Outer Limits 4x4 Board

hi
after my last weekend trip to watagans my tb42s developed really inconsistent idle speed. it is roughly 200 rpm lower then before and goes little up and down all the time. plus there is a bit darker smoke coming out of the exhaust and it smells different as well. i guess its something wrong with the carby. how difficult it is to rebuild it.
if that weren't enough my speedo is gone mad. when i take of it goes all the way up to over 180km/h. then when i reach something like 80 it goes back to normal. what is the speedo cable connected to anyway?
any advice appreciated
cheers

The speedo thing is normal for a GQ, I own two and they both do it, get used to it because I've tried changing the transducer at the gearbox and the speedo unit in the dash it self, neither made a difference.

The description of the carby issue sounds to me like it's running rich.

Why is another issue. I guess I'd start with the choke, but as the idle is lower rather than higher I'm not sure that's the problem.

Carby problem could be a range of things, worn/leaking needle and seat, contaminants in the fuel, the BCDD out of adjustment (easy), idle air fuel mixture or even the carby body bolts a bit loose.

Pull the front plate off the carby, drain the fuel into a rag or a small container and see if there is any crap in the bottom of the bowl. If there is, I'd check and replace the fuel filter, see if that's where the crap came from. Flush the lines too if possible.

If the BCDD were causing an issue, the engine would hold it's revs for longer than normal when taking your foot off the pedal and be really bad on fuel. If it is doing this a simple adjustment is needed. Now on the engine side of the carby is a small round housing with a rubber bung in it. Pry this out. Inside you'll find a small screw, Turn this screw anti-clockwise 1 turn and things should go back to normal, wind it out further and it disengages it altogether which actually isn't a bad thing.

Needle and seat adjustment/replacement will require a bit more work and if you're not confident doing it, don't attempt it. best to have a manual by your side if you do. If this were the problem though it would be indicated by fuel dripping off the boosters in the carby throats especially when idling.

Idle air fuel mixture is easy to adjust. With the engine at operating temp, look on the battery side of the carby, right at the base, you'll find the idle air/fuel mixture screw. It's easy to ID as it has a spring along it's length. Turn this all the way in and then back out about 2 turns. Start the engine and wind it out until the revs stop increasing, then wind it in half a turn. This is rough but close enough to set.


Hope that makes sense and is of some help

Rowen