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Discussion Starter #1
Howdy!

I'm trying to rebuild a pair of '72 carbs and have some
questions.

1. On some web page (can't think of the url) I read that it's

best to use N27 needs and jets in those carbs, so that's

what I built them with. Did I do something wrong?

(N27's are the ones from '70-71 carbs).

2. While installing my new N27 needles, the Haynes manual

said to slide them in so that the surface of the little ridge

around the base of the needle and the surface of the

piston line up. Well, that piston has a groove in it from

one side to the other, that the needle hole is down inside

of. Should I push the needle in so it's flush with the big

flat piston surface, or the surface inside the groove?

By reading the book, I got the impression that the needle should
be flush with the main face of the piston, not the surface of the
groove. I finished it up that way, but then when I got the
other carb apart, I noticed that the old needle in it was pushed
back all the way flush with the groove surface.

Which one works?

Thanks soooo much!!!
-rr
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Discussion Starter #2
Scott B. of Ztherapy told me the best way to adjust the needles is to loosen the needle in the piston and pull it out past the edge of the piston groove, then place the piston back in the carb and the jet-tube will push the needle in the proper distance. Make sure that you have screwed the jet tube all the way up before you do the adjustment then back it out 2 turns when you are done. This proceedure will insure that the individual needles are ajusted for each nozzel tube.

ps. Be sure to tighten the set screw on the needle when you are done.

> Howdy!

> I'm trying to rebuild a pair of '72 carbs
> and have some
> questions.

> 1. On some web page (can't think of the url)
> I read that it's

> best to use N27 needs and jets in those
> carbs, so that's

> what I built them with. Did I do something
> wrong?

> (N27's are the ones from '70-71 carbs).

> 2. While installing my new N27 needles, the
> Haynes manual

> said to slide them in so that the surface of
> the little ridge

> around the base of the needle and the
> surface of the

> piston line up. Well, that piston has a
> groove in it from

> one side to the other, that the needle hole
> is down inside

> of. Should I push the needle in so it's
> flush with the big

> flat piston surface, or the surface inside
> the groove?

> By reading the book, I got the impression
> that the needle should
> be flush with the main face of the piston,
> not the surface of the
> groove. I finished it up that way, but then
> when I got the
> other carb apart, I noticed that the old
> needle in it was pushed
> back all the way flush with the groove
> surface.

> Which one works?

> Thanks soooo much!!!
> -rr
> .
 

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Discussion Starter #3
> back in the carb and the jet-tube will push
> the needle in the proper distance. Make sure
> that you have screwed the jet tube all the
> way up before you do the adjustment then
> back it out 2 turns when you are done.

I tried this trick and it seemed to work great. According
to this, I had my needles pushed into the pistons too far
before!

When I screw the jet-tube all the way up, should I do it with
the little spring under the mixture adjusting nut intact? Or
should I take the spring out first?

I went ahead and did it with the spring intact, but if I haven't
put them back on the car yet so if I'm wrong I could still change
it easily.

Thank you VERY much for the tip!!!
-rr
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Discussion Starter #4
As far as I know the spring should be left in place. The idea is to adjust the needle so that both carbs are staring from the same setting, ie now fuel flow when seated. Good luck.

> I tried this trick and it seemed to work
> great. According
> to this, I had my needles pushed into the
> pistons too far
> before!

> When I screw the jet-tube all the way up,
> should I do it with
> the little spring under the mixture
> adjusting nut intact? Or
> should I take the spring out first?

> I went ahead and did it with the spring
> intact, but if I haven't
> put them back on the car yet so if I'm wrong
> I could still change
> it easily.

> Thank you VERY much for the tip!!!
> -rr
> .
 

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Discussion Starter #5
> As far as I know the spring should be left
> in place. The idea is to adjust the needle
> so that both carbs are staring from the same
> setting, ie now fuel flow when seated. Good
> luck.

Yesterday I put the carbs back on and tuned it. It seemed
smooth and nice so I took it for a test drive, where it spuddered
and resisted with about 1/4 power. Blah! :) Right at first
it seemed like it was doing okay, but it got progressivly worse
until I could hardly make it up my driveway. I was sure something
inside one of the carbs had come loose... so I got a big light
(it was dark by then) and took both of them off to get them
in my kitchen where I could disect them.

Everything looked fine inside, except for a fuel leak that I hadn't
noticed before near the fuel bowl. (Which was remedied with a
new washer from a carb rebuild kit.) So not really knowing
what else to do, I set all the tunings back to the starting point
and put the carbs back on. It started with a little hesitation
and cranking, and ran pretty roughly.

I read in a SU carb book the night before that there's a little
button on the outside of the carb that you can press up on
to manually lift the piston. It said in the book that that's a
way to tell if the carbs are running with the right mixture
or not. It said that if you press in the button between 1 and
2 mm, then it'll speed up if it's rich, and slow down if it's
lean. If it's just right, it's supposed to speed up just a tiny
bit.

