Running like a dog

[Gaz6oy]

Hello people
I have a suzuki sj fitted with a 1.6 8v vitara engine and su carb, it starts on the button every time ticks over at around 800rpm, revs to 5000rpm when ur stationary as soon as u start driving it will struggle to get past 2000rpm and it coughs and splutters as if its mis-firing i have checked all leads and plugs, so im wondering could it be either the ignition timing or a carb problem i dont really want to strip the carb Without having a new gasket set,

[timwilks13]

Could be a few things, check the timing, check the fuel mixture, is it an old air filter possibly restricting air flow.

[Gaz6oy]

Is there a standard setting for the air mixture, im just about to check the timing

[timwilks13]

Afraid not, each su wears differently over time, think there is an article on here somewhere of how too. I'll have a look and post the link.

[twiss]

you should be able to tune the emissions just by listening to how it runs... make sure 100% that your timing is correct first as anything else you do will be a waste of time if its wrong!

common mistake with the SU conversion is using an SU designed for a mini... its not wrong as such but minis use different vacuum advance. on an SJ you should have no vacuum advance at idle increasing with revs, minis have FULL vac advance at idle dropping off with the revs

this means that you timing will be advanced at idle by a substantial number of degrees

to check - remove the vacuum advance pipe from the distributor end and hold it up to your skin
if its got full suction and comes unstuck when you rev then disconnect it and block it off for now
if its got hardly any suction than sticks to your skin at revs then it is correct

you can redrill the carb to rectify the problem

[Edweird]

I had a similar problem with mine a few years ago. Turned out to be fuel starvation due to rust flakes in the fuel tank blocking the fuel pickup.

[donkeychomp]

I was going to suggest something similar, how old is the fuel in it?