Switching to Bike Carbs. Heres a write up!

[86Franklin]

http://www.youtube.com/watch?v=XzcVQ...ature=youtu.be

[YJSAABMAN]

http://www.youtube.com/watch?v=XzcVQ...ature=youtu.be

I had to go through and watch like 6 more bike carb videos to inspire me! Picking up my air filters later today. Here's hoping they clear the hood!

[86Franklin]

I know what you mean haha. Now I just need to win the lottery haha

[pnavarro]

Who was having problems with overflowing carbs? My #3 carb started spitting gas once again, so as it is time to clean and rebuild them, I unmounted them and see what was up.

I used silicone gasket maker to stop the flooding, as the original o-rings were too crushed. To make a long story short, today when I opened those float bowls, I saw that the silicone had begun to degrade... literally, I touched it and it just turned to jelly. It also had swollen, and swollen so much that it could have probably touched the floats, enough to prevent free movement, thus provoking the carb to spit gasoline.

So what's next? To buy new and original o-rings to seal the float bowls, or use less silicone (or rtv, I think it's called?)

This could be a possible solution to our overflowing carbs problem...

Don't have pictures, except in fb, so if you want to see of what I speak, add me facebook.com/pablo.navarro

[yeayeayea]

when my c arbs were overflowing, it was a result of too much fuel pressure, and too low of carb angle.

[Aaron22]

Great thread, lots of good info here... I have a couple questions though. I will eventually buy a jet kit and wideband to fine tune things, but what's a good starting point for jets for the following setup:

-2.0 16v block
-1.8 16v head
-zx6r carbs (36mm I believe)
-raceland header
-saab vacuum advance distributor

From what I've read, 160 mains is a good staring point?

I have an intake made up but haven't welded in bungs for vacuum yet. I have deleted my brake booster so I will only require vacuum for the dizzy. Should I place a bung in each intake runner? Does it matter where I position them?





Thanks for all the info guys

[pnavarro]

when my c arbs were overflowing, it was a result of too much fuel pressure, and too low of carb angle.

I remember that, the video showing the carbs literally puking gas...

[pnavarro]

Nice looking project! Really no, AWESOME looking project!

160 for mains? I'd think they would be too small, unless recommended otherwise, why not start at 2mm?

As for vacuum from the runners, I think that there is no problem where you place the bungs... but I could be wrong...

[yeayeayea]

I would think 36mm is too small for a 2.0. Hell I have a sneaking suspicion that my 38mm carbs are too small for my 1.8

[Aaron22]

Nice looking project! Really no, AWESOME looking project!

160 for mains? I'd think they would be too small, unless recommended otherwise, why not start at 2mm?

As for vacuum from the runners, I think that there is no problem where you place the bungs... but I could be wrong...

Thanks Maybe I'll start a little bit bigger and go from there

I would think 36mm is too small for a 2.0. Hell I have a sneaking suspicion that my 38mm carbs are too small for my 1.8

Yeah, it's crossed my mind. 36mm should still flow better than stock though Maybe my bro-science isn't quite accurate but if a bike motor can make ~180 hp on 42mm ish throttle bodies than shouldn't my 36mm carbs be able to flow enough for 150hp max?

edit: not disagreeing, just trying to understand this

[oldschool eighty8]

Thanks Maybe I'll start a little bit bigger and go from there



Yeah, it's crossed my mind. 36mm should still flow better than stock though Maybe my bro-science isn't quite accurate but if a bike motor can make ~180 hp on 42mm ish throttle bodies than shouldn't my 36mm carbs be able to flow enough for 150hp max?

edit: not disagreeing, just trying to understand this

Apples and oranges.
It has more to do with the size of the thottle plates compaired to your intake valves.

[86Franklin]

It actually has to do with both. Generally if you are making a high output NA you want the throttle plate size to taper down to the valve size. I would guess that in a 1300cc bike that both intake valves don't match or surpass the 42mm throttle plates. Where as running 36-40 mm carbs on any 16v would be tapering the opposite way I.e. valves large than throttle plate. Now for street driving this is fine but you will never see full potential from the engine.

[yeayeayea]

Let me preface this by saying I am no expert.


On a liter bike, each cylinder theoretically pulls in .25L of air per intake stroke.

This engine may make 150hp doing this 6,000 times a minute (12,000 rpm)

On a 2.0 L car, each cylinder theoretically pulls in .5L of air per intake stroke.

This engine may make 150hp doing this 3000 times a minute (6,000 rpm)

Therefore with half as many revs, and twice as much displacement per cylinder, it would seem that a car taking bigger gulps per intake would require larger throttle plates than a bike to make the same power.


All of this is open for debate, as I said before I am no expert.


Also remember that stock 1.8L 16v NA intake runners are 40mm, Stock 2.0L 16v NA intake runners are 42mm, and Eurospec 1.8L 16v KR intake runners are 50mm, with no throttle plate components robbing runner volume.. Now take a 36mm carb throat, subtract the cross sectional area of a throttle plate at WOT, plus any protruding jets or needle valves, and you can see how that fancy set of carbs may be doing more harm than good. Your mileage may vary.

[Aaron22]

Let me preface this by saying I am no expert.


On a liter bike, each cylinder theoretically pulls in .25L of air per intake stroke.

This engine may make 150hp doing this 6,000 times a minute (12,000 rpm)

On a 2.0 L car, each cylinder theoretically pulls in .5L of air per intake stroke.

This engine may make 150hp doing this 3000 times a minute (6,000 rpm)

Therefore with half as many revs, and twice as much displacement per cylinder, it would seem that a car taking bigger gulps per intake would require larger throttle plates than a bike to make the same power.


