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New Replacement Carburettor for D1/D3 Models
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cocorico
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February 19, 2021 - 9:33 pm
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Number6 said
...I've seen worse. laugh

Quite. When you realize it's a model that goes back to the 1970s, it's not much more modern than an AMAL, and it's a very simple carb. I suppose that for some it's purely the fact that it's a 'modern' carb that stops them using one alongside the electronic ignition, Todd head, D14 cylinder with Suzuki piston, etc. But as ever - your bike, your choice.

To me it's an option if the original carb is missing or damaged.

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GlenAnderson
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February 19, 2021 - 11:30 pm
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Yes, it’s odd what drives us, and the things that one person finds acceptable and another does not. 

I am an inveterate tinkerer, and hardly anything I own with wheels is as it left the factory. I do like things to look un-modified though; or to be either period modifications or factory options. I’m quite easy with anything not visible at first (or second) glance, so electronic ignition and 12v lights aren’t an issue at all for me. I’m also happy enough with modern tyres and stuff like stainless rims, which is something that I know others baulk at. 

If I’d not been able to source a decent Amal 523 I’d have accepted that a Mikuni or Dellorto would have been a compromise I’d have to make. I suspect that I’d have modified an Amal air filter to fit, or turned up an alloy bellmouth,  rather than use a plastic bodied filter though. I may still try one, as Number6 says, the potential for improved performance and better idle control is tempting. 

For me, aesthetically, the little D1 is the “perfect” motorcycle. Probably because I was imprinted on it at a young and impressionable age. It’s just such a shame that it’s performance is so lacking. If it hadn’t been my first bike, and one that my dad had bought me, I’d probably have gotten shot of it years ago. I had long intended to fit my D14/4 engine to it, indeed I bought the engine specifically with that in mind, but the experience with the tweaked D7 engine convinced me that there’s actually a thing as too much power for a rigid Bantam. The D3 engine I’m building for it, ignition aside, is at a specification that could have been done by anyone since about 1955, and counts as an entirely “in period” mod in anyone’s book I’d think.

Similarly, putting the 68 D14/4 engine in the 57 D3; that’s something I think will work very well and again, can be done with quite a bit of discretion when it comes to making things fit and look right. The later, stiffer frame and heavier forks can handle the extra go much better, and there’s plenty of space for the concentric and a proper filter, as well as a decent battery. 

Hopefully things will start to come together in the coming weeks. I collected my vapour blasted engine casings, rebored barrel and overhauled crank today, so the ball is rolling so to speak. 

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cocorico
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February 20, 2021 - 8:13 am
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GlenAnderson said
...For me, aesthetically, the little D1 is the “perfect” motorcycle...

I know exactly what you mean. Perhaps not "perfect", certainly "proper" - but that could start a whole other discussion. freaked-out_gif

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paulkentuk
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April 9, 2021 - 12:55 pm
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GlenAnderson said
Some time ago, there was a thread where somebody had been in touch with Amal/Burlen about new replacement carbs for the 261/361/523 models. If I remember correctly there was, at the time, little chance of tooling up to produce new copies of these carbs, but there was some talk of using a 400 series Concentric with a clip fitting. Do we know if there was any progress at all or did it just die a death?

 I ask, because I’ve just spent a considerable amount of money having a 523 reconditioned and it’s come back with a crack in the body. I don’t know whether to keep trying to get a better secondhand one, or explore other alternatives.   

Allen's Performance list brand new Mukuni VM20 - 00075 carburetors as a replacement for the Amal on the D1 125cc.

You will probably need to incrementally file some solder off the throttle cable nipple at the slide end of cable, so you can get it through.

Regards

Paul

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paulkentuk
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April 28, 2021 - 1:23 pm
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paulkentuk said

Allen's Performance list brand new Mukuni VM20 - 00075 carburetors as a replacement for the Amal on the D1 125cc.

You will probably need to incrementally file some solder off the throttle cable nipple at the slide end of cable, so you can get it through.

Regards

Paul  

I was annoyed to discover my VM20 0075 that arrived wasn't correctly jetted  🙁

Out of the box there was engine knock on idle, ( running lean) and the air screw was almost all the way in on the 25 pilot jet. I've ordered a 27.5 to swap in. In addition the engine bogged down when the throttle was opened, (running lean) I managed to improve that by swapping the 120 main jet eventually to a 145, and have ordered a 150 as the needle is currently on slot 4 towards the bottom  and I reckon that size main jet will allow me to then fine tune on the needle, ( from plug chop results) when the DVLA issue a registration number and I can get on the road !

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paulkentuk
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May 2, 2021 - 4:50 pm
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...

paulkentuk said

I was annoyed to discover my VM20 0075 that arrived wasn't correctly jetted  🙁

Out of the box there was engine knock on idle, ( running lean) and the air screw was almost all the way in on the 25 pilot jet. I've ordered a 27.5 to swap in. In addition the engine bogged down when the throttle was opened, (running lean) I managed to improve that by swapping the 120 main jet eventually to a 145, and have ordered a 150 as the needle is currently on slot 4 towards the bottom  and I reckon that size main jet will allow me to then fine tune on the needle, ( from plug chop results) when the DVLA issue a registration number and I can get on the road !  

 Oops ! when I put my glasses back on it was a 17.5 pilot jet fitted as standard and I ordered a 20 and 20.5 ... 

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