Hey all!

I need a little help diagnosing an issue I've run into with my nikki, I had some raw fuel leaking onto my engine so my dad and I pulled it off and did a rebuild on it.
We installed it yesterday and couldn't even get the car to start. This morning with a freshly charged battery and the idle adjustment screwed in a bit we were able to get it to idle. It sounds kind of rough and won't idle anywhere under around 1,100 or so. When I try to rev it it gets to about 2,100 before it seems to break up and it won't rev any higher.

We've checked the timing and replace the plugs, we know we have spark there. Adjusting the idle mixture screw does not seem to do anything to the way the engine sounds or revs. The only thing I can guess is I have a sizeable vacuum leak somewhere.

Oh knowledgeable gods of the 12a, Can you save me.

 

Definitely sounds like a vacuum leak. Retrace all the hoses, it's easy to forget one or more. Do you have the rats nest? After checking the hoses, go around and lightly spray carb cleaner around the carb to see if you hear the idle change.

After that you will have to start digging into the rebuild, not fun.

What rebuild kit did you use? Did you replace the needles? The newer ones can be junk.

 

Rats nest yes, the kit we used was the Hygrade/Standard kit. Yes we used the new needles. The float levels look about right, perhaps a hair lower than halfway but definitely in the ballpark.
I'll pick up a bunch of vacuum line and replace as much of the 35 year old lines as I can.
Should I be concerned about the gaskets around the spacer/vacuum block under the carb? Like if my carb is tight enough to prevent any leaks there? We tightened it down fairly well so I don't think that would be a problem but I want to eliminate any possibility.

 

Did you remove the gasket from the plastic plate under the carb or use the one in the kit? The plastic piece under the carb has a built in gasket and should not be removed or replaced. Just looking for possible causes of a leak.

 

Oof, I bet that's it, we removed the glued on gaskets and used the ones that came in the kit. And ouch, a new one costs $150.

I'd say that's probably my most likely culprit. I may have to order a new one : (

 

Place a Wanted To Buy in the For Sale section.

 

I hope you saved the old needles and seats as well. The new ones will cause random flooding and frustration.

 

I did, I’ll save them for the future if I have issue. Although I suspect someone has been into this carb before because a number of things were just not quite right. So they may not be the originals anyway

 

if it is running lean (red insulator spark plugs) and getting extra air from somewhere, check for a vac leak, you could try bleeding propane gas into the carb. if that improves things, then attach a hose to the propane gas bottle, and poke around. when the engine sudden runs better, you found your vac leak

 

UPDATE:

I ended up buying the new carb spacer... and no luck. Same symptoms.
All the vacuum hoses in the rats nest have been replaced with fresh ones, so a vacuum leak from there is probably unlikely at this point.

Just out of curiosity we pulled the idle mixture screw, and it looks kind of bent. Would that cause any serious leaks? It didn't take much to turn it.

Now running down the list, Altitude Compensator? The rebuild kit didn't come with a new gasket for that so we reused the old one. Would a leak there cause a major problem?

Or at this point are we most likely dealing with an internal carb issue? The carb was a little grimy on the outside but pretty clean on the inside. We we took out all the air bleeds and cleaned them and reassembled the carb.

Help me!

 

You don't say how you cleaned carb,at this point it seems you'll need to take carb back off and go through it thoroughly. I would soak all parts possible in chem-dip and rinse with water followed by aerosol carb cleaner like Berkible 2+2 gum cutter followed by compressed air to be sure all jets and air bleeds are clear and All the passages in carb are clear.
Be sure to blow thru passages in throttle plate(with mixture screw removed) Float level should be 1/2 way up windows on each bowl-be as exacting as you can with this,it affects many conditions from idle,hesitation on acceleration,steady cruise and full power.

 

All parts were removed and soaked in chem-dip.
And then the passages where hosed out with an aerosol carb cleaner. I’m fairly confident that we did a good job but at this point it might be a necessary to get into it again and double check.

I just checked with my dad and the little bit gas that’s in the tank right now is the 91 he uses for the lawn mower. That wouldn’t be a huge deal right? I know I should be tuning this on 87.

 

How old is it though? If its fresh shouldn't be a huge issue.

 

Less than a month, he just topped it off a few weeks ago. Now that I'm thinking it through a little farther, I fairly confident that my fuel pump is doing it's job, as it was running well enough after I replaced all the hoses but before I took the carb off. I just want to drive my car again : (

 

Have you tested the compression?

 

I have not, but this was a running driving engine three weeks ago, and the only difference between then and now is the carb has been removed and refreshed.

Things to mention, I noticed the shutter valve was not hooked up to anything when I had it off, it’s now hooked up to the diaphragm/solenoid it’s supposed to be.
there was no check ball in the accelerator pump nozzle, there is now.

I just had it running again and before the engine and carb had warmed up the idle was inconsistent from 1250 to 1400