Very rough idle 1.3 carb sj50

[BZOOK]

Gents. After dropping off the kids at school the Sierra decided it would stall unless I keep rpm above 2k. It seems to run ok at high rpm but it is struggling at idle. I've cleaned out the carb. Hoses look ok. Idle mixture screw helps then hinders. Fuel pump seems ok. Any other suggestions? It has the aisin carb. Engine is stock and has been fine till today. Thanks. Brenton.

[christover1]

Could be the cold weather.
Carby is heated by the water jacket, check for blockages,
or missing spacer in carb.

[BZOOK]

Ok thanks.

[BZOOK]

I've spent many hours tinkering with my idle issues. I've replaced all vacuum hoses, a leaking water pipe, fuel pump seems fine, timing is ok, plugs n leads ok except one spark plug that was a bit black, battery is fine. I'm assuming the carb is the issue. It starts but dies almost instantly and will only idle if I either hold it above 2000 rpm or up the idle speed to the same. Any words of wisdom? Thanks.

[christover1]

Could be a blocked idle jet, its tiny and is a common issue. My carby did similar, it was one of the vacuum actuator things sticking. If you put some carby cleaner in the fuel tank, and an extra filter after fuel pump that can help greatly. External spray carb cleaner on all the linkages can help, If fuel pump is old, bits of diaphragm can come off and block the carby up.

[BZOOK]

Ah the sweet smell of carby cleaner!! I've used about a can of the stuff all over the carb and into the carb. I've read about the swapping leads trick. Bit worried about that. I assume any appropriately sized fuel filter will do? Thanks.

[christover1]

I didn't like crossing leads to back fire thru carby, so I never tried that. I used to rev it up, with air filter off, and shove hand (or something safer) over the inlet, that sometimes worked. The line from pump is smaller than from the tank, so check pipe size. Cute little ones are now available.

[christover1]

New fuel pumps are still available and cheap, if you need or want one.
Make sure tank is clean, too. (some have a drain, some need removing to drain.

[BZOOK]

One other thing to add. It will hold well over 2000rpm. If.i give it a decent rev it backfires. I checked timing on the weekend. Maybe I should try a new set of spark plugs as well. Thanks.

[greyghost]

sounds to me like a blocked idle jet, until you mentioned that it backfires now i'm thinking change the coil