Carb Setup

[shaz_man89]

Hi guys

Ive got a HIFF44 SU 1"3/4 carb on a 1380 and its runnin rich or lean im not quite sure, im gettin flat spots when im acceleratin especially when its cold. When i pull the choke out its fine(was reccommended by a friend) he said if anyone know's which way to turn the screw to make it rich or lean and he'll have a mess about with it as he's excellent with cars. Anyone any ideas?

Thanks in advance

[Cooperman]

Sounds like it's running too lean. I think, but I'm not sure, that you unscrew I.E. turn anti-clock, to richen it, but trial and error will confirm this.
Clean the plugs, unscrew it a bit, run it and see if the plugs are blacker. If they are you have made it richer.
If it's too lean the plugs should be a very light brown colour,medium-brown and it'll be about right, rich and they'll be dark brown, black and they'll be too rich. Of course, that's only at tickover and a road test will be necessary, plus a bit of further 'fiddling' probably.

[fikus01]

its running lean but that screw only adjusts the mixture at tickover! you need a dyno seession and the needle needs changing or altering!

[shaz_man89]

cheers guys. ive been speakin to someone else who's well up on his mini's as well and he said take it upto minisport in padium and get it on the rollers, so gona do that this week i think, is 65quid cheap?

[guru_1071]

fikus01 said:

its running lean but that screw only adjusts the mixture at tickover! you need a dyno seession and the needle needs changing or altering!

rubbish, the screw moves the entire jet tube (that the needle moves in) up and down. if you move it in the mixture will be weaker at any given point through out the rev range, out and it will be richer.

you need to swop the needle for any large changes to be made, the mixture screw will only fine tune what the needle and spring are doing.

its possible to move a lean point on a needle by about 1000 rpm just by a few turns on screw - this is where a air fuel ratio meter is a very useful tool!! - for example, my car goes very weak at exactly 4000 rpm (with a AAA needle), by richening the mixture up the weak point moves up to about 4750 rpm, but still ticks over fine etc etc, any more richening simple chokes the car up. the needle will need filing (i guess, i have to go though my needle book to see if i can get on a little richer in the right place) to get it right, but at the mo it runs fine up to 75, which is good enough for now!

[Ben Magoo]

I can't recommend rolling road tuning sessions enough.

My 81 Mini 998 was a little rough and had a couple of flat spots etc, £185 at Specialist Auto Services in Peterborough and now she is awesome - 4 years down the road and she still starts first time everytime, pulls all the way through the rev range and never misses a beat!

He did a similar job on my 56 moggie running a 1275 sprite engine on a HIF44, flat spots and no top end - £215 later she pulls like a train, will get all the way to 90mph and will do 50mpg cruising at 65 70!

Budget for more than £65 for a propper tune and fettle. It is a fair amount of money but the benifits far outway the costs.

[DanGT]

Make shore that every thing is good (spark plugs points etc) befor you have the car on rolling road. Or you will end up paying a lot of money for some one to do that work for you. You can get a long way with out going to a RR but it should get the best results. All ways make shore that the person running the RR is an expert in you type of car eg minis. £65 will get you one run and maybe a small ajustmant. The probabilty is it will be more this will depend on what they find.

[GTRMikie]

guru_1071 said:

if you move it in the mixture will be weaker at any given point through out the rev range, out and it will be richer.

For a HIF44, screwing the mixture screw in will make the mixture richer, screwing it out will weaken it.

[fikus01]

£65 per hour is reasonable, most garages charge about this much, id budget for 2 hours! MOST minis i've seen or helped with at my local dyno are done within this time.

guru_1071 said:

fikus01 said:

its running lean but that screw only adjusts the mixture at tickover! you need a dyno seession and the needle needs changing or altering!

rubbish, the screw moves the entire jet tube (that the needle moves in) up and down. if you move it in the mixture will be weaker at any given point through out the rev range, out and it will be richer.

very true i do not mean to be quoting rubbish! the entire jet tube will move, you can move a flat spot or lean point in the revs up or down the rev range as per how the jet is setup without causing too much coking up of the plugs but you arent actually curing the problem! just moving it!, higher revs with a lean miture, if put into a high load situation CAN (very dependant on how lean) end in disaster for the engine very quickly.

i just felt it would be easier to say that than go through the shibang of explaination. by the way, try an AAU needle in your engine mr guru, bit richer up top than the AAA but mostly the same for the rest of the revs!

Edited by fikus01 on Tuesday 23 June 00:40

[guru_1071]

GTRMikie said:

guru_1071 said:

if you move it in the mixture will be weaker at any given point through out the rev range, out and it will be richer.

For a HIF44, screwing the mixture screw in will make the mixture richer, screwing it out will weaken it.

mike


well spotted! my brain said one thing, my fingers typed another! i was dreaming of hs4's where its the opposite!

[guru_1071]

fikus01 said:

try an AAU needle in your engine mr guru, bit richer up top than the AAA but mostly the same for the rest of the revs!

Edited by fikus01 on Tuesday 23 June 00:40

i actually started with an AAU, but its only the last two points (i.e very full open throttle) that are richer than the AAA, the lean point on my car is during very light constant throttle - so about a third down the needle (about 6 on the needle scale)- the AAA is richer than just about every 90 thou needle at this point. its an odd fault and not one ive come across before - i guess its the odd result of using a stage one kit, an hif38 and a open carb with a ram pipe. i cant fit a 1 3/4 in (not without maching all the top down) and am determined to fix the problem i have - so im going to either 'crop' the needle and move the whole needle up by 2 points on its scale, or try filing a flat down one side - though this seams like a little like guess work rather than a proper fix!

its very odd how it goes from perfect lambda to super weak in the blink of an eye!

[shaz_man89]

Cheers for all the help guy's i will be givin it a good clean before it goes in dont worry. and i think it is 65quid an hour. They are mini experts at minisport, there very recommended round here as its our "local" mini store lol. Ill let you all kno how it goes, and if anyone fancies havin a look at it first and kno's what there doin come up lol. its doin ma head in.

[guru_1071]

minisports rollers have a very good reputation.

[cone]

I'll second that , been a few times + recomended to lots of customers - all happy with results.