Intermittent Lean condition - 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 7 Old 06-09-2010, 11:19 PM Thread Starter
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Intermittent Lean condition

06 is driving me nuts! Sometimes it runs great, and sometimes it wont idle unless I leave the choke about 3/4 on. At these times if I flip the choke off it stalls instantly. When it runs good, it's perfect and idles like a dream.
Bike is stock except I have done the washer under the needle mod and have removed the mixture plug. What could it be that comes and goes? There seems to be no pattern to it at all.

Last edited by Kirkdob; 06-10-2010 at 09:05 AM.
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post #2 of 7 Old 06-10-2010, 02:21 AM
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Check the vacuum line from the intake to the fuel petcock. The hose can collapse when it get hot. Get a longer vacuum hose and route it over the top of the carburetor to the fuel petcock.

Tim

2005 KLR 685
2015 Yamaha Super Tenere ES, 5/23/2015
2012 Yamaha Super Tenere; Purchased 7/30/2011; Sold 5/23/2015
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post #3 of 7 Old 06-10-2010, 08:29 AM
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It is unlikely that this is a vacuum related issue.

The description you give indicates problems at the pilot / slow jet. When the bike runs only with the choke / enrichening lever pulled out, you have one or more jets obstructed by gummed or varnished fuel, or a possible "floater" providing blockage.

This can be intermittent. My first step would be a chemical attempt to cleaning the jets. A high dose of Sea Foam, Chevron Techron Concentrate Fuel System Cleaner, [not Pro-Gard, it's weaker little sister], Berryman B-12 Chemtool Carburetor and Choke Cleaner, or your favorite Witch Oil. [I like the Chevron] I would begin by draining the float bowl, pulling the fuel line at the petcock, and dumping in a 50 / 50 mix of gas and carb cleaner into the fuel line. Reinstall the line to the petcock. Add a strong dose of cleaner to the fuel in the tank. You are trying to correct a problem, not prevent a problem. Use a stronger dose of cleaner. Start the bike, and using the enrichener as little as possible, rev the engine a bit and shut it off, letting the jets soak in the cleaner for a few hours. After allowing the chemicals to work, start the bike and run it in the lower RPM range as much as possible, as that is where the blockage appears to be. While it seems a little inconvenient to perform this chemical treatment, it beats rolling the carburetor over and pulling the pilot jet, which is what you may be doing if the chemical jizz does not work.

If it comes down to a manual clean job, this is what you are looking at:



Bottom of carburetor, with float bowl and float removed.



Be careful not to strip or break the small pilot jet when you try to remove it. It may be necessary to grind the end of a small screwdriver to fit the jet just right. Even after soaking, the jet may still be plugged. Do not rely on visual inspection of the jet to determine that it is free of obstruction. Use a small "E" guitar string and push it through the jet. (A wire strand out of a wire brush may work. The wire brush should measure about .013" in diameter.) The smallest jet drill you can get is #80, which has a diameter of .0135". You can use the wire and not enlarge the hole, at least not by much. Some manuals say not to insert any wire jet cleaning tools into the jets. However, Honda and other manufacturers produce them as special tools for the dealer technicians. I find Brake Cleaner works well for jet cleaning ONCE THE JET HAS BEEN REMOVED FROM THE CARBURETOR. Don't use Brake Cleaner in the carburetor.

This cleaning process can be done without removing the carburetor from the bike. It will require you to be patient and careful, however. Not a good project fro those with ADD. There will be no adjusting to content with. You will reassemble what you disassembled. As long as you lose no parts, remind yourself that no large amounts of torque can be used on a carburetor, you should be OK.
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post #4 of 7 Old 06-10-2010, 09:04 AM Thread Starter
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Thanks for both of the write ups. When I did the washer to the the needle I was having the same problem at that time also. I sea foamed her before with no results, so when the carb was apart for the needle job, I fully stripped it and cleaned everything including blowing out all the passages. I have run a few tanks through that have also been fairly overdosed with seafoam. I suppose it wouldn't hurt to pull the jets again just to be sure and replace the vacuum line to the petcock.
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post #5 of 7 Old 06-10-2010, 09:49 AM
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Quote:
Originally Posted by Kirkdob View Post
Thanks for both of the write ups. When I did the washer to the the needle I was having the same problem at that time also. I sea foamed her before with no results, so when the carb was apart for the needle job, I fully stripped it and cleaned everything including blowing out all the passages. I have run a few tanks through that have also been fairly overdosed with seafoam. I suppose it wouldn't hurt to pull the jets again just to be sure and replace the vacuum line to the petcock.
Running on the "choke", indicates that the carburetor has a clogged pilot circuit. The pilot supplies idle fuel when the throttle's closed... if it's clogged, the only way you're gonna get enough fuel to run is via the enricher (choke) system. REMOVE the pilot jet. Shooting carb cleaner down the tower ain't gonna do it. Just because the jet is clear doesn't mean the circuit is clear. You'll need to remove the pilot jet and fuel screw and spray carb cleaner through all the passages in the carb then hit it with compressed air. I like the cans of "dust buster" you can get in the electronics dept. My air compressor has all kinds of contaminants I don't need in a carburetor. There are some very small spaces in the carb body itself that like to collect gunk from evaporated fuel. You probably can't see any obstruction that may be in there. This crap may be breaking loose, and providing "intermittent, non-patterned re-occurrences".
If you had a vacuum issue, there would be no gas in the bowl. The bike would not run, choke on or off. The problem with changing several items at once is that you don't know which one fixed the issue. If it reoccurs, you have no idea where to look. Methodical, single item approaches have worked best for me with fuel and electrical issues.

And when you tell a mechanic that you addressed several issues at once, all he hears is "ka-ching$". YMMV.

Last edited by vatrader; 06-10-2010 at 10:06 AM. Reason: spelin is hard
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post #6 of 7 Old 06-10-2010, 09:56 AM Thread Starter
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thanks, I'll do exactly that this weekend and see what happens.
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post #7 of 7 Old 06-12-2010, 11:53 AM Thread Starter
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I took Vatrader's advice and went for only one thing at a time. As Tomatocity mentioned, the vac line at the top of the carb was folded over on itself to the point where I believe it could intermittently collapse. I replaced it with a thicker wall hose and routed up and over the carb to remove the possibility of folding over again. bike runs great, last time it barely ran so we'll see. It has run good before only to crap out again.
At least this time I have some physical evidence of a problem. I'd like to believe it's not gunk in the carb as I have had it apart several times and blown out all passages. My tank has never rusted and fuel has never got old. Time will tell.
Thanks for the great advise.
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