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Amal 376 sticking

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Amal 376 sticking
Started at 07:28pm on the 1st November, 2018 by Rodders
Rodders Subject: Amal 376 sticking
I have the Amal 376 on my 500 twin.I had it cleaned with an ultra sound cleaner and it worked well for the first few hundred miles. I now find whenever I leave the bike unused for a few weeks the slider sticks solid. I can free it with WD or paraffin but then next time I go to the bike it's solid again. Any advice please?
Posted: 07:28pm 1st November, 2018
stinkwheel Subject: Amal 376 sticking
Not sure about the monoblocs but I know I have had terrible bother on my Mk1 concentric due to the throttle valve being made of the same alloy as the carb body. This has lead to extensive scoring and wear on both the slide and the carb body to the point the bike will barely start and the carb is essentially scrap. The solution would have been to fit a hard anodised slide from new but I didn't know this when I bought it.

If the problem is alloy corrosion sticking the slide in the carb body (you're sure it's not the cable that's sticking?) I'd imagine a hard anodised slide would be much less prone to this problem. You may already have one mind. The anodised ones are black in colour, standard ones are silver.
Posted: 08:34pm 1st November, 2018
Haggis Subject: Amal 376 sticking
You have probably over tightened the mounting bolts which will cause the same problem. Always remove and replace the carburetter fully assembled, with the float chamber and mixing chamber lid, throttle cable and slide components installed. This ensures maximum rigidity of the assembly while it is being installed. Tighten the mounting nuts carefully and evenly. Nuts and spring washers should be tightened until the spring washer is just flattened. Over-tightening the nuts will over-compress the flange gaskets at the flange extremities and may warp the flange, and in extreme cases the carburetter body, causing the throttle valve to stick. Mark 1 carburetters are not designed to bolt tightly to the intake flange and may distort if overtightened. It is only necessary to compress the O ring seal to ensure air tightness. When correctly tightened the carburetter flange and engine manifold should be no more than just touching. Nyloc nuts should always be used to mount Amal Mark 1 carburetters.
Posted: 09:44pm 1st November, 2018
John L Subject: Amal 376 sticking
Haggis has it.......virtually all the problems I've encountered personally with Amal carbs. are directly attributable to some previous owner's ham-fistedness, particularly in respect of overtightening. It is possible to straighten a bent flange on a Mk1 Concentric (with the correct technique and equipment) if the amount of distortion is not too bad, but further damage can frequently be caused to the mixing chamber cap and float chamber from overtightening. Any attempt to fix distortion of the flange by filing, sanding, etc. merely aggravates the problem as you are then left with a thinner flange which will warp even more easily, and ruins the fit of the flange 'O' ring, if fitted. Monobloc carbs. enjoy a better reputation generally for quality and service life, but if original fitment, many of these would be over 50 years old.......
Posted: 09:18am 2nd November, 2018
John L Subject: Amal 376 sticking
Sticking slides are not peculiar to Amal carbs. - the last one I had to deal with was in a Keihin carb. on a Honda. This has a bushed x-shaft in the top of the mixing chamber, and a cable drum with push-and-pull cables to operate the slide - i.e. POSITIVE opening and closing of the throttle. A precision instrument - slide-to-body fit is something you could only dream of with an Amal. Of course, this ensured that freeing off this stuck slide without causing damage was extremely difficult, and took weeks of soaking in fuel/penetrating oil/WD40 - you name it. The actual cause turned out to be nothing more than residue/gum from old fuel.
Posted: 09:37am 2nd November, 2018
Valsp Subject: Amal 376 sticking
If its a modern Amal the tolerances are pretty dreadful. I have a pair of replacement concentrics and if you swap the slides one of them sticks open! You can get a hard anodised slide for the 376 which might perform better
Posted: 12:56pm 2nd November, 2018
Rodders Subject: Amal 376 sticking
OK All, thanks for those comments. I'll have a look at those and see if I can remedy the problem. Rod
Posted: 06:43pm 4th November, 2018
PeteF Subject: Amal 376 sticking
Second that Vaslsp, modern Amals are pretty awful, even Mikuni copies are better. I think people fit Amals 'cos they look the part but there's no advantage.
Posted: 09:32pm 4th November, 2018
Adrian Subject: Amal 376 sticking
The current producers of the Amal Mk1 Concentric recognised that all was not well and brought out what they call the Premier version, they're supposed to be quite an improvement, aluminium alloy instead of zinc alloy bodies, hard-anodized slides and detachable pilot jets. Has anyone here tried them?

