TOPIC:

Hello Folks,

I'm part-way through a carb set rebuild and have noticed I'm missing one of the tiny push-fit (I think?) jets that goes into the lower end of the brass choke fuel lifting tube that sits in it's own 'well' at the back of the float bowl.

Do you think this is a critical part, in the sense of just getting an engine running, even if some short-term cold-running roughness might result?

I don't see the part listed in CMSNL or Zed-Parts in Europe, so not sure whether its a serviceable item or not?

I do need to treble-check that it's not glued in the bottom of that choke bore-hole in the float bowl, although they've all been diesel soaked and ultrsonic'd and all orifices blown through so I'm not expecting it to be there.

Another choke tube question arising is that I also notice this thin brass tube on all 3 of mine appears to rolled from sheet as each has a 'split' or join line running all the way up it.
To me the join looks wide enough to let fuel through, which would appear to defeat the point of the tube-end jet as well as the choke jet in the bottom of the float bowl, so what do you know / recall of yours in this aspect?

All thoughts welcomed, no matter how challenging!

Richard.

This is covered in the following
www.kz1300.com/index.php/forum/carburato...79-carb-rebuild-pt-1


The choke pick-up tube is a tube - not "rolled" . The reason it cracks (which is a predominant issue) is from the stress associated with having the metering jet pressed into it. The repair is easy. The pick-up tube and the port that allows fuel into the pick-up well, are both metered with a .030" orifice. Why 2 - I haven't figured out (yet)!
DO NOT attempt to remove the pick-up tube ! The choke circuit for this carb. will probably work fine but I have no experience with a "missing" orifice so your feed-back is valued.
Some creativity in replacing the missing metering-jet with something other then a specific one will be in order but shouldn't be difficult with some imagination and care..

Thanks Scotch, hadn't found that in my searches and yes it certainly covers it in excellent pictorial detail !!

As all 3 of my choke tubes have split, but also split most of their length, as well as sorting the 1 missing jet (not too difficult to fab as you say) and reinforcing the ends, I assume I must also remedy the longer splits and the risk they present of the tube (which I assume is immersed in the same depth of fluid as per float height via the bowl choke jet) drawing fuel in throughout the height of the split and presenting much more of a change to fuel flow that just the missing jet would.

Hopefully it's no worse than soldering lightly along the split in situ, or maybe run the outer brass sleeve you repaired with along the whole length, perhaps just tinned at the jet end, to 'close off' the fuel breach.
Out of interest, when you advise to not attempt to remove the brass tube, is that because it's not available as a spare part, or that it's pressed into the ally casting in a way that likely to destroy it? (or both!)

With regard to the pick-up tube being split for most of its length - You're correct in the repair method. A full length piece of brass tube, common at most hobby/R/C shops. I had to do this on a set I was rebuilding. In this case you can clean the pick-up ("Scotch-Brite" is great for this) and solder the two. I will suggest this: After cleaning the pick-up, flux it and with a soldering-gun ( not a "pencil" type...usually can't generate enough heat) pre-tin the pick-up tube. If cleaned and fluxed adequately a very small amount of solder is all that will be wanted. Even with care this thin layer will be too heavy for the re-enforcing tube to slide over. The easiest method to slide the re-enforcing tube on is to apply a little more heat to both. A small (Palm-size) butane torch with a pin-point flame is ideal and it's heating capability is perfect. Re-flux - Heat - slide. More heat will be needed the closer you get to the carb-body. Any excess solder will be displaced and can be removed later. The open end of the re-enforcing tube should be flush with the end of the pick-up. It may be noticed that the solder migrated to the metering jet; in which case you're done aside from some cleaning. Otherwise: clean the end, flux and apply a "touch" of solder.
I don't recommend attempting to remove the pick-up tube because I've tried and I was concerned about it breaking off, before it released. Most should be able understand the ramifications involving a repair.
Let us know how it all works out and if you detour successfully with an other method - let us know those details as well !
scotch