TeamSwift

I've searched the forums looking for triple carb setups and can't seem to find the information I am looking for. I have seen set ups for 4 bangers but even the information on those is lacking. No one has said much in the way of how they rigged the carbs to work and little in the way of the important details.

I am looking for information on:

Vacuum lines:
Do motor cycle carbs have vacuum ports? Or vacuum be run from the plenum? What is to be done with the charcoal can vent line?
Would a 3 into 1 into 2 pull enough vacuum for brake booster and vacuum advance dizzy?

Fuel:
Is an external fuel pump needed to add pressure to fuel lines for 3 carbs? What pressures do motorcycle carbs run at and are fuel pressure regulators needed?

Carburetors:
Can a rack of 4 with linkages for throttle and choke. Have 1 carb removed and still function as a rack? What are the best carburetors for a G10 mk1? After a bench sync, will the carbs need to be individually tuned?

Any and all information is welcome. I found a guy locally that has a rack of 4 Mikuni's that were rebuilt by Mikuni for a damn good price.
And would like to begin work as soon as I can on this project. Just need more info before I dive in head first.

Thanks,

BBM

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1987 Chevy Sprint base 1.0 3cyl 993cc (R.I.P.)
1986 Chevy Sprint base 1.0 3cyl 993cc (Totaled)
1994 Geo Metro base 1.0 3cyl 993cc (Had to sell)
1996 Geo Tracker 1.6l 16v 4cyl 1590cc (Daily)

I will try to help with the limited experience I have from the three bikes I have owned.
74 Kawasaki H1H 500cc triple two stroke
82 Suzuki 1100GLD
86 Yamaha FZ700
74 Honda 250M Elsinor


Vacuum lines:
Do motor cycle carbs have vacuum ports? Or vacuum be run from the plenum? What is to be done with the charcoal can vent line? Vacuum ports can be in either location depending on where the manufacture decided to put it
Would a 3 into 1 into 2 pull enough vacuum for brake booster and vacuum advance dizzy?If you use a vacuum manifold, it will smooth your vacuum signal as would a vacuum reservoir.

Fuel:
Is an external fuel pump needed to add pressure to fuel lines for 3 carbs? What pressures do motorcycle carbs run at and are fuel pressure regulators needed? Most bikes use gravity feed since the carbs sit under the fuel tank. A low pressure pump and regulator would be needed. 3 maybe 4 psi should be plenty. Bike carbs are VERY sensitive to float/fuel level.

Carburetors:
Can a rack of 4 with linkages for throttle and choke. Have 1 carb removed and still function as a rack? What are the best carburetors for a G10 mk1? After a bench sync, will the carbs need to be individually tuned? Most of the bikes I have worked with had the carbs connected to "rails" to keep them indexed to each other. The throttle cable "usually" connects to a quadrant in the center of the rack. The individual carbs are linked thru interlocking "fingers" or splines on the ends of the throttle shafts. One carb can be removed from the end and not affect the others. You may have to remove an inner carb and move the outer carb in depending on how the fuel delivery is setup. The Kawasaki I had a 3to1 throttle cable. One cable at grip was split to three for the carbs. Yes they will need to be synced once on the engine and running and before connecting a vacuum manifold. As to which ones to use I cant help you there.

_________________
"If you think education is expensive, try ignorance." - Derek Bok


1990 geo metro 1.0 5 speed 3-door hatchback "herbie"
1990 geo metro 1.0 5 speed convertible "sportie"

Thanks for the reply.

So basically parts list is:

Build manifold
Buy carbs (rack of 4 or 3)
maybe a vacuum manifold or block
Fuel pressure regulator
Fuel lines
Vacuum lines
Manifold gasket

Anything else I am missing?

Also I read somewhere that there is a coolant line that runs into the stock manifold for the MK1's. Is this true? If so when building the manifold will I have to add a bung for the coolant? Or can that just be omitted?

Also could I just hack off the top of a stock manifold and just use the 3 ports of the plenum to mount the carbs? I mean that would still give me a vacuum port to work with. OR is the shape of the manifold too square to do so?

_________________
1987 Chevy Sprint base 1.0 3cyl 993cc (R.I.P.)
1986 Chevy Sprint base 1.0 3cyl 993cc (Totaled)
1994 Geo Metro base 1.0 3cyl 993cc (Had to sell)
1996 Geo Tracker 1.6l 16v 4cyl 1590cc (Daily)

Have you tightened up those three bolts holding the throttle body onto the main carb body yet?
Remember?
The ones you access by holding this

over your head?

