Binks carb

[jonathanjoy]

Hi
I need to replace the needle valve on my three jet binks. Does anyone no of a supplier or another make that is interchangeable.
Has anyone tried to regrind one with success ?

regards Jonathan

[Dripfeed]

Have recently made a float needle for a vetran FN carb I used a hard facing welding rod , to produce the point that mates with the seat I used a high speed pilar drill (the o a p Drummond is not fast enough )I used a medium and fine oil stone then lapped it into the seat using fine pumis powder . It needs a tad of patience with the oil stone Regards D F e

[jonathanjoy]

Thanks dripfeed,

I’ll give that a try, what sort of speed did you use ?

Jonathan

[BRIAN MARSHALL]

If it is the later type of three-jet Binks, with just a knurled ring top to the mixing chamber, the entire float chamber assembly is identical to the Type 6 Amal, so all the float chamber parts are readily available. The earlier three-jet has a very heavy body, a large hexagonal top to the mixing chamber, and a large diameter banjo connector on the bottom of the float chamber.
Brian

[jonathanjoy]

Thanks Brian,
Its the later type Binks, so I’ll check out the Amal 6.

[Dripfeed]

I did not check the speed as fast as produced a good finish . it was the type of needle that is a single diameter with a steep taper for the seat and a press fit thimble to engage with the float weights . Regards D F.

[jonathanjoy]

I’m not sure why I’m having such problems starting the engine. How can I tell if I’m flooding the engine ?, are there any top tips, using a three jet Binks.

It will fire, if I’m lucky run for a few revs, then nothing. Warming the plugs seemed to help a bit. I’m using new fuel and the spark is reasonable ❗

Any ideas

[BRIAN MARSHALL]

It sounds more like fuel starvation to me, and I have a pet aversion to Binks carburettors. I would try and borrow a known good carburettor, preferably an Amal, and I suspect that will result in the bike running OK…..
Brian

[jonathanjoy]

Hmm, just thinking along those lines myself, Brian. I’ve not got another Scott carb, but I’ve got an Amal of a BSA. I’ll try to mount it on the inlet. It sounds like you’ve had bad experiences of Bink’s carb. They look pretty simple, but I’m not sure about how they meter fuel / air accurately

[BRIAN MARSHALL]

No throttle stop, no primary air screw, no spares availability, and all you can do is change jets and alter the float height. I presume that you have set the float height properly ? A tricky job…. Slightly loosen the bottom banjo bolt, turn petrol on, do not ‘tickle’ the float chamber. Using a mirror, just edge the float chamber body backwards until you see petrol just beginning to seep out of the shortest jet, then edge the float chamber backwards a gnat’s whisker from that position, and retighten the bottom bolt. This may involve a bit of British Standard Faffing About, with bits of tissue drying off the top of the jet, to make sure that the petrol level is not too high. It should be just a fraction below the top of that jet, so that the air rushing over it when you operate the kickstart pulls a spray of petrol into the engine, by the venturi effect. If you think that you have got it correct and then see petrol seeping out of the jet, it may mean that your float needle is not seating properly, and is letting the float chamber flood, in which case you have just wasted your time trying to set it up !! Of course you must do it with the bike upright and off the rear stand, so you may need an assistant.

I don’t think that I have ever revealed this technique before, so everyone with a three-jet Binks please make notes…..

Jim Best told me how to do it about 25 years ago, but I got so fed up with Binks carbs that I have only had to do it a couple of times.

Brian

[jonathanjoy]

Yep, limited design, unlike an ad I’ve seen for the Bink’s of that era ,some things never change.
I’ve been adjusting the stop of the throttle by altering cable length. The float level by packing washers to the needle shoulder. On mine the float chamber is at a fixed angle, so I can’t alter its angle to adjust the level, is this what you mean or have I misunderstood. ❓
by the way, thanks for the help (yet again )

[BRIAN MARSHALL]

The float chamber should be free to pivot when the bottom banjo bolt is loosened, and if you move it backwards and forwards you will see that this raises and lowers it due to the 38 degree downdraught angle of the mixing chamber. In theory, using this method is a bit of a bodge, but in use the float chamber is never perfectly vertical anyway, because the bike is leaning from side to side, and going up and down hills, so in practice it works OK, and is much easier than trying to lower or raise the float needle off the float. Or are you saying that you have a horizontal carburettor on a separate stub ?
Brian

[jonathanjoy]

Sorry I misunderstood, realized that you rotate the float chamber around the banjo axis to adjust the level, thats quite a neat trick I’ll try it
thanks

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