Explanation on carbs needed

[FuriousD]

ok i'm looking to change the carbs on my 93 zzr 250 which runs a ex-250 carbs to a newer set.
i understand that i need to find a set of carbs that jet the same amount. I've found info ( http://forums.ninja250.org/viewtopic.php?p=825921&sid=8969592539d0d92075ecbc8d4fc7140d#825921 ) but i don't understand it and was wondering if someone could please explain it.
I was thinking that the carbs from a newer bike running a newer ex-250 carbs would work right?

Thanks
Daragh

[onearmedbandit]

First question. Why are you changing the carbs?

[FuriousD]

because i was informed that the ones i'm currently running are worn out. and if i get a set of the same year they will probably have the same problem

[bogan]

I'd get a nice folding lawn chair, and smack the prick who told you they were worn out in the face.

Carbs are fickle things with many parts, I've not heard of any carbs wearing out, though small bits in them certainly do. Get a better explanation of what is wrong with yours before trying to fit other ones, which will likely be a massive headache.

[FuriousD]

well i have managed to fix the carbs in ten minutes by just playing with random nobs that i have no clue what they do (i have a phd in tinkering).

so i would to do what is advised above but i shall refrain from doing that or naming names (he cost me alot of money for something i have fixed myself....)

on a plus note, i have learned yet another useful tit bit of knowledge. :niceone:

[bogan]

If you've just mucked around with the fuel screws (I assume they are the random nobs), chances are it works but isn't fixed. Maybe give us a run down on the initial problem, and the fixes you've tried etc. Carbs are one of those things that are near impossible to get right with just tinkering, you need a decent amount of tuning theory to get em right.

[FuriousD]

ok initial problem was (as i was told) that the part that lets the idle fuel in was worn and the needle that adjusts it didn't fully close it. this was because when the idle screw was fully in the bike still ran.

so since when the mechanic worked on it i have been running the bike with the chock at about half on, it would idel at 3k revs. this was the only setting the bike would happily run on.

so today, after trolling the internet i decided to see if, by adjusting a small black nob on the left had side, which goes to the carbs, i have managed to get it to idle just under 2k with chock off.

[bogan]

Firstly, the choke will be a fuel enricher, which delivers a rich mixture of fuel and air to the engine, along with whatever is coming through the main carb circuit. The black knob sounds like it is simply the idle adjustment, essentially preloading the throttle.

See if you can drop the idle down to about 1200-1500, which is about where it should be. Do that while it is running, then see if it will start again.

[spanner spinner]

all the ex250's zzr250's ect with the twin cylinder engine share the same engine so any carb set from these models should interchange with your bike, just check the trottle cable connection at the carb end. the year of the bike is not important the milage is. a late model bike with high k's will have the same wear issues as yours and i have seen this problem before with high milage kawasaki 250 twins. Yes bogan carbs are mecanical items and they do wear out, wear in the slides will allow air to leak past stuffing the mixture it sounds like this is what is wrong with yours as the leaking air leans out the idle miture, the only fix is new slides and carb bodies not an economical fix. early gsxr's suffer from the same problem as well as worn slide needles and seats so it not just your model of bike that suffers from this problem.

if you want to understand how carbs work a goos start is http://en.wikipedia.org/wiki/Carburetor

[bogan]

A small air leak past the slides should be easily adjusted for via the fuel screws. Certainly conceivable that it might occur, but I've never heard of it happening. It sounds like the mechanic has twidled the idle adjuster, and told him to buy new carbs. A much more thorough DIY investigation and diagnosis would be advised before going down that route.

[Flip]

I hope this helps..... Items 52 to 56......

http://www.dansmc.com/mc_repaircourse.htm

[FuriousD]

I hope this helps..... Items 52 to 56......

http://www.dansmc.com/mc_repaircourse.htm

that is quite a nice bit of info. I have done what was advised earlier and it no sits happily at around the 1300-1500 mark which im happy with.
Hopefully this has fixed it. If the problem comes back I'll look into it more thoroughly.

Thanks lads :niceone:

[ducatilover]

Now you have it idling happily I suggest you get on it, warm it up fully and smash the throttle open in third from just above idle, come back and tell us if how it's pulling and if it's a bit funny, at what revs.