Posted: May-21-2008 08:54AM

One question: you said your carbs came off an MGB. Is there any correction necessary for an HIF to correct the float bowl angle when mounted a mini intake manifold? The float bowls have to be level to work properly, and the engine is tilted on a mini. But I only know how to adjust this on an HS carb with the separate bowl.

Anyway, just a thought. Maybe if this was an issue it could be something that only shows up when cold starting requires that extra amount of fuel?

Norm

Posted: May-18-2008 03:58AM

thanks people for your replies

the head is reoc < 5000km ago with new valves and valve seats, guides etc. I will check the manifold vacuum (easy as i have a vacuum gauge hooked up) Never noticed what it was at cranking but good >25mmhg vacuum on deceleration makes me think very little leak in manifold area.

I reckon the butterflies are worth experimenting with thank you dan. I was always told that the first thing the choke should do (on pulling it) is open the throttles before it richens the mixture. This is how i have always set up my hs carbs but it has always been easy to see the choke mechanism move down and the throttle spindle move. with these HIF style carbs i am not sure at what stage the rotary choke valve is actually opening the choke circuit so hard to figure out.

I will play around with it and see how I go. how do the rest of you set up your choke operated throttle adjustment / cam on HIf style carbs (single or double)

cheers

andy 

Posted: May-15-2008 09:09AM

just two wild thoughts here - "thinking outside the carb box"

no air leak in any crankcase/breather hoses connected to the carb area?  or leaking mounting gaskets? The relative proportion of leaning from either such leak is far worse at low rpm than high.

state of intake valves? I once had a non-mini with a bad intake valve. Not bad enough while running to notice, but just enough "backflow" into the intake manifold at start-up to pressurize enough to interfere with needed vacuum on choke/cold start.

Doing an intake manifold pressure manometer reading may answer both these possibilities. 

 Harvey 

Posted: May-15-2008 07:34AM

Just a wild guess here... what is the throttle plate position when on full choke? Are the butterflies too wide to obtain enough vaccuum to pull on the choke orifice? Or maybe too much air is going past the butterflies to provide the rich starting mixture.

I don't know the details, but I seem to recall reading that the position of the butterfly edge relative to vaccuum ports is critical... maybe if your throttles are too wide (or not wide enough) the position of the butterfly edge does not induce the required suction on the 'choke' orifice.

"Hang on a minute lads....I've got a great idea."

Posted: May-15-2008 04:15AM

hello everyone

 I need some advise as i am at the end of my tether.

I replace the 100 in my 65deluxue with a warm 1275 about 1 year ago. Around that time I bought a BMW mini so ended up not driving the old mini too much so never really bothered about my cold starting problem too much but now it really annoys me and i want to trouble shoot it

I have twin hif 38s from an MGB mounted on mini manifold. It is tight but they fit and the throttle and choke mechanism move freely. When the motor is warm it runs fine no problems. When cold ( an i am in australia so my coldest is still about 5degC) I can not get it started without squirrting fuel into the manifold or down th carby throats. This works most of the time but sometimes needs to be repeated several times until it is warm enough to run off the normal needle/jet running circuit

I have removed the carbs several times to check the choke mechanism. THe hif carbs have a seperate choke circuit activated by a rotatry valve. When i blow compressed air up through the hole in the bottom of the under carb float chamber (on the rim of the flange which takes the bottom plate) it comes out the "off midline" hole downstream from the main running jet. When the choke is closed compressed air doesnt come through this hole which makes me think the choke mechanism is working as well as it was designed to work. clearly without a flow bench I cant test this any more realistically out of the car.

also there is another hole inside the carb body (visible from above when you take the piston out). It is in the midline and downstream (closer to butterfly valve) from the main jet right next to the hole through which the choke circuit (off midline) empties into the carb. what is this hole - is it another circuit ?accelerator circuit of some sort

Can anyone help me out with any other suggestions as I am going spare. I am considerign going back to hs4s for their ease of operation and easily visible choke operation.

thanks you and i hope this makes sense

andy