1979 KX250 Stock Carb Specs

[ctharre]

Hey all,

I'm in the middle of getting a new project bike going.  I picked up a 79 kx250 in real bad shape last summer and am in the middle of making it trail worthy again. 

I'm running into the problem that I cannot find any good info on specs for the bike.  I would like like to get the carb set back to stock and see how it runs, but right now I don't even know what carb it has on it and if it is the original or not.

Anyways if anyone has any information on this model the help would be appreciated.
thanks
chris

[Foxx4Beaver]

this might help a bit....until someone else can hopefully come up with something better...

http://www.partzilla.com/parts/search/Kawasaki/Motorcycle/1979/KX250-A5/CARBURETOR%20(78-79)/parts.html

*EDIT*
Welcome to the site by the way!

[ctharre]

Thanks man. What that link shows for the jets does not match up with what is on the carb now. I think I recall the diagram showing a 172.5 main and a 50 pilot. They are hard to read but I think I have a 300 main and 40 pilot pulled out from it.

Now I'm pretty carb ignorant so I don't know if it really matters but I'm thinking that the carb that I have is not original. I know it's a mikuni vm type and I see a v10 stamped on it, but that name doesn't match up with anything I've seen looking on the internet. I measured the inside diameter of the carb on the engine side and it's about 38-38.5mm. Not sure if that identifies it.

I guess if I don't have a stock carb, i would like to know what I do have and if I can make it work, you know?

[Foxx4Beaver]

If it's got a 300main in it, I would think it's not the original carb, but I'm really not sure. I was hoping someone else would've chimed in that knows something about the A5's.

Do you know if the bike ran with that carb you currently have?...if yes, I wouldn't sweat it too much, just give it a good thorough cleaning...and check the spark plug a couple times to be sure it's not burning excessively lean...the plug insulator will be fairly white if it's too lean.

If you don't know if it's been run with that carb....then you're gonna be swinging in the dark a bit...but I still wouldn't sweat it too much. Again, give it a good thorough cleaning, set the needle clip in the middle position(if it's not already)...once you get it running, pay attention on how it reacts when you turn the throttle. If it wants to die right out once you start cracking the throttle off idle, there's a good chance it'll need a bigger pilot...and again....check the plug several times...if the insulator is anything lighter than a "coffee brown", then you know you'll need to go richer.

Another possible option, you could contact Sudco, and see what info they can give...and depending on your budget...you may be able to buy a brand new carb from them.

http://www.sudco.com/

[ctharre]

Thats what I was thinking too. 

I did run the bike this fall but really just rode around the yard a couple of times because the back brakes were broken and I didn't feel like getting too crazy on it with half the brakes gone.  So yes it was running on that carb, but I remember it didn't feel like it was running quite right.  The biggest think that stuck out was that it was idling very high.  Other than that I really didn't ride enough to diagnose anything.

If it the bike will work with this carb even though it's not original I'm ok with that.  I've done a good cleaning on the carb and it seems in real good shape.  I guess it will just take some tinkering with the jets to get it right. 

To start this tinkering, where should my baseline with the jets be? Should I leave the setup it is in now from the p.o, or should I get it set with the original jet sizes from that part diagram?   At 5 bucks a pop for jets I'd like to not have to buy too many to get this working since this is supposed to be just a budget trail bike and not a full restore!

Thanks for the advice so far

[Foxx4Beaver]

the 1st thing you wanna do is determine why it's idling high....it could be as simple as just needing to adjust the idle screw...or you could have an air leak, which would be a problem.

Is the idle erratic(rpm's up and down), or is it a steady high idle?

I would inspect the intake manifold area really well, for cracks in the rubber, and any oily wet areas anywhere around the motor.
once you're sure that's taken care of, and there's no air leaks...then yeah, start off with what jets are in there. You'll need to do some WOT plug chops...that will help determine how close, or far off the jetting is.

[ctharre]

As for the type of idle, I recall it was a steady high idle- not erratic.

I actually had a similar problem with a high idle on my 75 yamaha dt250. It would run normal until it got the engine warmed up it seemed, then it would start to do a very high idle and sound like it was gonna keep revving faster until the piston flew off!  I replaced the crankshaft oil seals for that and I haven't had the problem since.

I've got this bike to the point where it really wouldn't be that much extra work now to replace the crankshaft seals, so I actually just ordered the pair and will be doing them soon here (besides, i'm in iowa, so riding is still another month or two out).  Also I have already replaced all of the other gaskets- so hopefully I will have any air leak problems taken care of and it will just be carb adjustment this spring. 

As for the intake manifold-  mine looks a bit gnarly from the outside, but I have looked at it closely on the inside to see if any of those surface cracks on the exterior make it all the way through, and I did not see any at first glance.  I will check this out again to be sure. 

Now back to the gnarly exterior- I was thinking of buying a tube of high temp silicone to apply over the whole outside and hopefully seal up the existing cracks and give it an added layer of protection.   Obviously won't be pretty, but this is just going to be a trail bike and the only replacement parts I've seen online are way out of budget.  Any thoughts on this fix idea?

Thanks for the help so far.  I appreciate it.

[Foxx4Beaver]

Now back to the gnarly exterior- I was thinking of buying a tube of high temp silicone to apply over the whole outside and hopefully seal up the existing cracks and give it an added layer of protection.   Obviously won't be pretty, but this is just going to be a trail bike and the only replacement parts I've seen online are way out of budget.  Any thoughts on this fix idea?

Thanks for the help so far.  I appreciate it.

that all sounds good...you're going about it correctly by replacing the crank seals...

the carb boot, yes...you can smear it with silicone to get by.
another thing I like to use, that I discovered from friends on another forum, not bike related...is 3M Window Weld...stuff is amazing how well it works for just that reason.
It's a little expensive, but holds up very well...just gotta scuff up the boot really well, then give it a good cleaning before applying...

[ctharre]

Nice- I'll take a look for it at Menards tonight... then straight to the garage for tinkering!