checking mixture co2 reading on gas analyser

[xpress]

however, are the old hands saying that unless the needle was modified for better fuel consumption, its design prevents the user from creating a leaner mixture when the car is moving, ie on load? after all, there's no injectors or jets to adjust. just one jet.

[pegasus]

Pm sent let me know if they havent come through ok.
Mark

[bmcecosse]

The original needle was of course chosen with great care when the car was new....... Since then - fuels have changed greatly, and jets have worn - and many of us have modified the engine one way or another. So yes - set the idle mix up as best you can by whatever means comes to hand - but it's no guarantee that the mix will be perfect right up the range. The gas analyser will be a great tool if it's working correctly - but quite what you will do with the results remains to be seen!

[xpress]

thanks for that mark, i will give the old car a test when she's warm and will report back. bmc, maybe a new needle and or jet would help with fuel consumption?

[bmcecosse]

If it's running rich - hence the plug colour check.......

[xpress]

ok, this is interesting. today i wound the brass nut up and the spring was tight. i tightened up the handbrake cable a few turns, it was 22 threads so i tightened it up to about 25. now it comes on much better at 5 clicks. it was a bit tight getting in to the right side cable nut.

back to the carb mixture, i counted the flats. it takes exactly seven flats to wind it up totally. i wound it back out, but this time, six flats. immediately after starting her up without choke, she was much quieter and calmer, out on the road. the engine was quieter discernably. seems to make quite a difference on the movement of one flat. i might back it off another flat and see if it starts to misfire. it seems that at seven flats the idle was a bit raggy, now it's much quieter. was quite amazed.

what do you think?

also, i am going to advance with the micrometer adjustment until i notice pinking on fourth gear with throttle to the floor on a straight then back it off some and then try it on a hill. how many clicks at a time should i adjust it to be advancing it? is there a limit when you have to actually turn the whole distributor by undoing the clamp bolt or will the micrometer advance happily as long as you keep advancing it? also, if the ignition is advanced correctly, will i see any improvement in mpg and how much?

also, is the mixture setting and advance setting something that you return to tweak when gapping the plugs and servicing etc, regapping/replacing points?

[MarkyB]

Get everything else right before adjusting the mixture and timing including the tappets, points and plug gaps.

[xpress]

yes, marky all that is already right.

i don't seem to have the pickup part of the hawk analyser (the rectangular thing with the 3 pin male that clips onto the bumper) and 3 of the springs aren't there either. if anyone knows where i can get a replacement please let me know.

[Trog]

I'm all for the "tweek it and see" method, the problem with the plug chop these days is the crap fuel on sale which gives a dirty plug. back in the 90's I raced bikes using 100LL AVGAS which is leaded petrol for piston engined aircraft and still used today. I was told it was the equivalent of the old five star road fuel which of course was the diet of Mog back then. AVGAS runs cool but burns clean and gives a white plug. The trick on the track was to see how the engine behaved out of a tight turn, if the bike "bogged" then it's rich, a misfire was weak.

[bmcecosse]

Good engine gives nice clean plugs on today's fuel too - but don't put in any silly 'additives' !

[Trog]

Must admit I'v not done a plug chop in years so will give it a go today and post some pics

[Trog]

Not much chance of a text book plug chop but had a hard run up to salisbury today (40 miles) and pulled in for a quick look at the plugs. 95 RON unleaded, nothing added, standard 1098.

seemed a little on the rich side but would have expected the "sooty" look back in the days when unleaded first hit the shelves.

The Visard "finger up the tail pipe" test failed so I'v turned the brass jet screw in a flat to see what happens, having said that I'v not seen a light grey tail pipe on the road for many years [frame][/frame][frame][/frame]

[bmcecosse]

They are not bad - as you thought - a little weaker won't go wrong.