Amal float bowl screw threads

[ewgoforth]

Hello,

I seem to have slightly messed up the threads one of the carb tops on an Amal 932. Does anyone know what the thread is? I was going to try to clean it up with a tap, but I'm afraid I don't have the right one.

It appears to be #10-32 UNF, but I've tried to run several of my screws into a 10-32 UNF die and they sort of stop halfway through. I have a few old float bowl screws. I could just cut a couple flutes on one with a dremel. I did that to clean out the threads where the fuel line banjos connect with an extra banjo bolt.

Eric

 

[MFB]

Hello,
It's probably 2BA, which is very close to #10 UNF. That would explain why the screw sort-of fits into the #10 die. L.A.B. would know for sure.
For those of us in metric countries, 5mm is also very close to the other two and can be used to resurrect damaged threads. Also handy when imperial screws are lost and only metric ones are available.

Cheers
Martin

 

[swooshdave]

2BA sounds right. 10-32 is real close. I've retapped the gearbox cover to 10-32 so I could put some socket head screws there. Same concept. I don't know how well the pot metal carbs will stand up to retapping.

 

[pierodn]

Threads?
Why!

Ciao
Piero

 

[Brooking 850]

I thought us antipodeans were the Number 8 wire crowd????
Well done !!!

 

[L.A.B.]

It's probably 2BA, which is very close to #10 UNF. That would explain why the screw sort-of fits into the #10 die. L.A.B. would know for sure.

Yes, 2BA.

 

[Danno]

2BA sounds right. 10-32 is real close. I've retapped the gearbox cover to 10-32 so I could put some socket head screws there. Same concept. I don't know how well the pot metal carbs will stand up to retapping.

I suppose this is the reason the stainless socket head kit (5 screws) for the gearbox is more spendy than the one for the timing cover (14 screws) which is 1/4x20.

 

[o0norton0o]

I retapped both screws of one carb to use 5mm socket heads because one thread was stripped enough to need a nut on top of it and a long screw. I decided to take a chance and tap them both for the 5mm thread and they came out perfectly. I like the allen head better facing upside down...

Of course, tapping pot metal is one step above tapping a firm chunk of cheese, so you need to thread things gently. Also, I took the bowls and trued their surface on a glass plate with a sheet of 400 wetndry sandpaper on top to flatten them up. (they weren't flat)

 

[gtsun]

You can buy any British taps or dies you need for a Norton including nuts, bolts, screws etc from Britishfasteners.com they have it all & more & on top of that they are super nice and fast shippers. Great people.

 

[jaydee75]

I tapped mine out to 10-32 years ago and works fine with socket head cap screws. Easy to get off with a ball-end hex wrench. Did the same thing with the cap on top.
Jaydee

 

[Hobot]

pierodn I will take your bailing wire semi permanent rescue to heart and carry a some appropriate wire. In a pinch IIRC can steal a screw from the cable cap to get back home ok. Best ant-seeze to eliminate over tightening in pot metal and adequate lockite w/o so much resistance it messes with screw slots is RTV smear on threads.

 

[DogT]

This may be a little off subject but somewhat relevant. I re-tapped the blind 2BA threads in my S silencers to accept 10-32 button head socket screws for the shields because the price difference was worth it to me. They've been holding up fine. Just an observation.

 

[motorson]

I just ran into the difference between the 2BA thread and 10-32. I have an extensive thread gauge which has a ton of abnormal pitches on it and none of them exactly fit the Amal Carby screws. The correct 2BA screws are .1815 diameter and the 10-32 screws are .1835 inches so the American 10-32 is .002 larger in diameter. I had ordered some float bowl screws on eBay and they came 10-32. I plan to complain but have already left positive feedback.

I did notice that the 10-32 will screw right in where the 2BA came out without tapping and goes in quite tight. Under my little high power magnifier the 2BA threads look like a lot better quality machining.

Now it is back to eBay to find the 2BA screws in a stainless socket head.
Dan.

 

[Brooking 850]

Is the thread pitch and diameter in the carb slide tops the same as the float bowl retaining screws?
Regards Mike

 

[Nortoniggy]

Is the thread pitch and diameter in the carb slide tops the same as the float bowl retaining screws?
Regards Mike

Yes it is.

Be careful if using socket screws in the float bowl as it's very easy to over tighten them and distort the bowl.

Ian

 

[CanukNortonNut]

I used a 10-32 helicoil on one main body to fix a stripped thread. Worked a charm. I also use the Allen head cap screws (2BA) on all the carbs I rebuilt once these were re-sleeved and when tightening up I just use just the short leg of the wrench. You can't use a whole lot of force on these old instruments as the material choice of the day was used for ease of casting to a cost. Instead use a dab of blue locktite along with the small split washer and it should hold. Watch the gasket once you turn the petcock on and give it a tickle and see if the gasket gets really wet from fuel. If so turn the base a little tighter. But before that use new gaskets and make sure the bowl at the screw entry points are not distorted. You can massage the tabs back by placing feeler gauges of equal thickness near the tabs on a flat surface and then apply pressure on the bowl with an arbor press or drill press. Again be gentle here. Then take an emery paper or wet and dry and sand the base of the bowl dead flat. Over torquing the bolts at the body and nuts at the intake flange is what plays havoc with these soft metal carburetor bodies.
Regards,
Thomas
CNN

 

[Hobot]

Just a heads up on my carb bowl screws, found blue loctite grips too strong it injures Philips slots trying to remove especially with poor driver angle with carbs mounted so switched to a smear of RTV which works good to hold and seal w/o cranking hard on pot metal threads yet releases enough not to strain the screw head. Works on the manifold nuts or interior allens for the single carb manifolds. Btw it is about impossible to access the carb cap screws away from home with normal size Philips driver.

 

[CanukNortonNut]

Just a heads up on my carb bowl screws, found blue loctite grips too strong it injures Philips slots trying to remove especially with poor driver angle with carbs mounted so switched to a smear of RTV which works good to hold and seal w/o cranking hard on pot metal threads yet releases enough not to strain the screw head. Works on the manifold nuts or interior allens for the single carb manifolds. Btw it is about impossible to access the carb cap screws away from home with normal size Philips driver.

Steve,
I have not had a problem with the blue loctite so far. I use 242 in this application. The 222MS (pink) would also work and is a lower strength Loctite product.
Regarding the Philips screws, that's why I went for the Alan heads. The tool you carry is smaller and if you choose this type wisely get the one with a ball end on one end. This way you can approach the inside screws and get at them easier. If you have to take the top screws off you are taking the tank off as a matter of necessity.
FYI
Cheers,
Thomas
CNN

 

[ewgoforth]

I lost the float bowl screws off one carb and managed to get home by taking out one screw out of each top.

 

[seattle##gs]

Another good product at BRITISH FASTENERS ....The have the CORRECT color coded fuse holder..BROWN/BLUE wire and it looks a lot better than the usual aftermarket ones. You have to request a larger gauge wire than what they provide but they will furnish, no problem.