Air Fuel mixture

[shorty92]

G'day all, my tb42 is having trouble idling when it's on the go it drives sweet but it dose back fire and gurgle a bit when you back off im pretty sure its the air fuel mixture iv spent hours trying to tune it but it hasnt really helped much is ther any specific way to tune it i was told screw it in and when it starts to run shit go back till it runs shit again and then go half way, the carby was rebuilt about 3 months back its been doing this for a while it some times goes away and comes back but now its at the stage where you have too keep the revs up at the lights or she'll stall
any ideas would be great

cheers paul

[TUFF MAV]

Sounds like the idle circuit in your carby is blocked

Kyle

[David_S]

Have you checked for air leaks - carb/manifold, manifold/engine, vacuum take-off lines and torqued all bolts?

Does sound a bit like the idle could be blocked though.

For tuning without a CO meter:-

1) Check idle speed and adjust.
2) Check ignition timing with timing light
3) Screw idle screw in and then back out approximately two turns
4) Adjust engine idle speed again using throttle adjusting scew
5) Adjust the mixture screw until engine idles smoothly at the highest achievable rpm. You will need an rpm meter for this. Analogue ones are easier to use than digital as they have an instant visible response. As you adjust the screw the revs will increase or decrease slightly or the ngine will falter. Adjust till the engine sounds sweet. There can be quite a flat peak where this occurs depending on the carb. I tend to leave mine at the "in position" i.e. at the earliest smooth running position when screwing out. Screwing in leans the mixture, out enriches it.
6) Set idle speed with throttle screw.

And don't forget to check you have a clean air filter before you start!

David