Posted: 10:03pm 4th November, 2018
scotty Subject: Amal 376 sticking
Pick up amal carby drop in waste bin buy jap mikuni fit and live happily ever after.
Posted: 04:19am 5th November, 2018
John L Subject: Amal 376 sticking
Rodders - I think scotty is trying to tell you that you simply haven't thrown enough money at the problem.....Quote "Pick up amal carby drop in waste bin buy jap mikuni fit and live happily ever after". No mention of sourcing/paying for/adapting to fit (and there's a can of worms in itself!)/jetting/re-jetting/testing/etc. etc. and finally becoming so frustrated with a bike that no longer runs right that you revert to a Monobloc or sell the bike.....But it does follow what appears to be the Enfield creed of "If it ain't broke don't fix it", or "If it ain't broke fix it till you are". Better the devil you know ?
Posted: 10:46am 5th November, 2018
Super45 Subject: Amal 376 sticking
Rodders Im having a similar issue with my Mikcarb where the slide sticks at the top of its run and twists sideways if you open it wide open, worse when it's cold out and will do it then even if the bike is up to temp, didnt do it in the summer we've just had at all at all, however ive come to conclusion that it has had a hard life in its 37,000 kms with a good chance its been twisted by over tightening onto the head so is duely knakered and is ripe for replacement as their cheap enough but the amal might be salvageable with some carefull rebuilding
Posted: 02:17pm 6th November, 2018
Aethelric Subject: Amal 376 sticking
Super45, when I got my sixty-5 with standard Mikarb, the previous owner said the throttle can stick if it is wide open and it's a well known problem. The solution was to slacken off the top of the carb.
But then the slide could lift clear of its locating peg! Your problem sounds similar
I did get a "spare" Mikarb with the bike. Upon examination I found it had a thinner O ring seal (where the carb top fits.
As the top was being tightened down, the O ring was not being pushed into it's groove.
Pushing it in as far as I could and adding a little vaseline before replacing the carb top sorted the problem and I can now tighten up the carb top properly and no throttle sticking.
This worked with the thicker O ring too.
Posted: 02:57pm 6th November, 2018
Super45 Subject: Amal 376 sticking
Hi Aethelric I was advised the same previously and so far it dosent matter how tight the carb top is screwed the o ring the slide still sticks at the top when its cold weather in my case the O ring is asnt round in cross section but a flat rubber seal about the same thickness as a piece of paper so wheather it is correct or not i cant say, will have a look with a thicker O ring though to see if that improves things before replacing the carb
Posted: 10:10am 7th November, 2018
John L Subject: Amal 376 sticking
Rodders - This thread seems to have wandered off-topic somewhat. Any progress with your misbehaving Monobloc ?
Posted: 10:10am 7th November, 2018
Rodders Subject: Amal 376 sticking
Hi John, You asked if there was any progress with my sticking carb. First a confession. I wasn't with the bike when I wrote the post. I looked up the type of carb on the nearest available info which was the illustrated guide to REs which has my bike having a 376. Wrong - it's actually a pre-monobloc 276, complete with copper float chamber. This is confirmed by the original spares and replacement parts booklet (price 2/-) which I was fortunate to inherit when I bought the bits. I purchased an aerosol carb cleaner and gave it a good squirt with that - it seems to have done the job. I think it must have just been a build up of petrol varnish, the bike having stood around whilst I had the primary chaincase skimmed, which has finally solved my oil leak. I can now hope to travel more than 30 miles, the furthest I could go before I lost all the lubrication. Thanks to all for the contributions. Rod
Posted: 08:18pm 11th November, 2018
Super45 Subject: Amal 376 sticking
Hi Rodders Good to hear youve solved the leak and the carb, im currenty in process of sorting out my 350 bullet and only live in next village, Andrew Prince ( keeling Lane Birchover) has actullay passed me your phone number and I was going to call to suggest a ride out once my bike is back on the road Cheers Phil
Posted: 11:41am 12th November, 2018
Rodders Subject: Amal 376 sticking
Hi Phil, Yes definitely give me a ring when you get a chance. I went for a short ride today. Oil leak still present but much better. Carb seemed ok. Regards Rod
Posted: 06:53pm 12th November, 2018

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