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D1 carburettor replacement with modern Dellorto PHBG 18AS
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baker7
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December 4, 2013 - 9:58 pm
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Hi I just came across these, and thought they maybe of intrest. both are for the Dellorto Carbs

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baker7
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December 4, 2013 - 11:15 pm
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Hi a wee bitty of help please.

Does anyone have any thoughts on the Dellorto PHBG 19AS, I take it it has a 19mm choke size rather than the 18?

Will it work on a D3, or is it a wee tad too big?

thanks for the help in advance.

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Cornish Rooster
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December 5, 2013 - 9:11 am
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If you do the Maths then the cross-sectional area is quite a bit more even though it is only 1 mm bigger, saying that I can't see it causing a problem, more of an issue is getting the jet size and needle position correct. Going back a bit to the previous posts I would as a starting point try somewhere around an 80 main jet for a D1 and around a 90 for a D3, and starting with the needle in the second groove from top, try a few tests and adjust from there. The idle jet size is not so important as this flow can be adjusted by the mixture screw, as long as you can get a good fit on the stub it will be possible to get good running with these Dellorto's, I may revive my experiments once "Project Gilera" is complete.

Phil 

BSA Bantam D1 "150" in use regularly often as general purpose transport, quite a few other bikes as well. Cornwall Area Rep. 

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Cornish Rooster
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December 5, 2013 - 9:26 am
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The "AS" designation means this is a carburettor for two-stroke applications by the way. 

BSA Bantam D1 "150" in use regularly often as general purpose transport, quite a few other bikes as well. Cornwall Area Rep. 

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baker7
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December 5, 2013 - 9:45 am
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Cheers for that. I bought a 18 but was sent a 19. just not sure if i should send it back.

 

Thanks for your help

 

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cocorico
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December 5, 2013 - 12:27 pm
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Cornish Rooster said
The "AS" designation means this is a carburettor for two-stroke applications by the way. 

I think you'll find that the 'AS' referred to the fact that the idle mixture screw was on the left (A Sinistra), as opposed to 'AD' (A Destra) - on the right.

A 2T atomiser is an 'AU' and a 4T a 'AN'

 

1956 D3 running, lights to sort. 7 other bikes in the Barn, 6 runners (when I get time!) and a still in progress Morini 250

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Cornish Rooster
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December 5, 2013 - 12:51 pm
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Just going by what my Dellorto Guide says for Atomisers:

Two -Stroke, AU, AQ,AV,AS,AB

Four-Stroke, AN,BP, K,D,AE,AG,P,T,BC,

Also Atomisers AB,AF, and AR can be used for both 4 and 2 stroke engines. They certainly give you plenty of options !! 

BSA Bantam D1 "150" in use regularly often as general purpose transport, quite a few other bikes as well. Cornwall Area Rep. 

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cocorico
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December 5, 2013 - 3:09 pm
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Just been looking at my set up.

The minimum inside diameter of the inlet stub on my D3 is about 16mm, with about 18 at the junction with the carb.

I suppose that means that the best size would be a PHBG 16 to give an undisturbed gas flow.

I've got a 17.5mm and a 19mm to choose from, think I'll concentrate on the 17.5.

As said, the Dellorto Guide gives lots of options (have you looked at needles?), but not a lot of guidance IMO.

All good fun.

1956 D3 running, lights to sort. 7 other bikes in the Barn, 6 runners (when I get time!) and a still in progress Morini 250

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Cornish Rooster
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December 5, 2013 - 3:58 pm
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Yes know what you mean regarding the inlet stub internal diameter 5/8ths (16mm) fairly sure both the D1 and D3 are the same even though the D3 has a bigger (very slightly) carburettor.

For the carb I have there are nine different needles if I remember correctly, I have a couple and used one with a slightly steeper taper than the one originally fitted to richen up the mid-point, its a bit trial and error but I still think a good result can be had and even a reliable tick-over !

The fella who does my MOT's said if ever I need it to pop up and use his exhaust gas analyser, that's worth thinking about for me as the results over the throttle range would give an idea where it needs adjusting and the main jet/needle setting and type. I do wonder how well it would work with a two-stroke though ? There are also formulas to work out jet sizes etc if you are good at Maths, some of it takes me back to my College days, Stoiciometric air and so on.

The more you read up on carburettors the more interesting it gets, a real science if ever there was one, unfortunately probably a lot of experience and knowledge has disappeared since the advent of fuel injection, but we are "Old School" and keeping these old skills alive (well trying).

BSA Bantam D1 "150" in use regularly often as general purpose transport, quite a few other bikes as well. Cornwall Area Rep. 

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Cornish Rooster
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December 5, 2013 - 8:31 pm
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Just been reading up on Atomisers, at least now I understand why the last Bantams (B175 was it or D14) had four-stroke atomisers fitted.

BSA Bantam D1 "150" in use regularly often as general purpose transport, quite a few other bikes as well. Cornwall Area Rep. 

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CockSure
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December 6, 2013 - 2:33 am
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Lads I know this an earlier post -- but that could be a good thing for a late comer like myself --that is , have the advantage of lessons learned by those who have gone before ?