So, knowing that, I pressed the buttons, and the engine slowed
way down! (Indicating a lean mixture!)

The Haynes manual says to turn the mixture nuts until they seat
and back them off 1/2 to 1 turn. (And you said in a earlier
post that 2 turns is the right distance...) Then the Haynes
manual says to *tighten* the nuts 1/8 at a time evenly until
the smoothest and fastest idle is obtained.

Well, I had taken your advice and backed them off 2 full turns
before puttin' them on the car, and it was still running too lean!
(According to my test.) By looking at the machine, I gather
that tightening the nut leans the mixture. That's right isn't it?

So I backed the nuts off towards a richer mixture and the idle
started to smooth out! I don't really know how much I backed
the nuts off after the initial 2 turns... but my guess is another
2 turns! I just kept backing them off a little bit and trying my
mixture test that I found in the SU book.

Finally after all those turns, pushing up the button made the
idle increase slightly.

I ran it after all that, and it had plenty of power again and
didn't hesitate or studder anymore, but it got about 10 MPG
and stank of gas fumes somethin' terrible! Once again, they're
way too rich!

Does anybody know of a better way to adjust the mixture
nuts so it comes out right? If I went according to the Haynes
manual, the engine would run *way* too lean... hmmm!

Thanks for any advice, sorry this was such a long post!
-rr
.
 

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good solution

I feel your pain, i had a **** of a time with the mixture on my 240. I finally broke down and bought a Coulourtune engine analyzer for 60 dollars from eastwood, they are also in the victoria british catalog. These things are awesome, after synchronizing my carbs i used the colortune and got excellent results. I cant imagine not owning one now!!

This is a clear spark plug that screws in the sparkplug hole and allows you to see into the combusion chamber, once the flame is bunson burner blue, the mix is just about or perfect. This is so easy to use even a little kid could do it!

Hope this helps- evan

PS if you have any other questions just put up another post, im on daily.
 

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Discussion Starter #7
Re: good solution

> I finally broke
> down and bought a Coulourtune engine
> analyzer for 60 dollars from eastwood, they
> are also in the victoria british catalog.

Yeah I saw that in the Victoria British catalog, but the advertising made it look hokey, so I didn't think it'd really work. But now I know! I'll order one tomorrow morning.

It's amazing to me how much of a performance difference there can be between a funky mixture and a good one. I just managed to get it a little closer to the right setting by tweaking with it, and the next time I drove the car it seemed twice as peppy! I can't wait to get the tool and see what the thing will do when it's really tuned.

Victoria British shows it for $49.95. That's an okay price right?

Thanks!!! I can't wait to try this thing out.
-rr
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Discussion Starter #8
Re: good solution

How did you manage with the colortune?, when I tried to use one I had a lot of trouble getting the flashes consistant unles I reved to 2000-3000rpm and this made it hard to get a good mixture setting. I found at idle the flashes seemed intermittent in fact I took it back and got a refund. How does yours work I'm wondering if I had a faulty unit
thanks howard

> I feel your pain, i had a **** of a time
> with the mixture on my 240. I finally broke
> down and bought a Coulourtune engine
> analyzer for 60 dollars from eastwood, they
> are also in the victoria british catalog.
> These things are awesome, after
> synchronizing my carbs i used the colortune
> and got excellent results. I cant imagine
> not owning one now!!

> This is a clear spark plug that screws in
> the sparkplug hole and allows you to see
> into the combusion chamber, once the flame
> is bunson burner blue, the mix is just about
> or perfect. This is so easy to use even a
> little kid could do it!

> Hope this helps- evan

> PS if you have any other questions just put
> up another post, im on daily.
 

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107,695 Posts
Discussion Starter #9
Re: good solution

How did you manage with the colortune?, when I tried to use one I had a lot of trouble getting the flashes consistant unles I reved to 2000-3000rpm and this made it hard to get a good mixture setting. I found at idle the flashes seemed intermittent in fact I took it back and got a refund. How does yours work I'm wondering if I had a faulty unit.
thanks Howard

> I feel your pain, i had a **** of a time
> with the mixture on my 240. I finally broke
> down and bought a Coulourtune engine
> analyzer for 60 dollars from eastwood, they
> are also in the victoria british catalog.
> These things are awesome, after
> synchronizing my carbs i used the colortune
> and got excellent results. I cant imagine
> not owning one now!!

> This is a clear spark plug that screws in
> the sparkplug hole and allows you to see
> into the combusion chamber, once the flame
> is bunson burner blue, the mix is just about
> or perfect. This is so easy to use even a
> little kid could do it!

> Hope this helps- evan

> PS if you have any other questions just put
> up another post, im on daily.
 

