Derbi Bullet injector oil leak

[johnny340]

My '09 Bullet has the 'big bore' kit on it (72cc Cylinder, Bigger carb, Pipe, Variator, etc). The fuel petcock has no shut off (weird) and the carb leaks injector oil out the overflow tube when parked. I was going to see if the needle valve is sticking....or is this 'normal'?

[mpathus]

Hey there!

Leaks are not "normal". You may want to check to see if all those little tubes to your carb are secured with hose spring clips to keep them from oozing (or coming off) - if that's the problem. Float level may need to be checked, and the whole carb gone over to be sure all the little gaskets and o rings are present and correct. Rebuild kit may be in order?

When I pull my Dellorto's slide to change needle height, I see blue tinted fuel (injector oil) in the throat. I'm guessing that your overflow is premix (?) fuel overflowing from the bowl due to a seeping float valve. Replacing a missing fuel petcock or vacuum operated fuel shut off valve may help the situation.

Best luck!

[johnny340]

Thanks for the reply.
I'll check it out and see what needs replacing.

[johnny340]

Well I gave it a good going over and everything looks mint. The carb is only a year old so that was no surprise. The needle was perfect. There is no fuel shut-off on the petcock.
The fuel/oil seems to leak from the line that attaches to the bottom of the float bowl. There is a screw with an o-ring on the end (in good shape) that screws into the float bowl. I'm not sure what this does or how it affects the fuel being allowed to exit the float bowl line.
Here is a pic of the carb I have.

[mpathus]

Mint condition is good!

Consider installing a working manual petcock to stem the fuel overflow when parked? I've read where some installers poke a whole in their vacuum operated fuel petcock's diaphragm to increase flow (yikes!!). Mine is stock, but I needed to fashion spring clips to be sure tiny tubes were secure and not going to weep.

Maybe you need a new o ring to fix the seepage, or there is a hairline crack (use a loupe) if your fuel bowl is plastic?

My Dellorto carb was leaking some fuel past the bowl's gasket so I cleaned everything up; got some NICE socket head stainless machine screws with lock washers to replace the stock phillips screws, even reused the gasket and buttoned everything together using just the least torque so as not to over compress the paper gasket - no leak! Lucky that time.

Something may look alright, like a o ring, but when compressed it may deform enough to cause problems.

Sometimes the simplest thing to replace does the trick.

So, keep on fiddling until fixed.