You will probably notice an instant improvement in power, idle, and fuel consumption once those three bolts are tight again.

Once you solve your stock carburetor problems, you can get into the more esoteric issues of fuel/air mixtures and go ape sh*t on crazy fabrications for wild horsepower.

It's nice to dream; fix that car of yours!

_________________
DIY Broken Bolt Removal: viewtopic.php?f=22&t=41042
DIY Clutch Adjustment: viewtopic.php?f=9&t=48281
DIY Wheel Bearings: viewtopic.php?f=2&t=29003
DIY Shocks: viewtopic.php?f=10&t=45483
DIY Wheel Align: viewtopic.php?f=2&t=42479
Once you get the cars dialed-in (compression, leaks, bearings, alignment, brakes) swap in new rubber and glass, you've got something which should last for years!

I couldn't tell you anything about a MK1 manifold since I have never dealt with one. But in general if there are coolant passages in it you should be able to bypass with out a problem. You just have to check your water flow. You might try cutting a manifold but I think by time you get it cut short enough to be straight it may be too short to clamp boots to. If you get the manifolds with the carbs you might be able to cut the manifold flange off and use it as an adaptor flange to screw the carb flanges to. Just check the port size and shape. If you make a manifold start with a thick flange so you have enough material to grind/mill it true again. If engine is out of car and on a stand just remember it is tilted 15 degrees clockwise when looking at the pulleys.

As far as your list goes, its a good start and pretty much covers it. A little piece of advice I got along time ago from fabricator friend....cardboard, masking tape and foam board are a lot cheaper than aluminum and steel. Its easier to swallow a mistake with a cereal box and paper towel tube than a laser/plasma/water jet cut flange. Take your time and do it right the first time. Its cheaper and easier.

Have fun.

_________________
"If you think education is expensive, try ignorance." - Derek Bok


1990 geo metro 1.0 5 speed 3-door hatchback "herbie"
1990 geo metro 1.0 5 speed convertible "sportie"

Well , I have a bad news for you , you cant bypass water passages in Mk1 manifold. They are integral part of the cooling system and include thermostat housing among other things.

That's the advantage of a forum, the exchange of information, knowledge and experience.

_________________
"If you think education is expensive, try ignorance." - Derek Bok


1990 geo metro 1.0 5 speed 3-door hatchback "herbie"
1990 geo metro 1.0 5 speed convertible "sportie"

Yep, I fixed it. Thanks phil. Should have told you I did. Sorry M8.



Hehe. Yeah I used to work at a machine shop and fabricate/make parts for odd stuff. Mostly steel and aluminum. I am well versed in measure 20 times cut once.



I had a feeling I would have to add an extra bung for the coolant line. May have to take a closer look at that manifold.



I agree this forum has been a huge help in figuring out problems with my sprint. Without it I'd be stabbing blindly in the dark.
Again thanks for the information!

I hear that bike carbs have a problem with lateral G forces. So when turning they will get fuel starved. Is this true? And is there away around this by adjusting the floats?

_________________
1987 Chevy Sprint base 1.0 3cyl 993cc (R.I.P.)
1986 Chevy Sprint base 1.0 3cyl 993cc (Totaled)
1994 Geo Metro base 1.0 3cyl 993cc (Had to sell)
1996 Geo Tracker 1.6l 16v 4cyl 1590cc (Daily)

i have a set (3) from a yamaha 750 3 cyl

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it doesent have to be surrounded by water to be a island and dont forget it's a 3cyl Blow,Suck,Bang

Seems the hardest part of this is going to be the manifold. Seeing as the thermostat housing needs to be part of intake manifold to make the car stay cool. The thermostat housing is connected to the manifold its self and the new manifold would somehow need to incorporate a new housing and pipe to run coolant to the head. I feel this will be a most difficult task. As the housing its self is cast.

Any ideas?

_________________
1987 Chevy Sprint base 1.0 3cyl 993cc (R.I.P.)
1986 Chevy Sprint base 1.0 3cyl 993cc (Totaled)
1994 Geo Metro base 1.0 3cyl 993cc (Had to sell)
1996 Geo Tracker 1.6l 16v 4cyl 1590cc (Daily)

I have never seen a MK1 manifold so I cant give any suggestions. The MK2 heads have the thermostat out the back of the head below the distributor.

_________________
"If you think education is expensive, try ignorance." - Derek Bok


1990 geo metro 1.0 5 speed 3-door hatchback "herbie"
1990 geo metro 1.0 5 speed convertible "sportie"

Ok. Let's get down to the nitty gritty.

