mechanical throttle linkage, what's the problem ?

[240Z240Z240Z]

If that is the case, then this problem would be apparent on brand new Z cars with brand new carbs. Which it is not and was not. I still hold that this is a worn part problem, either in the ball and sockets or in the carb bushings

I agree with you that it does get worse with worn or dry bushings (I think I said that), but I'm guessing many folks here also set their idle RPM higher than they did at the factory. If you're setting the idle to 1000 RPM its too high IMHO, even the E-Type guys with tripple SU's and a 4.2L set their RPM down around 600-700. Also, I think the bushings used in several places are Nylon which is known to produce stick-slip behavior when dry. So combine dry nylon bushings, with higher than necessary idle RPM and you get an initial sticky throttle press. Before I took my carbs and linkage off recently I had the sticky throttle issue. Now I'm in the process of putting my carbs back on and plan to do some experiments and see if what I've been thinking is true.

[bartsscooterservice]

Let's wait and see, I do agree with Kenobi, he has a point there. I bought the ztherapy rebuilded carbs from Grannyknot, and will put them on when they arrive, and see what happens...

[Zedyone_kenobi]

If those are fresh rebuilds inlcuding the linkages, then I predict your problem will be a think of the past. I am eagerly awaiting an update buddy;

[bartsscooterservice]

Yup, they are practically new, he had them on for a few hundred miles, let's hope the problem is solved with it... then we also know the answer to the problem.

[bartsscooterservice]

Problem is GONE. To confirm: it was in the carburetor butterfly axles ( to much drag/wear ). Pedal feels so smooth now, it's even to sensitive !

[Zedyone_kenobi]

HUZZAH!

Good for you man! Way to work through an issue!

[240Z240Z240Z]

As I indicated earlier, I took my carbs off and have been going through the linkage bits to ensure everything is working properly. Besides discovering that my carb heat tube was completely plugged I found that the Nylon bushings of the bell crank were super snug on the support shaft. I had to pry the bottom one off, its like they shrunk down over the years. I ordered some new ones from MS and they turn like butter.

[bartsscooterservice]

I guess there could be different reasons for the problem. But i'd recommend anyone to look @ the carbs first. I also tried everything else, but it came back to beeing the carbs.

[2fiddyz]

I remember back in the day I worked in a Z car junk yard, and I had every make an model at my disposal. So I mixed and matched pieces from 240's 260's, 280's and Maybe even 280ZX's and solved it 95%, but it seemed that the last pivot above the throttle linkage had the most amount of resistance. If you can duplicate that last item with a set of teflon lined heim joints (spherical rod end bearing) that makes a BIG difference. Also, if you have the resources to press the factory bushing out of the intake manifold boss and bore it out to accept a needle bearing and seal from a parts shop, that might solve all of your problems.

But many above are correct, the beginning of the travel for the factory linkage is a bit over-center and it makes the initial depressing of the throttle abrupt if the pivots are not lubed properly.

I 100% stock is your goal, I remember graphite on the bronze bushing in the manifold/carb helped. A filling each nylon cup with synthetic lube helped quite a bit.

Also you could have an oilite bushing machined by a local machinist pretty cheap, then pres it in the factory location. The raw bushing material can be purchased from McMaster Carr.

[bartsscooterservice]

HUZZAH!

Good for you man! Way to work through an issue!

Yeah..it really works perfect now. It was like new carbs mounted...and when I pressed the pedal with running engine my jaw dropped to the floor on the difference it made...