What could i do to make it easier to take off with my nikki? In other words, what could i do to make it easier to take off from a stop when i go to stall the clutch and go. I've tried Raising the idle. I have it idling at 1600 rpm on my monster port 12A (when it's warm that is, it's easier to take off warm). And it seems to be good there, i think anything over 1700 would be too much, i like it at 1600 rpm.. I'm just wondering what else i could do to help takeoff or maybe could there be something wrong with my nikki? I just rebuilt it a week ago.

Thanks,
Crispin

 

Possibly adjust/mod the accelerator pump. Search the forum for that and you should find a thread done by Sterling showing how to do it. Aside from that, get smaller ports.

 

How do you have your vacuum advance hooked up? Do you still have the rats nest?

If no rats nest:

If hooked up to manifold vacuum, then it will retard the ignition resulting in lower engine speed and reduced torque, right when you need those things most.

If hooked up to ported vacuum, then it will advance the ignition when you first start to open the throttle, resulting in increased engine speed and more torque.


Other than that, just verify that your accelerator pump is not leaking, and is squirting a healthy shot into the carb when you work the linkage...





.

 

Not the ports, although they're huge it took off great when i ran my weber.

But, that's not the issue. It seems that when you give it just the slightest bit of throttle it's not squirting fuel but's the butterflies are opening up. But if you give it just a little more throttle it starts to squirt fuel. So, there's something wrong with my accelerator pump. Not the pump itself but whatever is triggering it to pump fuel. It has to be worn just the slightest bit, because when you're giving it anymore then a hair throttle everything works perfect all the way to full throttle all the way through the band.

 

Oh no. Not again. Where's Purple82?

 

Oh God, let's not go through all that again!

To the OP: have you checked the accelerator pump? Just pull the airfilter off and move the throttle linkage. You should see two healthy squirts of fuel getting shot into the smaller (primary) barrels of the carb when you first start to move the linkage.

And you didn't answer my question about your vac advance either...

 

I have checked the accelerator pump, as i stated. It squirts fine, but not when you're giving it just that fraction of throttle, like when you're trying to take off. Otherwise, when you're giving it any more throttle then just a very slight fast idle it's great.

Sorry i didn't answer your question. I didn't understand what you meant.
Vacuum advance? I'm not running the rats nest. But i'm interested to know what the difference is in Ported and Manifold Vacuum..

Appreciate the help guys.

 

Ported goes to the spacer under the carb, and only sees vacuum when the throttle is opened. Manifold is straight to a port on the intake manifold and sees vacuum at all times. Check your accelerator pump linkage and make sure everything is tight. How fresh is your carb? Rebuilt recently?

 

I have it setup manifold right now, i'll switch to ported and give it a try.

I just swapped my weber for this nikki a week ago. I got it from a local friend who owns/maintains a rotary shop. I rebuilt it that day and put it on. I'm sort of 'new' to the nikki, but not new to carburetor tuning. I've had my weber on my car for almost four years now, and after only having my nikki on for a handful of days i absolutely love it. I just need to do some fine tuning like i did on my weber to get it right.

The accelerator pump linkage is good but could be better. It's something that i custom did myself(all of the linkage including throttle that is), so that'll be what i'll work on next with the ported advance.

 

Changing it to ported vacuum has really seemed to help.

 

just food for thought... stock Nikki will not flow enough CFM to support a monster port. Wouldn't be causing your issue, but nonetheless it is a bottle neck.

 

Not near enough. But it's my DD. So it's a bit more logical.




In regards to other nikki problems i'm having, now that i've driven it extensively i'm not sure if the Ported Vacuum setup helped much, it really didn't change anything at all. But, i noticed that it doesn't stumble at that fraction of throttle whenever the engine temp is above 180ish.
So, i'm still confused on what could be causing. I know that the accelerator pump linkage isn't helping though.

Also, in the higher gears- that is 3rd and 4th gear whenever you're full throttle above 5000 rpm the power doesn't seem smooth. It sort of 'pulses' but it's not too abrupt.
Any other ideas? I'm stumped.

 

The tip-in stumble sounds like the accel pump linkage is a bit out of adjustment.
Vacuum advance should never be hooked to manifold vacuum, regardless of what purple82 has said in the past.....repeatedly. Doing so makes it a vacuum retard, kinda like suggesting it does............
The "pulsing" doesn't make sense. Can you give a bit more detail about what is going on? There are numerous items that can cause this, but more details are needed to have an idea where to start looking for the answer.

