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Discussion Starter #1
Hi,

I'm new to the forums. I've got an '08 which I bought back in '08. I rode the crap out it, putting almost 11,000 miles on it before I started being plagued with electrical problems. Eventually I got frustrated and parked the bike in the garage where it sat neglected for about 5 years. Recently I got inspired to get it going again, knowing that it would involve a deep dive into the black arts of motorcycle maintenance.

The battery was toast. The carburetor was a disaster. I didn't drain the float bowl before I walked away. I painstakingly tracked down the electrical problems, and now the bike runs pretty well. I'm not releasing it for full-time duty until I've done some work on the brakes, checked the valves, greased the swingarm pivot, done the doo, and replaced the rotten bald tires. Luckily I just lost my job and I have lots of time to lavish attention on the bike.

I think it's essential for this project not only to have the Clymer and shop manuals, but be a member of an online forum so I can get advice. Besides, my friends and family don't want to hear about me trying to get my bike fixed up, but maybe people on this forum won't mind. After some research I decided I liked the vibe of this forum more than another one I looked at. I'm not really good at wrenching so I sometimes need to be pointed in the right direction.

Speaking of which, I have a question if anybody wants to answer it. I am going to install an aftermarket pilot air/mixture screw which will allow me to adjust the mixture more easily because it's got a large brass knob that extends past the channel. I think my current setting is wrong because if I try to use the choke at all the bike dies, even when it's cold. I don't know if that would cause that. It also seems to pop a bit when I'm decelerating. Like I said, I'm not particularly adept at motorcycle maintenance so I'm just kind of guessing the fuel/air mixture is my problem. I did the 22 cent mod and drilled out the hole in the slide slightly. My question is how far do I back out the pilot screw from the fully seated position? I know that's just a starting point and I have to adjust it from there, but where do I start?

It's good to be here. I look forward to meeting people and getting my bike where I would like it to be. Thanks for any help anyone can offer me.
 

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Hi, good to have you here. Welcome!

It can be hard to diagnose this sort of stuff because the bike was sitting, the carb got mucked up, and you've gone into the carb. There are things that can go wrong when putting them back together. You might want to look at this thread and have a look at the videos:https://www.klrforum.com/how-tos-tech-guides/45258-care-feeding-cvk40.html

My first thought from your description is that your idle is too rich. The choke ain't a choke in the conventional sense where it chokes off air to force more fuel in per unit of air, thus reichening the mixture for easier starting. It technically an "enrichener" in that it dumps more fuel into the carb. Same effect, different mechanism.

If your bike stalls when the enrichener is activated then perhaps it is getting so much fuel that it goes way too rich and stalls. That's odd because the KLRs are set up extremely lean from the factory and the pilot jet is almost too small.

That said, a decent starting point for the screw is 2 turns out from gently seated. That doesn't quite hold for the knurled-knob jobbie because it has a different taper to it.

Other things that can go wrong would be an improperly installed main needle, a missing needle jet (they fall out when you're not looking and roll under the bench or down the shop drain), a sticky slide, a torn diaphragm, an improperly seated diaphragm, and so on...

You're in a better position to fix this than we are since it is in front of you, so have a look at that thread and the videos.

Those knurled-knob jobbies are good for adjusting your idle mixture because it's a stone-cold bitch to do it without one, but once it is set they are almost of no further use. Still, I have one and like it.

Popping on decel is normal. It's caused by being lean, which contradicts what I just said, but it's all in "how much does it pop?". I can make mine pop if I try hard and it sure ain't running lean.
 

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Discussion Starter #3
Hi Tom. Thanks for the welcome. When I was researching my carb problem I did read the article you mentioned. It was sort of useful as a general overview. The carburetor is such a complex little beastie though, that I haven't quite wrapped my head around it yet. The videos you linked to I watched carefully as I disassembled and then reassembled the carb. They were invaluable.

I soaked all the metal bits in a 50/50 mix of Pine-Sol and hot water and I replaced the rubber bits with a rebuild kit I got off Amazon. I thought I got it completely clean, but it still wouldn't run when I put it on the bike and I had to do it again. I'm reasonably sure I got all the pieces back in the right order.

