Received a package today with a couple gems inside. For the last month or so I have been chasing a lean condition just off idle on my 240 motor. Cold it was hard to start even while being choked, a condition I have not experienced since purchasing my Ztherapy carbs in early 2001. Trying all of the normal problem solving I finally did the “starting fluid test” and found that when I it sprayed on the rear side of the back carb  the idle was effected. Closer examination I discover the shinny silver cap over the throttle shaft was missing and covering the hole definitely changed the idle.  Engine ran good at 2500+ RPM.
Steve at ZT called me back and we discussed the issues and he advised me the throttle shaft seal was probably blown out. (A backfire can do that). He offered check the carbs if I would send them to him. That day I UPS them off to him and in less that two weeks I received a package back. My 20 year ZT old carbs look brand new and based on the cost of a ZT rebuild kit the price was a steal. They are one of those companies that you can’t say enough good thing about. 
THANK YOU STEVE

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Yes sir, great service!!

I agree with that. Probably the last "good guys" out of state business I'll ever use. I called with a question some years ago and they gave me Mr. Bruce Palmer's personal cell phone number. He answered on the 3rd ring, answered my question/problem and over-nighted new valves at his expense.

A+ Better Business Bureau. 

Couldn’t agree more! Ztherapy is how all businesses should be run! Bruce and Steve are the best.  

Good recommendations from some smart experienced people. 

I ordered a set of carburetor parts from Bruce today.  Great, friendly service.

Business must be good since the current turnaround time for rebuilds is March of 2021.

Found some time to work on the rebuild carb install.  Awesome working on clean well adjust parts. They send along a nice set of instructions that I actually read and learned something new: before making any adjustments to balance the carbs disconnect the throttle linkage at the center of the balance tube. Then when done work backwards from there to the gas pedal. if it needs to be adjusted it will be obvious. 
Note line 3: they set float level from the top of the float to the bottom of the cap to .55 in.  

The rest are a nice reminder of order to balance carbs.

last here is a pix of 20 year old technology. gross jets.

Still working after 20 years. Had easy time setting up. 
Balanced at idle (choke and throttle linkage discounted)

balanced at 2000

adjusted the valves

reset timing to 9 degrees BTDC. Max advance to 36 degrees

rechecked balances

added 1/2 turn to both mixture screws to improve smooth idle 

rechecked balances

shorten throttle pedal linkage  ( checked for WOT )

Best $300 of 2020 money I have spent lately . Hope this help someone who is undecided. 
 

 

 

Edited October 12, 20204 yr by 7tooZ
Added content

What exactly is the Starter fluid test?  What's the procedure and how do you do it, and how do you interpret results?  I'm having a helluva time tuning my carbs.  I sprayed starter fluid on throttle shaft bushings today and it affected idle negatively.  I did both carbs individually and got similar results.  What does this indicated?  THANKS!!

Edited March 1, 20214 yr by Jughead
typo

The fact that the starting fluid affected the idle indicates your throttle shafts and or the carb bodies are probably worn and pulling air through the gaps. Before you decide that's the whole problem, describe the trouble you're having. Most SU problems are caused by the wrong float level (the primary mixture adjustment) or the airflow in the carbs not being balanced. There's a few more things that can cause trouble but those are normally caused by extreme wear or abuse. ZTherapy has a great DVD "Just SUs" that goes into SUs in detail.

I own the Z Therapy Tune up and "Just SU" videos and am on my 3rd viewing.  I've rebuilt both carbs using Ztherapy kits.  Balanced with a unisyn.  Set mixture using push pin and Colortune.  The engine idle smoothly.  Vacuum is @ 20 PSI.  No smoke from exhaust.  But... 

It backfires out of carbs under load when I drive.  When I enrich mixture, the plugs fouls and and backfires out of exhaust.  Timing is set at 12 degrees (verified with liming light.   I have installed a Pertronix ignition with a 3.0 ohm coil which I got from MotorSport.  New plugs, wires, rotor, cap. 

As stated above,  I sprayed starter fluid on throttle shaft bushings  and it affected idle negatively.  I did both carbs individually and got similar results.

I have NOT adjusted carbs or check timing chain stretch yet (was hoping to avoid this).  Thought about what to (re) check?   Thanks!!  (Will report back!)

 Does the backfire out the carbs occur during acceleration or at cruising speed? Assuming you used the mixture (nozzle) screws to enrich the mixture, and they were pre-set at 2 1/2 turns down, how far down did you go with the nozzles? 

Both Carbs go down to 4 - 4.5 turns to get a decent mix per the Colortune.  I know I probably need to adjust the floats (again), but would that cause my car to run poorly?  In other words,  if the mixture's right (per ColorTune, "push pin" test, and muffler smoke/sound), does it matter how many turns I have to screw the adjuster "nut"?   

BTW:  I forgot to mention that  I used Float-Syncs to check the float levels & they both show the level at approx. 9/16" above the metal base of the Float-Sync.

 

Edited March 1, 20214 yr by Jughead
typo