Ok, so I think the tuning on my mini is not right, but I wanted to get an idea of how to go about tuning twin carbies.
If someone has a good method maybe a 'How To' on the topic would be useful?

Anyway, so here are my symptoms:
(Engine spec is 1310 - possibly an-ex Moke 1275, twin 1.25" SU's)

1) My car is a daily driver, and I drive in mainly 80,90 and 100 zones on my way to work. At these speeds the car seems to have trouble keeping a consistent speed, I tend to get a surging feeling with a consistent throttle.
2) I occasionally get a light backfire under light acceleration at these speeds.
3) Driving with the choke half out reduces both of these symptoms significantly but not completely.
4) Hard acceleration performance at these speeds (80-100) is great, and this also goes for stand still acceleration.
5) Spark plugs are only lightly coloured. (At least last time I checked)

My thoughts are that maybe the fuel mixture is too lean.
Any other suggestions?

My engine has recently been rebuilt, and all gaskets etc in my carbies were replaced.


Cheers
Jonesy

_________________
Michael Jones
Minis In The Gong
[email protected]
www.minisinthegong.com.au

Check your dwell angle (Points gap) and Ignition Timing. Also inspect your distributor cap and rotor button.

yes , sounds like you`re at least a little lean,,,

Now here`s a guess for you---> if you have a "29D" distributor,??? (that`s the guess part) if so then i`d be looking at maybe removing the vac advance hose off it & blocking up the port in the carb, just for the moment... then look at replacing the dist or repairing it

That was just a guess about the type of dizzy you`re running tho mind you

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

Thanks for the idea's, I'll be sure to have a look.
The other thing I meant to say is, with the surging feeling, I've heard of twin carby's fighting each other before and it sort of feels like that might be what is happening.
I think I'll richen it up very slightly and see how that goes first.

_________________
Michael Jones
Minis In The Gong
[email protected]
www.minisinthegong.com.au

4myego's 1360S was doing this surging, then we found that the carbs were just set too lean was all.
The needles in the HS4s were fine (#6).

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Bring it around on the weekend Jonsey and we can have a play! You still haven't taken me for a proper drive in it yet!

_________________
Ryan Filippi
Minis In The Gong
[email protected]
www.minisinthegong.com.au

yeah it`s probably just the lean-ness

but the surging part is why i asked about what type dizzy you have, cause the Aussie 29D thing is renowned for horrible base plate wobble when they wear & can cause the points to ---> open shut open shut open shut , with the vac advance hooked up

It`s a bit tricky to explain here but it`s simply the vac advance pulls on the base plate, which then CoCks because of the wear in the crimping & the nylon buffer, & then the revs will drop cause the points have opened up,,,, then cause the revs have dropped the vacuum drops & the vac advance letsa the base plate back down, in turn closing the points back up, advancing the ign again,,, & on & on it goes

so,,,, sorry to invade the carby thread with distributor sh!t , just that the "Light throttle surging" statement always makes me ask the question---> what dizzy have you got fitted? 29D???

_________________
No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

i checked my dizzy and its a lucas dizzy, but I didn't know whether there was a marking of 29D on it or not, however, the vac advance thing on the dizzy is plugged, so does this completely rule out the dizzy as the problem?

Cheers for the help mate.
Jonesy

_________________
Michael Jones
Minis In The Gong
[email protected]
www.minisinthegong.com.au

So, the car has been backfiring and stuttering even more in the heat yesterday and today, so I thought it was about time to have a look into it.
I finally got around to having a play with the fuel mixture this afternoon.
I richened it up slightly and took it for a drive, and it was even worse. So naturally I figured it was too rich already, so I leaned it off a bit and it seemed to improve slightly, but I haven't taken it on the freeway yet.

Might have another go at it tomorrow. Ryan, you busy tomorrow? Will see how I go, but I might see if I can pop around if you're at home...


Cheers
Jonesy

_________________
Michael Jones
Minis In The Gong
[email protected]
www.minisinthegong.com.au

Well the winner for this round is GT mowog.
The points gap had essentially completely closed. Obviously it must have not been completely closed though...
Next problem, the screw head to allow me to adjust the points gap is badly damaged, and is done up STUPIDLY tight , and I can't get it undone. I have tried the half metre long screw driver with all my weight against it, and it won't budge.
Anyone had this problem before?
Assuming that it is not possible to undo with a screwdriver, how do I remove it? The surrounding area is so thin I can't get any form of multigrips on it. Was thinking about trying to tighten up an electric drill around the screw head and then trying to run the drill in reverse...
Any other ideas???


Cheers
Jonesy

_________________
Michael Jones
Minis In The Gong
[email protected]
www.minisinthegong.com.au

well,, ok,,, i was close then

well done GTMowog tho,,, good pick

_________________
No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

So, I got a mechanic to remove the screw, and one of the supports of the base plate in the dizzy is broken, which is why the points closed up.
Now to try to scavenge a base plate out of an old dizzy to rebuild mine.

Jonesy

_________________
Michael Jones
Minis In The Gong
[email protected]
www.minisinthegong.com.au

That would explain a few things! Are you coming around to get a new plate? Pop in and see me.

_________________
Ryan Filippi
Minis In The Gong
[email protected]
www.minisinthegong.com.au

Points..... who would use them by choice these days?
Last time the points in my 1310S motor's 45D dizzy closed right up (and gave it a power band of 4500-8000, misfires below), I tossed the points and fitted a Pertronix Ignitor kit.
Best thing I ever did...
More power, runs smoother, timing stays right, no bloody points to adjust or replace...
Since replaced with a Nissan Pulsar one as the 45D was worn. I did modify the advance curve though. Well worth doing.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

On the subject of dizzys, get the guts out of a hitachi dist that is fitted to holden barina with the izuzu eng. these will fit into a mini dist body[just a little file out of screw holes,metric/imperial] the cam/ rotor is same taper and the electronic componets fit into the mini dist. the hitachi rotor button is about .015" longer than mini so file down to suit mini cap. easy electronic dist. the advance curve is almost some as std mini and can be easily adjusted.
Like most jap stuff ,just copied the poms

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com