big_wig_074

wtf???? i read about carbs yesterday to try understand the basics of them,get my bike carbs today,er........wheres the venturis?the booster venturis? why is there a bit that slides up and down as well as a butterfly? hmmmmmm.......

GTechR

They'll be flat slides then mate...

Anonymous

carbs = outdated wank

HTH

gurnE

Nope, flatslides don't have butterflys.

Most bike carbs are CV (Constant Velocity, hence no venturi), the throttle butterfly(s) is controlled by the throttle (or ECU) and the airflow lifts the carb slide which has a needle on the bottom regulating the flow of fuel.

If you crack the throttle on a set of flatslides at low revs you will bog the bike with too much fuel too soon where as on a CV carb you just open the butterflys and the airflow dictates the movement of the slide and therefore how much fuel is sent winging towards the cylinder.

gurnE

Hardly fair mate. Outdated yes, technology moves on but a nice smooth, easily set up method of fuelling imo

Anonymous

easily setup?


tell you what, give me an hour with some TBs and you an hour with some carbs, and see who finds it easiest to get the fuelling right all the way up the range on his vauxhall engine with no "base map" or "roughly right jets"

gurnE

I meant easily set up by monkeys with a box full of jets rather than the computing power of NASA

I was thinking along the lines of dynojetting a bike in comparison with writing a fuel amp for a power commander.

I've no experience of setting up carbs on a bespoke application but would expect the two to take roughly the same amount of time? Happy to be wrong tho!

Anonymous

you must be VERY happy then

Anonymous

seriosuly though, depends on what you are used to i guess, but ive always found carbs much more compomised and much more time consuming to setup

gurnE

Ecstatic

big_wig_074

butterfly setup

slidey thing down

slidey thing held up


so theyre controlled by the airflow then?makes sense looking at them tbh


on the first pic,top left theres a bit that looks like a choke cable would go or something?it moves a piece of sliding metal thats attached to all 4 carbs,moves them side to side,whats this doing?

gurnE

That would be the choke

Kawasaki carbs?

big_wig_074

gurnE yup off a ninja
bloody cheap so i thought why not.
thats the choke then,right,all good,how do u change jets?
i always thought carbs just have one inlet for fuel,this has 2?
what does this adjust?

and these?

vacuum?

and this is one end of the fuel line!dammit,can spares be had?

gurnE

If you pop float bowl off you will have two jets.

A slow running jet and a main jet.

Just unscrew and replace.

1st pic - mixture

2nd pic - bowl drains

3rd pic - fuel line I think. They have no vacumn take off on the carb. Most bikes take vacumn of one of the inlet manifolds

4th pic - Those pipes that run along the bottom of the carb hook up to the cooling system as Kawasaki had a few problems with carb icing so to combat that they ran warm coolant through them

I think you'll spend alot of time/effort/money getting that all running right tbh

What car is this going on? Are you sure it's worth the hassle?

big_wig_074

im not gonna spend much cash on it,they were very cheap,so i thought id look into it anyway,if it turns out to be a pain ill pay someone to do me a set up on bike carbs or tbs! but till then im learning!
ahhh the famous coolant warmed carbs. 200sxs have these on injection! thats fine then,it will not be needed straight away.
what are bowl drains for?obviously to drain the bowls,but WHY would u drain them?
sorry about the questions but its interesting to me

gurnE

Water ingress, draining old petrol after a long lay up, that sort of thing.

No worries, happy to help mate

big_wig_074

good good,just had the bowls open,plastic floats,2 jets,one on top one recessed. all getting simpler by the minute!

gurnE

Float height is important btw.

You may need a different float height to standard unless the carbs are mounted at the exact same angle.

big_wig_074

how u change that?ill have to find the right angle!

gurnE

The float needle rests on a metal plinth which you bend to get it to the right height

big_wig_074

cheers fella!

Garage19

Compared to 45s, bike carbs are a doddle to set up and get running right. They don't bog like badly set up 45s and are just much smoother.

The last set i tuned were on a pinto that a friend had built. We spaced the carbs out to suit the port spacing so we could have straight runners on the inlet manifold. See sig.

Within about 10 jet/needle changes we had the fueling pretty good across the range.

The whole setup including carbs and manifold cost under £50. weber 45s with linkages can be £600+.

After the owner drove the car with the bike carbs he was so glad i talked him out of 45s.

However i am a fuel injection die hard and really agree with chip, changing jets is a thing of the past!

big_wig_074

cheers fella!