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TB'S/Bike carbs on 1275 A Series
JONBEE - 30/9/08 at 06:45 PM

Anyone know if fitting TB'S/bike carbs to a 1275 A series has been done?
If so, what parts were used, and was it succesful?
Would think they would have to be from a fairly small capacity bike..600/400.

NB: now i'm staying with the A series in the moggie, i have a MT75 rwd gearbox from a 1990 2.0 dohc sierra. mileage is unknown, but was told it was very good when recently purchased. £40 ovno or will do a deal with a low mileage 1300 maestro engine, preferably with the ancillaries.
message me if interested, and i'll return my mobile number, unless i can call you.
thankyou
Jon

mr henderson - 30/9/08 at 06:49 PM

A series has siamesed inlet ports. TB's are usually used in one Tb per inlet port situations.

Unless you are constrained to use an a series engine, I would look for something more modern, plenty of better engines around. A series was good in its day, but that day is long gone

John

COREdevelopments - 30/9/08 at 07:18 PM

keep the a series engine. get a k100 bmw 16v head to go on the a series block, has been done a few times. looks fab and will give you an 8port head, lot of work done but worth doin if you want to keep it a series. there one in the new mini mag atm.

rob

Syd Bridge - 30/9/08 at 07:21 PM

For twin carbs, look under the bonnet of an MG Midget. Done years ago.

Bike carbs, or tb's with an ecu shouldn't be much of a problem to get working. The key is to use two injectors per inlet, and fire them 180deg apart. Easily done in Megasquirt as firing bank 1 and bank2.

From the racing experience, you should be looking for diams of about 42~45 mm.

Cheers,
Syd.

[Edited on 1/10/08 by Syd Bridge]

paulf - 30/9/08 at 07:22 PM

The A series wont work with fuel injection very well due to the siamesed port configaration causing charge robbing.
Basically the charge for one cylinder is partially taken by the other one of the pair causing them to run out of balance. Rover did inject one of the later A series Minis but i think it was either single point injection or used a complicated management system.
A few people sem to have experimented with it, so a search on the megasquirt site may find more info.Even bike carbs would be a waste , the best conversion seems to have been a single 1.75 inch SU.
David Vizzards book on tuning the A series is a good starting point and relevant to a lot of other engines also.
Paul.

lsdweb - 30/9/08 at 07:39 PM

This has been covered before and there a few web sites that'll explain how difficult it is because of the charge robbing.

I'll try and find the links.

coozer - 30/9/08 at 08:11 PM

Ring Bogg Brothers, they will advise and are very helpful.

They will give you the definitive advise

lsdweb - 30/9/08 at 08:16 PM

Have a look here
and Dave Walker's article here

Wyn

[Edited on 30/9/08 by lsdweb]

graememk - 30/9/08 at 08:17 PM

quote:
Originally posted by COREdevelopments
keep the a series engine. get a k100 bmw 16v head to go on the a series block, has been done a few times. looks fab and will give you an 8port head, lot of work done but worth doin if you want to keep it a series. there one in the new mini mag atm.

rob


wasnt the k100 8v the k1100 is 16v

JONBEE - 30/9/08 at 08:22 PM

Thankyou all for the info.
Please enter any other info i could use to decide what i'm going to do, but at the moment sticking to tradition with the A series.
Jon

udo - 30/9/08 at 08:37 PM

Been member for a while but dont post due to not actually ever going ahead with a locost but still lurk for general info.

I have fitted 2 out of 4 R1 carbs to a 1293 A series see link below

http://www.theminiforum.co.uk/forums/index.php?showtopic=39131&hl=

Previously had a weber DCOE45 on in before but the R1 carbs were a lot better for low down torque with same top end power and better economy.

Have now moved onto the BMW K1100 16v head on a 1380cc A Series as mentioned above

Phil.J - 1/10/08 at 07:27 AM

You could be more adventurous and fit the 16 valve head from a BMW k series bike engine to the A series bottom end. Not a too difficult conversion, Google it there's lots of info.

iank - 1/10/08 at 08:07 AM

The proof that the a-series can work with fuel injection is the MPI mini, but a normal ECU doesn't work very well.

The CANEMS ecu has special programming to deal with the siamesed inlets.

http://www.canems.co.uk/siameseports.php

The other option not mentioned so far is a 7 or 8 port head casting - not cheap but both give a port per inlet.

MikeCapon - 1/10/08 at 09:38 AM

quote:
Originally posted by graememk

wasnt the k100 8v the k1100 is 16v


Grame is right. Most of the K100s were 8V heads. The only 16v heads on 1000 models were fitted to the K100RS1 16v and the K1.

COREdevelopments - 1/10/08 at 06:49 PM

yes graeme is correct, i did actually mean the k1100. my bad.

Rob