Here is a picture of the MK1 1.0L intake manifold:




Circled is the thermostat housing.

Now here is a question. Since I don't have an intake manifold for the turbo 1.0L....I was wondering if using it on a MK1 N/A block is feasible?

I circled what I think to be the thermostat housing for the turbo? Am I correct in thinking this?




Now if I can use this and can block off and unnecessary holes. Could I just chop the top off of the plenum and use the pipes for the carbs? If not just making a manifold from there?



Again thanks for the help!

BBM

_________________
1987 Chevy Sprint base 1.0 3cyl 993cc (R.I.P.)
1986 Chevy Sprint base 1.0 3cyl 993cc (Totaled)
1994 Geo Metro base 1.0 3cyl 993cc (Had to sell)
1996 Geo Tracker 1.6l 16v 4cyl 1590cc (Daily)

That helps with the visuals. I see a couple issues with using the lower half of a turbo manifold. First, the runners appear to get pretty close, may have trouble with carb spacing. Second is the runners will be getting long which will change your power curve

_________________
"If you think education is expensive, try ignorance." - Derek Bok


1990 geo metro 1.0 5 speed 3-door hatchback "herbie"
1990 geo metro 1.0 5 speed convertible "sportie"

for what its worth, im working on this, but will be using a geo metro head/engine.
mikuni vm26 carbs from china.
l

_________________
"muchos tanks, village destruidos"
"muchos sanks, menos submarinos"
"its the dreams that keep you alive"
-vernon wasser-

88 sprint, 4dr sold
87 turbo 2dr, never ran
86 sprint, 2dr current DD!

So is there any update on this and just to say any one with the ability to build a intake for the 3 and 4 cylinders could make some good money.

_________________
02 bmw 330ci zhp
'91 Geo Metro Convertible 5-speed parts car
'92 project squishy viewtopic.php?f=36&t=43375
'98 Chevy K2500
'76 Harley Davidson FXE

well i had a triple mikuni running at idle with a custom manifold, then life got in the way, and some good old fashioned stupidity.
i basicly bought some 1/4 aluminum plate and cut the holes, then had it welded at a local shop. that manifold is cut apart, it was too long.

right now that car is 3rd on my list of cars to fix.

but the idea is sound. ended up getting vm30's. pretty sure they are factor rejects. minor scratches and stuff.
the biggest problem was fueling, how to keep the fuel pump running.

i was after this, cus if i can get it to run on carbs, then i can shave the crap out of the head and run 13:1 compression and get a true E85 conversion, well that is my crack pipe dream.

right now i got to get my CNC machine up and running. im greaing up to make lots of manifolds
but i got to fix a dead sprint, then a dieing versa, then i can get to this.

_________________
"muchos tanks, village destruidos"
"muchos sanks, menos submarinos"
"its the dreams that keep you alive"
-vernon wasser-

88 sprint, 4dr sold
87 turbo 2dr, never ran
86 sprint, 2dr current DD!

You have any pictures of the MK2 head with the carbs installed? I'd like to se the set up. I don't have any sprints they died. But I did pick up a Metro though and that triple carb idea is still floating around in my head. I am thinking of using a triple Mikuni rack. As the racks can be made to work off one throttle cable.
Maybe an electronic fuel pump and FPR would be needed and probably some sort of engine management. like say a mega squirt. As the MK2 is a totally different system. efi vs carb'd.

_________________
1987 Chevy Sprint base 1.0 3cyl 993cc (R.I.P.)
1986 Chevy Sprint base 1.0 3cyl 993cc (Totaled)
1994 Geo Metro base 1.0 3cyl 993cc (Had to sell)
1996 Geo Tracker 1.6l 16v 4cyl 1590cc (Daily)

no pics, but i will try and get some up here later.
i did have trouble with coolant leaking into the cylinders, the 1990 head still had the passages cast into the head like the older mk1, really weird.
and no, the mk2 head will not fit on the mk 1 without some work. oil check valve is in the head on the mk1, and in the block on the mk2.
i have a mk2 block and head and intake i will swap into the sprint later on.
first off, tho i will need a fuel pump. walbro 255 reged down to 5 psi or so. that is how i fed the mikunis the first time, a cheap ebay fuel regulator. manifold needs to have 16 degree down angle.

_________________
"muchos tanks, village destruidos"
"muchos sanks, menos submarinos"
"its the dreams that keep you alive"
-vernon wasser-

88 sprint, 4dr sold
87 turbo 2dr, never ran
86 sprint, 2dr current DD!