Check your stubs!

[stevepm2011]

While I have the Jota's carbs off, I decided to remove the stubs from the cylinder head and replace the o-rings.
This turned out to be a good decision!
The o-rings were flattened, but more disturbing were the casting flaws in one of the stubs - see picture.
I would guess that the flaw in the ring groove may well have bridged the o-ring sealing surface, leading to an air leak...
A potential cause of idle instability / one cylinder always a bit leaner than the others?
The porosity in the inner wall of the stub fortunately doesn't go all the way through.
So if you have a hard-to-trace carburetion fault, it may be worth taking the stubs off and having a look.

regards to all,
Steve

 

[Paul Marx]

Araldite.
Paul

 

[Vince]

I replaced the O ring with a vitron one,more fuel resistant.Major error was this O ring was a bit thicker and I snapped off an ear,the stubs ear not mine trying to compress the O ring.Didn't take much force,be careful.

 

[Paul Marx]

I usually mount the lot with a bit of non drying gasket goo.
For peace of mind.
Paul

 

[nick7]

Junked the lot for modern billet made ones...

 

[CLEMTOG]

available from elegog on ebay, good product, nice and cheap, but need a tad of finishing, I have found that the stubs which slide into the plastic heat sleeves to be about 6, maybe as much as 8 thou oversize, if you jam them on you will surely split your carbs open, and they don't need a lot of help in doing that as standard, so be warned
CLEM

 

[Robin Webster]

available from elegog on ebay, good product, nice and cheap, but need a tad of finishing, I have found that the stubs which slide into the plastic heat sleeves to be about 6, maybe as much as 8 thou oversize, if you jam them on you will surely split your carbs open, and they don't need a lot of help in doing that as standard, so be warned
CLEM

Been there, done that!

Robin.