Carb balancing - Problem?

[G0FHM]

Hi Guys,

My set of vac guages arrived yesterday.

I've just hooked them up, and notice that all 4 needles are fluctuating wildly between 0 and about 10, making a reading impossible.

I've trawled youtube, and have found a couple of videos of people using the same guages, and theirs seem to twitch a needles width either way but nowhere near as violently as mine!

This is one of the videos:

http://www.youtube.com/watch?v=B-JlxteetJM" onclick="window.open(this.href);return false;

And this is mine:

http://www.youtube.com/watch?v=uh2LM2jEWH8" onclick="window.open(this.href);return false;

Do you think I have a valve timing issue here?


J

[johnr]

no. its your gauges, they should have also come with some small valves that are fitted in the tubes from the gauges to the carbs. these damp out the pulses as each carb sucks then stops then sucks then stops, which, undamped causes the needles to fluctuate wildly, you just wind the valves shut till the needles wild fluctuations are removed, and they move in a smooth arc with the throttle opening and closing. did you not get the valves?

[johnr]

you can get the valves from some garden centres as they are used on some irrigation systems used in glasshouses, theyre tiny plastic things and only a quid or so.

[G0FHM]

John,

Yes, I did get the valves.... But seeing as there were no instructions on how to actually use them, and me being a carb balancing virgin, I thought they may have been for a different task! (such as holding the needle to a particular reading or similar).

I'll go try again!

Thanks,

J

[johnr]

put the valves about 2 inches below the gauges, as long as theyre all the same distance down the tube then they are ok, wind the valves completely shut, start the engine and then just open them a fraction till you can see the needles begin to move.

[johnr]

you know the sequence to balance them in dont you?

[G0FHM]

Yes, I have the manual here.

From what I read, it's B A C (ie middle, left and right), using no 3 as the master.

Is that correct?

J

[johnr]

i do it in pairs, assuming the throttle cable is in the middle, balance the 2 right hand pots so they are the same as each other. then balance the 2 left pots so theyre the same as each other, (they dont need to be the same as the other pair, just as each other) then finally if you adjust the centre adjuster so that the middle 2 pots match, this will mean that all 4 match. the most important thing to remember when balancing is that you dont balance all 4, you balance pairs to match each other. dont tie yourself in knots trying to balance all four at once, only adjust pairs.

[G0FHM]

Ok,

I'll give that a go... That sounds more logical!

Thanks,

J

[johnr]

and after youve done, adjust the tickover to what you want it at using the tickover adjuster underneath the middle two carbs.