Got a problem with my carbs...

[New_BE]

Hello, when i first got my car it was only runnin on the first three cylinders... then i let it run for a bit since it hasnt' ran in like 3 years stuck some rislone in the crank case and soem other stuff to "clean" out the engine-well whatever it does. I noticed this week that it ocasionally want's to run on three when i start it up..so i started wiggling things around the carburetors..Underneath where the adjusting nuts and all that stuff is on the back three cylinder where it isn't running when i start it it's all loose and ****. you can wiggle it easily. IT was also kinda sticky. where the choke and all that stuff was... what do i need to do? I think a rebuild is probrally needed, it's all pretty old and ****. anyways thanks fro your help

[New_BE]

oh-yeah.. My dad took a look at the vacum advance and it isnt' working..how do i go abotu fixin this aswell.

[visionary]

I assume you have the SU type carb. You might want to read the post from Rick Hanson under the "needles?" subject in this forum. He gives an address and number for a specialist in Colorado. If your mixture adjustment assembly is loose you have problems with the jets and needles, otherwise you would have to post more information about the problem.

A conversation with a carb specialist could be the answer.

Keith

[smg1404]

I am not the most experienced SU guy. Most of my experience with them came from a BMW motorcycle I had, several years ago... The things I learned were to

make sure there is oil in the resavoir, make sure the piston moves freely,and ther are no vacume leake at the base ot the carb.If it still does not seem to work, check the diaphram in the top of the carburator.. SU's rely on vacume to acuate the piston. The piston is actually what allows fuel and air into the engine. The idea is that a perfect mixture can be had in all operating conditions, independant of barometer, etc.... Sounds good. But they can be perplexing to someone not used to them.

[skip260z]

Check these places out..

http://home.istar.ca/~datsun/att06.htm

http://www.ztherapy.com/

(go here for the SU fuel lines, how-to videos, and REAL rebuild kits)

http://www.jetlink.net/~okayfine/sutech.html

Get a carb rebuild (actually just a refresh kit) kit for the front carb, the one for the rear carb (different than front), and new floats from any decent parts store. Get your fuel lines from ZTherapy, DO NOT USE the crap in the refresh kits. Watch the ZTherapy video and you'll be on your way. The video explains a lot.

BTW, the vac advance is taken from the front carb, the tiny, tiny vac port on the float-bowl cover is easily clogged. Maybe that is the issue(?).

Lastly, in the absence of a Z mechanic in your area, don't forget that SUs are Brit carbs, and the local MG and Triumph garages can probably get them in tune for you.

[laffeaux]

If you;ve not seen the ZTherapy "Just S.U." video, it's well worth seeing. See if you can borrow a copy somewhere, or spend the money on it. After seeing the video, the SU carbs seem so simple. It's hard to imagine not being about to set them up properly.

[ZwolleY]

Is the ZTherapy video set up so that it shows step by step the process for rebuilding and tuning? In other words, can I have a video player sitting on my bench and a remote control in one hand and step my way through the rebuild and tune?

[ZmeFly]

i got the following from an 'olde Motor Manual i find useful in troubleshooting...hope it helps you locate the cause.

run on is caused by improper idle speed and/or high temperature. high idle speed will increase the tendency to diesel because the inertia of the crankshaft and flywheel. too low an idle speed with a lean mixture will result in higher engine temps especially if idled for long periods of time.

because advanced ignition timing raises idle speed and retarded timing reduces idle speed, timing influences the tendency to diesel in the manner noted above.

enriching the fuel mixture decreases run-on by causing the engine to run cooler. as does high octane fuel. plugs of too high a heat range can cause dieseling. if the throttle plates are not aligned properly, a lean mixtture occurs.

if the popping back is in the intake, the usual causes are:

1. lean mixture (often due to dirt or water in fuel)

2. engine cold and choke too lean

3. leaky or sticking intake valve or weak/broken intake valve spring

4. leakage of current across distributor cap or two mixed-up plug wires

if it is a muffler explosion, it could be caused by:

1. late ignition timing or valve timing

2. burnt exhaust valve or weak/broken exhaust valve spring

3. tight exhaust valve

4. if ammeter swings away from zero when charging...intermittent open in primary

5. if ammeter swings toward zero when charging...intermittent short in primary

6. short in coil or secondary coil wire

if you got a subdued put-putting at the tail pipe, it could be a leaky exhaust valve. this is mostly to occur when the mixture is lean.

this is just some other things to also look at so you have your car running well as a whole