Klx250s with cvk34 carb. got the bike from a Friend who let it set outside for awhile. Wouldn’t start. He said he found the needle jet stuck / corroded into the carb from old gas, and sitting too long. He purchased a Chinese replica carb that was too small for the boots. I rebuilt the original Keihin CVK 34, cleaned/ soaked real well. Replaced float/needle/ pilot screw. Put back together with issues getting the diagram to seal.Finally got it, checked with vaccuum, and it was slow to respond, but did.
Now back on the bike , and a no start. Plug good, air filter good/clean.float level checked with the miniscus method, level is correct. Any suggestions/ help is appreciated.....Thanks....Tonebone

 

To resurrect a trashed out CVK, you have to do waay more than soak it and replace the "float/needle/pilot screw".

You have to dismantle the pilot system and the main fueling system. Insure that all circuit passageways in the carb casting and bowl casting are clear and clean and flowing correctly. Insure that the pilot jet, and emulsion tube, are either replaced or made to be brand new (not an easy job). Then you have to reassemble it correctly - not leaving out the needle jet or putting it in upside down..

You have to read, study, and become a "CVK guy"...

 

i have done all that.... I didn’t simply just put in new parts, part of the soak and clean is to ensure all passageway are clean and clear. All seals replaced. The only thing I’m not sure of, since I’m not a “CVK Guy” , is the diaghram , and it’s potential role in not starting. I am not new to carbs, but this is my first experience with a Keihin CVK with the diagram .

 

If there is no fueling at startup without choke, the pilot jet system is non functional. If there is no fueling for startup,even with the choke pulled out, you've got "big" fuel delivery problems.

If you've done proper disassembly and cleaning, tell me how you managed to clear/clean the pilot jet pinholes - especially the one down the center ? I have only found one way to do that - and it's kinda crazy, and not always successful - so I am always looking for a better method..

 

I use a bread tie, remove the paper or plastic covering from the tie. The remaining little wire is enough to pass through the small holes in the pilot jet, emulsion tube, jet needle orifice, inlet valve orifice etc.... compressed air then . I appreciate your comments on the pilot jet system being a possible culprit.

 

I did the passages on a Honda MB5 using a copper wire strand from a scrap of electrical wire I had laying around. Not the fat singe wire Romex stuff, but the multi strand wire from a switch I wired into a lamp. Real fine and small, can flex/bend a bit if necessary, and it will not damage any inside orifices.

Having worked in a shop I have to say one way to clean deeply for carbs is if you can find a bike or car shop that has a carb washer or ultrasonic cleaner. They work cleaner in places that are near impossible to get otherwise and the fluid will work its way in as well. We used to run them for a couple hours in the machine.

One other option would be to toss the CV and install either a Mikuni pumper flat slide, a bit costly, or one I've wondered about for years, a regular flat slide, which can be had for reasonable money. No accel pump, but they have been the go to carb for the Yamaha SR/TT/XT 500 for a couple decades. They used the round slide VM36 or 38, later going to the TM36-2. No accel pump on the TM36-2, but there wasn't one on the VM36 either and they functioned pretty well on the SR - speaking from experience. Clearly the TM36-68 pumper is best from a comments I've seen here and in the ADVrider forum, some say best bang for the buck because of the burst of power from the pump and the direct control of the slide. D. Pippin has some information on the application on his KLX250 web site. So there are options beyond the OEM CV unit.

 

OP, generally you should get the bike to start with just the choke circuit even when the pilot jet is clogged. I'm assuming you also ran cleaner, compressed air, and a wire through the choke jet? That jet is not removeable. This is what usually happens to clogged carbs. The owner is able to get the bike to start on the choke, but it will not run without the choke on due to the pilot/idle circuit still being clogged. It sounds like you did a fairly thorough job on the cleaning, but of course something is still amiss. It also sounds like you checked the fuel level with the clear tube method.

I'm taking your description to indicate that the bike was not running at all since in your possession. Do you have spark? Is the airbox/air filter path clear? A big unknown here is what happened to the bike before the PO parked it and perhaps what happened to it after it sat outside...chewed wiring, etc. You mentioned "plug good"...so you did see a good spark when cranking the engine? With a bike like this that could have numerous issues, I'd shoot some starting fluid into the carb opening via the airbox with the air filter removed. If you can at least get it to fire on starting fluid, you can eliminate a few gremlins on the bike.

 

TNC..... I did pull the plug and spray starter fluid, replaced the plug and it runs with the fluid. Prior to that, multiple attempts to start yielded a dry spark plug when inspected. I think I’m gonna pull the carb again, revisit the pilot circuit cleaning again.

 

There is always the little inline (actually inside the fuel line) fuel filter... Just in case you are not getting fuel into the bowl ( as checked with the bowl drain screw..)


I've always plucked a wire off a wire brush for pilot jet cleaning..

 

Thanks everyone for the responses/advice. I’m gonna go back in it, and I’ll post here afterwards. Thanks again