My carb fell off. Oof.

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Bonzo said:
Odd that a previous owner would go to the trouble and expense of installing Premier parts (stay-up float, Viton tipped needle, anodized slides etc.) and then not fit gaskets to the bowl(s?).
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'Either the previous owner removed them, or it's possible the last mechanic that worked on them just forgot but that's unlikely.'

IF it's been worked on by a third party, you have to trust they're au fait with these old bikes. Maybe they had no gaskets to hand and thought they could get away without?
 
Tornado said:
With one screw falling out, the remaining would be placing more bending load on the bowl flange. Best to remove bowls and place on a known flat surface (a flat sheet of glass is good or stone counter tops etc). Check in all directions for any wobble against the sealing surface and flat surface. Some also try shining light from far side while looking directly along the sealing surface to see any light passing 'tween.

If needed, put some 200 or finer wet/dry sandpaper, WD40 or similar oil on paper and move the bowl around in a figure 8 to make it dead flat again.
Click to expand...

If the float bowl lugs are bent then in my opinion it's better to press them back into position as much as possible, keeping any sanding to a minimum.
My carb fell off. Oof.


"Float Chamber​

Inspect the gasket surface of the float chamber carefully for damage. The gasket surface should also be inspected for flatness. Light damage and irregularities can be remedied by dressing the surface using fine abrasive paper on a flat surface, or fine grinding paste on a plate of glass. However, if the surface is reduced too far, the depth of the slot for the float spindle will become too shallow and may cause difficulties with the operation of the float. Over-tightened Allen bolts, which are a popular modification, can bend the lugs and cause an air leak within the float chamber into the idle circuit. If the lugs are bent the float chamber should be replaced."
 
Interesting...I've never had any carb screws loosen and I don't use safety-wire or loctite on anything carb-related, including manifold to head and carb to manifold fittings. Maybe the settings on the iso's or the head steady 'adjustment' has an effect? I wouldn't think so since the engine vibrates however it's going to vibrate and the carbs/manifold are all bolted directly to the engine.
 
MexicoMike said:
Interesting...I've never had any carb screws loosen and I don't use safety-wire or loctite on anything carb-related, including manifold to head and carb to manifold fittings. Maybe the settings on the iso's or the head steady 'adjustment' has an effect? I wouldn't think so since the engine vibrates however it's going to vibrate and the carbs/manifold are all bolted directly to the engine.
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I'd think the gasket compression (totally missing in this case) keeps the screws from loosening.
 
In the video, it looks like the standard engine breather has been blanked off as the spigot and breather pipe (to the oil tank) are missing!
My carb fell off. Oof.


The chokes have also been removed. The stainless braided rocker feed (that looks far too long as it seems to go up, over, then around in front of the cylinder head either under or over the coils to get to the L/H banjo bolt!) would normally go from the timing cover to the R/H side of the head.
 
L.A.B. said:
I'd think the gasket compression (totally missing in this case) keeps the screws from loosening.
Click to expand...
I agree. In fact I'm surprised that there wasn't petrol everywhere with no gasket.

I have had these screws come loose but only on a race engine mounted in a featherbed frame. And only once.

I do use the Allen screws with small spring washers under them and find them much easier to use especially on a race bike with the carbs on and off at frequent intervals.. I actually think you have more control on tightening them than with a screwdriver. You can feel them snug up against the gasket and it's easy to get them just right I think with the leverage of a small Allen key.
 
A few years back I bought a set of these from a seller in OZ, they come with a modified main jet holder and brass sleeve nut that secures the float bowl from the drain plug, eliminating the warping risk. Couldn't locate the seller for my T140 so I made up a new set myself.

My carb fell off. Oof.
 
Nortorious said:
Here's a new one (I think). I'm riding along and start to lose some power. Have to keep the rpms high. Still enjoying the ride and figure I'll just turn around and head home. I do a u turn and start dumping gas. A closer look and the two screws that hold the bottom of my Amal carburetor in place must have fallen out. I haven't touched them in over a year..