 

It only does this when the secondaries are open, i think anyways; it's mainly above 4500 rpm i'd say (i'm running vacuum secondaries still BTW.) It's not nearly as bad or not noticable at all when at WOT in 1st and 2nd gear but when in 3rd and 4th gear its very noticable. The power is just not smooth, it's there and then for just that half a second at WOT it'll fall off and then come right back in on and off all the way up to 7000 rpm at WOT. It's not sputtering. 'Pulsing' is the best word i can use to describe it.
If this doesn't spark any ideas i'll try to get a video of it when i can. Although you won't be able to see/hear it as well as you can feel it.
Could it be a vacuum leak? i've never had one before, and am pretty sure i don't have one now. But, could that contribute to any of my trouble?

I'm trying to explain things the best i can.
I really appreciate all of the help guys.

 

Kinda sounds like either a fuel supply issue, or ignition issues.
In the lower gears, it may not be as noticable, since the load is lower on the engine. Or, it could be a fuel starvation problem that doesn't manifest itself until after getting into 3rd/4th.
Check for decent fuel supply. Are you using a stock or aftermarket pump? Recent fuel filter check/change? Still have the fuel return line hooked up? All these can be factors. Heck, even the inlet screens in the carb could be partly blocked, restricting the fuel flow into the carb, or the floats set a hair too low.
Then, there's always the potential for ignition weaknesses. Old plugs/wires/cap/rotor just not capable of providing adaquate spark under hard accel.

Like I said, many variables to contend with. Any or all of these could be causing this type of issue.

 

Exactly what i'm thinking, it will be noticable in the lower gears. Which is where i'm having the problem.
I'm pretty sure my fuel pump is good. It's just the stock pump, haven't changed it in the four years i've had my car.. I've thought about going aftermarket.

The return line is still hooked up.
I'm not running inlet screens in the carb.
I'm almost 100% sure the floats are right. I've spent every day since i put the carb on getting them just right. I'm almost 100% sure the ignition is good too. I'm running good plugs, that have less then 1000 miles on them. Just put on Wasted Spark ignition about 2 or 3 months ago and added new wires with it and all new coils except for trailing.

I just adjusted my accelerator pump spring after this last drive. I loosened it up a whole bunch(approximately 15 turns counter-clockwise), it was as tight as it could go. I really think that will help.
The other thing i did was pulled apart the secondary accelerator pump(since i'm still running vacuum secondary) and cleaned it up and sprayed alot of carb cleaner down the little hole on the side of the carb for the secondary accelerator. (although i couldn't find a little red stray to spray with so i don't know how good of a job it did.) So, the next thing i will do is drive it and test to see how it drives, then i'm going to try and get a new secondary accelerator pump diaphragm and spring. And a new bottle of carb cleaner with straw so i can clean in there good. SMW said that's pretty important to make sure whatever is in that hole is clean..

 

Just for my own info, when you guys say you are using "ported" vacuum, where is that coming from? I understand that "manifold" vacuum would obviously come from the intake manifold. But what is the source of "ported" vacuum? Can someone explain in layman's terms what makes the two different?

The reason I ask is that I'm going to be using an old Rx-3 intake manifold, coupled with a Sterling carb on my 85 GS. Using the Rx-3 manifold will cause me to lose the black phenolic carb spacer, because the intake manifold is slightly taller. I have to get rid of it, so that I can still fit everything under the hood. I need to find a way to get ported vacuum still without using the black phenolic spacer.

What is the source of ported vacuum?

Jamie

 

Well, I'm not running the black heat shield spacer and i have an 84-85 mani and an 84-85 carb. I just took vacuum from two of the small vacuum ports on the drivers side carb base. Or you could use them from the passenger side carb bass. There is two on that side also.

 

You may want to make sure your throttle valve's aren't hitting the manifold runners. It's my understanding that the valves will hit the runners and not open fully.

Glazedham, ported vacuum only see's a signal when the throttle plates are open. The spacer has channels that go to ports on the bottom and top of the spacer and match up with ports on the manifold and carb. I have no clue which ports got to either, but it's a hunch that the vac advance would go to the carb.

 

So as long as long as I only see vacuum when the throttle is open then it doesn't matter what I connect it to?

 

Basically, yes.
Ported is the common term used, but technically, it's actually venturi vacuum. It's drawn from above the throttle plates, so it is only present when the throttle plates are opened. It's all part of the venturi effect inside the carb.

I don't know exactly how a person would go about connecting to the venturi vacuum without the black spacer. The vacuum port for the advance is contained on that spacer, and goes into the base of the carb.
It was easy to do on my SE. The RB intake accepts the edelbrock carb, and the carb has a port specifically made for the vacuum advance.

 

The one way I know of to tell for sure is to hook up a vacuum gauge and see which ports show vacuum at idle and which don't. Some of the nipples at the base of the carb are ported, but some are manifold.

I believe it is the nipple farthest forward that I use (can't check right now).

 

I've got all my 'issues' solved. It was honestly all in the AP adjustment. I ended up modifying it a little bit. It wasn't fully closing at idle/off throttle. It still stumbles just a tad. But I'm pretty content with it, there's still a lot of other things I plan to do that will help my nikki.