21 replies to this topic

[Steve-O 2014]

We swapped the carb on the mini from a HiF44 to a HiF38 with I think an AAA needle for the mods done to the engine. I set the mixture up using a Gunson Gasmeter and managed to get it to sit at around 4.5 - 5%. At first it was at 17% but screwing the screw in dropped it to this figure. But now after the engine has cooled I can't get the car started!!! It just turns over even with the choke out.

 

What have I done? have I adjusted too much? The needle is 2 turns out from being fully screwed in.

 

Thanks

[dennismini93]

what cc is it? if its a 1275 id put the 44 back on (that wont be your issue though). have you got a spark? might not be fuel related

[grumpy dad]

Hi 

I don't understand (The needle is 2 turns out from being fully screwed in.)

do you mean the mixture screw on the side of the carb ?

if so as a rough rule that is about right

if it just wont start from cold

sounds like you haven't got the choke cable or something right  

[Steve-O 2014]

Hi, yes I mean the mixture screw on the side is 2 turns out from fully screwed in. that gave a reading of around 4.5 - 5%

 

The screw was originally quite a few turns out and the CO reading was about 17%

 

How should the choke cable be? If worked fine before doing the adjustments.

 

 

Do I need to adjust the timing when fitting a new carb? 

[grumpy dad]

Hi 

(Do I need to adjust the timing when fitting a new carb? )

no you should not need to 

 

try taking the cable of and lift the choke lever buy hand as you try to start

is the carb new to you ?

did you see it working from cold 

IE with the choke out 

its possible the choke is not working inside the carb 

[Steve-O 2014]

Hi, the carb works as when I fitted it the car ran and the choke operated as it should starting the car from stone cold and the car ran for about 30 mins or so as I adjusted the mixture screw

 

I will re adjust the mixture screw and see what happens, maybe I have sooted the plugs up too much

Edited by Steve-O 2014, 24 March 2014 - 09:25 AM.

[KernowCooper]

Hi, yes I mean the mixture screw on the side is 2 turns out from fully screwed in. that gave a reading of around 4.5 - 5%

 

The screw was originally quite a few turns out and the CO reading was about 17%

 

How should the choke cable be? If worked fine before doing the adjustments.

 

 

Do I need to adjust the timing when fitting a new carb? 

The HIF type of carb the mixture screw when screwed in lowers the jet and richens the mixture, and out weaken the mixture as it brings the jet back upwards, so when yours was quite a few turns out it should have been weaker, so when you wound it in it would have gone richer not weaken the mixture off? something odd going on with your adjustments.

 

You always do a engine tune including timing before carrying out any carburttor adjustmants

 

Are you sure your linkage is not damaged internally (they break) and your jet is moving freely not adjusted by the screw.

 

In is always richen on a HIF, and out on the screw weaker.

Edited by KernowCooper, 24 March 2014 - 06:44 PM.

[Steve-O 2014]

The timing was all setup with the HiF44 fitted, I then fitted the 38 and it ran but when I put the Gasmeter in the exhaust it was reading 17% CO which I thought would mean it was running rich. Naturally I thought screwing in would lean the mixture and it dropped the CO reading as I screwed it in so thought it was leaning the mixture out.

 

I can see the jet moving up and down when adjusting the screw so thats working

 

I took the plugs out today and they were very very wet with fuel and thick black so Im guessing thats why it wasn't firing up, cleaned the plugs and will put them back in tomorrow.

 

I set the carb back to what people say to start off with (Set the jet level and then screw the screw in 2 turns) 

[KernowCooper]

Once you have it running and warmed up adjust the CO to 3-3.5% at idle and see what results you get

[Steve-O 2014]

Should making the mixture richer increase the CO rating?

 

If so, why when I screwed the screw in it reduced the CO rating? 

Edited by Steve-O 2014, 24 March 2014 - 10:19 PM.

[Steve-O 2014]

I have an uprated dizzy fitted with no vacuum advance, The vacuum advance on the carb has been connected to the inlet manifold, could this be changing the reading at all? Or would this not alter anything? 

[Steve-O 2014]

Ok, reset the Jet to what people recommend as a good starting point (Flat and then 2 turns in) and put the clean plugs back in and on first turn over it fired up right away.

 

I think I just fouled the plugs up too much from overfueling / setting it too rich

[KernowCooper]

If you have no vacuum advance fittted and its a road engine then your loosing torque, normal drivability and mpg, what distributer are you using ? if the vacuum advance pipe which is normall fittted is not connected to a vacuum advance on the distributor, then it must be blocked to avoid drawing in air and weakening the mixture.

 

Also what timing are you setting the engine to? as if your using a distributor designed for a race engine like the Aldon Red which has only 20degs of mechanical advance, then your engine wont be producing its maximum torque as with the static setting of a normal timing setting + mechanial advance could be short of the required 34degs +/- to suit fuel.

[Steve-O 2014]

Its an Aldon Yellow 100AYP

 

The Advance has been connected from the Carb to a port / nipple on the Inlet manifold, Should I block these off instead?

 

I dont know what the timing is set to.

 

We bought the Mini like this so no idea whats been done but he said its rebuilt high compression engine with head work and has a full maniflow system etc fitted.

 

Thanks

[KernowCooper]

No point in having the link pipe between manifold and carb on the vac pipe, yes block them off. If used on the road yes fit a vacuum advance unit, better torque/mpg for road use.

 

If your engine is standard then it will run better on a standard distributor, I'd check the timing at 1000rpm and see what its set to just to see whats its currently set at, if the advance curve is wrong then it wont perform as you expect.

Edited by KernowCooper, 25 March 2014 - 10:02 PM.