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 Post subject: mixture adjustment
PostPosted: Mon May 05, 2014 11:32 pm 
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Location: Ballarat, Victoria
Hey All,

I'm pretty new to this home mechanic thing... so i've got whats probably a simple question...

To get the carby running a little richer do I just turn the nut on the bottom?

Should I be able to do it by hand? or do I need a special spanner? standard spanners seem way to big (long) to do the job and from my attempt tonight, it seems too stiff to do it without one.

also, what size spanner would I need if i have to cut one down? (my mini is bog stock so i presume its a HS2 carby yeah?)

thanks!

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 Post subject: Re: mixutre adjustment
PostPosted: Mon May 05, 2014 11:38 pm 
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Location: Under the bonnet son!
No spanner required, although they will resist movement a little.

To richen, turn the nut you have found clockwise looking from on top. ie you will be unscrewing it down.
Only a flat at a time is required. Push the piston up a tiny amount to sense the rpm movement. No mare than a few millimeters from when the rod touches the damper piston.

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 Post subject: Re: mixutre adjustment
PostPosted: Mon May 05, 2014 11:51 pm 
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cheers for that..
i'll give it a shot tomorrow

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 Post subject: Re: mixutre adjustment
PostPosted: Tue May 06, 2014 12:04 am 
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I got to mine tonight with a 4" shifter. Just turned it 1 (flat) and sounds do much better on idle and giving it a bit of a rev.. Was leaning out big time around 3-4k rpm. Picked the car up Saturday from a lady owner think she had it tuned for granny performance.

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 Post subject: Re: mixutre adjustment
PostPosted: Tue May 06, 2014 8:40 am 
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Oh God, i've ruined it now....

I'm not sure if i bumped something I shouldn't have, or what, but after turning that nut 1 flat cockwires like like Mick suggested last night

I started the car this morning to go to work, and it just jumped straight to like 3000 rpm.

So i shut it off and went under the bonnet to check it out, and there was petrol dripping from the floatbowl...

urrrgh...

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 Post subject: Re: mixutre adjustment
PostPosted: Tue May 06, 2014 9:13 am 
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Give this a read I found it this morning from another thread.. Just make sure u played with the right nut and not something else eg choke or idle screw..

http://1978mgmidget.com/Tuning_SU_Carbs.pdf

Page 14, pic 3, no.13 is the jet adjustment nut that should have been turned clockwise.

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 Post subject: Re: mixutre adjustment
PostPosted: Tue May 06, 2014 9:22 am 
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hmm... maybe i've losened off the jet locking nut.... that could be what has caused the leak...

i'll have a look tonight when i get home

I hope its something simple like that... i really would like to be able to get to work on my own steam this week... the boss is starting to grumble that the mini isn't a real car!

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 Post subject: Re: mixutre adjustment
PostPosted: Tue May 06, 2014 10:07 am 
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Location: Under the bonnet son!
Holy crap, that went south pretty quickly.

Did you take a spanner to it? That nut should be pretty damn tight. If you have, then you might have changed the jet centering as well, which will wear out your needle over time. You might learn a second trick as well if so. That is how to center a jet. Keep us informed on how you go.

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 Post subject: Re: mixutre adjustment
PostPosted: Tue May 06, 2014 10:27 am 
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Mick wrote:
Holy crap, that went south pretty quickly.

Yep... is basically what i thought at 8am this morning when i started her up

The carby is due for a rebuild anyway... the car sat for years before I put it on the road last year, and i've never looked at the engine/carby really besides basic servicing (points, plugs, leads, oil, timing, etc)

i was just hoping to get it running better for a little while until I had another long weekend to look at it..

but yeah... I've ruined it now.

If tightening that screw doesn't fix it tonight.. i'll just tow it to the local mini mechanic and get him to sort it out I think.

oh well

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 Post subject: Re: mixutre adjustment
PostPosted: Tue May 06, 2014 10:31 am 
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Mick wrote:
Did you take a spanner to it? That nut should be pretty damn tight.


Thats the problem, I only used my fingers... so if that nut is not the problem.. i'm kind of at a loss.

The only other thing I can think of is that I've some how knocked the flxible hose that goes between the floatbowl and the jet assembly and its split, or come loose.

But its not like i was rough of anything i just reached in there, found what I thought was the correct nut, and gave it a tiny twist.

All the boys at work think its fraken hilarious that the mini is broken again.... damn them any their fancy new cars.

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 Post subject: Re: mixutre adjustment
PostPosted: Tue May 06, 2014 10:56 am 
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Location: Under the bonnet son!
That was my thought. Luckily if you have somehow loosened the wrong one, then it is easy to tighten it back up. It might just be petrol leaking down over the jet and out the bottom as the nut is loose.

There's a good chance the centering is still good. You can test that easily by taking the oil out of the dashpot and checking the lift and reseat of the needle in the piston. Then you can try adjusting the mixture using the right nut again.

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 Post subject: Re: mixture adjustment
PostPosted: Tue May 06, 2014 10:12 pm 
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well... i had a look just now...

that jet locking nut seems to be tight as... after given its location im certain i wasn't twisting my hand around that far to get it to.

I got the lovely wife to turn the engine over so i could see where the leak was coming from, and it certainly seems like its from the flexible hose... especially given it seems to be the only thing that gets wet.

So i guess i may as well learn how to rebuild a carby now hey?

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 Post subject: Re: mixture adjustment
PostPosted: Tue May 06, 2014 10:21 pm 
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Location: Under the bonnet son!
Whats the worst that could happen? :shock:

How do you think it broke? Weathered, or did you accidentally lean on it ?

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 Post subject: Re: mixture adjustment
PostPosted: Tue May 06, 2014 10:46 pm 
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lol... chances are I leaned on a 39 year old flexible hose and it didn't have quite enough flex left in it

Its annoying... but it could be worse.

At least I didn't burn it to the ground!... yet

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 Post subject: Re: mixture adjustment
PostPosted: Wed May 07, 2014 8:27 am 
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Yeah unleaded fuels tend to make hoses go hard, particularly pre-unleaded fuel rated ones.
Make sure you buy a genuine jet & hose, DO NOT buy a `fuel miser' one! Their hoses don't like unleaded fuel or E10. Mine swelled shut and I had to bin it...

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