24 replies to this topic

[flamejob]

My girlfriend and I spent the weekend getting our lovely Sprite ready for it's MOT by getting rid of the Cat and fitting a Minispares Stage 1 kit to it. We also fitted a new water pump and 2 core radiator.

We also put new coolant, oil and filter for good measure while the car was up on it's stands.

As far as I could tell everything went by the book. I have done this conversion to two other minis in the past and everything went fine.

The problem came to starting; nothing, not even a cough.

I checked the spark; superbright and long, disconnected the fuel line; petrol *Drunk or yellow human water* out like there was no tomorrow. I took the dashpot off and turned the car over and there was neigh a sign of fuel coming out of the jet. So we whipped the carb off and took a look at the float chamber (my first HIF carb, way neater than those old SUs ) which was, as far as I could tell, working fine. I blew into the fuel inlet and pushed the float up and the needle stopped flow as it should. The jet was smooth and unworn and you could see all the way down to the white elbow at the bottom.

One thing I was concerned about is that the choke has no effect on the jet height. Does the choke work another way?

Stuck the carb back on and attempted to push start the mini with MINI (using a big squashy thing in the middle). Nothing.


Help

On the positive side I think I have made a mechanic of my loved one!

[Dan]

Carbs don't force fuel out of the jet, not if they're working properly. The fuel is drawn out by the venturi of the air flowing through it but if the dashpot is off there will be no venturi present. The choke works differently in HIFs.

Is the timing and firing order right? Is the carb set to initial position?

[black jack1275]

Put a small amout of petrol down the carb then turn it over, it takes a fair amout of cranking to get the carb float chamber to fill up

[Jammy]

For some reason I think its going to be more to do with the ignition, if your not even getting a cough or splutter! Try starting the engine again, and then take one of the plugs off, the spark plug should smell of petrol, and be wet.

If you've had the engine steady off, check that you've connected the earth lead again. I've done that before!

Also check you haven't inadvertedly knocked a wire off the coil.

Also, if your mini is a 1992 carb, whilst a CAT isn't a requirement for the MOT (as far as I can remember) you'll find it VERY hard to pass without one.

[flamejob]

Ta for the replies

I am pretty sure the ignition is in good shape 'cause we checked the sparking and it was very strong. The leads, dizzy and coil all look fine. It ran perfectly before the exhaust swap.

I'll try and put some fuel down there when the battery has had a chance to charge today and report back.

I checked with my local MOT garage about the test and they had a look at the car and said it was fine. The carb killed the Cat anyway. They said they check carb cars as carb (3.0), if it had a cat they would check it at the 0.3 level.

Thanks again!

Edited by flamejob, 17 September 2007 - 08:50 AM.

[Jammy]

Thats not how it should be done! Technically by what they are saying, if you fitted a carb to a modern engine it would then be tested to different emission levels, which is not correct.

The emissions test goes on the date of the car, or the date of the engine, whichever is earliest. If you have the original engine (or a later replacement one) in your 1992 Sprite then it should be tested to the more stringent Cat. emissions test (1991 onwards I believe). You'd probably find this is the case should you have to take it to a different MOT garage at any stage in the future.

Its the reason why Rover spent a whole heap of money fitting injection to the A series engine.

[flamejob]

Thats not how it should be done! Technically by what they are saying, if you fitted a carb to a modern engine it would then be tested to different emission levels, which is not correct.

The emissions test goes on the date of the car, or the date of the engine, whichever is earliest. If you have the original engine (or a later replacement one) in your 1992 Sprite then it should be tested to the more stringent Cat. emissions test (1991 onwards I believe). You'd probably find this is the case should you have to take it to a different MOT garage at any stage in the future.

Its the reason why Rover spent a whole heap of money fitting injection to the A series engine.

I'm not arguing!

[Jammy]

Ha ha, neither would I if I was in your situation!

But thought I'd mention it in case you ever have to go to another garage in future, etc.

[flamejob]

We were so dis-apointed, after two days of working on her, I was so looking forward to see what the new exhaust sounded like...

[strebblo]

This may be off the mark but have you checked all the HT leads are on in the correct order? If you've not taken more than 2 off at a time then there should be no prob, but I just thought that - yes you may have a strong spark but it's no good if it's not in the right place..

just a thought...

[Jammy]

Have you changed the needle to suit the stage 1 kit? If I would you I would set up the carb again for initial use; ie. adjust the mixture screw until the bridge is level with the something else (sorry, can't remember the name), then enrich it by two turns.

[flamejob]

Leads never taken off...

Yep, changed the needle.

So... if you turn the mixture screw the jet rases/lowers. I assume you mean the jet is level with the main venturi bit?

[Jammy]

I don't know enough about carbs to be able to describe this accurately, so maybe someone else can pick up from where I finish, but;

I believe if you adjust the mixture nut it adjust the gold coloured 'collar' that the jet pokes into. You need to adjust the mixture screw so this is level with the 'bridge' that it sits in. Then turn the screw twice more (i think its two more flats, rather than two full turns) to enrich it.

[Dan]

The initial position for SU carbs is described in the Haynes and should always be the starting point for any tuning. It's the same for all SU carbs (H, HS, HIF etc.) and in short, set the cables all to have a little slack, wind the throttle screw to 1.5 full turns clockwise from where it begins touching the cam (one turn on twins), turn the fast idle screw right out so it's well clear of the cam, set the jet level with the bridge (or as high as possible but no higher than the bridge) and then wind it 2 full turns of the screw down the jet bearing.

Edited by Dan, 17 September 2007 - 11:29 AM.

[Jammy]

Thats what I said!