anodized slides don't fit

If I were to consider honing these carbs, what would the correct tool for that be?

I would say a mill and boring bar, but I don't have one; so, after trying to squeeze it back to round, I would use 600 grit sandpaper and a finger. I would measure in many spots and lightly rub the "high" spots until I had it round enough that the slides moved smoothly. This has worked for me when the top was over tightened - haven't tried it when the whole carb was distorted by the flange being over tightened.

An alternative would be a brake hone, but although it would enlarge it enough to get the slides to work, the oval shape would likely remain.

In any case, if they are tight at the bottom it will be very hard to correct.

I think I'm just gonna call it a $120 mistake and keep using the carbs that are on the bike now. They work fine. These will go back into their boxes and sit on the shelf another 10 years.

L.A.B. said:

Same thing, so 932/R42 and LH would be 932/L43.

Edit: Presumably, your 'Fastback' is an 850 with Fastback parts?

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Yep. Its a 73´ 850 engine.

I bought the bike in 1997 as a early 1969 Fastback. But its 750 engine was really worn out to the limit.
And after my accident last year it has turned even more "special"

Anyway, the carbs have stay up floats, hard anodized slides (Amal stamp) and the pilot jet modification.
Needle jet is the correct 106 size.
They came with flat top spray tubes and short needles.
I changed that to sectioned spray tubes and long needles.

The engine accellerates nicely without any hickups.

But the spark plugs get sooty when the bike is idling for a while and then it starts to misfire on both cylinders.
When i thrash the bike a little bit, the problem disappears.
Next traffic light: same problem.

Its also suspicious that i can start the engine from cold without using the air slides.
Obviously too rich.

I didnt check the pilot jets before mounting the carbs.

So i will take those mongrels apart agin.

maylar said:

I think I'm just gonna call it a $120 mistake and keep using the carbs that are on the bike now. They work fine. These will go back into their boxes and sit on the shelf another 10 years.

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I just made the jig shown here https://www.accessnorton.com/NortonCommando/amal-de-warping-jig.30033/
and used it on 4 different 932 carbs that would not accept new Amal anodized slides. Fixed all 4 of them.


Maylar, you can easily tell if your carbs are warped by putting the flange on a flat surface and see if it rocks. All 4 I had rocked, some up to 0.007". The flange warp goes hand in hand with the bore warp which the new slides don't like. If yours are warped, maybe we can work out a way to fix them rather than having them sit on the shelf for another 10 years.

Thanks Nick. I'll put them on a flat plate and check the flanges.

maylar said:

The boxes say Amal. I bought them from Classic British Spares and their web site says genuine Amal imported from England. I will contact them for feedback/advice.

Original slides both measure 1.3700. The anodized slides measure 1.3725 and 1.3730. That's 3 thou over sized.

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These guys are good and will definitely help you out.

Going back to the original post in this thread, I have a similar problem fitting a Premier slide into an original Concentric body. The bike’s odometer shows 19,000 miles, but the carbs really do seem to be in pretty good shape. I borrowed the Premier slides from a friend to try a richer cut-away. The original slides and the Premiers measure the same 1.371”, but the Premiers suffer from intermittent (but frequent) sticking. I checked the carb bores with magnification and there are very slight burrs alongside the anti-rotation slot. The springs, as they compress, impart a torque to the slides and in reacting that torque the slot and the projection on the slide wear and raise the burr. I removed the burr and the Premier slides move freely in the bodies when moved by hand, but on the road they tend to jam, both when opening the throttle and when closing it i.e. I can’t open the throttle beyond a certain point and when I close it, one or other of the slides remains partially open. I’m at a loss as to what is causing the jams. Yes the carbs are old and worn, to some extent, but I have removed the most obvious, likely causes of sticking. The fact that the majority of the time they do not stick implies that there may be some way to prevent them sticking at all.

Regarding the Premier slides, I don’t like that the anti-rotation feature is a cylindrical projection whereas the regular concentric slide has a rectangular projection with much greater bearing surface area.

Eliminating the torque generated by the spring acting on the slide is a potential improvement I wonder if two springs in series one wound left hand and one right hand would be possible/worthwhile?

Others have noted that the bore into which the spring is installed on the Premiers is only slightly larger than the spring itself and that the spring OD does increase as the spring is compressed. I don’t think that is causing the jams on my bike, but unless Amal/Buren thought that through carefully and provided just enough clearance that could also be another problem area.

Not saying anyone is wrong about anything. That said, IMHO:

There is no such thing as a "Premier Slide". The hard anodized slides have been available from Amal for a very long time.
New, non-anodized slides often don't "fit" either. It's generally not the new slide but the warped body and worn slide that matches it that causes confusion.
The round rather than rectangular projection that keeps the slide from turning is round precisely to reduce drag and to not catch in the slot.
The internal construction of the anodized slide is different from the non-anodized slide and it controls the spring more - I have no idea if this is good or bad as I've never had a problem with either.

