Carb fuel inlet size

[Marty_d]

Hi,

 

I'm a bit confused about the fuel fitting to the carbs.

912/914 parts list shows part 941853 which is a double ended male thread, however in the Rotax Heavy Maintenance Manual it shows a banjo bolt going straight in and the original part crossed out.

 

Anyone know what the inside thread size is?   Is the banjo bolt system necessary or can it just be a barb to thread type fitting?

 

Thanks, Marty

[IBob]

Hi Marty, I believe what you are looking at in the Heavy Maint Manual is what you get if Rotax provide all the engine fuel pipework, including the splitter/manifold that ports to the 2 carbs, fuel gauge and return line.

For my build, the splitter/manifold was supplied by ICP, and the engine came (new) without the pipework to the carbs.
The carbs came with the banjo fittings, with barbs, to which I then attached the flexible fuel lines supplied by ICP.

 

Sorry, I don't know what the thread size is.

 

I guess an advantage of the banjo is that it keeps the flexible fuel line close and compact to the carb/engine without any tight bend.

 

[Blueadventures]

4 hours ago, Marty_d said:

Hi,

 

I'm a bit confused about the fuel fitting to the carbs.

912/914 parts list shows part 941853 which is a double ended male thread, however in the Rotax Heavy Maintenance Manual it shows a banjo bolt going straight in and the original part crossed out.

 

Anyone know what the inside thread size is?   Is the banjo bolt system necessary or can it just be a barb to thread type fitting?

 

Thanks, Marty

Just serviced two 912 ULS carbs last night for a mate.  The banjo is three parts the banjo (hose barb 1/4" od) a spacer about 10mm long and the banjo bolt plus the three copper washers between the pieces.  The banjo bolt goes into the carb body.  Bolt with copper washer, banjo fitting, copper washer, spacer, copper washer.  Hope this helps somewhat.

Edited January 26, 2022 by Blueadventures

[Marty_d]

9 minutes ago, Blueadventures said:

Just serviced two 912 ULS carbs last night for a mate.  The banjo is three parts the banjo (hose barb 1/4" od) a spacer about 10mm long and the banjo bolt plus the three copper washers between the pieces.  The banjo bolt goes into the carb body.  Bolt with copper washer, banjo fitting, copper washer, spacer, copper washer.  Hope this helps somewhat.

Can you get the banjo stuff aftermarket?  I did contact Bert Flood about the fuel setup but they said it would be prohibitively expensive to get Rotax stuff.  Even the compensator tube which is basically a bit of bent aluminium pipe is around $1,000.  (I made one myself out of a piece of hard fuel line, with a ridge formed at each end to hold the short rubber hose each end).

[Blueadventures]

You must be as they are used on allot of machinery.  You would need the thread into carby.  Maybe 8mm by 1.25 or 1.5 pitch.  I didn't take that much notice.   Try ENZED, Blackwoods or similar.

The spacer was 10 or 11mm long to stand it off the carb body.  Cheers.

[Marty_d]

Thanks Mike.

 

I might pull a carby off and take it into Enzed.  That way I'll get the right thread.

[IBob]

Marty, FWIW they are Bing 32mm carbs, though I'm not sure that is much help, as I have been unable to find the details you are looking for online.

[facthunter]

Motorcycles use banjo fittings sometimes.. By using copper washers for sealing the seal is simplified and works in a multi directional sense as it can swivel and is a sharp change of angle and takes up little room. It's a dead easy thing to mass produce  from bar stock good grade aluminium alloy and if someone had it done properly in good material you'd be better off than trying to buy inferior (diecast) stuff. You can even make them ONE OFF with a small lathe. It's a bit like a rose Joint (Ball with flats). Nev

[Kiwi]

20 hours ago, Marty_d said:

Thanks Mike.

 

I might pull a carby off and take it into Enzed.  That way I'll get the right thread.

Don't forget that it's off a "motorbike". 

Some places won't sell you parts if it's for a aeroplane.