The diaphragm was not torn and I got it seated back in the groove with great difficulty. It could have popped out again during installation.

When I first pulled the carb off, the float bowl valve was glued into the orifice with some kind of green crystalline crust. I think it might have come from some gas stabilizer I had put in. The crud was on everything. Nothing moved. Everything was plugged. Pine Sol did the trick but left a matte finish on all the aluminum. It slightly etched the metal I guess.

Thanks for the reply. I have high hopes I'll get this running correctly. Two turns out from gently seated: I'll start there. Then on to replacing the brake fluid and hoses.
 

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Skook, Welcome to the forum.

The detail about stalling 'with any use of cold start enrichener' (choke) could indicate that your float bowl fuel Height may be TOO High and is just near Flooding all the time.
If using a manual fuel petcock and forgetting to turn it off could possibly result in flooding the engine cylinder & the crankcase oil with 6 gallons of gasoline.
The USA model CVK carb float bowl does Not Have an overflow stand pipe in it.

Did you by chance notice the 3 tiny little low speed pilot Transition outlet holes below the Bottom lip of the throttle butterfly plate?
They get their fuel from the pilot jet as does the adjustable low speed mixture screw.

If you spotted them, did you by chance use a tiny wire (bent 90 degrees) to poke down thru them & back flush the passageway with aerosol carb cleaner & compressed air? If one then Closes the adjustable screw, one can spray aerosol cleaner up thru the pilot passage & confirm 3 full streams of fluid flowing thru them. Then set the mixture screw at 2 turns open.
 

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...The USA model CVK carb float bowl does Not Have an overflow stand pipe in it...
For about two years I have been staring at a float bowl that is on the bench in the Shop of Horrors.

The stand-pipe boss is there and it looks like the drillings on the bottom of the carb are correct for drainage of overflow. All that is needed is to drill a hole for a stand-pipe and stick one in.

I think I will do this, either over the weekend or when I get back from fishing.

What could go wrong?
 
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Tom, I just removed the float bowl from a CVK 32 ATV carb.

Its stand pipe is .130" OD / .075" ID / stands .340" above used bowl o-ring. Good Luck. :)
 

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Thanks for that, @pdwestman. I even have some of the right brass tubing laying around.
 

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Discussion Starter #8
The detail about stalling 'with any use of cold start enrichener' (choke) could indicate that your float bowl fuel Height may be TOO High and is just near Flooding all the time.
I checked the float bowl height, but I wasn't entirely confident in taking that measurement. My carb is off right now so I can easily check that again.

If using a manual fuel petcock and forgetting to turn it off could possibly result in flooding the engine cylinder & the crankcase oil with 6 gallons of gasoline.
The USA model CVK carb float bowl does Not Have an overflow stand pipe in it.
I did just put a manual fuel petcock on. My old one was spewing gas on my leg when I was riding it. I thought the manual was a simpler and cheaper way to go rather than rebuilding or replacing the original.

The idea that it could dump all my gas into the crankcase is a little disturbing. I guess I'll have to be extra vigilant. I don't know what an overflow stand pipe is, but I can guess what it does.

Did you by chance notice the 3 tiny little low speed pilot Transition outlet holes below the Bottom lip of the throttle butterfly plate?
They get their fuel from the pilot jet as does the adjustable low speed mixture screw.

If you spotted them, did you by chance use a tiny wire (bent 90 degrees) to poke down thru them & back flush the passageway with aerosol carb cleaner & compressed air? If one then Closes the adjustable screw, one can spray aerosol cleaner up thru the pilot passage & confirm 3 full streams of fluid flowing thru them. Then set the mixture screw at 2 turns open.
I sprayed carb cleaner through every orifice I saw, but I don't specifically remember those three or if I reamed them out. I don't think I did. I'll just check that before I put the carb back on. Then two full turns.

Thanks man.

Also, I'm not so adept at forums. How does one do multiple quotes like I just did above? I mean easily. I quoted the whole post and
then inserted the html tags to break it up, but I know there must be an easy way of doing it on the fly.
 

