Rich/lean question

[davy mcclelland]

Hi Guys,
Just out of curiosity, if an engine is idling ok(neither rich or lean), what would cause it to run lean at mid range or wot????
Thanks, DAVY

 

[iwombat]

Re: Rich/lean question

There's essentially three sets of jets (or two depending) for a carb. Each begins to take over the majority of fuel delivery as more/less air passes through the carb body.

At idle, your idle jets are the primary provider of fuel. At midrange your midrange jets are the primary provider. At WOT your main jets are the primary provider.

If you're lean above idle, then you've probably got clogged, misadusted, or badly sized midrange or mains

 

[tashasdaddy]

Re: Rich/lean question

Davy, always tell us what motor and year.

 

[davy mcclelland]

Re: Rich/lean question

Thanks lads,
It,s not an issue I think I have - just happened to see in another thread, that someone made the statement that you can be idling OK, but, be running lean at wot - which I wouldnt like to happen to me. Was curious as to the reasons why this could happen to any motor, & more importantly, how would you know it was happening????
Is the only way of telling, by visual inspection of the plugs????
DAVY

 

[tashasdaddy]

Re: Rich/lean question

multi carb motors, can run lean on one carb or all carbs, if the carb is dirty and not delivering proper fuel mix. thus it can cause catastrophic damage.