Author Topic: T35 Carburettors  (Read 5243 times)

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Offline vha500

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T35 Carburettors
« on: 13 Oct 2005 at 20:51 »
Hello everyone.
I hope this isn't considered as heresy, but I was thinking of fitting something a little more modern than the old AMAL 274s to my T35.
 Can anyone suggest a suitable type of carb, that will fit without too much work, and suitable jet sizes?
Thanks, Marc.
Aut devorabis amabisque,
aut cras prandebis.

Offline aggettd

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Re: T35 Carburettors
« Reply #1 on: 30 Oct 2005 at 12:07 »
Marc:

I don't have any experience with alternate carburettors for Douglas bikes but in the May/June issue of the New Conrod (LDMCC Newsletter) there was an article by a Mr. Doug Cross who seems to have made some interesting modifications to his Mark V engine. He uses it as an alternate (test) engine in his T35.

From what I can gather he has fitted Suzuki GS650 pistons, raised the compresssion ration to 9:1, fitted a hotter cam (something referred to as No. 3 cams?), bored the inlet tracts to 24 mm (from 19mm), and using a tapered adaptor, fitted 28mm Amal MK II Concentrics. He fitted 150 main jets.

I know that's not much help with selecting a direct replacement, but it does imply to me that the Douglas motors are relatively tolerant of major modification, suggesting that:

1. if you want to fit another carburettor, the trick is not so much picking one, but attaching and fettling it:
2. the motor is quite tolerant of modification, especially with respect to the inlet tract.

I kind of like the look of the original 274s, despite incessant leaking and poor performance, but if I was looking for a modern replacement, I'd go for something more adjustable, like a Mikuni.

Best of luck.

David A

Offline trevorp

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Re: T35 Carburettors
« Reply #2 on: 01 Nov 2005 at 07:58 »
just be carefull as the test in the new conrod was on a mk3 engine which was designed for better flow, if it is a mk 1 engine you are on your own

Some of the differences between mk1 and mk 3 are, mk 3 has different valve size both head and stem, different valve springs,different pistons flat not domed,different barrells ,different heads, thicker diameter push rods, different head gaskets, rocker arms
larger bolts holding on head even different carby slides
i am currently working on both i will post some pictures shortly to show the differences

Also 28mm amals are not that easy to get and the big drawback is u will have to make up inlet manifolds as i havent seen the downturned flange on many other carbies
i agree these carbies with an inlet diameter of 19 mm are very small but air speed over the jets is critical and fitting a larger carby will increase high performance but u will lose some down low power


Offline vha500

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Re: T35 Carburettors
« Reply #3 on: 03 Nov 2005 at 10:09 »
Thanks for the input, chaps. I'm thinking that Mikunis may be the answer, if I can make a flange manifold for the head. A well-known UK company wants 170 each to refurbish my original carbs!
Marc P
Aut devorabis amabisque,
aut cras prandebis.

 

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