Cornish could you formalise your finds as to the best carbie/needle /jet for for the 150 cc engine

by the way --love your work!!......thanking you in advance .....Cheers CS

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Postie
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December 6, 2013 - 7:32 pm
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Just a thought folks.

Mikuni PIT Bike carburettors are selling on E Bay round about £30 brand new. They are described as Mikuni but I suspect they are copies, nevertheless they are supposed to be quite good. They are, as I understand it, fixed to the manifold with two studs similar to Amal Monoblocs and Concentrics.

Does any body have experience of fitting such a carburettor to a D1 Bantam with the slide/push fit? If so what did they use for an adaptor?

I have a Post Office Bantam (1958)  which gets plenty of use and still running O.K. on its original carb. Generally starts second or third kick after I have flooded the carb. I fancied trying one of these Mikuni carbs .

 

Cheers Postie

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Cornish Rooster
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January 15, 2014 - 5:23 pm
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Simes,

This thread, err plenty of reading here !!! 

BSA Bantam D1 "150" in use regularly often as general purpose transport, quite a few other bikes as well. Cornwall Area Rep. 

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South Aus Dave
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January 16, 2014 - 4:29 am
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For those looking to purchase Dellorto gear, forget Dellorto Direct (I think they're a US company), I ordered on the fourth of December a lever and small stack, which they posted on the 11th of Jan. They also charge a premium on postage, which I would have been happy to pay had they been prompt. I suspect flea bay is much better. 

Also the temp here is 47C (about 116F), so I'm resting the poor old girl till the heat passes.

Cheers Dave!

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South Aus Dave
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February 1, 2014 - 11:39 pm
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Lever and new trumpet have finally arrived. Lever makes a huge difference in terms of knowing where the plunger is. I suspect the wider trumpet will allow better air flow. Currently the main jet is an 82, the needle is on the second spacer from the top, and the atomiser / is a 262. Cold (which is a blistering 38oC first thing this morning) she starts about the 5th 'kick', actually the first 2 are gentle strokes to encourage flow. Warm, about the 3rd kick the first one being a 'stroke'.

 

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CharlieCeng
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February 2, 2014 - 12:20 am
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South Aus Dave said
For those looking to purchase Dellorto gear, forget Dellorto Direct (I think they're a US company), I ordered on the fourth of December a lever and small stack, which they posted on the 11th of Jan. They also charge a premium on postage, which I would have been happy to pay had they been prompt. I suspect flea bay is much better. 

Also the temp here is 47C (about 116F), so I'm resting the poor old girl till the heat passes.

Cheers Dave!

I bought some guitar parts from the US a few weeks ago. The Royal Mail charge an £8 fee fo processing the import duties payment...

cheers for now,

Simon.

 

'42 Ariel W/NG, '58 Ariel Huntmaster, Masquerading D3, '51 Ariel Square Four Mk1 http://ariel-sq.....ogspot.com

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frankpelletier
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February 12, 2014 - 3:40 am
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Good day everyone! Anybody fitted a PHBG 18 BS (the one with the rubber sleeve)?  I would assume it would fit as good as the PHBG 18 AS??

Other questions for my  fellow Canadian brothers: Where do you buy parts without paying insane shipping fees (i.e. tires!!)

 

Thank you!

BSA BANTAM 150cc engine on a 1949 D1 frame

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cocorico
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February 14, 2014 - 8:55 pm
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frankpelletier said
Good day everyone! Anybody fitted a PHBG 18 BS (the one with the rubber sleeve)?  I would assume it would fit as good as the PHBG 18 AS??

 

It fits the existing stub OK, with just about enough room for a K&N type cone filter (on my Major, anyway).

1956 D3 running, lights to sort. 7 other bikes in the Barn, 6 runners (when I get time!) and a still in progress Morini 250

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South Aus Dave
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February 15, 2014 - 2:08 am
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frankpelletier said
Good day everyone! Anybody fitted a PHBG 18 BS (the one with the rubber sleeve)?  I would assume it would fit as good as the PHBG 18 AS??

Other questions for my  fellow Canadian brothers: Where do you buy parts without paying insane shipping fees (i.e. tires!!)

 

Thank you!

 

Just done it, sorting out the jets, found the lever choke much better than the cable. Still quite a way to go. 82 main, 292 AU (I think -check my previous posts) atomiser. This is probably a good place to start, and you can buy sets of jets for very little, a pack of ten costing about the same as three purchased individually. (From bitter experience, avoid dellorto direct)

Good luck keep us posted.

Cheers Dave

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frankpelletier
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February 15, 2014 - 2:19 am
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Thank you cocorico! Which model of filter did you use?

Thanks Dave! I was looking to buy the lever choke as well! Ordering parts is very costly in Canada... I visited a Moped store around my place and the only Dellorto they have is the PHBG 19DS Racing (the black one)... As I read on this post, it would probably be possible to fit this model however, I might still order a 18DS from Italy... Just to be on the safe side!

And thanks for the Tip about Dellorto direct... I was going to order from them! :)

BSA BANTAM 150cc engine on a 1949 D1 frame

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