Topic: PD carbs leaking from the overflow.

[70CB750]

Two carbs - 3 and 4 - are leaking from the overflow tube.  I have the whole set on the work table and test just the bowl itself.  If I cover only the drain screw hole, its ok but if I go any higher, it starts dripping.  It drips even with a new drain screw and yes, the screw is tight.

The overflow tube seems to be ok by looking at it - I polished it lightly and there is nothing looking like a crack.

Would it be between the bowl and the overflow tube?

Is there a way to test it and fix it? 

I cleaned those bowls in ultrasonic cleaner - if it makes any difference. 

[madmtnmotors]

Good detective work there. I know others that would be continuously setting the float height and pulling their hair out... possibly myself included! Maybe fill the bowl with fluid, put your finger over the top of the tube, and introduce low pressure compressed air from underneath...

Then follow the bubbles!

[newday777]

Good detective work there. I know others that would be continuously setting the float height and pulling their hair out... possibly myself included! Maybe fill the bowl with fluid, put your finger over the top of the tube, and introduce low pressure compressed air from underneath...

Then follow the bubbles!

Great idea. Probably should use new tubing and blow with mouth air pressure to control the flow.

[BenelliSEI]

+1 to these ideas. I repaired a cracked tube about a year ago. The split ran straight up from the bottom of the bowl for about 1/4”. It was extremely difficult to see. Testing with a hose and a bit of air pressure would have made detecting it easier…… Will be very interested to hear what you find!

[70CB750]

Thank you, gents. 

I applied the shrink tubing and it worked, no more leak. 

But I asked my friend, who is a motorcycle mechanic for many years.  He said to cover the tube with solder.  I think I will keep the tubing for now and if and when it fails I will do the solder. 

[BenelliSEI]

Thank you, gents. 

I applied the shrink tubing and it worked, no more leak. 

But I asked my friend, who is a motorcycle mechanic for many years.  He said to cover the tube with solder.  I think I will keep the tubing for now and if and when it fails I will do the solder.

I’d worry about that stuff in today’s fuels…. Solder it.

[Floshenbarnical]

Thank you, gents. 

I applied the shrink tubing and it worked, no more leak. 

But I asked my friend, who is a motorcycle mechanic for many years.  He said to cover the tube with solder.  I think I will keep the tubing for now and if and when it fails I will do the solder.

I’d worry about that stuff in today’s fuels…. Solder it.

This thread has been like a lighbulb going off. My PD carbs have been leaking from the #2 drain since just after I installed them. I've replaced all the float needles, floats, measured with clear tube, everything. But they still leak!

I bought these carbs from a refurbisher on eBay and to his credit they were fantastic. But the overflow tubes were shrink-wrapped when I got them. I figured they were supposed to be.

After a couple days I had to re-jet, and when I pulled the bowls all the shrink wrap had deteriorated and was all loose and floppy and falling apart.

So I agree! I would not put heat shrink in the bowls.

But now I'm thinking the bowl itself is leaking so I shall be blowing bubbles (hopefully) through a tube into the bowl.

[BenelliSEI]

Curious what you will find. I have repaired split over flow tubes but also tossed away a few that annoyed me. I wonder if a leak passage can open up between the tube and the cast bowl???

[newday777]

Curious what you will find. I have repaired split over flow tubes but also tossed away a few that annoyed me. I wonder if a leak passage can open up between the tube and the cast bowl???

Maybe if the tube was loose from the bowl.