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how to tune cbr 600 bike carbs
Stuart_B - 21/1/09 at 06:20 PM

hi all, now i have passed my sva i want to sort out my fueling issue. at the moment the car is running way to lean. so i was wondering how can i adjust this?

where are the mixture screws loactted as well which way can do you trun them to pump more fuel in to the engine?

or do i have to unscrew them and drill them out and put them back to where they where?

thanks

stuart


coozer - 21/1/09 at 06:51 PM

Take it to Bogg Brothers.


UncleFista - 21/1/09 at 07:24 PM

What have you done with 'em so far ?

Are they standard, as they were on the bike or have you fettled 'em at all ?


Stuart_B - 21/1/09 at 07:25 PM

hi, Bogg Brothers are miles away as i live in clacton on sea essex.

i have not done anythink with them, they came off the bike, i cleaned them up and put them on my pinto.

stuart


Danozeman - 21/1/09 at 07:31 PM

Theres no scers as such to turn only for idle mixture.

You need to play with the jets and needles. Im trying to get mine running right with zx9r carbs. Honestly its a right pain in the arse. If you can id take it somewhere.

How do you know its running to lean?
If your going to have a bash yourself id start with the jets. see what youv got and slowly increase the size. You can drill them out in .5mm increments.


UncleFista - 21/1/09 at 07:36 PM

Firstly have you read a copy of THIS ? It's the workshop manual for the CBR600 fuel system and carbs.

All we did with our carbs was to drill the mains out to 1.65mm, we bought a set of drill bits off the 'bay and did a bit of trial and error tuning

1.65 seems about right, it's definitely not running lean, and not "too" rich.

If you cock it up you can either replace the jets with standard weber jets or solder them up and drill again.

Good luck


coozer - 21/1/09 at 07:40 PM

Not able to get there, give them a ring and he (steve) will tell you a very good starting point.

They are very good at tuning aka in the real AND on the phone.


David Jenkins - 21/1/09 at 07:42 PM

To do it properly, you either need

(a) An air-fuel meter connected to a wideband lambda sensor - plus the knowledge to use it

or

(b) An expert with a rolling road (like Bogg Bros) who will set it up for you.

The theory isn't hard - but you do need to see how it performs under load to set it properly.

For me, the stages were:

1. Set it to a moderately fast rpm and balance the carbs (you need some form of gizmo to measure air flow or vacuum, according to your setup).
2. Plug in the AFR meter and go for a wide-open-throttle (WOT) blast up a quiet road - see whether you're running rich, lean or just right.
3. Adjust the hole in the main jets until a good air-fuel ratio is achieved at WOT.

Then you adjust the mid-range AFR by fiddling with the needle shape and position (a REALLY big PITA and faff-around!).

Fortunately, once I got the main jets right, the mid-range, idle and over-run mixtures were acceptable so I didn't have to fiddle with the needles - but I am looking into doing those at some time.


Stuart_B - 21/1/09 at 07:45 PM

i know it is running lean buy the colour or the plugs and the emmsions.

i can not open that file from UncleFista, i do not think i have the right software.

thanks

stuart


whitestu - 21/1/09 at 08:29 PM

I'm running 1.6mm jets in ZX6R carbs [38mm] ona Zetec 2.0, which seems about right from driving it. I haven't had an AFR meter on it yet though.

Stu


UncleFista - 21/1/09 at 08:49 PM

quote:
Originally posted by Stuart_B
i can not open that file from UncleFista, i do not think i have the right software.

thanks

stuart


Winzip or winrar will do it, it's archived