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Here you go- RobRoy and Howard

Heres the lowdown, i too paid 49.95 for the Colortune(this seems to be fair market price). I had no trouble setting my mixture with the colortune. The problem I have is that my tach isnt working so getting it perfect is tough. I highly recomend timing and syncronizing carbs first!! The one thing i didnt mention was that I have a crane HI-6 spark box and the PS91 coil, i am getting an extremely hot spark. This has made my Z easier to start sometimes too.

Howard: I dont know how well this works with stock ignition. I am assuming that you have one. I had a hard time setting the mixture too, but found it easier once i had properly set the carb synchronization and messed a little with the timing (I have an isky cam and noone seems to have a cut and dry setting on the timing).

I hope this helps you guys and good luck- Evan
 

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Discussion Starter #11
> Yesterday I put the carbs back on and tuned
> it. It seemed
> smooth and nice so I took it for a test
> drive, where it spuddered
> and resisted with about 1/4 power. Blah! :)
> Right at first
> it seemed like it was doing okay, but it got
> progressivly worse
> until I could hardly make it up my driveway.
> I was sure something
> inside one of the carbs had come loose... so
> I got a big light
> (it was dark by then) and took both of them
> off to get them
> in my kitchen where I could disect them.

> Everything looked fine inside, except for a
> fuel leak that I hadn't
> noticed before near the fuel bowl. (Which
> was remedied with a
> new washer from a carb rebuild kit.) So not
> really knowing
> what else to do, I set all the tunings back
> to the starting point
> and put the carbs back on. It started with a
> little hesitation
> and cranking, and ran pretty roughly.

> I read in a SU carb book the night before
> that there's a little
> button on the outside of the carb that you
> can press up on
> to manually lift the piston. It said in the
> book that that's a
> way to tell if the carbs are running with
> the right mixture
> or not. It said that if you press in the
> button between 1 and
> 2 mm, then it'll speed up if it's rich, and
> slow down if it's
> lean. If it's just right, it's supposed to
> speed up just a tiny
> bit.

> So, knowing that, I pressed the buttons, and
> the engine slowed
> way down! (Indicating a lean mixture!)

> The Haynes manual says to turn the mixture
> nuts until they seat
> and back them off 1/2 to 1 turn. (And you
> said in a earlier
> post that 2 turns is the right distance...)
> Then the Haynes
> manual says to *tighten* the nuts 1/8
> at a time evenly until
> the smoothest and fastest idle
> is obtained.

> Well, I had taken your advice and backed
> them off 2 full turns
> before puttin' them on the car, and it was
> still running too lean!
> (According to my test.) By looking at the
> machine, I gather
> that tightening the nut leans the mixture.
> That's right isn't it?

> So I backed the nuts off towards a richer
> mixture and the idle
> started to smooth out! I don't really know
> how much I backed
> the nuts off after the initial 2 turns...
> but my guess is another
> 2 turns! I just kept backing them off a
> little bit and trying my
> mixture test that I found in the SU book.

> Finally after all those turns, pushing up
> the button made the
> idle increase slightly.

> I ran it after all that, and it had plenty
> of power again and
> didn't hesitate or studder anymore, but it
> got about 10 MPG
> and stank of gas fumes somethin' terrible!
> Once again, they're
> way too rich!

> Does anybody know of a better way to adjust
> the mixture
> nuts so it comes out right? If I went
> according to the Haynes
> manual, the engine would run *way* too
> lean... hmmm!

> Thanks for any advice, sorry this was such a
> long post!
> -rr
> .

I guess I should have told you that I have not started my engine since I rebuilt the carbs. I have just finished rebuilding my engine and should be ready for its first start in a week. I am sorry if the info wasn't useful. Let me know how the colortune system worked. I may be needing to use it soon.

I am also thinking about buying a motorcycle carb manometer. I hear they are much better for syncing the carbs. Have you heard any info on them?

later
 

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Discussion Starter #12
> I am sorry if the info
> wasn't useful. Let me know how the colortune
> system worked. I may be needing to use it
> soon.

Oh the info was totally useful! I didn't mean to say that the carbs performance didn't improve, I just couldn't figure out the right mixture to set it at. Your advice about how to adjust the needles led to an awesome idle! It purrs silently and smoothly now.

I ordered the colortune thing this morning from Victoria British. They're in Kansas and I'm in California, so it'll take about a week and a half to get here.

That's okay though, because I just took my Z for it's last ride. I just finished clearing out a 4 car garage and have everything organized, so I'm going to begin it's restoration.

(I'll still try out the colortune though, before the engine's out.)
:)

> I am also thinking about buying a motorcycle
> carb manometer. I hear they are much better
> for syncing the carbs. Have you heard any
> info on them?

Nah I've never heard of them. The syncing part seemed to work pretty automatically for me though with my Uni-Syn flow meter. It acted a little fishy, but all the bad symptoms of unbalance went away afterwards.

Thanks and type to you later,
-rr
.
 
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