So now I'm waiting for the Uber and I guess I'll see how hard it is to get ahold of those screws. Advice and commentary welcome.
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I had that exact same failure, the smell of gas alerted me. I harvested screws from the carb tops to clamp the bowl & finish the days ride.
I've since carried spares, two of which I gave away to a guy at the DGR this year, same failure.
 
concours said:
I had that exact same failure, the smell of gas alerted me. I harvested screws from the carb tops to clamp the bowl & finish the days ride.
I've since carried spares, two of which I gave away to a guy at the DGR this year, same failure.
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I suffered the same experience, but only lost 1 screw. I didn't realize the upper screws were the same until later. I tightened the remaining screw and rode home holding the bowl home with my free hand. Needless to say, hand and left carb area were degreased :cool:
 
acadian said:
A few years back I bought a set of these from a seller in OZ, they come with a modified main jet holder and brass sleeve nut that secures the float bowl from the drain plug, eliminating the warping risk. Couldn't locate the seller for my T140 so I made up a new set myself.

View attachment 97028
Click to expand...
Yes I looked at this mod and liked how it simplifies things.
Used to be an Ebay listing for it.
 
It looks like the the genuine Amal float bowl screws part number 622/086 are Pozidriv (Pozi driv) and not JIS, for anyone who is curious. I can't say if they've always been this way.. O had to check since I have pozi bits but not JIS. Here is a close up picture of the screws I just got that shows Pozi markings.
 

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Nortorious said:
It looks like the the genuine Amal float bowl screws part number 622/086 are Pozidriv (Pozi driv) and not JIS, for anyone who is curious. I can't say if they've always been this way..
Click to expand...

Yes, they are and were Pozidiv same as the vast majority of cross-head screws on British bikes of the time.
 
Nortorious said:
It looks like the the genuine Amal float bowl screws part number 622/086 are Pozidriv (Pozi driv) and not JIS, for anyone who is curious. I can't say if they've always been this way.. O had to check since I have pozi bits but not JIS. Here is a close up picture of the screws I just got that shows Pozi markings.
Click to expand...
I believe JIS (older name now changed to an ISO code designation) works in old philips and pozidrive screws just fine. Its the use of philips drivers in other screws is what leads to damage (even happens on philips screws).
 
My carbs are rubber mounted. I bought the adapters from Hemmings years ago, at the same time as i bought the carbs. If your carbs a rigidly mounted, you can get frothing inside the bowls which can cause rich mixture and make your motor slower.
 
acotrel said:
My carbs are rubber mounted. I bought the adapters from Hemmings years ago, at the same time as i bought the carbs. If your carbs a rigidly mounted, you can get frothing inside the bowls which can cause rich mixture and make your motor slower.
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It's a road bike Al not a race bike
During your time riding a commando did you notice it running rich ?
If so then the Isos may have been set a bit tight
 
Nortorious said:
I came across those today in my search:

"Amal float bowl screw w safety wire 376/151 622/086 576/079 Concentric monoblock"
steadfastcycles.com

Amal float bowl screw w safety wire 376/151 622/086 576/079 Concentric monoblock

Amal float bowl screw w safety wire 376/151 622/086 576/079 Concentric monoblock
steadfastcycles.com
Click to expand...
You can drill your own in about 3 minutes each rather than $20 for 4. Besides if you do the tops too you'll need four more so that's $40 for screws. Seems a bit rich.
 
It happens. Check more often, or safety wire as said. Not a fan of blue loctite in this application but I guess it can work.
I bought a couple of long hex head screws for the inners. Those were always hard to reach for me.

Carb Drain Bolt Leak

Looks like a Monobloc main jet cover. Maybe you turned a taper on the bowl, to match it.
www.accessnorton.com www.accessnorton.com
 
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