MG MGB and MGB GT Tech Talk
The engine is running fairly good now particularly at higher RPM's, but I think it is a little lean. However, I have the needle fully CW. Do you think I need to raise the gas level a little in the carb. chamber? Would that let me back off the needle?
The best ways to deal with a ZS is get the book and special tool for it or float test it. Float testing is simple and requires the use of a lot of gas for most of us. For the mose effective float test drive to your nearest ocean fishing pier and drop the ZS in the water. If it floats work on it some more, if not, get a Weber.
You need a manual to understand that carb, and probably a special tool to set it properly. I taught myself about the water choke on them, but don't know much about the rest. Tony Barnhill probably knows more about them than anyone on the board, He'll spot your post and reply after while.
John, I knew whem I typed ZS I would catch hell. I do have the tool, and it is a new carb. I just ran out of adjustment and figured there must be a way to correct it without changing out the needle. Hell 3 days ago it was a flooding problem.
PS I cant afford to float test it at this point....but if I do a float test, it may be the whole dang B ...... Thanks John
If you have the book and the tool you'll end up the winner. I had a pair of ZSs on a '70 Volvo for 14 years, put diaphrams in them once and that's all they ever needed other than oil now and then. They're good carbs, just a little different, and persnickety now and then.
Larry, I'm surprised that the ZS is running lean with the needle fully CW. Usually, you can't get the things to run lean fully counter clockwise. Have you checked for proper placement of the needle? If its seated correctly, there's a groove where the grub screw retains it into the piston. That should help put it in the ballpark. I'm a newbie, so take this with a grain of salt. Unfortunately, Tony hasn't seen your post yet. He's the guy for ZS questions.
Craig Kubiak
'79B
Larry,
I'm with Craig and surprised to hear it's running lean. What gave you that conculsion? They usually are running rich, so it might be that it's in the right range, but after running rich for so long it might seem, well, lean.
Craig is also correct about the placement of the needle, but I'm not sure if you can get that too far out, but double check as well. Raising the float won't help unless it's starving for fuel, which if it's running at high RPM's well doesn't sound like it.
Do you have oil (tranny fluid, brake fluid, olive oil-whatever is suggested on here) in the damper????
Every MG until recently I've had (9) had ZS. And they usually didn't run great, but ran well. If you say it's running good, leave it alone! Don't mess with Karma!
Ok...I don't like 'em either, but they're simple, original and can be made to run pretty darn strong. I don't know about anyone else, but float level was a BIG problem for me. Ran fine at light load and high RPM, but had NO power uphill. I raised the level some and it made a world of difference. But you have to be sure you have no vacuum leaks at all, because the vacuum is what raises the needle. Also, good fuel flow through the filter and float. Running rich is often caused by the water choke. What needle do you have? (I think 45M is what came with the 79).
