Carburetor Help - Unable to Cold Start After Rebuild - Kawasaki KLR 650 Forum
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

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post #1 of 40 Old 04-28-2020, 01:50 PM Thread Starter
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Carburetor Help - Unable to Cold Start After Rebuild

Hello Everyone!

I'm having issues with cold starting after recent carb cleaning and rebuilding that I hope I can get some help with...

Here's the events leading up to this issue. I have a 2007 KLR with 11,660 miles that I haven't ridden in several, or more, months. I've been riding my other two bikes recently at the expense of my KLR. I didn't intend to stop riding it altogether it just kinda got put on the backburner so I didn't prepare it for storage and now I'm paying the price...

When I took it out of the shed a couple of weeks ago, I found that the fuel petcock diaphragm had failed and leaked fuel all down the side of the stator case, ruining the paint on the case. I generally try to avoid ethanol gas altogether but I must have put some in the tank at some point and left the fuel tank was about 1/2 full. When I looked in the tank, I found, as you probably have guessed by now, that it was full of rust.

I ordered the Carb Rebuild Kit, Extended Pilot Needle, Coaster Enricher Diaphragm Kit, and Petcock rebuild kit from Eagle Mike's to rebuild the carb and petcock after a through cleaning. I used 4.5 gallons of the Evapo-Rust branded rust remover as well as water, denatured alcohol, gasoline, diesel, followed by more gasoline to get the tank back in working order (I will say the tank came out really great: highly recommend the Evapo-rust product!). I was sure to ensure the float height was set at 17.5mm when reassembling the carb. I didn't see any rust in the carb but all the float needle and coaster diaphragm were all badly damaged/deformed. I also replaced the fuel line. I initially set the pilot needle to 1 3/8" out from the seated position. I also cleaned and reoiled the stock air filter.

After reinstalling everything bike on the bike, I found that it was nearly impossible to start when cold. Previous to this fiasco, cold starting always required full use of the "choke"/enricher for the first few seconds of starting and running. Now, I find it won't start with or without the use of the choke. I rechecked the float height using the clear tube method and that method shows the level to be correct as well.

The only method, I've been able to consistently start the bike with is to 1.) set choke to off (not enriched), 2.) apply full throttle briefly while cranking over, 3.) releasing the throttle and starter, then 4.) cranking a second cycle without throttle application. It starts right away and then idles well at 1200 rpm. After running, even briefly, it then starts and runs well. I found this method through desperation and experimentation, I never had used the throttle at all for starting prior to this issue.

I took it on a test ride and the engine runs, accelerates, decelerates very well: better than it ever has. No issues whatsoever.

I am the second owner of this bike. I have owned the bike for about 7 years now. I have never checked the valve clearances or compression before and I'm unsure if the the PO had or not. However, I was not having any starting issues prior to the recent carb work.

The fuel/air system is all stock and has not been modded with the exception of the Stead Engineering Cable-less choke.

I have also ordered the manual fuel petcock: I'm done with the vacuum-operated one!

Any recommendations on what might be causing the issue or what steps to take would be greatly appreciated.

Thanks!

Last edited by Eric Frazier; 04-28-2020 at 02:15 PM. Reason: Clarification of use of starting procedure
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post #2 of 40 Old 04-28-2020, 04:02 PM
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I don't have Gen I carburetor experience, but assume it's the same as my Gen II.

If so, this is what I would do at this point. Adjust the the idle/pilot/low speed jet needle (2) turns out from lightly seated. Then try to start the bike with say a 1/4 of the enrichner activated and with the throttle against the stop; do NOT twist the throttle as you crank over the engine.

Try the above and let us know the outcome.

Jason
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post #3 of 40 Old 04-28-2020, 06:24 PM Thread Starter
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Jason,

I turned the pilot jet needle out 2 turns from lightly seated, pulled the enricher knob out about 1/4 of its travel and then cranked it over without the application any throttle. The result was the same: it continues to turn over without any sign of starting. I repeated this procedure twice more with 5 to 10 second pauses between start attempts with the same results.

Eric
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post #4 of 40 Old 04-28-2020, 06:55 PM
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Your carb is probably not clean.

There are some very small drillings just in front of and just under the throttle plate. There are four of them. If these drillings are not clear then you have no functional idle circuit. If one or more of them are clear but the others blocked, you have a half-assed idle circuit. Either that our your idle jet is plugged.

What you need to do is take something pretty volatile, like a spray carb cleaner, and remove the idle jet, then spray this stuff into the idle circuit. You must be able to see fluid coming out of each of these drillings. I don't like to poke at these things because if you bust something off in them you are well and truly screwed, but sometimes you have to. If you find you have to, then I recommend a strong probe that won't weaken and break off in the hole, and what fits that requirement pretty well is to snip a few inches off of your neighbor's Fender Telecaster first string. A Telecaster will work, too, but they are pretty cliche. A Les Paul is nice but I wouldn't touch one lest you draw back a bloody stump.

Seriously, if you can find a bit of .010" electric guitar string it will work well. I think you can buy a whole set of strings for a couple of bucks. Don't know if you can just by the one wee string. If you have a pricker for a SVEA 123 or an early MSR stove, that would work, too.

