Large Model Association Forum

I have reconfigured my Zenoah 38 SC with a carburettor inlet elbow. This has brought the black plastic fuel pipe nipple, on the Walbro carburettor, pointing in an awkward direction. I have tried (gently) to turn it but it resists. Is it actually possible to alter it? Advice please. . . . .

Chris Lane

I doubt it but there are plenty of Walbro service videos on YouTube.

Hi Peter
The black plastic is moulded on to a sedated brass nipple that is a push fit in to the carb body it will turn and come out but not easily. I found this out when a friend crashed his model and it broke off the plastic bit. Hope this helps.

Thanks for your replies guys. I had a look at getting the carb apart, to see if I could push the inlet out from the back, but it is in the body and removing the nearest cover does not access the back. It looks like a complete dismantle to do that. I also looked at turning the carb over 180 degrees on the elbow but there seems to be a vent channel which only lines up one way!

I will order a new inlet and then drill and slot a piece of bar to fit over the pipe so that I can line it all up and apply torque carefully. If it breaks it then it is a matter of extracting the brass core and pushing in the new part at the angle I need.

Chris Lane

The fuel nipple can be rotated................but it is a very delicate job and done completely at your own risk. (the following description came to me from Toni Clark)

The moulded plastic nipple will jump a spline or 2 on the brass insert. If you insert the plain shank of (IIRC) a 2mm drill bit into the nipple (to stop it crushing), gently grip the main body of the nipple in a pair of pliers & rotate using the drill bit as a 'handle' for a little added force. It's stiff but it will go having done it several times myself.

Phil

Thanks for that advice Phil.

As this was clearly going to be risky I drilled a piece of 10mm Al bar 7mm dia. and then milled a slot down from the end with a 3/16" end mill. This fitted nicely over the fuel inlet nipple. I lightly clamped the carb body in a vice in the vertical slide on the Myford and lined all up with the 10mm bar in the chuck. This allowed me to guarantee that I was applying pure torque to the fuel nipple. A 2mm drill wouldn't fit but a Number 50 drill did. I had to apply quite a load on the chuck (by hand!) and eventually there was a snap sound and the nipple moved and could be rotated. The slot in the bar was subsequently found to have been spread slightly!

Got there in the end but frightening. . . . .

Chris Lane

I would have been really worried by the sound it made. Is the fuel nipple still tight in the carb body??

It remained stiff to turn after the initial sound and it still seems to be tight. I have yet to try petrol through it. If it proves faulty I propose to extract it and tap the hole for a proper banjo fitting.

Chris Lane