LizardFC

iTrader: (1)

So you've just pulled the Nikki out of the car for the third time since you rebuilt it and you're stumped on what went wrong this time. This might help you narrow it down a little. You can test to see if the main fuel jets are flowing fuel even if you have the carburetor sitting on your garage floor. All you need is a "stand" to set the carb on and an air compressor.



My "stand" consists of a roll of masking tape with a cloth over it. You want something that will allow the linkage to sit off of the ground, and also have clearance in the center for the butterflies to open. A couple bricks or 2X4's with a gap in the middle should work too. The cloth is there to soak up fuel that sprays through the carb. That way you don't end up with a flammable puddle on the floor.

I think it's easiest to do this with the air horn off. First, fill the bowls with gas or a carb cleaner (I used Seafoam). You just need enough in there to completely submerge the main jets:



Now, check the accel pump by quickly opening the primary butterflies. You should see a stream of fuel shoot from either side of the nozzle into each primary venturi:



Next, hook a blow gun up to the compressor. You won't need much pressure - 10 PSI or so should do. You just want to simulate airflow through the carb. Open the primary butterflies all the way and hold them there. Aim the blow gun directly down the center of one primary venturi and spray air through it. You should see fuel spray out of the tube in the center. Repeat the test with the other primary venturi. To test the secondaries, twist the secondary shaft to open the secondary plates and repeat the procedure. You should get a sizable spray of fuel from the secondaries because of the larger jets:



If you got the accel pump and all four venturis to spray fuel, then congrats! You've proven that the fuel jets are clear and the main and transition circuits are working. This doesn't test the idle circuit, so it doesn't mean your carb will bolt up and run. It does, however, rule out clogged jets which is a root cause I see on a lot of Nikki issue threads. And you didn't have to spend all the time installing it to find out!

Crispin38

iTrader: (3)

Awesome post. +1

Glazedham42

iTrader: (4)

I see you trimmed your booster venturis. Looks good! I've been working on mine. Just about done with them. Fun project, although rather nerve wracking at times.

DivinDriver

iTrader: (15)

That's my kind of science!

LizardFC

iTrader: (1)

Thanks guys. Oh yes, much has been trimmed from that carb. Glazedham, I know what you mean about it being nerve wracking... I ruined at least 1 venturi, a couple throttle butterflies, and an entire air horn in the process of building that thing. As well as a lot of stuff I didn't need anyway. It took three spare Nikkis to build one SuperNikki

Oneiros

Sounds good. What else did you modify?

LizardFC

iTrader: (1)

Pretty much everything I could think of. I bored and polished the main venturis, polished the booster venturis, removed the choke and trimmed/polished the air horn, ground down the shafts and trimmed the butterfly screws, and removed most of the linkage. It has one cam for the throttle cable, the return spring, the teeter-totter, and the cam for the secondaries which has been tied up for mechanical operation. Much simpler and easier to work with.

diabolical1

iTrader: (3)

great work and great thread.

do you mind sharing what tools you used for this? i so wanted to do that to the Nikki i built and modified, but frankly, i was to scared to screw it up.

LizardFC

iTrader: (1)

Thanks. I used a dremel and a rotary grinder for pretty much everything. The larger bits of the rotary grinder were handy at boring the venturis. That and a very steady hand. I don't recommend trying any of this stuff on your only carb.

I'm going to do a whole thread on it possibly tonight. I just have to go through all the pictures.