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Jamiepo
28th March 2006, 01:39
I am having a huge dilema here, basically the carbs off my bike are stuffed, cheapest set I can find at a wreckers is $150, would Keihin CVKD 30 x 2 (gpx250) carbs work for my bike as I could probably get these a bit cheaper. Would it be a matter of chuck them on tune them up and off I go or would I have to rejet them to get them to work? Any info would be much appreciated.

Cheers,
Jamie

imdying
28th March 2006, 07:46
'Tuning them up' is changing the jets. If you have to ask, then you haven't got the knowledge to do it yourself. Have you asked the carb shop (or someone like them) if they'll rebuild them? What makes you think the old ones are stuffed?

Ixion
28th March 2006, 07:58
Bear in mind, this is a single - twin port. The original carb is really a weird composite thing, a single carb with two venturis. A slide body that functions at low to mid throttle, then a diaphragm body that comes in above about one third throttle. With a common float bowl etc. At a casual glance it looks like a twin carb setup, but it's not.

Word is you can either fit a pair of small carbs from a 250 twin, or a single larger carb . Either way it's not completely simple - there are clearance problems with two carbs (too close together) , and you need to fabricate new throttle and fuel connections. A single carb means making up a manifold.

And the result is unexciting. In particular, reports of harder starting and worse fuel consumption.

Why do you think the original is stuffed ? They are weird, but not complicated? The adjustment is not at all intuitive, you need to check the manual. Otherwise, apart from a perished/ruptured diaphragm, they're not much can go wrong.

imdying
28th March 2006, 10:11
If you do end up changing carbs, and need a throttle cable change, I'm your man. However, unless your carb is really really poked, it's a harder job to swap than fix.

Motu
28th March 2006, 11:21
Twin 30mm carbs will be way too big for a 250,but that's a common mod for the SRX600.As the others say,properly set up and with a good diaphram the standard carbs will work well.The biggest problem is no one knows how they work,the incesant fiddling puts them so far out of wack you can't get them tuned.Strip and rebuild - back to basics and square one.

Jamiepo
28th March 2006, 11:26
Bacisally the problem with the carbs is that the guy before me left them sitting with water in tehm for about a year and a half. I have talked to a couple of places round town and they said I would be better off getting a new carb. By tuning I meant getting it to idle/run and I thought there would be the normal adjustments on the carb for that. Basically I was looking for something to bolt on and go and $150 seemed a little bit pricey to me. At the moment I am time rich but cash poor (being a student and all) so spending time fiddling around with something isn't a problem for me but spending massive amounts to get it there is.

imdying
28th March 2006, 11:51
Boil the old carb up in Rinso once you've stripped it (do it outside on your spotting stove). That'll degunk it, the rest depends on the condition of the bits inside it. Hows the diaphram? It'll have an idle mixture adjustment, just twiddle it till you get the revs as high as possible, then back the idle off, rinse repeat :)

Jamiepo
28th March 2006, 12:13
Diaphragm looks to be in good order still, its just the not knowing enough about this carb thats giving me problems. Where do I get rinso from?

Ixion
28th March 2006, 12:33
Rinso, ask your Mum!.

The idle mixture adjustment is at the front of the carb , on the left (ie the front of what appears to be the "left hand carb"). It's what looks like a hole, vertically upward, but theres an adjuster screw at the bottom (ie top) of it. You'll need a very small VERY SHORT screwdriver. I cut the handle off one , because there is VERY little clearance between the hole and the crankcase. Turn the adjuster in and out until you get the "idles fastest" point. The idle speed itself it just a throttle stop at the left rear. It's a thumb screw you can turn it by hand. Make sure you have some slack in the throttle cables.

Then look through at the carbs from the right hand side. In the middle between the "carbs" (ie between trhe venturis) near the top of the carb , you'll see a gizmo with an adjusting screw and locknut. It's real hard to get to unless you remove the tank and seat. This is the interconnection between the left and right hand throttles. As you twist the twist grip, you'll see the gizmo move. Eventually it comes up against a little cam on the right hand side "carb" and starts opening that throttle. Set the adjuster so that it just starts opening the right hand throttle on about one third throttle.

That should be enough to get the bike running reasonably well. For fine tuning, either consult the manual (or one for the XT250/350 DOHC) or just tweak by ear. Change only one thing at a time, by just a little and try each.

Bear in mind to have the engine fully warm before adjusting.

Other thing is these carbs seem very sensitive to float height, but I have no idea what the correct setting is. Consult said manual.

All this assuming of course that the diaphragm is OK, that the needle jet is not totally oval, that the float bowl is clean , that there is no gunge in there, and that no-one has dicked around with needle settings and so on.

Jamiepo
28th March 2006, 12:43
Cheers for the info guys I will give it a go and see how I get on. Oh and do I just get rinso from Paknsave or ther like?? and what amount should I use in say 1.5 litre os water?

imdying
28th March 2006, 13:00
Not sure what other names Rinso has, anyone able to help? Float height is pretty critical, don't neglect to find out the correct setting. Just boil it up in a potful of water, keep adding water when it boils up. About half an hour should do it. Post back if you're stuck :)

Jamiepo
28th March 2006, 17:17
I picked up some sugar soap from the supermarket so I will mix that up with some water and see how that does, it will usually take anything off

Ixion
28th March 2006, 17:19
Uh be careful with that. It may be TOO strong. Sugar soap is pretty alkaline, and those carbs are made of fairly shitty metal. Y'don't actually want to dissolve them. Just ordinary soap powder is fine.

Jamiepo
28th March 2006, 17:30
Ok , I will try that instead then, cheers

Motu
28th March 2006, 20:45
My KT250 had been left out overnight in the middle of Anzac Bay,stuck in the mud.Most people wouldn't of even bothered with a rebuild,but as it only cost me $25 I thought I'd give it a go.To clean the cases I found some boiler tube cleaner lying around,it's a strong acid of some sort...one of those ones I can't spell,hence the lack of detail.A quick scrub and rinse and they came up pretty good....but had to paint the engine black after that.Um...then for some silly reason I thought I'd clean the carb like that too.When I dropped it in,it foamed up like detergent in the Mission Bay Fountain so I quickly pulled it out and gave it a rinse.Ah,I thought,no damage at all,it looked perfect - but when I went to put it back together I found it smaller and bigger in every way.Learning curves...some are off camber and decreasing radius....