cracks in new Amal carb

Paul · Jun 7, 2009

After only a few hundred Km. I noticed there are some cracks in one of my new Amals. Should I ask for a guarantee replacement or are those only superficial and nothing to worry about ?

79x100 · Jun 7, 2009

If they're definitely cracks and not just dirt on the die-casting marks then you should certainly take them back. I would clean them off and have a good look inside.

A structural failure on a new carb is not something to be expected.

Paul · Jun 7, 2009

Thanks for the fast reply, 79 x 100. Btw, I was attracted by your avatar and now I found out why: I took that picture myself last year on the BBA café racer meeting in Waregem (Belgium)...
And btw2: the BBA meeting this year takes place today :shock:

Where do you live 79x100 ?

Per G · Jun 7, 2009

Give them a good clean to verify that it is cracks (the front one certainly looks like a crack). I would not like to use carbs with several cracks (might be more cracks where you don't see them), if you are unlucky you could get a loose piece sucked in the engine.

Have any forum member ever seen a crack on an old Amal carb? Maybe there is a reason to choose to keep and re-sleeve the old carbs instead of buying new ones?

/Per

kommando · Jun 7, 2009

Have loads of old carbs, mon and concentric, never seen a crack in any of them.

seaguy · Jun 7, 2009

I would use only carb cleaner spray.. no brushing of any kind. That has to be a bad batch of potmetal or what ever they use now. They should have to replace them both and be sure the replacements are from a different run of castings.
Rich

Rich_j · Jun 7, 2009

I don't think the crack is actually a crack.

If you run your nail across it you'll probably find its got a raised edge, this is because there's a well documented crack in original casting dies.

Basically they're all like that.

swooshdave · Jun 7, 2009

Rich_j said:
I don't think the crack is actually a crack.

If you run your nail across it you'll probably find its got a raised edge, this is because there's a well documented crack in original casting dies.

Basically they're all like that.

I'd say casting marks too. I've also never seen a cracked Amal. The metal is too soft to crack like that (that's why they deform so easily by over-tightening the mounting nuts). That's not to say the new Amals aren't different.

L.A.B. · Jun 7, 2009

Paul said:
After only a few hundred Km. I noticed there are some cracks in one of my new Amals. Should I ask for a guarantee replacement or are those only superficial and nothing to worry about ?

They are not cracks!

Apparently they are marks from the casting die, as Rich_j pointed out, that cracked some years ago, but they continued to use the same die until fairly recently as all new Mk1s are now produced from new dies!

Both my Commando's carbs have the same markings, and so do my T140 Bonneville's probably original 930 carbs, in fact most if not all replacement Amal Mk1s except the very latest ones will carry those marks, I believe.

Here's my Commando's R/H carb

And my Bonneville's R/H carb:

As can be seen both have identical 'crack' markings in the castings

Paul · Jun 7, 2009

Hi,

I just returned from a café racer meeting and - of course - I asked the opinion of some experienced British bike riders. One of the reactions was exactly the same as what has been posted here: cracked casting dies.
Watching the photos of L.A.B. there's obviously no doubt possible.
So nothing to worry about. Thanks a lot for your reactions ! I really appreciate your help. Great forum indeed !

79x100 · Jun 7, 2009

My sleeved 'R33' stamped OE carb doesn't have those marks, so the die probably altered some time after early 1975.

Glad this one's turned out OK.

swooshdave · Jun 7, 2009

Paul said:
Hi,

I just returned from a café racer meeting and - of course - I asked the opinion of some experienced British bike riders. One of the reactions was exactly the same as what has been posted here: cracked casting dies.

Just goes to show that we're at least as smart as cafe racers. :lol:

Paul · Jun 7, 2009

Actually, calling a Norton Commando Production Racer a "café racer" is an insult. Most people even don't know the difference, but who cares ? There are only few opportunities overhere to meet owners of classic bikes (most of those do not even correspond to the definition of a "café racer"). The meeting is small-scaled, the atmosphere is very friendly, and that's what matters.

ranmar850 · Jun 7, 2009

I personally know of one cracked Amal. Owner, off an Australian forum, and new to Commandos , had a bad rough-running/backfiring problem. The carb was indeed cracked, it was through tthe body at the mounting flange. It wasn't a new carb.

An acquaintance had a new set of Amals recently, bad running was traced to swarf in the float bowl and jets. He contacted the distributor, and they promptly replaced them, asking for the return of the first pair. Good service indeed.He said the replacement pair appeared to be made of a different quality die-cast material.

seaguy · Jun 9, 2009

Well there is one sure way to tell. Sand it with some 220. If it goes away....etc
Rich

cracks in new Amal carb

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