I acquired a 71 Austin Mini about 3 weeks ago and under full throttle I believe there is a slight pulsing hesitation or maybe that's just how these engines sound. This is the first classic mini I have been around/owned so I'm only as familiar as google has made me over the past couple months I had been thinking about classic mini's and the 3 weeks I've owned one.

The car was "restored" in the UK in 2007 including the 1380 "stage 2" engine and 1 3/4" HIF carb (which I'm guessing might be an HIF44?)

• First of all I wanted to see if anyone could verify what carb I have from the fallowing pictures. Also if you could point out the adjustable components as I'm used to adjusting fuel with a laptop and have only made some minor adjustments on dirtbike carbs in the past.

• Since the car was tuned in the UK, I assume the fuel may not have the same ethanol content making the tuning slightly lean because the addition of ethanol causes the stoichiometric burn rate to go down a little.

Any other advice on carb tuning or just general advice on owning a classic mini would be greatly appreciated.

Thanks,

Jeremy

 

There has been a lot written about the SU Carbs and in particular about the HIF series. Some information can be found here:
SU CARBS - Connection, HIF type
SU Carbs - HIF, a more finely honed instrument
Installation of HIF-6 or HIF-44 Carburetors
SU CARBS - Connection, HIF type
And more can be found here!

 

a few points to begin with (reference I have a 1275 with an HIF-6 on minsport manifold, lcb & playmini exhaust, cone filter ...)

1. Are you running the highest octane you can get your hands on short of racing fuel? 92 or better? If I try even to run mid-grade in my car everything gets sloppy. These lil beasts want the good stuff and let you know if you try to save a few cents.

2. There is a rule of thumb that you NEVER mess with the fuel system until you are 120% sure the ignition is absolutely spot on. Timing good? All vacume ports and hoses leak free? One little vac' leak had my car running like crap until it was found.

3. I've an HIF-6 which I believe is virtually identical to the 44


4. A good book about the SU family of carbs is SU Carburetters Tuning Tips & Techniques which I believe MiniMania still carries.

so that's the ready, set part ....

5. While there is a mix screw on the SU on many of the later HIF series it is actually sealed as these emissions control carbs were considered non-adjustable and you may need to remove a plug to get to it.

6. Then there is the way an SU works. Your mix adjustment is really just the idle mix. Your mix profile is the whole purpose of the needle. Actually tuning an SU along the full running profile is accomplished by changing the profile of the needle ... usually by changing the needle. There's a BUNCH of needles out there. Finding the best needle is as much an art as anything else. Many references will say the ONLY way to properly tune an SU is on a dyno, with a gas ****'zier hooked up and a handful of needles at hand. Changing anything in the fuel/air equation can cause a different needle to be needed. For example that cone filter you have in place of a stock 'pan' means a different needle is required. What you REALLY need is someone with a good working knowledge of SU/Mini set up to give you a best guess on the right needle. I'd say you have two options at this point.
a) assume you actually have a decent needle choice and pursue other options for your flat spot; or
b) find an SU/Mini expert to talk to. MiniMania boards maybe, or a call to Seven (but buy something too)

7. Clean things up - what shape is that cone filter in? Consider a new clean one or at least clean it. Take the top end of the carb apart - it is easy. The 'pot' or suction chamber cover can be removed via the 3 screws you see. That allows you to get to the piston and piston spring, the needle and the chamber. First time I went in here there was your typical carb buildup of varnish that was making the piston stick occasionally. Standard carb cleaner got everything moving again. Easy stuff.

8. Consider a subscription to MiniWorld. Their tech articles are first rate. Well worth the somewhat crazy cover price here in the US.

welcome to the world of Mini ... what's your 20?

http://www.teglerizer.com/suneedledb/index.html

lots of dead links here but some good stuff too if you dig around
http://www.teglerizer.com/sucarbs/index.html

bonus question
is the oil damper filled? with what weight oil? What do the plugs look like - what color are the electrodes?

 

Capt-bj,

That's the kind of info I need! I'll check the oil damper later and after some google searching I assume I'll fill it with SAE 20 unless you have a better recommendation.

I used the K&N filter cleaner/re-charge kit on the filter the first weekend after getting the mini. Only thing I use is 93 oct and avoid stations that only have 92. Just about every vehicle I've owned have required 92+.

As for my concerns of possibly being lean is mostly the theory of it being tuned using a fuel lacking ethanol and everything available to me contains at least 10%. I was surprised how well the car starts, runs, drivability etc and the area I think might be off, the engine pulls smooth up through the rpm band, but it sounds like there are a couple pitch changes that may be a result of the difference of fuel/possibly a little lean condition idea I have stuck in my head and could just be the way the car sounds.

I may try to get out and take some video/sound clips to post and see if you can pick up anything from it.

Thanks for your help so far,

Jeremy

 

carb oil I use 3 in 1 oil now - spousal unit got mad when I used all her sewing machine oil. Is it better????? I like it thin. So long as it is not empty you are doin good.

You may be able to find ethanol free gas around you. Look for a commercial fuel supplier - the guy that supplies construction equipment. It won't look like a gas station but our local guy DOES have a pump where he sells to lawn services and the like. Supposedly very small engines like weed whackers don't like the ethanol at all - the seals break down fast. Around here it is also available at marinas as outboards don't seem to like ethanol for similar reasons. You can carry a jerry can to a pier and buy it . . . I ran the eth free for a time and can't say I noticed a difference.

But for what it is worth there have been tests that say the ethanol power loss discussions don't hold water and ethanol was actually concidered an octane booster before all this new 'forced' ethanol issue came up. I used 'gas-a-hol' in my car and bike when I live in central Indiana in the early 80's (PURDUE, MS, 82 .. go Boilermakers) I think that was like 50% ethanol.

Check the plug color - you want a 'biscut' tan - it is a very good tell tale of the rich - lean issue not just at idle but overall.