sd 102 restoration. where do I start ?

[Charles uk]

Think I've found it, on the equipment I've got access to it appears to be a 5/8 UNEF 24 TPI, taps should be available in the US.

But I can't measure the angle to see if it's 55 or 60 degrees.

They are available on ebay uk I've just bid on 1 that finishes in less than 2 days, don't bid me up please.

Will let you know if it works.

[Oyster 49]

Excellent, the bolt I have here is also 24 TPI. Intriguing this detective work.

[The Tinker]

Charles u are correct the tap size is right. I make an insert with 18mm fine on the out side and fit it in the carb then tap the 5/8 internal thread. insert gets very thin. I am going to make my next ones from bronze. First ones from are made from ali.

[Oyster 49]

I was hoping to find a correct size helicoil, to make the repair quick and easy, there does not seem to be any around of that size. Boo.

So next option is to look at finding or making a new bolt, to the same size but with a 5/8 UNF x18 thread. Helicoils of that size are easier to come by, so the repair would be to fit a helicoil and supply a new banjo bolt.

I've ordered a few bits to play around with. More to follow..

[The Tinker]

A lot easier to make the insert

[charlesp]

Easier still to give Amal a ring and ask them what the thread actually was, then get a suitable tap.

Epoxied or soldered (HTS2000 or JB Weld) an insert,cut a thread, Bob's your Uncle, still using all standard bits, job's a good 'un.

[Charles uk]

There seems to be 2 ways of doing this that don't need the cost of remanufacturing a new bolt which has got to cost more than £5 for a one off, in time & material if you have access to a lathe.

A, The new Zealand way, where you make an insert with a thread on both sides then drill & tap the carb body to suit, which would require access to a machine shop & might well be easier if they were done in batches of 10 or so to bring the cost down, then sold on an exchange basis.

B, Make a batch of internally threaded inserts to suit the existing bolts, lightly knurled on the OD, that John could stock & supply (sorry John). Then ask the owner to drill an 18mm ish hole to the correct depth & centrally in the carb body, not difficult if the owner has access to a mill/drill, but might be problematic with a hand drill, then Arldite in place. These holes & insertions might well have to be done on a batch basis which would entail 2 way postage cost.

These could end up a £20 repair, cheaper than an ebay carb, but still dear enough, perhaps your right I am a tight Bast**d!

[skyetoyman]

I would go for B as a pillar drill and vice is all that's needed . It surprises me just how poor the threads are at both ends -- were they just cast.

[Charles uk]

Be kind Terry, your carb is collecting it's pension, & I think all the threads were machined.

I doubt very much that Amal expected a carb of that years production would still be asked to do it's stuff in the second decade of the next century after it was cast from mum's milk pan.

[woodbutchergraham]

Charles if you’re a tight bast*** what would that make me !
Oh I’ve tried the epoxy thread technique no such luck for me but it’s great for sticking the inserts in. I found that if you put the body of the carb in the jaws of the lathe you need an insert to stop the body from distorting and then the slide sticks. Charles is correct when he refers this ally as an old milk pan it has soft spots in parts.

[Charles uk]

Graham perhaps a " Northern tight Bast*** " with a capital B.

[skyetoyman]

Thanks to Oyster49 for the replacement carb chamber which arrived today. Thread is very good. Bit tight on my original piston , so a little work to get it to fit .
I assume wet & dry on the points were it catches the bore is the way to go .

[Oyster 49]

Should have checked that first

Yes, wet & dry and a long thin finger should do the job.

[skyetoyman]

I am sure their is a joke there somewhere

[Charles uk]

That is normally a symptom of a cylinder that about to throw it's toys out of the pram because of too much crud in the water jacket!