RXTbone

I have done a few searches and haven't found exactly what I need to know...

I just had the stock Nikki carb rebuilt on my '83. I'm having slight hesitation when I tap (and I mean tap) the gas. It creates a situation where I have to double pump the pedal lightly on launch. Beyond that, the car is running like a bullet train through the RPM range...

Assuming everything else is OK with the fuel system (i.e. fuel pump, filter, etc.) - can I tune out this hesitation by adjusting the idle mixture?

Thanks!

Rx7carl

Check the accelerator pump. The linkage probably needs adjustment. Whats your idle speed?

RXTbone

1000 RPM - which I will probably drop to 750, where it should be...

The rebuild was a result the "Shutter Valve" problem I was having. The carb rebuild went fine, and the old girl is running great - I'm just left with this little annoying problem.

It's not easy being ****.

83gslRX-7

i just dropped my "rebuilt" carb in yesterday and im haveing the same preob. but mine has mech secs. and i think that has something to do with it but im not sure.

RXTbone

Thank RX7Carl - that headed me off in another search, in which I found this thread by Sterling (83gslRX-7 check this out, good info):

https://www.rx7club.com/showthread.p...ump+adjustment

I'll definately check into adjusting the accelerator pump.

But, back to my original question, so that I understand the effects of adjusting the idle mixture screw: By adjusting that screw, it wouldn't effect the hesitation problem?

Thanks!

Sterling

No- idle adjustment won't affect the hesitation.
The carb is'nt making much use of the idle circuit at that point.

I would have to say it's definitely the AP.

RXTbone

I think it's the AP also - I attempted to adjust it, to no avail. I ended up taking the adjusting nut completely up and down the thread and there was no change in the hesitation...

Can you change out the diaphram without taking off the carb? It looks like you can - but it's going to be a royal PITA.

As always, thanks for the help!

RXTbone

Actually - I have the answer in Sterling's write-up...

What pisses me off is that I just had this f'n carb installed - and the AP was fine before the rebuild!

Sterling

Do you see it squirting when you operate the linkage?

RXTbone

... well, I think I know what you're talking about...

When I "tap" the gas, during the hesitation, it's dry. Should I really press the pedal, I get a nice squirt of gas - along with the car revving nicely...

Sterling says: "You're fucked. Read my write-up and change the AP diaphragm."

LOL... sorry, I'm trying to have a sense of humor about this...

Also, when you rebuild carbs, do you usually check things like this out? Should I have expected the mechanic to replace this during a rebuild? I think the kit came from Victoria British. What I'm pissed off about as much as anything is I was sent off with it like this (I was giddy beyond reason about getting the Mighty RX back, I was without her for 5 weeks!) ...

Maybe I should take her back and pitch a bitch.

Sterling

I would!
The AP diaphragm comes in the rebuild kit!

There should be no excuse.

How much did you pay for the rebuild?

Wankelguy

Switch to Amsoil.

Rx7carl

Hmmmm. So if you tap the gas pedal, no squirt? But if you romp on it, it squirts? And the adjustment nut does not affect it? Somethnig is fishy in Denmark then. Possibly the spring didnt get put back in, or your missing a checkball/ or checkweight.

Oh, and when we rebuild carbs, we strip it down to nothing, and EVERYTHING gets cleaned, inspected and replaced as necessary. Nothing is left to chance.

WG- whats your user text translate into????

DONNA

yes you can replace ap with out removing the carb, but you will have to buy the whole kit to get the one part, cause mazda wants the same price for just the ap, but whom ever rebuilt your carb should replace it for free since he shorted you, but if you want to do it you can by first removing the lower left screw then slide the linkage slightly to the left and remove the lower right screw and then the upper ones,,,,remember to put the lower left screw in LAST upon re installing,,,makes it much easier, and use a magnetic phillips head least you loose the screws in never land,,,but i would hit up the rebuild dude first......
and yes you should see a squirt of gas from the center post of the carb when you depress the gas pedal running or not.
,,,,,,,...like sterling said, it should have been with the kit when installed..........

Sterling

Ya know, on second thought, Carls probably dead on, because even with my short experience as a carb-putter-back-together'er, even I have come to realize that most of the carb ailments complained about are attributed to only two things: Dirty or old needles & seats, and a bad AP diaphragm or stuck AP circuit components.

-It should've been the firt thing he would do if he were going to do minimal work to try to get away with something.

-He probably did'nt put a spring or wieght back.

Really would like to know what he charged. (PLUGPLUGPLUGPLUGPLUGPLUGPLUGPLUGPLUGPLUGPLUGPLUGP LUGPLUGPLUG!)

RXTbone

I ended up paying right around $300 for a rebuild, and then the tuning (or lack thereof).

... then, of course, I noticed your pricing. And frankly, I wouldn't have minded changing out a rebuilt carb, I just didn't want to rebuild it.

Live and learn.

I'm going back and pitch a bitch. I will say, though - it's pretty amazing what a rebuilt carb will do for performance on a 20 year old, 100,000K RX - even if it is stock.

83gslRX-7

hey sterling i just bought a "rebuilt carb" and slapped it in and it too is running like **** and doing the same thing his is... and it will not start for like 5 min. my old carb started her right up one pump and bam... .. this so called rebuild that i bought was from someone on this forum and he is a good guy he is sending me the money back minus shipping charges which was only 20$ . so my question to you is since i have an extra nikki how much is it to send to you guys for a rebuild and mech secs.? the nikki i bought had mech secs. but i dont really feel a diff at all. pm me with your response i need to get on this i cant stand not having my roxette run well. thanks

Sterling

You have to email me.
The link is on my sig.
DON'T PM ME ABOUT IT!
(everybody's been PMing me instead of emailing me!)

Rx7carl

RXTbone

I've read mention of "throttle circuits", or something like that. Can you guys briefly explain what they are - and how they could/or would not relate to my acceleration hesitation?

Rx7carl

Heres some good info.

http://www.grapeaperacing.com/GrapeA.../carbterms.cfm

http://auto.howstuffworks.com/question377.htm

RXTbone

Thanks for the info - now I just need to find out where the hell that's at, and how to test it.

I love this forum.

God Bless America (and Canada... and any other country that's represented by a Forum Member, or FB owner (does that cover it?)).

Wankelguy

lol, it's a phonetic spelling of the way a Japanese person might pronounce "banana peel slippery", which is a euphemism I sometimes use to describe slick road conditions. You DO speak "Ingooreesh", don't you?

I know, pretty arcane.

Sorry for the OT.

Rx7carl

Ahhhhhhhhhhhhh, ok.

RXTbone

I have literally been all over this engine trying to tune out my little moment of off idle hesitation. The AP diaphragm was replaced during the rebuild. I have done the following:

Check the AP squirt - OK
Adjust the AP linkage - Done
Check the timing - OK
Check the Idle Mixture - OK
Check for vaccuum leaks - None
Adusted idle speed to 750 - Done

Yet, when I tap the pedal, I can still get it to stumple off idle. This problem almost seems to be intermittent also - when I pulled in for the "RXTbone tune", it wouldn't do it. After a bit though, it continued...

So... I'm not sure what to do next. The car revs really nice through the RPM range, and drives well - albeit with a little more throttle massaging during launch.

Question/Theory: Can a new AP diaphragm be firm enough as to not allow for a large enough push of gas at launch?

... just reaching...