Anybody know where you can buy larger main jets for a Nikki carb? I'm hoping to find something like 180-190 jets for the secondaries.

 

Mazdatrix.

A word to the wise though: 180-190 for sec main jets might be a little too much for a 12A (is it streetported?). Don't ask me how I know.

 

I know how you know!!! Do holley jets fit? I remember hearing somewhere that they do...

 

Thanks for the info man! Stock is 160, and she seems a bit lean at the high end so I'm looking for something a bit bigger. Another forum member suggested 185 or 190 but I wasn't real sure (neither was he though).

The engine is a stock 12a with full RB exhaust and some other stuff you can see in my sig. Just looking for a little more go power. Thanks again for the info.

 

at most i would only go up to a 170. get a better pump and regulator. that's usually the first thing you do to get more fuel up top. your fuel pump is probably getting tired and just isnt doing the job.

 

Not really convinced that its a lack of fuel getting to the carb, it doesn't sputter or anything like that. It just seems like its running lean at higher rpms, but I really have nothing to base this on I guess.

Fuel filter is good, and the carb is finally all cleaned out. It just seems like it used to go to the redline so fast that you'd hit the damned buzzer before you had a chance to shift. Now it seems like it takes a lot longer to actually get near the redline.

But like I said, no chugging or sputtering. Power is smooth all the way to the redline, but there just doesn't seem to be a whole lot of it. Got to find more ponies!

 

Only on Sterling carbs. I think.

 

I hear you. Well, first of all, to get the obvious and basic out of the way, you want to run lean at high rpms. Not too lean, but leaner than at low/mid rpms. That said, you can go ahead and try what bigger jets do. But going 4-6 sizes up in jets is not recommended. Try one size up, maybe two. Also, remember that small pressure differences can affect mixture as well. I hope you have an aftermarket fuel pump and regulator with a good quality guage. Small pressure changes is a part of tuning. Then you have the accelerator pump, which also can be 1) adjusted and 2) modded for a bigger squirt.

My $0.02. Sterling can probably give you better advice, and he would probably tell you "leave yer secondary jets alone!".

 

Fuel pressure eh?

It has been my understanding that as long as there was adequate fuel in the bowls, then the carb has what it needs. If the fuel was draining from the bowls at a higher rate than it could be replaced, then I should be able to feel it sputtering or bogging or something along those lines.

Either I'm missing something here, or fuel pressure is not the issue. Please correct me if I am wrong... Thanks.

 

Here's some reading for ya.

http://www.yawpower.com/fueldel.html

 

Both volume AND pressure are important. You cant see whats happening in the bowls while your driving. A simple clogged filter can cause hi rpm power loss due to fuel starvation. And it wont necessarily manifest itself in the way you described. It would depend on the severity of the starvation.

Upgrade the pump and get an FPR and a gauge.

Oh and 180-190's are too big for that carby.

Some of Sterlings writings.
http://www.sterlingmetalworks.com/main_circuit.html

 

Thanks Chief. This will be next on my list then...