Carb jets

[Marsho]

H i, does anyone have any info regarding Dellorto carbs I am running quad 45 down draughts on a griff 5.0 engine and the plugs sow its running weak, am I right in thinking it needs larger main jets? any info appreciated regards David.

[bill shurvinton]

Plug cuts are not that reliable with unleaded fuel. The real way to sort things out is to get a wideband lambda hooked up to the car and log the fuel curve, then you can quickly see where you are rich, where you are lean and where you are spot on. Larger mains won't help low down and if you actually need smaller main air bleeds will just overfuel the midrange to get the top end right.

A dellorto has 3 circuits, Idle, main and acceleration, all of which come into play to get the tune right. it isn't hard to lean how to tune them when you have the right books and tools, but it doesn take time.

[Marsho]

Many thanks for the reply, unfortunately I dont have any access to the lambda tuning stuff, so I am setting it up as I go type of thing, if bigger mains would give me a richer mixture at the top end all well and good , what do you think , regards David

[bill shurvinton]

I think you need to get access. Otherwise you will be chasing you tail and risking messing up your engine. If you can drive a PC then you can work out how to tune your engine. PM me if you want the full details on how to do it.