Once you are satisfied that the idle circuit is clear, turn your attention to the pilot jet. I like to take the used one and throw it away and put a new one in. The reason is that the pilot jet is very small at less than .015" diameter (and that's for a #42 which is larger than stock) and they can be hard to clear of ethanol spooge. Clean it if you have no other option, using the guitar string and the carb spray. Make sure you can get the guitar string through. Clean the emulsifier holes that are cross-drilled in the jet as well.

That oughta fix you up.

You should check your valves at some point in the not-too-distant future, too, but I doubt that is your issue at this point.

Tom [email protected]

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Last edited by Tom Schmitz; 04-28-2020 at 07:15 PM.
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post #5 of 40 Old 04-28-2020, 07:11 PM
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For the sake of the remote possibility that we could get an argument started, here is what I believe is happening with your semi-successful starting ritual. By twisting the throttle, you are opening the butterfly valve. This allows air through the venturi and across the jet needle. The needle is buried in the jet needle and the main jet, but there is still a bit of clearance in the main jet. A bit of fuel gets sucked up and dumped downstream of the venturi.

When you close the throttle and hit the starter again, there is a much larger vacuum, which picks up the fuel and gets the beast going. Once going it can keep going on the main jet.

I reserve the right to be wrong, but that's mu story and I'm sticking to it.
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Tom [email protected]

“On the way downtown I stopped at a bar and had a couple of double Scotches. They didn't do me any good. All they did was make me think of Silver-Wig, and I never saw her again.” -Philip Marlowe

“'Why' and 'How' are words so important they cannot be too often used.” -Napoleon Bonaparte

Sting like a butterfly.
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post #6 of 40 Old 04-28-2020, 07:23 PM
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Quote:
Originally Posted by Tom Schmitz View Post
For the sake of the remote possibility that we could get an argument started, here is what I believe is happening with your semi-successful starting ritual. By twisting the throttle, you are opening the butterfly valve. This allows air through the venturi and across the jet needle. The needle is buried in the jet needle and the main jet, but there is still a bit of clearance in the main jet. A bit of fuel gets sucked up and dumped downstream of the venturi.

When you close the throttle and hit the starter again, there is a much larger vacuum, which picks up the fuel and gets the beast going. Once going it can keep going on the main jet.

I reserve the right to be wrong, but that's mu story and I'm sticking to it.
Yeah, that's the only thing that makes half-ass sense about that particular starting method.

Jason
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post #7 of 40 Old 04-28-2020, 07:58 PM Thread Starter
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Tom,

Thanks! That sounds like a reasonable explanation to me. I'll take it back off and have another go. As far as the pilot jet itself, I did install a new one when I had it open. But I will pay closer attention to the to the ports and circuits this time around. I thought I did a thorough job but this was my first attempt cleaning a carb with the exception of small lawnmower/weedeater single-stroke engines. I did go through a whole bottle of carb cleaner but I didn't make any attempt poke a wire into any of the ports. My brothers are both guitar players: I'll check to see what they have laying around! I'll be sure to report back...

Eric

Last edited by Eric Frazier; 04-28-2020 at 08:04 PM.
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post #8 of 40 Old 04-28-2020, 08:06 PM
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Quote:
Originally Posted by Eric Frazier View Post
Tom,

Thanks! That sounds like a reasonable explanation to me. I'll take it back off and have another go. As far as the pilot jet itself, I did install a new one when I had it open. But I will pay closer attention to the to the ports and circuits this time around. I thought I did a thorough job but this was my first attempt cleaning a carb with the exception of small lawnmower/weedeater single-stroke engines. I did go through a whole bottle of carb cleaner but I didn't make any attempt poke a wire into any of the ports. I'll be sure to report back...

Eric
The engine would not "idle well at 1,200 RPM" if those idle/pilot passages are plugged. But it can't hurt to double check their cleanliness.

Jason

I'm referring to your quote in the original post: It starts right away and then idles well at 1200 rpm.

Last edited by Norton 850; 04-28-2020 at 08:23 PM.
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post #9 of 40 Old 04-28-2020, 08:53 PM
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If the low speed mixture screw outlet & 1st transition hole under the throttle plate are Open, it can idle just fine.

I'll suggest that possibly the non-removable cold start enrichener jet needs the guitar string pushed thru it & blasted with carb cleaner & compressed air. Pulling the handle opens the air port, but varnish must be blocking the cold start fuel jet. So technically it is leaning the mixture, rather than enrichening the cold start mixture.

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post #10 of 40 Old 04-28-2020, 09:45 PM Thread Starter
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All,

It does seem to idle well wherever I set the idle speed at.

I do have the carb off the bike and disassembled again now. I will see what I can do with the ports on the enricher circuit. Not quite sure how to get at it...

Everything I've looked at so far looks clean to me. I've passed a .025 and .06 wire thru the passages on the carb body without any issue. It all looks clear to me. Looks like maybe the bowl seat of the float valve could use a little more attention. Any suggestions on how to best clean that?

I also noted that the main jet that Eagle Mike supplied is a 150. The stock size I removed was a 148. Also, the EM supplied pilot jet is a 38. The OEM one I removed was a 40.


Any other suggestions while I'm I've got it torn down would be welcome as well.

Thanks again, Eric

Last edited by Eric Frazier; 04-29-2020 at 12:22 AM. Reason: added info on pilot jet size
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