Nikki Modification finally

Engine related articles specific to induction (carby, EFI etc.)
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geminilover3236
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Post by geminilover3236 »

Ahh yer mate, well definitely scour this forum as you will find all the information you need. I have learnt most of what I know on here and my gem goes pretty sick. I'd recommend trying to find some spare Nikki's that you can use for parts.
l8nytalumni
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Post by l8nytalumni »

this thread is very helpful bro. just got mixed up about the vacuum and mechanical on the secondary. is there really a difference? because i also tried the mods posted by troyrotor but i still have the diaphragm,linkage and the spring just in case vacuum is better. :)
geminilover3236
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Post by geminilover3236 »

G'day mate, yer, I was using mechanicals for a while but it started to piss me off. carby is off the car currently, going to rebuild it again and modify the vacuum secondaries so they open a tad sooner.

Basically, all you have to do is find a spring that is a tad lighter and chuck that in and just make sure that when the secondaries are full open, they are actually fully open.

I'm going to hit up my local carby shop and see if they can supply me the spring I'll need.
l8nytalumni
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Post by l8nytalumni »

thanks for the info bro. what if we cut the spring shorter for the diaphragm?
by the way, this is what i did

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i tied the lever for the secondary butterfly and put a srew to adjust the timing when i want it to open.
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the screw is now visible in the pic.
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do we have the same carb? i'm in the philippines bro.
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stock g161 of my 1979 isuzu kb.

good day to you bro!
troyrotor
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Post by troyrotor »

it is the same carb.

when i did mine i found it worked awesome on my car. geminilover3236 has my modded one at the moment and he said he didnt like the machanical secondaries. so may be something more to do with the timing curve and jetting.

i like your idea with the timing screw but i found i needed the full travel. if i had a little screw in there the secondary would not have completly opened at full throttle.
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geminilover3236
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Post by geminilover3236 »

Yer, I think cutting the spring shorter might do the trick. as it is fairly compressed already. So we shouldn't need to lengthen it again.

Our setups look exactly the same. I never added in that screw that allows it to open up sooner. Because you dont really want to be opening the secondaries until about 2500 - 3000rpm anyway as there just isn't enough suction from the engine.

Have you trialed the setup yet, how did it go?
geminilover3236
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Post by geminilover3236 »

Sidenote; Troy,

I chucked my old modded nikki on the paddock basher on sunday with a stock cam and supposedly stock dissy and it went completely insane with stock jets. Hitting valve bounce in it, barely even noticed the mechanicals coz it reved up so quickly. didnt have an exhaust at all though
l8nytalumni
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Post by l8nytalumni »

@troy

i really appreciate this thread. i've learned a lot since i'm a newbie.
nice work.
by the way, about the screw adjustments, before i installed it i made sure that the secondaries completely open at full throttle and it doesn't open too early.
l8nytalumni
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Post by l8nytalumni »

geminilover3236 wrote:Yer, I think cutting the spring shorter might do the trick. as it is fairly compressed already. So we shouldn't need to lengthen it again.

Our setups look exactly the same. I never added in that screw that allows it to open up sooner. Because you dont really want to be opening the secondaries until about 2500 - 3000rpm anyway as there just isn't enough suction from the engine.

Have you trialed the setup yet, how did it go?
it went pretty well on mine. i can feel the kick compared to the stock.my only issue is that if i suddenly max the throttle it sounds like it's flooded. but if i do it slowly to full throttle it works fine.
do i need to check my dizzy? problem is i don't know how to adjust it. :(
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troyrotor
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Post by troyrotor »

all good mate, its good to know people are trying it instead of buying a weber or paying someone to do it.
sorry i just had another look at the screw, i see that it just reaches full open earlier. good thinking.
if you are having toubles bogging down with mechanical secondaries when you flatten it. muck around with the accelerator pump timing and try to make the volume of the pump larger.
the main reason it will stutter is because of the huge amount of air and harldy any fuel compared to what the carby was designed to do.

hey segway thats awesome maybe thats why it went so well on my car as ive never had a restricting exhaust. i first registered the car with extractors only. the road worthy bloke said i had a small exhaust leak hahah
you should try the purple carb on the basher and see if it hits boost like i said hahaha
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luke20
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Post by luke20 »

My car doesnt hit Boost. It only hits VTEC YO.
I've joined the dark side.......... Toyota AE86.

Also bought my Gem back... awwwww shieeeetttt
l8nytalumni
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Post by l8nytalumni »

[quote="troyrotor"]all good mate, its good to know people are trying it instead of buying a weber or paying someone to do it.
sorry i just had another look at the screw, i see that it just reaches full open earlier. good thinking.
if you are having toubles bogging down with mechanical secondaries when you flatten it. muck around with the accelerator pump timing and try to make the volume of the pump larger.
the main reason it will stutter is because of the huge amount of air and harldy any fuel compared to what the carby was designed to do.

so that's why it sound to me like it's flooded but it is actually lacks fuel? did you use the acc pump for the g200 on your g161 carb?
troyrotor
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Post by troyrotor »

i really dont know what i used. i had a random carby that was stuffed together on the car i bought.
earlier in the thread is some info on making the pump work better with a bigger amount of fuel.

yer thats right not enough fuel
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l8nytalumni
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Post by l8nytalumni »

troyrotor wrote:i really dont know what i used. i had a random carby that was stuffed together on the car i bought.
earlier in the thread is some info on making the pump work better with a bigger amount of fuel.

yer thats right not enough fuel
thank you, troy. okay, i'll try to figure it out and find a spare carb.
geminilover3236
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Post by geminilover3236 »

Oki doki boys,

Troy, your purple carb is now back on my engine with some modifications.
It has vacuum secondaries now. I cut 2 coils off the spring that was inside it.
And, I can see the use of that screw now. When I put it all back together the secondaries weren't opening completely so I added a screw in there and it did the trick. However, an unseen benefit was that if you open it right up, it comes back around and cracks the secondary open a tad. So you get this little boost before the vacuum kicks in to open them up. Running stock jets as I think they are fine. stock being 113 and 175.

Goes hard as, plenty of down low, however had a couple little stutters when cruising which Ill figure out later, dont think its pinging.

Had to use a different carby hat though as the one you painted troy was starting to flake.

Had a look at your fuel pump and noticed that its way smaller. like where you can normally see the spring, you can barely see it on yours. I didnt investigate much more than that, just put it back together. The one in my paddock basher delivers way to much fuel and will flood the engine if you pump the pedal once before starting.

But Im a beliver in vacuum secondaries now. Maybe another coil off the spring though to get them opening a tad earlier. Flows heaps better though, even changes the exhaust note.
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