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You can find a vacuum leak by affixing a lenth of rubber hose to a small propane gas cylinder and with the engine idling , turn the gas on and play the gas (carefully) around any area (carb to manifold?)

If the engine RPMs increase you have found your leak. :rolleyes:

A quick way of cleaning Sh*t out of carb orifices is to remove the air cleaner assay, and with the engine at an fastish idle (1000/ 15000 RPM0 stuff a Clean rag into the choke of the carb you suspect has a blockage.

The RPMs will decrease and the engine might die(hang on to the rag)! :)

Basically you are using the engines vacuum to draw out any obstruction in the carbs circuitry. :lol:

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You might have a leak on one of the 'O' rings on that cylinder. It might be worth replacing all the rings, they aren't expensive and do deteriorate over time, especially if the carb' to manifold bolts have been over tightened in the past.

Also I found it difficult to get the float heights correct. I thought they were OK but on about the fifth attempt, I saw they were too low. Raising them removed a flat spot.

Edited by nicksoldies

"If everything seems under control, you're just not going fast enough."

- Mario Andretti

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i've got a colortune and a mercury vacuum guage, i used them on my elite and thought they were the muts nuts. i tried the colortune on the esprit and was getting the same problem as you. no 1 was nearly fully undone. i tried again in the dark to make sure i was getting the right reading and it was virtually the same. then i spoke to igor who used to own arnolds garage . this is how he told me to do it, and it works pretty good.

screw out the all the mixture screws two turns.

start with no1, slowly screw out listening for an increase in rpm( i actually used a tach on a timing light to help)

when the rpm fails to rise with further turning out,return to the point of maximum rpm, and screw back in a quater.

repeat this with all four

then starting with no1 remove each spark plug cap in turn, listening to the drop in rpm that is caused.

the one that has the most dramatic effect on the engine rpm is the one that is working the hardest(richest)

screw the mixture screw back in until the removal of the ht lead has the same effect as the rest

you may have to adjust more than one to get them all the same.

then remove the leads of one and two together, and then three and four together. you may find that one of these combinations causes the engine to stop this will be the pair that are working the hardest, if they both cause the engine to stall increase the tickover slightly then adjust the throttle linkage of the pair that is richest.

i then checked them all with the vacuum guage and adjusted as neccessary

i would also like to check the co reading so iam going to buy one of these gunson gas analysers

the idea being to then increase or decrease them all identically to get the correct reading

hope this may be of some help. i personally wont be using the colortune again.

regards shane

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I will qualify what I say straight off by saying I have NO personal experience in this area whatsoever!

I do however, recall reading very recently about people being very unhappy with the results of the colourtune method and someone reporting that it resulted in them losing an engine because it was so inaccurate (ie colourtune was reporting it correctly yet it was SO wrong they lost the cylinder :) ) There may well be all manner of other explanations of this but I thought I ought to report what I had read :rolleyes:


"When I was a kid I used to pray every night for a new bicycle. Then I realised that the Lord doesn't work that way so I stole one and asked him to forgive me."


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Shane Fenton's got it right. The whole point is to get all 4 cylinders doing the same amount of work and the method he details is the same as I have been using for far too many years on engines with multiple carburetters. One thing, though; it's less painful if you can arrange to move the plug caps back abit to bare the connections, then short them out in turn with a suitable insulated screwdriver! Galvanic therapy used to be all the rage in the 1900's, but after afew doses of several kilovolts, it gets a bit tedious..

Float heights are also pretty critical and somewhat tricky to measure, but a methodical approach will yield results. One thing which could be fooling you is the throttle buttterfly settings, if one is opening sooner than the others, all the idle mixture adjustment won't help.

Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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Thanks Guys, all great ideas.

I will give the 'one spark plug at a time' process a try on the weekend - sounds like great sense, and re-check the float heights. From your similar expirience, I am sure that will get me back on correct tune.

Not surprisingly, the book details the procedure as descibed, but only two at a time (second part of your test).

I use a carbebalancer to synchronise the throats, but again the book calls out a piece of rubber pipe and a good ear!

I don't have a monometer yet, which sounds handy, but I am suspecting too many gadgets and not enough skill in my garage at present.

I replaced the o-rings on engine rebuild, but if I am still not getting anywhere I will check for leaks and overtightening.

I'll update on the weekend. Thanks. :lol:


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Ok - I had a whole Saturday to myself - all Lotus time!

I fitted the tacho and wound in No 1 and out to 2 turns. Watching the rpm I turned it out and I could hear the rpm increase, but hard to see the needle move - anyway, at about 4 turns it stopped increasing, so quarter turn back and onto the next one.

I found just listening to the engine was easier that the tacho - maybe a digital readout would help.

Next, I did the one lead at a time routine and found No 3 working hardest - 1/4 turn in, and tried again - all seemed the same, and the tacho said the same.

Now I had completly moved all mixture screws - why not try a drive? (complete disbelief that I had a good tune).

First thing I noticed is my wheels spun on take off, then that great feeling of acceleration! :)

Yeah yeah yeah - my car is back! <_<

Thanks for the tuning tips guys. I must say that the colortune tool is a bit off, well in my hands anyway.

I suppose my MPG will go down now - I forgot how much fun it was to spin wheels ....heh heh heh


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ive colourturned my S1 and it runs like a dream evern the exhaust tail pipes have a grey colour to them this shows the engine is runing 100% and every thing is spot on.

im saying that non of my mixture screws area in the same place as each othere No2,3 and 4 area close and yes No1 is screwed out more and can only guess this has some thing to do with the vacum take off for the brakes comming off No1's inlet so im gressing again that a small amout of extra air gets into No1 after the carb to to over come this you have to richen the mixture on that carb.

So guessing again if you cant get the right colour ie its to weak (light blue/white colour) there could be a air leak on the vacum pipe to your brake master cylinder there is a sort rubber pipe from the inlet on No1 to a ally pipe that runs the lengh of the car and then a sort rubber pipe upto the master cylinder. if i was you i would make sure the rubber pipes are ok.

the other thing you could try to see if its the vacum take off giving you the problem is take it off at the inlet end and block it off and try colour tune again if you get the right colour you know its something on the vacum take off giving you the problem.

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