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Discussion Starter #9
The float bowl height was 16.5 mm, which is right in there. I have four tiny holes right under the butterfly valve. I reamed them as best I could, and sprayed carb cleaner through them. I think I was getting flow through all them. It's a tricky little operation. I sprayed compressed air through them also. I checked to see that the slide was moving freely. I backed my cool new knurled brass pilot screw out 2 turns.

I'll put it back on the bike later today after my aluminum choke cable plunger cap arrives at the local cycle shop. I stripped the threads on the old plastic one. That thing's a bear to take off and on.

Thanks again Tom and pdwestman for the guidance. I'll forge ahead.
 

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You can easily double-check that the floats are floating and the valve is valving with this handy method:
 

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A float bowl overflow stand pipe is like the oveflow pipe in a toilet tank. It lets out any excess before it overflows at a place it should not be, That would be UP thru the jets and down the intake ports of the KLR engine. Or on to the floor of your house, instead of down into the basin of the toilet.

On a single posting quote, I just space the sentences or paragraphs and bold my responses. I'm not very well versed in 'puter, either.

And then add other comments below like you did. We'll all get the message either way.
 

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Discussion Starter #12
Tom, checking the float bowl that way is brilliant.

pdwestman, thanks for the info about the overflow stand pipe. I guess you guys are talking about making your own. You'd drill a hole in the bottom of the float bowl and cut threads in it. Then you'd cut a little piece of pipe of the perfect diameter to the proper length and cut threads on that. That sounds like a delicate operation.

So then when you forgot to turn off the petcock and if the float bowl valve failed your entire gas tank would dump onto the ground instead of running through the carburetor into the engine, right?
 

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...Tom, checking the float bowl that way is brilliant...
Like so many things, this is an ancient method. It has to go back over 100 years; there is very little that is new under the sun

SU carburetors were invented 115 years ago and were known as Constant Depression carburetors. CDs are also known as Constant Vacuum (depression being another word for vacuum) and Constant Velocity. CV is the vernacular currently most used and is what the Keihin CV carbs are called.

A very long time ago, before Al Gore had invented the internet and global warming (the better to give us a means to argue and something to argue about), even before we walked on the moon, I was introduced to SU carburetors. MGAs, Spridgets, and Healey 100/4s are neat cars, but dang if they aren't hard to tune when the carbs are worn out. I soon called them Constantly Depressing carburetors based on trying to get them cars to run while I was in High School. They usually leaked both fuel and air and, later in life, I spent hours on a small lathe making bushings and glands for butterfly shafts and hours on a Bridgeport line reaming those bushings so that they at least didn't leak air. The result:


Real old-timers told stories of attaching a bit of rubber fuel line to the SU bowls and slowly lowering the hose until they found the fluid level in the float bowl. Thank goodness I have always lived in the era of clear hoses and some old-timer figured out you could use it that way.

So I can't take credit.

The overflow pipe should not be hard to do. These carbs used to have them and it is all but there. The boss that it was mounted in is still there and the nipple that the gas is to run out of is still there and still has a hole in it. It seems that all that is required is to drill a hole of the same size as the ID of the overflow tube (probably 9/32") through to the factory drain hole, then counterbore it 1/8" and install an overflow tube, cementing it in place. JB weld should do.

I think I will have time tomorrow.
 

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Discussion Starter #14
That sounds easier than how I was thinking. There’s really no point in threading it.
 

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When adjusting the knurled brass pilot screw with the carburetor in place it is difficult to tell if you have moved it 1/16 or 1/8 or 1/4 or 1/2 turns. If you cut notches on the side of the knob at the quarter points, it is much easier to tell how far you have adjusted it.
 

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Discussion Starter #16
Thanks for the tip, GoMotor. I set the screw before I put it on the bike. I put a scratch on the top as a reference. Now that it's on the bike it's hard to tell how far I've turned it. I might put a few dabs of paint at the 1/4 points. It would be hard to notch it now, and I don't want to take it back off if I don't have to.

I haven't dialed it in yet. I'm leaving on a 4 day backpacking trip in a few minutes. I'll have to wait until I get back to try to get it where I want it.
 
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