Carburettor repair

I guess that when it comes to rebuilding old (and relatively rare) motorcycles, beggars cant be choosers over the parts they need and acquire.
I was really disappointed to find that my original eBay purchase of the bike didnt have a carb on the engine.  I thought this would be a real stumbling block, but within a few weeks I had purchased a Gurtner J14 (from Roy) and I once again re-enthused that perhaps I could get my machine up and running.

However, on stripping the carb I was faced with a couple of challenges - why is nothing ever simple?
Firstly there is no fuel-in banjo fitting.  I thought this would be a simple thing to overcome, but no-one that I spoke with (from Scooters, to lawn-mowers to vintage motorbikes) could find anything that was remotely close, and so I prepared myself to make a suitable fitting (and stole a little selection of brass tubing from my dads garage)

The second challenge was to repair the bodge of someone elses doing - I find it incredible that some people think they can overcome mechanical problems with the most outrageous and inappropriate bodges (though that said, in this instance, this bodge probably did work and got some fool out of trouble for a while).  At some stage someone has sheered the top cap retaining screw in the chamber body, and to make things worse then simply rammed in an oversized screw into the remaining couple of millimeters of hole.  This has distorted the slide chamber, making the needle slide impossible to remove without filing flat the distorted chamber wall



I had a couple of options to repair this.  One was to purchase a left-handed 2.5mm drill bit and gently left-hand drill the sheered remains out - I read somewhere on the internet that using a small piece of brass tube that fits snugly in the hole can help centrally align a pilot hole.  The theory behind the Left-hand drill is that it would reduce the amount that the thread was driven futher in and might perhaps even help to unscrew the thread (much like an ezy-out).  I discounted this option as my pillar drill doesn't have a reverse drive

I decided in the end to drill the old thread completely out with an oversized hole, and plug that hole with a 4mm dia piece of aluminum rod, and then re-drill and tap to the correct M3 size

Incidentally; as I was tossing and turning one night thinking about this problem, I wondered about what adhesive I should use to bond the plug into the drilled out hole.  In the middle of the night on my iPhone i started to read forums where people had asked the same question with regard to petrol resistant adhesives.  Lots of people were saying that JB weld was the stuff to use but it wasn't easy to find in the UK.
In my local hardware store, they sold "Araldite Rapid Steel" which claims to be "Ideal for most types of metal including steel, aluminum, iron, copper and brass, and is oil and chemical resistant" ..... "oil and chemical resistant?" what about petrol?  I decided to put it to the test.
I made up a sample piece of two bits of aluminum rod bonded together with the 'rapid steel' - left it to harden for a couple of days and then submerged it i petrol for 5 days. The result?  Well, no degradation as far as I could see - so I'm going to use it.  It will certainly be good enough to get the thing running and give me time to find another Gurtner chamber if necessary 


Drilling the hole out to 4mm is a maginal job, Ive just about avoided breaking the wall of the slide chamber, but it has distorted it a little.  
After flatting back with needle files and emery paper, the job is quite neat but it has exposed a patch of the 'rapid steel' adhesive.  If my test piece is anything to go by, I shouldn't have much to worry about.  I'm guessing also that petrol shouldn't really get up the sides of the slide.  We shall find out.

In the meantime - while Ive been thinking about and fiddling with this repair I was having a little email paper-chase too.
Klaus Faak of Faak-Tilmanns UG had come back to me saying that he could supply Bing carburettor parts, but not Gurtner carburettor parts, but suggested I speak with Jean-Noel Benech in Toulouse who might be able to help.


Monsieur Benech came straight back to me with a Gurtner J14 parts list and asked me to identify the bits I needed.  I was amazed that I could simply pick the bits I wanted from a parts list.  I sent him my wish list and I await his reply with prices.  Maybe I wont have to make my own banjo after all


UPDATE; I never did hear back from M. Benech, but I did manage to buy another Gurner carb - and used that as a donor for the banjos