The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Amal, Carburation => Topic started by: Seabee on 19.03. 2021 18:42
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Hi guys,
I need to determine what size slide is in my carb. I'm still having trouble with a way too fast idle. I need to see if I have the wrong size cutaway. The slide is a little worn, but it does bottom out and the jets are correct. I have to retard the timing to get it to idle down to a proper RPM.
Seabee
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hi Seabee,
the cutaway is not responisble for idling.
Its the airscrew, tourning out the mixture is richer, turn in it will get weakThere is a blindscrew at the opposide from the airscrew. If you turn it off there is a realy little hole (ca 0.7 mm) visible where the fuel gets thrue. May be this is blocked.
cheers Klaus
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G'day Seabee.
Slide cutaway is measured in 1/16 inch. #3 slide has a cutaway of 3/16".
A worn slide will be allowing air to pass around it giving a lean mixture that will hinder idle mixture.
Cheers
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Thanks Klaus and Musky. It has been very frustrating trying to get it to idle slower. It seems to have a good mix as the revs are steady, just too damn high! I love having the correct carb on the RR. It is my "show" bike, so it gets ridden very little anyway. The SR is the work horse and is a great rider. I'm breaking in the hi-comp, 357 cam engine I built for it over the winter. It is much harder to kick over with the high comp pistons, but has a nice bark to it! *smile*
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BTW if anyone has a 'wrong-sided' new TT slide they want to swap.... I have a genuine one I bought about 30 years ago, but it's a Left Hand one and I need a Right Hand one. 10TT9 carb (for a Velo).
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I'm showing my ignorance here, but I've run a T10TT carb on my Enfield sprinter for 30yrs and haven't known about left and right handed slides. I've just bought TT slides. Have I been lucky and what's the difference?
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On the inside face of the slide there's a what I can only call a shallow tongue, this mates and slides within a slot in the jet block (that's what they call it), so the slide is held at the right angle to the airflow by this mating slot. Otherwise the slide would be free to rotate. An option for me might be to remove the jet block and machine a slot in it at 180deg to the existing one.
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I know the piece you're talking about, I'll check my spare slides, but I've never noticed a difference.
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Hi Joolstacho,
you have a 1.1/16 TT Carb, only this size has the righthand slides. Its because the chocke slide is on the opposid side to the other TT carbs. It s hard to find the angled floatboals, for the right side.
Yes you can, slot the jetblock to use the left ones.
cheers Klaus
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Close mate, it's actually 1 3/16" (30mm) came as original equipment on my '64 Venom Clubman. I've been running Concentrics on it for about 45 years, and I thought it would be good to get it back to original with the TT. (yes the float angle is correct). I'll pull out the jet block and probably machine the slot to suit my lovely new slide.
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I've checked my slides and they all have that tongue on the left looking from the cutaway with the slide upright.
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Here are mine. The original one that came with the Velo when new- on the right. Note slot on the left.
The new one on the left, slot on the right. This slide is marked in pencil: LEFT HAND 10??? 175/559 -Amal marked I'd bet.
(https://imagizer.imageshack.com/v2/xq90/924/NYXn3r.jpg) (https://imageshack.com/i/poNYXn3rj)
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Looking at my Amal spares list, all Velo tt carbs are fitted with the standard tt slide (throttle valve in Amal speak). Number is 375/3114 to 3117, the last No being the cut away. No mention of a left hander. They should be available from Burlens. Here's a selection of mine, all (worn) and are the same type with diferent cutaways.
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I removed the 10TT9 jet block to see if I could alter that to suit my new old stock slide by cutting a channel down it on the opposite side to suit my slide.
That part of it looks quite possible but, the only thing is that because the choke is on the other side there's a large diameter drilling on that (choke) side of the base of the jet block, I'd have to duplicate that, and I'm not sure where the drilling goes. I'm sure I could do it, but to be honest I don't really like doing drastic alterations like that on rare-ish parts.
Or, I could just use my old worn slide (It's pretty well worn!)
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You need only the new slot, no more drillings turn the block 180 degrees and the whole for fixing the block is right.
See pictures.
cheers Klaus
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Ah thanks Klause, but what about that small drilling at the lower end of the block that aligns the block with the main carb housing and consequently aligns the slide, using the small external screw, if the jet block is rotated 180 degrees, this small drilling will be not be correctly aligned because that small screw that normally keeps the block aligned, would now 'float' within that larger 'choke' drilling. So the jet block (and slide) could be maybe 10 or15 degrees out of line.
?
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*whistle*
I´m wrong with turning the block. Cut only the slot and everything is fine.
Klaus
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I can see that working as long as I align the jet block accurately and then tighten it down hard so it can't rotate.
But... what about the choke passage, -that large drilling that goes horizontally in at the base of the jet block.
The choke won't work surely?
The other option is to convert the new slide. I could silver-solder a tongue that would engage with the slot in the block. But then I'd have to grind away the existing tongue on the other side. making the slide VERY thin at that point.
Bluddy'ell maybe I'll just run with the old worn slide!!!
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Have a look at the second pickture. This is the recut slot, its on the side where the choke is.
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Silly of me -I didn't look properly. Thanks Klaus.
Obviously the new slot can't go right down as low as the 'factory' slot, but I can see that's not a problem.
Now to figure out a way of cutting the slot accurately (wish I had access to the mill-drill I used to have).