The new AL Premier carbs are built, set, and tested by Amal in-house. So far, every set I've checked had the float height spot-on, no swarf, and all passages open.

I agree warpage in the bores and maybe heating of carb bodies leads to binding of the fresh slides.
You could try some smoothing with fine emery cloth on bores. There was a thread somewhere on a method to square up a warped bore using a suitable diameter solid rod.

Also, having bodies resleeved to a fresh set of slides would be a low cost option. I had a set done for $75 per body from Brian Chessel in Ontario fairly recently.

Ultimately had further issues with those carbs and I went to premiers from marshg246 at very good pricing.

If Burlen/Amal is going to go solely to ally bodies it would be a good idea to get new carbs. Seems to me that if so
slides would benefit by being brass as it is a dissimilar metal and heavier. Would heavier slides assist in keeping any
pulsing of the slide and could you use lighter springs? I like light springs!

Slides fit any better if you switch sides? Mine did. Then, with enough movement, wore in to an acceptable level.

Sticky old Ethanol-laced gas in the carb bores can cause them to stick also.

marshg246 said:

Not saying anyone is wrong about anything. That said, IMHO:

There is no such thing as a "Premier Slide". The hard anodized slides have been available from Amal for a very long time.
New, non-anodized slides often don't "fit" either. It's generally not the new slide but the warped body and worn slide that matches it that causes confusion.
The round rather than rectangular projection that keeps the slide from turning is round precisely to reduce drag and to not catch in the slot.
The internal construction of the anodized slide is different from the non-anodized slide and it controls the spring more - I have no idea if this is good or bad as I've never had a problem with either.

The new AL Premier carbs are built, set, and tested by Amal in-house. So far, every set I've checked had the float height spot-on, no swarf, and all passages open.

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I'm not dissing the "Premier slides", more wondering what could cause a new slide (regular, anodised or chromed ) fitted to a used body, to jam. I don't think my carb bodies are distorted as I can move the slides, freely, through their full range of travel by hand.
I don't think the cylindrical anti-rotation feature is an improvement, its limited bearing area will wear more rapidly than the original rectangular feature . It is more likely that a rectangular feature could not be easily incorporated into a machined (rather than die cast) component; and yes the rectangular feature might snag in a worn body, but I doubt they designed the Premier slide with used (as opposed to new) bodies in mind.

You might check his out:

NickZ said:

You might check his out:

Amal de-warping jig

Found this tool posted on the BB forum while searching for info on my A65, I believe the bike has the original carbs (no drain plug in the float bowl), and they are in OK shape aside from the stuck slides, so I fabbed this up and it does the trick. I warmed the carb bodies up a bit, and used...

www.accessnorton.com

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Thanks for that. Now that I've had a closer look there is some distortion in the bore and I may have caused it by attempting to flatten the flanges in a non-too clever fashion. I wonder if that jig could be used in some way to reverse the damage I may have done?

Surrey Cycles stock Concentric brass slides chrome plated made for Autocycles, these unlike the Amal failed attempt do not flake off chrome.

ggryder said:

Thanks for that. Now that I've had a closer look there is some distortion in the bore and I may have caused it by attempting to flatten the flanges in a non-too clever fashion. I wonder if that jig could be used in some way to reverse the damage I may have done?

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Using that process to remove bore distortion usually eliminates flange distortion at the same time.

kommando said:

Surrey Cycles stock Concentric brass slides chrome plated made for Autocycles, these unlike the Amal failed attempt do not flake off chrome.

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I know Wassell makes a version of this chrome-plated brass as well. Might be the same?
I have found the chrome slides to be a lot more slippery than the Amal annodized slides.

Don't know where their "Heavy Brass" (non-chromed) slides would be in terms of lubricity. Probably more friction than both the above.

elefantrider said:

I know Wassell makes a version of this chrome-plated brass as well. Might be the same?

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I doubt it as Wassell's do their own sourcing and its mainly from Asia, the Surrey Cycle slides manufacture were commissioned by Autocycle Engineering of Dudley who also get Gold Star parts remanufactured which they took over from Eddie Dow. So I assume Autocycle still use mainly UK sources.


CARB - MK I. throttle slides, all series, incl. 1000, alloy, brass and chrome, all cutaways and o/sizes

This is what I don't like a about the new anodized slides as used in the Premier carbs, but also available for retro-fit into Mk1 Concentrics.............

Anti-rotation features: on the right, original diecast slide with 20,000 miles ; on the right, nearly new anodized slide. Compare the contact surface area.