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#807516 05/02/20 9:43 am
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Background: Bought 90% finished '65 TR6SS nine years ago. Over next year or three completed it to a good working bike standard with lots of much appreciated help from this forum. Amongst other things, converted from 4CA points to 6CA and bought new stuff such as AMAL 389 carb. Anyway, got it it tested (UK MoT), brought it home to tidy up the odd detail. It ran well on four mile round trip to testing centre. Got distracted by other things and then came back to the bike some time later. Took it out, and after a couple of miles, bike cut out and took a lot of kicking with open throttle to get started. Eventually got home and found plugs were a very sooty black. Left bike.

Covid -19 comes along and thinks wouldn't it be great to get that Triumph running properly, so like the Prodigal Son here I am again!

What I've done so far is checked timing/points gap. They're fine. Moved needle down a notch in carb. Doesn't seem to make a difference. Banjo filter clean. Checked float level using a perspex float bowl cover. Fuel is 2mm over where blip in cover would be. Is this critical? Changed float and float needle to spares. Exactly the same. I noticed that when tickler is pressed down, fuel doesn't emerge from tickler, but drips from back (filter side) of carb. That seems wrong. I'm getting all the indications that bike is flooding. Bear in mind carb is new.

Does anybody have any ideas?

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Checking through the Perspex cover, does the fuel level rise or go very frothy when you rev up to road rpm?


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DUHC #807518 05/02/20 10:50 am
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Try without the air filter on.
What element type is it?

DUHC #807523 05/02/20 12:17 pm
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Thanks, chaps.

Unfortunately, didn't get engine running with perspex cover on and it annoyingly split and broke up after a couple of dismantlings. Filter is original type paper element in perforated chrome/black housing. These recent findings were with filter off. Fuel seems to be either dripping from venturi, or one of those holes at the bottom of the opening.

Last edited by DUHC; 05/02/20 12:17 pm.
DUHC #807530 05/02/20 12:44 pm
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Check the float for seams or flashings that might catch and stop it rising correctly, check the float needle valve and seat, clean the seat with metal polish.
I suspect the ignition system points/ condensers, Look at the points with ignition on, kick over , do you see big sparks across the points?, if you do, then the condensers have failed


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Swapped floats and needle valve and same situation with both. Haven't checked seat, bearing in mind this is a virtually new carb. Fuel got to the aforementioned identical level with both floats/needles and stopped there.

Agree that the majority of 'fuel probs' are ignition ones, but points are fine, gapped correctly, small spark as one might expect when flicked.

Still the mystery of why fuel doesn't come out of tickler when tickled (it has on all my previous AMAL equipped bikes) and why it comes out of back of carb - which I've not seen before.

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There’s nothing to stop fuel running out of the pilot air hole and the compensating air hole in the intake horn. For petrol to emerge at the tickler button, it has to flood in faster than it dribbles out of those holes.

Maybe your tickler isn’t pressing the float down very far, or something else is slowing the fuel flow.


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DUHC #807666 05/03/20 10:06 am
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Thanks, TT. That's useful. The flow rate does seem quite slow. As said, new carb and all components in fuel line are clear. New fuel taps since issue identified. Possible partial kink in fuel pipe, so replaced pipe.

Tickler depresses float, bearing in mind fuel level is 2 mm above notional blip on float cover. Experimented with spacer on top of float, but this brought it 2mm below blip and tickler no longer reached. I've compared/swapped all components involved and they appear identical with spare bits I've got, including seat and needle.

So, how critical is the correct float height?

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In the end I swapped the brand new fuel valve seat for a spare old one I had and this reduced the height of the fuel in the chamber to the correct height. This was checked using a manometer tube. After riding the bike a few miles it seems to run sweetly.

Now a different issue. It seems to run better on the wrong plugs! The earlier fouled N4Cs were replaced temporarily with the nearest spec I had which were N9YC (a long nose plug that had come out of my MGB). On these wrong plugs it has a nice even tickover, but if I kept them in there I'm guessing it'd damage the pistons with the sparks being that much closer and the wrong spec. With the cleaned N4Cs it's a bit lumpy. I'm going to get some correct spec N3Cs and hopefully get back to the smooth running of the wrong plugs.

Anybody any thoughts or recommendations?


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