What Amal carbs?

nopdog

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I think I should invest in some new Amal’s so need some advise please.
Bike is a 1971 Roadster.
It’s currently running a 930R66 on right and on the left no number.
Petrol tends to drip out the underside of the right side KnN air filter not all the time but may coincide with hard starting that’s happened once. I have pulled off bowls etc recently after noticing fuel leaking for first time.

From what I can gather a 71 commando roadster should be running 930/68 and 930/69 as standard. Are these the best to get or are there others that will work better.
Any advise is appreciated.
 

Tornado

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Have you solved leak with new bowl gasket? Another possibility is a poorly set float height, such that fuel is overfilling before shut off via the float needle.
Finally check the float needle is new (viton rubber tipped) and that the needle seat is clean. To clean, put a Q-tip cotton swab in a drill chuck, dip end it Autosol metal polish and give the seat in the bowl a good bit of spinning polishing tip work. Should come up nice and shiny.

There is an excellent Amal setup guide known as Bushmans Guide to Amal Tuning, found on the Technical Information sticky thread top of this forum.
 
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L.A.B.

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It’s currently running a 930R66 on right and on the left no number.

Are you sure '66' isn't 68?
The number pad of the LH carb is also on the RH side so the RH carb needs to be removed to read the number.
 
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You have asked yourself the question about new carbs... so I suggest you buy new carbs, otherwise you'll be tinkering forever and always wondering 'what if'

Amal do PACK111 for your bike (the Premier version, which is well worth the extra)

It consists of the 930/69PREM (left side) and 930/68PREM (right side)

As @L.A.B. suggests, look at your old ones closely, it could well be an 8 not a 6 on yours (the 930/66 is for a 71 Triumph T120)

...the new carbs run a little leaner than the originals - you may want to go straight for the #19 pilot jet,
 
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Hope you find some, I was quoted minimum 8 weeks delivery by AMAL for 932's two weeks ago, hopefully yours are in stock!
 

nopdog

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Thanks just ordered a pair from Andover. Amal were out of stock.
 

nopdog

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Took existing bowls of again yesterday.
Carb bodies are marked 930l301 and definitely 930/R66.
Did the Q tip with autosol no luck still leaking.
Switched bowls over and leak went to other side.
I have a box of old carbies etc that I should of thrown out years ago but found a bowl that looks the same so cleaned it up and threw it on.
No luck still leaking via the float needle.
Is there anything else that could cause this leak.

New carbs won't arrive till about the 12/5.

I know Bushman's pretty well over the years especially with the BSA singles.

Over the years, of the now 5 old bikes in the shed 4 were given new carbs soon after purchase. The fifth is about to follow.
I think the reason for this is/was that it eliminates most if not all fuelling problems.
And hopefully you don't get that old 90% of fuel problems are electrical and 90% of electrical problems are fuel.
 
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The 930/301 is the generic model number that Amal supply for non-model specific requirements.

Dealers and resellers typically buy these, and build the carb up to the spec needed.


But the 930/R66 is definitely for the 71 Triumph T120.


I often see leaking at the float needle when replacing the old floats (which are usually half full of fuel) with new stay-up floats.
They seem to sit higher on the fuel in the float bowl, and hit the roof of the carb body underside before the shut off.

Amal say you can tweak the stainless steel tangs to get the height right, but I personally don't like doing this.
Instead, I leave the float bowl in a bucket of boiling water for a few minutes, then push out the brass float needle seat a little.
I use a small drift (3.2mm) and push up from inside where the banjo union attaches - two light taps is usually perfect.
 

nopdog

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New carbs arrived today.
That was quick, thanks Andover.
Question is that the new carbs don’t come with provision for the crossover tube between the carbs via the bango bolts on the bowls.
Is it ok to use the new single spigot (no crossover tube)?
Or do I reuse the existing double spigots with the fuel crossover tube?
Thanks in advance.
 

nopdog

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Thanks Tornado.
Another question or two, I kinda know the answer but please bare with me.
On the existing set up there was no gasket between the carbs and the manifolds just the O ring.
Between the manifolds and the head was gaskets and gasket goo.
I’ve always put gasket and O ring between carb and manifold. No goo.
Between manifold and head gasket and no goo.
Is this ok
 

Tornado

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Opinions seem split on what to use. Some feel just o-ring at carb to mani risks inducing warping of the mounting flange with over tightening. I've used just the o-ring, o-ring plus an insulator (bakelite "gasket" ), and just the insulator without o-ring at that location. I usually put a non-setting dressing goo Hylomar Blue on the o-ring and/or insulator. Seems to make a good air tight seal, is easy to clean off during carb R&R, and doesn't risk leaving small bits to get stuck in the carb slides or jets.
For mani to head, again I use insulators with hylomar. I once had a slide stick open after stopping for fuel. Carb bowl got too hot to touch and i'd rolled throttle open before starting just by chance. It did not roll closed until carb cooled down some minutes later. I run insulators ever since. That issue was with a single amal into a one to two manifold, so likely it transferred more heat than two single manifold and dual carbs (more surface area). But seems insulators are a good peace of mind for me.
 

L.A.B.

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Question is that the new carbs don’t come with provision for the crossover tube between the carbs via the bango bolts on the bowls.
Is it ok to use the new single spigot (no crossover tube)?
Or do I reuse the existing double spigots with the fuel crossover tube?

Your "1971 Roadster" would have had the 'H' type fuel line with single-spigot banjos originally...

The later 180-degree banjo fuel line which you appear to have can certainly be used.
 

NIX

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I just took a lot of attention to my carb stuff as my bike came with a complete wrong constellation of carbs and parts. Figuring it all out, I cleaned al of them, making sure the pilots were open, but before mounting anything, I put the bowls and all flanges on some waterproof sandpaper on a thick glass plate (old no longer fashionable coffee table). You wouldn't believ how warped everything can be. After that, I had to adjust the float lever in all 5 bowls I had. I warmed them up with a heat stripper and tapped with the wooden back side on the top a 3,5mm drill. That worked perfectly. I now have 1 set on 2mm and one 1mm. Of course yo need to keep bowl, float and nedle together as a set. Mounting things back, I may need some silicone gasket on th isolators as there's no ring on that side of the manifolds, but the ring should be plenty on the other side, especially now everything is sanded straight.

About putting together carbs the right way, I don't know about carbs for a 750, but I would start at bodies being the same left and right in diameter and spray nozzle. From that point on, build them with the right needles, jets (both main jet and needle jet) and the right slides. Older bodies can have a lot of rough marks, I carefully sanded out mine. You can smoothen the old slides, but anodised ones are not the world in costs. And as said make everything straight, clean and adjust the float heights.
 
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