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I think it's a sticking needle jet.

This has happened three or four times now. I start the car, back it out the garage, do stuff for the next couple of minutes and when I'm about to get in the car (or just a little bit down the road) it starts missing. First time by judicious removal of plug leads I was able to determine it was the front two not firing which led me to the front float chamber which was just about empty. The float an needle seemed to be moving ok, so I put it back and all was ok, at least for that trip.

It has happened a couple of times since - by the time I have pulled the top of the float chamber presumably the jolt has unstuck the needle - it always works when I put it back.

I'm assuming it's not an intermittent blockage elsewhere as the rear two cylinders continue to fire and their float bowl is second in line for the fuel.

Once out the needle and float seem quite free to move (pic below).

I haven't yet examined the end of the needle as it seems tricky to get out - no obvious way of removing the needle without the float, and no obvious way of removing the float.

Also, the needle has a small springy plunger in the end - is that standard - what's it for?

Should I change the needles and jets as a precautionary measure even though they seem free and fine, or is there a way of cleaning them? Or have I got a different problem?

Thanks, Ali.

 

Front Float.jpg

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The brass pin usually just pulls out to take the float off.  The springy plunger is to ensure the needle valve doesn't chatter.  The genuine Burlen needles are usually aluminium rather than plastic I think . The needle should be quite free in the brass body - it just lifts out. If it is sticking maybe that one has swollen a bit ?

Maybe best to replace the whole needle jet with one having a viton tip.  Burlen Part number  VZX1101 but they seem to be out of stock at present. 

http://sucarb.co.uk/float-chambers-spares/needle-valve-kits/standard-needle-valves/needle-seat-kit-viton-tip-0-096in-spring-loaded.html

If you remove the jet for cleaning make sure you screw it down properly on re-assembly. You really need a socket or tubular spanner for that.  Not long ago someone on here had a jet unscrew itself and drop out. 

 

 

Edited by RobH
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I used to get that sometimes, a sharp tap on the front float chamber with a small spanner always fixed it.

Yes it is the needle sticking in the jet. Mine seems to have stopped doing it now !

Bob

Edited by Lebro
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Thanks guys.

Just an update ...

The float did come off quite easily. It had looked to me like the little shaft had been peened at both ends, but not so.

Rob, thanks for the link, but you were correct that sucarb.co.uk are out of stock. But I managed to get a pair from southerncarbs.co.uk who appear to have plenty. Good service - ordered yesterday, here this morning.

Here is the old needle compared to the new one - I think it is pretty obvious why it was sticking ...

 

Old & New Float Needles.jpg

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