All of this is open for debate, as I said before I am no expert.


Also remember that stock 1.8L 16v NA intake runners are 40mm, Stock 2.0L 16v NA intake runners are 42mm, and Eurospec 1.8L 16v KR intake runners are 50mm, with no throttle plate components robbing runner volume.. Now take a 36mm carb throat, subtract the cross sectional area of a throttle plate at WOT, plus any protruding jets or needle valves, and you can see how that fancy set of carbs may be doing more harm than good. Your mileage may vary.

Thank you, it seems I've forgotten that engine speed is important with regards to flow. I'm clearly not a powertrain guy I guess I'll continue with the zx6r carbs just to get the motor running then upgrade to something bigger once I get the funds/chance

[oldschool eighty8]

bike carbs are easy to come by an cheap, I would ditch those for something bigger before you start

[pnavarro]

Mother of carbs, I love this thread...

[bmxguy]

so iv been sitting on all my carb stuff for too long waiting to put them on. all i need to purchase is jets and wideband (currently have narrow band for some kind of monitoring). i have r1 carbs of course and they are going on a 1.8 16v, im thinking around 2.00 mains to start. what do you guys think? also will the carb fuel pump (carter whatever) operate fine off of cis pump wires? i dont see how they would cause problems but you never know. TIA for any input.

[pnavarro]

so iv been sitting on all my carb stuff for too long waiting to put them on. all i need to purchase is jets and wideband (currently have narrow band for some kind of monitoring). i have r1 carbs of course and they are going on a 1.8 16v, im thinking around 2.00 mains to start. what do you guys think? also will the carb fuel pump (carter whatever) operate fine off of cis pump wires? i dont see how they would cause problems but you never know. TIA for any input.

I don't think you should buy additional jets... a friend has his 2.0L 16v with 2mm jets... you could start with... 1.8mm instead? and work your way up from there...

[yeayeayea]

I know on my cbr 900 carbs, I think i went with 1.73mm jets, and then played with needle heights to get it where I wanted it. Not saying that r1 and cbr carbs are apples to apples, but 2.0mm still sounds pretty hefty

[oldschool eighty8]

The r1 carbs I have were previously run on a 20/20 set up and have 1.70's in them.

[bmxguy]

okay i think ill probably just get some 180s and start there. gunna cut up some manifold today.

[yeayeayea]

okay i think ill probably just get some 180s and start there. gunna cut up some manifold today.

you can always drill larger. to go smaller, you have to solder the holes shut, then redrill. Not a permanent fix but allows you to go down a step for tuning if you overdrill.

May want to start at 160s if you have a 1.8 8v, 170 for the 16vs

[86Franklin]

Bike carb related content just for fun
http://www.youtube.com/watch?v=-pOrr...ature=youtu.be

[bmxguy]

i have a 1.8 16v. im not planning on drilling the jets. im going to get legit jets. also has anyone cut a stock 16v lower manifold to fit the carbs? i have one im ready to cut but it seems like it almost might not work. would like to be certain it will work.

[pnavarro]

you can always drill larger. to go smaller, you have to solder the holes shut, then redrill. Not a permanent fix but allows you to go down a step for tuning if you overdrill.

May want to start at 160s if you have a 1.8 8v, 170 for the 16vs

I support this comment, 1.8 8v and I'm with 1.6mm...

[YJSAABMAN]

How about an ABA/crossflow 8V? I guess prob 160s, like the counterflow. Getting ready to go through my carbs and maybe make this beast run this year! Got my air filters and they fit great! K&N part number 62-1480.

[pnavarro]

That looks beautiful

160 seems about right to get started!

[cabby85]

got my 3/8" aluminum flange back today, fits like a glove im going to be using 1.75" O.D. aluminum pipe for the runners if i can find any. what thichness of tubing do you guys use for runners?

[pnavarro]

Sounds about right!

[yeayeayea]

Well 1.75" = 44.45mm. Stock bore of a 1.8 manifold is 40, and a 2.0 is 42, for 16v engines. That would only give you 1.225mm wall thickness if you wanted to maintain the 42mm ID.

also, bolt up the water neck and check it for clearance. I had to grind my intake manifold flange to clear the upper water neck

[Dr.Steels]

Does anybody have a schematic for there 16V intake manifold? I want to start cutting and building but I need some numbers first. I am getting carbs from a 98-2001 R1 (still hunting for a decent local set)

Numbers I would like.
Carb angle
Engine angle (at mounting surface)
Plenum spacing (Stock)
Carb spacing
Carb angle

Also is there a choke for these carbs?

[86Franklin]

The only ones I'd be able to help you with is intake surface angle and spacing but I don't remember them of the top of my head. Also yes there's a choke.

[Dr.Steels]

The only ones I'd be able to help you with is intake surface angle and spacing but I don't remember them of the top of my head. Also yes there's a choke.

id love to get those numbers off you!

[YJSAABMAN]

Does anybody have a schematic for there 16V intake manifold? I want to start cutting and building but I need some numbers first. I am getting carbs from a 98-2001 R1 (still hunting for a decent local set)

Numbers I would like.
Carb angle
Engine angle (at mounting surface)
Plenum spacing (Stock)
Carb spacing
Carb angle

Also is there a choke for these carbs?

Why local? I picked mine up off eBay for $117 shipped. No damage, just an apparently leaky float bowl.

As for carb spacing, I built a jig out of muffler clamps to hold my runners for welding:





As for choke, I used a Mr Gasket 6' choke cable and some Help! cable ends.

[pnavarro]

Great solution, I wish it were that easy for counterflow heads...