Thread: Gilbert

Originally Posted by whitehillbilly64

OK,
Found out points changed 1976,
Gilbert is a 77 model but motor I rebuilt, came out of another series 3 thought to be 77, but must be 76, or Dissy swap at some point.
Can the engine date, be confirmed somewhere by listing engine No ????
Thanks

whitehillbilly

I've always struggled with a definitive engine numbering guide - there's bits and pieces all over the place - but I've never seen anything all in one place - if anyone knows of such a thing please let me know.
cheers,
D

Working on the Carby at the moment.
Anyone done the O ring mod, mentioned in this article ????
[ame]http://c0007716.cdn2.cloudfiles.rackspacecloud.com/instructions/RNC959I.pdf[/ame]

whitehillbilly

The modification is unnecessary if the mating surfaces are both flat. And it will not fix all the problems resulting from their not being flat.

So probably better off lapping them flat.

John

Originally Posted by JDNSW

The modification is unnecessary if the mating surfaces are both flat. And it will not fix all the problems resulting from their not being flat.

So probably better off lapping them flat.

John

Bugga. And here I was thinking it sounded good.

For those of you who will be needing to lap things... or do any flat grinding, an alternative to finding a piece of flat glass is to go to an opp shop and get a marble cutting board. Dead flat and stable, just like the glass (I used to use mine with wet/dry paper to put a genuine razor's edge on wood planes when I was building boats).

Looking at the amount of warp with the Zenith carby, I wonder if adding the heat shield, in a hot climate, such as ours, will add to problems, as the shield directs the hot air up onto the carby.
This would be OK in wet, colder climates.
Maybe this is why they were removed ????
What are your thoughts ?

Whitehillbilly

I don't think heat has anything to do with the warping. The warp is simply the result of the top casting pressing against the O-ring in the middle, with the pressure applied by screws round the edges. Combined with inadequate depth for the structure of the top cover, or inadequate thickness of metal, the cover warps.

I don't think the temperature has much to do with it - long before the temperature got high enough to affect the metal properties, the petrol in the bowl would be vaporising, causing running problems - something that is virtually unknown with this engine (it can happen, usually the result of slight air leaks on the suction side of the pump). Worth noting that except for the carburettor, the entire fuel system is on the opposite side of the engine to the exhaust system, probably by design.

John

Thanks John,
Did notice the casting was quite thin, in some areas.
Who would have thought one little 'O' ring would cause such problems.
How are the 'O' rings in the after market kits.
Is there a general guide for clearance of 'O' with gaskets fitted, before screwing the to halves of the carby together.
No squish, and it doesn't seal.
To much causes un nessesary destoration of the carby halves.
Thanks

Whitehillbilly

I don't know of any actual specification for the amount of squish, but if there is no gap for the screws to pull down then it obviously won't seal, but how much is too much, I don't know.

However, I suspect that the problem may be not how far it is pulled down, but how hard the material of the O-ring is - and this probably varies unpredictably, as I'd just about bet that the kit makers use off the shelf rings, and the material is likely to be different with each batch.

Probably a good idea not to assemble a carby in very cold weather, or if you do, to soften the O-ring in boiling water first.

John