Nikki Modification finally

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

i used one of those ties you get on your backery bread. The stuff you tie tomatos to streaks in the garden with. I just stripped off the plastic
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dbart1961
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Post by dbart1961 »

I was going to do this mod but when I pulled my old Nikki out of the cupboard and saw how small the bores were I decided not to bother. Hard to imagine you can get the same power from those little bores compared to a Weber.
Regards, Dave
troyrotor
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Post by troyrotor »

i ould put money on mine over 32/36. i reckon it would flow better now. remember nikki's are used on alot of cars for a reason, they are good
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luvtheG180
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Post by luvtheG180 »

are you running te same carbs as the US G series mikunis? or is there an entire different carb setup for Au domestic isuzu engines
troyrotor
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Post by troyrotor »

we use a 2 barrel nikki carburetor made by stromberg. what are these mikini ones like? any pics?
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luvtheG180
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Post by luvtheG180 »

[quote="troyrotor"]we use a 2 barrel nikki carburetor made by stromberg. what are these mikini ones like? any pics?

i havent done enough posts to post pics i will fix that real quick

as far as performance i have gathered that they aren't much of a powerhouse flowing carb, often swapped out for the weber carb kits. i haven't been able to run it myself since im in the process of swapping out the bad engine from my luv that was in it when i bought it and putting in the new one i bought.
the luvtruck.com forums have alot of information on the g series engines and various components.

as far as i know mikuni is a japan based company, i know they also make carbs for motocross bikes and street bikes.
Last edited by luvtheG180 on Sun May 23, 2010 7:30 pm, edited 1 time in total.
luvtheG180
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Post by luvtheG180 »

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luvtheG180
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Post by luvtheG180 »

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troyrotor
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Post by troyrotor »

thats the same carby we have, a few differences with choke and maybe some other things but the main body is identical.

anychance you would be able to measure the barrel sizes so we could confirm
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luvtheG180
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Post by luvtheG180 »

troyrotor wrote:thats the same carby we have, a few differences with choke and maybe some other things but the main body is identical.

anychance you would be able to measure the barrel sizes so we could confirm
the differences could be because it is the carb from a 1980 chevy LUV (isuzu KB in AU i believe?) some modifications may have been made for different power specs in a truck vs a gem although it is still the G180 engine
im working on getting the specs on the carb
luvtheG180
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Post by luvtheG180 »

i was told its 23/30mm but i am not positive since there are several mentioned
i was told the carb is a mikuni DCH340 which is also used on early model Datsun trucks with the L18 engine
the specs i have found for it are
venturis: 23/30mm
main jets fuel/air: .975 .65
secondary jets: 1.70 .60
T-valve: 30/34mm

however there is also the same named model for the L20 with different sizes
http://dimequarterly.tierranet.com/arti ... guide.html
about 3/4 of the way down the page is the table of sizes
beevus
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Post by beevus »

so, a few weeks ago, i took an air horn from a 2 litre to work.

in my lunch break i pressed out the venturis removed the emulsion tubes cleaned the jets in thinners and then blew them out with air and then blew through them with my mouth to check they were clean. i then removed the unnecessary arm from the emulsion tubes, and pulled out my needle files and polished the outside of them for smoother air flow.

i also spoke to a guy who builds bikes for the southern classic and has done a few carbs, he said not to polish inside your emulsion tubes or venturis as the casting marks will aid emulsification.

i removed the venturis because i was going to re machine them but at the time the lathe at work was up the s*#t, but i fixed it today so who knows.

anyway, i've been running a 1600 carb for a while now and i cracked the sads cuz it was just not running right (i have a 2 litre btw).

it took one hour, while the carb was on the car i pulled the top off, swapped the emulsification tubes, fuel pump thingo and jets.

well, it ran better for sure, and i did definatley notice a power increase. not a huge one, but significant enough.

i didn't bother with the mechanical secondaries as opening the secondaries premarturley is just a waste of petrol, combined with a huge loss in power. so i figure why bother having to be aware of when i want to open the secondaries when i can have a machine do it for me automatically about when they need to open, and probably more accuratley than i would as i would probably end up being too eager.

cant be certain it was worth it as i changed the jets at the same time, but i would say it prolly was, even though all i did was remove that useless arm.

just as a note, part of the reason sterling got such a huge cfm rating was because he compromised the vacuum created by the venturis by making the narrower part slightly wider. he admits this and probably says it in a more reader friendly way.

also if you look at the venturis they have curved sides, so the angle of entry or exit is not constant. i do believe this may be better than machining harsh angles on the venturis.

hope some of my rant helps,

Cheers,

-Beevus
troyrotor
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Post by troyrotor »

i know what you mean with the mech secondaries, its pretty easy to just put your foot down and flood your engine. im pretty sure it does actually work better as the vacuum setup has a bit of delay im not sure on the technical side but for some reason its supposed to be better.

as for the shape of the venturies, i left mine stock i just cleaned them up to get rid of casting and glued on s*#t from over the years. reshaping them is so complicated and getting it wrong is much easier than getting it right so i thought stock would be fine.

as soon as we get a list of jets to use we will be very happy
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troyrotor
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Post by troyrotor »

oh and to mr washington i think the carbi we use would be the DCH 340 L18 carbi. with the 30/34 openings.

it says in the table that the total area is larger than the 32/36 weber??

interesting
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luvtheG180
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Post by luvtheG180 »

troyrotor wrote:oh and to mr washington i think the carbi we use would be the DCH 340 L18 carbi. with the 30/34 openings.

it says in the table that the total area is larger than the 32/36 weber??

interesting
yeah sorry for that little mixup... little bit too much of the "green tobacco"
anyway
that would make much more sense. im curious to see what type of modifications can be made to the Mikuni (or Nikki) to make it flow and perform more like a Weber. a lot of the idea from the beginning of the thread seem like good options but some are a little more on the overkill side i think?
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