klr 650 dies with throttle


i am working on a cvk40 carb on a 2009 klr650 with no success so far. bike dies with slight throttle but idles fine. I have cleaned jets and inspected slide membrane and all appear to be fine. the only way I can throttle without bike dying is to cover the carb vent line(on airbox side of carb) with my finger. When doing this I can feather throttle and eventually get to near full throttle. As soon as I remove my finger from vent line it dies again. I am thinking of replacing slide membrane or adjusting float level, but I feel i am missing something simple. Any insight would be greatly appreciated.

What's the plug look like

hello, thanks for the reply. before all my tinkering and after the initial stall on throttle it was dry and looked healthy. I have not checked it since the carb clean out though.

forgot to add that this all started after pulling bike out of storage. refilled gas tank started down the road reached about 45 mph, gave it some throttle and it died. ever since, it will idle fine but die with throttle. I had carb out and attached shop vac to engine side and verified slide moves with vaccum when butterfly valve opened. But i would guess this is more vaccum then engine creates so maybe not a good test.

does anyone think plugging the carb vent line could help a leaking diaphragm or correct a fuel flow issue through main jet. I have heard of the plugged line stopping the carb from functioning, but in my case it seems to help at least with throttle.

I have done the following:

removed jets,pilot screw, enricher diaphragm, choke and cleaned

removed diaphram/slide and cleaned slide

blown compressed air through every orifice I could find on carb

removed pilot adjustment screw and inspected

cleaned inlet fuel filters inside tank

cleaned/inspected petcock

cleaned air filter and re oiled with some spray on air filter oil

checked for vacuum leaks with wd40 but did not see any

looked at a cross section of the carb, thinking I may still have a plugged pilot circuit.Maybe a carb soak or clean out with a torch tip cleaner will help. from what I've read pilot circuit is engaged up to 1/4 throttle.

is the tank venting? those klr caps have some umbrella valves in them that can cause you grief

also is the vac hose to the petcock hooked up? see any fuel in that hose from a bad petcock? vent lines all in the right place?

Make sure the choke plunger isn't sticking.

When you removed the fuel(pilot) screw did you verify that the spring, washer and o-ring were there, in good condition and in the right order?

Ask yourself, when you plug the carb vent line, what effect does that have on the carb. It robs the float bowl of atmospheric pressure. Ok, so how does that affect things? It seems to me that it would make it difficult for the venturi effect in the carb throat to draw fuel thru the jets to mix with the air, effectively leaning out the air/fuel ratio. So when you plug the vent line, if the engine responds "better" to opening the throttle, that would tell me that there is a rich condition to begin with. Like a sticking choke plunger.

Make sense, or is my thinking all wrong?

Edited by Trailryder42

thanks to all for the replies. Choke does not appear to be sticking. also tried running with gas cap open. still no change. petcock appears fine and no gas in the vaccum line. I pulled carb again and cleaned with aerosol carb cleaner then seafoam. still dies with throttle. Pulled the plug and its black. Other than throwing parts at it(new jets?

), i am not sure what else to try. I have the pilot screw turned out 1.5 turns from seated position.

Are all your vent lines clear? I had a dirt dobber stop a vent line up once and I got the same results (no throttle). I'm sure you prolly took the jet apart and checked the portals on the pilot section. I bet it is the vent line stopped up.

thanks for reply. the only line I know of is out the top of the carb and it appears to be clear. I'll have to pull it and verify that the plastic fitting that connects it to the carb is also totally clear. other than that the only other thing I have noticed is a very slight rounding/wear on the main jet holder at the point where it meets the collar that the slide needle sets in. I wouldn't think it would be that sensitive, but maybe worth a shot to replace.

had an embarrasing revalation. I think I have the inner workings of the slide assembled incorrectly. should be needle, spring retainer,spring, cap. what I've been doing is putting the spring retainer in 1st then setting the needle down through the top of it. this would raise the needle up a good half inch off of where it should be in the collar allowing an extremely rich condition. plugging the vent line probably reduces travel of the slide and keeps more of the needle in the collar which is why I can throttle with vent plugged. I hope correcting this should fix it

had an embarrasing revalation. I think I have the inner workings of the slide assembled incorrectly. should be needle, spring retainer,spring, cap. what I've been doing is putting the spring retainer in 1st then setting the needle down through the top of it.

OOPs. Yeah, I bet that would cause your problem.

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