Petcock rebuild problems(solved)

[rider123]

Hey guys,

I had my Petcock leak through the vacuum hose to the number 4 cylinder on my 05 Bandit 1200, so I bought a K&L petcock rebuild kit part #18-5023 to rebuild it but I'm having problems with the new diaphragm.  With the new diaphragm on there it leaks out the fuel line spigot almost as much as if I had it on prime. With the old one on there it doesn't leak at all. For fun I popped on the old diaphragm on there and the bike will work properly for a bit then it will start to seep fuel out the #4 cylinder again. So obviously I need to get the diaphragm replaced but the new plunger on the new diaphragm can't hold back the fuel like it should. I didn't even bother trying to put it on the bike to see if the vacuum line is not seeping fuel as I would have to soak my bike in fuel just to test it. Does anyone have any experience with these rebuild kits? I have noticed that the new plunger does seem to have the O-ring seated a mm or so below the end of the stock plunger. Maybe I got a lemon? Looks well machined though.

[rider123]

I think I may have a solution......

Heres an email back to the place I got it from.


Hi Jennifer,

I ordered it on Ebay.

I'm going to try something that may help. It seems that the plunger with the O-ring doesn't exactly fit tight up against the valve. So I think I'll try 2 options...1 Either bevel the plastic spacer so that the diaphragm sits deeper in the plastic recess to add more pressure to the O-ring sealing the valve. Or 2 push gently on the diaphragm to bend the back plate slightly so it will have the appropriate depth to push up against the valve. I've been looking at this kit out there on the internet and it seems they've slightly changed the position of the O-ring on the plunger. It used to be closer to the tip which would provide more sealing pressure when installed, just like the stock plunger. I'm sending a picture of an identical kit to give you an idea of what I'm talking about. I'll try and see if I can make it work and get back to you guys so at least you have an idea if it can be fitted. If I install the stock diaphragm it seals no problem. Just after a while it starts leaking through the vacuum hose to #4 cylinder(hence I bought the rebuild kit). The stock plunger has the 0-ring very close to the top of the plunger so it has enough pressure to seal the valve. I have to wait unfortunately since I have too much fuel in the tank right now to take the petcock out but I should have enough out in the next 2 days or so and will let you know how it goes so if you have another customer with the same problem you can suggest one of the solutions I'm trying. I've installed these K&L petcock rebuild kits on a few different bikes and usually they are a no brainer, maybe this kit just needs a little fiddling with. Thanks Jennifer,

[rider123]

Ok so I solved it. What I did is I bent the back plate concave so that the plunger has more pressure to push up against valve body. I also stretched the new spring a bit but it was alot beefier than the stock spring. I put just over half a tank of gas in there and only have a slow drip drip drip coming out of the petcock when stopped. I was in a hurry today so I couldn't fine tweak it by bending it a bit more but maybe on Monday when I get back I'll bend it a bit more and see if that helps even more. What the issue is is that the O-ring sits an extra .8 or so of a mm from the end of the plunger on the new kits as compared with the stock or the older kits. Perhaps they've machined them slightly differently on this new batch. If you get a 2nd generation Bandit 1200 kit check the end of the plunger compared to the stock. If you have some extra clearance from the tip of the plunger to the o-ring, just bend the back plate a bit so that the plunger sits deeper in the petcock spacer recess and stretch the spring for good measure. On Monday, I'll grab some more gas in a jerry can and fill slowly up to full and keep bending the back plate until it will hold back the fuel with a full tank or at least have just a drip coming out and if your seats and needles are good like mine it should hold back the gas no problem.