10 replies to this topic

[Awlred Drives a Quant]

Okay so I know its probably come up a million times. Buuuuuuuuut I'm gonna ask anyways

I don't have a colourtune, but I have an exhaust moniter and a timelight gun thing. Is there anyway of getting the mixture right with these.

Everything is pointing towards it being too weak, it over heats within a 10 miles run, and I'm talking red area. But it runs fine, when I press the check pin in it holds steady for a couple of seconds then it stalls, I've turned the nut clockwise about 2 full revolutions with very little difference. Sooooo can anyone tell me what to do PLEASE.

Oh its a SU HS4 Carb with a lift pin.

Cheers

[fikus01]

hello i used to use the lifting pin til i came across a carb that didnt have one!! and i gave up on timing lights too!!

ok i slack off the dizzy til i can just turn it by hand but not loose!! then i start the engine and retard the timing til the engine revs drop!! just to get a referance point!! then advance it slowly!! the revs will go up again! keep going until the revs settle and that should be about right!!

adjust your tickover to normal

as for fuelling!! blip the throttle for a split second!! if it trys to stall its too weak!! if it takes a while to settle down its too rich!! i usually lean it off before i start to play jsut so i know where it all is!! then id put on the exhaust monitor and see what it says!!

i would use the timing light to set up a mini but every time i set one up to std timing it seems too retarded!! no harm in lookign to see what its at with the light!! but i prefer doing it by ear!!

jsut curious have u fitted a performance air filter or anything?? the needle mite be too weak further up the revs!!

Edited by fikus01, 05 October 2006 - 08:07 PM.

[miniboo]

How do you use the lifting pin to tune Fikus??

i have one but when i lift it the engine just conks out!!

[1984mini25]

See that will tech you for boasting

With the engine running (full warmed up) lift the piston-lifting pin till it hits the piston and then a further 1 mm on the side of the carb and listen to what happens,
If it cuts out the mixture is too lean, if the idle increases the mix is too rich and if nothing happens the mixture is about right.

The Haynes manual goes into much more detail, Pages 4A .15 and 16 fuel systems.

But the bit you probably haven't been doing while playing with the timing or fuelling is this...
All tuning should be done with the engine warm and vacuum line to the dissi disconnected. Settings you make are more reliable this way. If the vacuum is connected then every time you change anything even slightly such as tweaking the throttle a bit it sends a pulse down the vacuum line, which pulls the advance on a bit, and messes up what you are setting.

[miniboo]

ahh makes more sense now.

timing is ok on mine

sorry to hi-jack

[Big_Adam]

me learned from this:

http://www.mintylamb...page=sutune.htm

[minislapper]

Don't forget this method only adjusts the mixture at idle which will make it tickover smooth and pass the MOT but not necessarily give you the correct settings for all speeds and loads !!!

The only way to do this is a rolling road !!

[fikus01]

yay someone mentioned a rolling road tune best thing to happen to an a-series!! as long as dyno operator is good

i always used to set timing on my 998 to factory settings 10degrees @1500rpm vac pipe disconnected, or something close to that!! and it always seemed flat to drive

hard as i tried under load it would never pink!! i read haynes said about load testing in 3rd, low revs up hill etc and decided to keep advancing til it pinked as it said!! best thing i ever did!! ol girl went like stink!!

[Big_Adam]

what is pinking(or is it plinking?). i keep hearing about it.

it confounds me.

Edited by Big_Adam, 05 October 2006 - 11:04 PM.

[fikus01]

pinking also called pre-ignition or knock!! it is where the spark happens too soon on the compression stroke!!

the cylinder pressure builds up too high as the pistin is still rising trying to forcy the piston down as it rises, eventiually the noise you hear is the piston taking the brunt of this!!

not a good sound at all tho i often hear novas driving about like it all the time!!

a carb'd a-series in good condition should just quietly slightly make this sound at very low revs under extreme load!! ie where you'd never guna drive it tho its not a problem if it doesnt!!

[Big_Adam]

cool.

learn somthing everyday.