Datsun Roadster Forum-311s.org

I put the new Z Therapy SU carbs on my stroker. Carbs are not my thing and I can't get them right.

I started with 15w fork oil in them. Adjusted them to 2.5 turns out. Under wide open throttle they have a flat spot in the mid-range. It's actually worse than the old carbs had. Haven't adjusted the advance on the blue tooth distributor at all.

So I changed out the oil to atf as recommended and then turned to 1.5 turns like the old carb. Seemed lean so I went to two turns. Still really flat and I continue to get the big pop out the exhaust at shut off which says rich.

I need someone who knows what to do with these things. It shouldn't be that hard I would think. Used the Unisyn on them.

But it does idle smooth now.

I would love to help you, but the commute would kill me. That being said, the instructions in the shop manual are actually pretty good if you follow them exactly.

spl310 wrote: ↑Wed Sep 19, 2018 2:49 pm I would love to help you, but the commute would kill me. That being said, the instructions in the shop manual are actually pretty good if you follow them exactly.

Which shop manual? I looked at Keith's and the Z therapy DVD but I'm missing something.

Think Keith mentions in Wiki Tech that 1600 needles tend to run rich at idle lean on top. Recommends ADQ needles for the R's. I think he has some.

nismou20 wrote: ↑Wed Sep 19, 2018 4:10 pm Think Keith mentions in Wiki Tech that 1600 needles tend to run rich at idle lean on top. Recommends ADQ needles for the R's. I think he has some.

Okay, I think I need to get hold of him. Thanks.

nismou20 wrote: ↑Wed Sep 19, 2018 4:10 pm Think Keith mentions in Wiki Tech that 1600 needles tend to run rich at idle lean on top. Recommends ADQ needles for the R's. I think he has some.

I looked at the link on here to his web site but no contact info. Not sure what name he is on here.

Never mind, I found him.

Curtis wrote: ↑Wed Sep 19, 2018 3:57 pm

spl310 wrote: ↑Wed Sep 19, 2018 2:49 pm I would love to help you, but the commute would kill me. That being said, the instructions in the shop manual are actually pretty good if you follow them exactly.

Which shop manual? I looked at Keith's and the Z therapy DVD but I'm missing something.

The factory shop manual - available on Wiki:

http://www.311s.org/PDFs/SPL311ServiceManualSML.pdf

See the Wiki for the "magic number" method for nozzles adjustment. Much more precise, and you can adjust from there if necessary.
Linda

You'll find the magic number method in http://www.311s.org/pmwiki-311/pmwiki.p ... ion.SuTech

Has worked great for me.

Dan

greydog wrote: ↑Thu Sep 20, 2018 10:28 am You'll find the magic number method in http://www.311s.org/pmwiki-311/pmwiki.p ... ion.SuTech

Has worked great for me.

Dan

I copied and pasted this in to a document and highlighted it. Thanks.

If you use this method, measure each nozzle first to see how far off you are. I was way off...
Linda

Linda wrote: ↑Thu Sep 20, 2018 2:18 pm If you use this method, measure each nozzle first to see how far off you are. I was way off...
Linda

We'll see. I would think a freshly built set of carbs would be right on but you never know. Z carbs are their first and foremost so maybe they just get them in the neighborhood. But they are pretty!

They were right on til you turned the adjustment
Linda
I'd look for vacumm leaks at the spacers too etc

Linda wrote: ↑Thu Sep 20, 2018 2:36 pm They were right on til you turned the adjustment
Linda
I'd look for vacumm leaks at the spacers too etc

All fresh gaskets.

I think that the nozzle adjustments can not be exactly determined by Z Therapy since engines are different. Therefor some tuning would be necessary. Then it is easy to mess up the balance using the " x number of turns out" method.
But new gaskets and firm tightness is one less thing to worry about
Seems a lot easier than electrical, which you are a whiz at!
Also I know that U20 carbs are different than R16 carbs, and since you have a stroker, which is closer to a U20, perhaps you need the U20 carb? I do not know the answer ..
Linda