a new one.

https://www.fowlersparts.co.uk/parts/4779566/cb600...

[stepaway]

fred bloggs said:

Yes. The leak is from the petcock. You'll have to buy a new one.

https://www.fowlersparts.co.uk/parts/4779566/cb600...

Thanks for that, I’d already come to the conclusion it was the petcock itself. My question should have been clearer perhaps as I’d rather not replace it entirely.

If I got the diaphragm rebuild kit would that solve the leak or is there any other areas/seals etc within the tap itself that can fail?

[Benni]

The "On/Off" lever is turning a round metal part, there is a rubber disc behind it with holes.
The rubber part may have shrunk / hardened over the years.
If you want to rebuild it, bore/tap out the rivets, then you can dismantle the petcock "valve" part.
These rubbers come in different diameters, thicknesses and hole number/designs/diameters.
but can be found in a well-sorted (online) shop, maybe look in the "Vintage / Oldtimer carb parts" section.
Example here : https://www.mgcycle.com/index.php?main_page=produc...
Owners of oldies sometimes have to rebuild their cocks hehe, maybe Srob might know where to find these rubber discs.
the rivet holes would have to be tapped and small screws inserted, there also should be a "springed washer"
which provides the correct tension on the lever so it can be turned, but keeps the rubber disc tight.
Hope you can understand my word salad.

[gareth_r]

fred bloggs said:

Yes. The leak is from the petcock. You'll have to buy a new one.

https://www.fowlersparts.co.uk/parts/4779566/cb600...

£262.86

I'd be exploring overhaul kits and aftermarket options first.

According to the Fowlers website, the tap is shared with the CBR600.

[Rubin215]

Ebay.

You will get a pattern one for under £40 and save masses of time and hassle.

[CousinDupree]

Don't bother rebuilding it. They all leak after a while. Get a new one.

[stepaway]

Thanks for all your answers everyone

I've investigated aftermarket options and the only ones available have the ports for the fuel and vacuum lines on the bottom of my existing OEM tap on the side (so horizontal rather than vertical) - do you think this is going to cause any flow issues or should this be ok with regards to correct fuel supply?

[podman]

stepaway said:

Thanks for all your answers everyone

I've investigated aftermarket options and the only ones available have the ports for the fuel and vacuum lines on the bottom of my existing OEM tap on the side (so horizontal rather than vertical) - do you think this is going to cause any flow issues or should this be ok with regards to correct fuel supply?

You should be as long as the new outlet doesn't foul the frame or anything else.

I had this same problem with a first generation VFR400 (1988 IIRC), I bought a kit which worked perfectly but as mentioned above, meant drilling out the rivets holding it together,

Then install the new diaphragm / O ring and refit with some extremely small nuts and bolts supplied with the kit.

Not sure if this would suit your needs?

https://www.ebay.co.uk/itm/305090059455?fits=UKM_C...

[stepaway]

podman said:

stepaway said:

Thanks for all your answers everyone

I've investigated aftermarket options and the only ones available have the ports for the fuel and vacuum lines on the bottom of my existing OEM tap on the side (so horizontal rather than vertical) - do you think this is going to cause any flow issues or should this be ok with regards to correct fuel supply?

You should be as long as the new outlet doesn't foul the frame or anything else.

I had this same problem with a first generation VFR400 (1988 IIRC), I bought a kit which worked perfectly but as mentioned above, meant drilling out the rivets holding it together,

Then install the new diaphragm / O ring and refit with some extremely small nuts and bolts supplied with the kit.

Not sure if this would suit your needs?

https://www.ebay.co.uk/itm/305090059455?fits=UKM_C...

Thanks for this - i've managed to have a chat with a UK ebay retailer who seems to know his onions who has a complete and apparently good quality new unit for a reasonable price so i've ordered one from him - will update if i have any success!