engine tuning

Hi all whats the best way to tune a 2.25 petrol as my 2a seems to be going through a huge amount of fuel, it pulls strongly its got a zenith carb on it is it time to re jet it or by how much do i turn the mixture screw in and what do i listen for to know that its set up about right

What colour are your plugs? That will give you a good indicator of both your burn and your timing.

What type of distributor do you have?

One way to set up is to get your engine warm, set it at aroound 1000rpm and slaken off your distributor. Turn it clockwise until your revs increase and then start to drop off again. At this point, back it off a couple of degrees and tighten it up again.

With your carb, screw in your adjuster until you are on the point of stalling and then adjust your stops out to give you a tickover of around 600rpm.

Take it for a run and see if that makes any difference. As you will now have your timing set, all the other adjustments will be to the carb.

Have a good firkle until you get both the power and the speed set up until you are satisfied.

You will also fine that your fuel consumption decreases as you will get more mpg than previously.

Hope this helps.

i have the timing set up but its the carb thats getting my goat and royaly ****ing me off just need to play and sort it such is life

Did you set your timing with a strobe light?

no i have not needed to re set the timing its a 17 000 mile engine i will check the timing though as its always worth doing

All you can adjust is the slow running mixture and tickover. Zenith carbs have a habit of warping which allows fuel to leak from the float chamber into the throat - there's also IIRC a big o ring in there which can harden. Loads of articles about refurbing zeniths for landys on here and on the net. Probably worth it 'cos it's a nice carb when running properly.

oxides said:

All you can adjust is the slow running mixture and tickover. Zenith carbs have a habit of warping which allows fuel to leak from the float chamber into the throat - there's also IIRC a big o ring in there which can harden. Loads of articles about refurbing zeniths for landys on here and on the net. Probably worth it 'cos it's a nice carb when running properly.

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ill second this but add

with the engine warm and sat idling ( ticking over ) theres a screw with a spring on the right side of the carb as you look at it from the passengers side

turn this slowly clockwise no more than a quater turn if the engine cuts out or starts struggling turn it back verry slowly till you hear it run right again then find the bite point of this behaviour

ideally you need to get it just on the good side of this point and see how it goes if its still useing ( drinking ) petrol seriously look at refurbing or replaceing the carb

added note after this tweaking it may need a little more choke than usual to start from cold usually that first thing in the morning start

Adjusting the mixture screw might give you a nice tickover but it won't help the fuel economy much - it only adjusts the mixture when the carb is at or near tickover. Stopping the carb from slurping fuel directly into the engine, bypassing the carb jets, will help a lot more!