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jd 300 carb problems?


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#1 zr600 OFFLINE  

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Posted November 08, 2011 - 11:39 AM

My 300 has some carb issues. It won't run without the choke except at idel. I does run good with the choke open but if you close it the engine dies. I have had the carb apart replaced the needle and seat all the gaskets and cleaned the crap out of it. It still is doing the same thing now except before the cleaning it wouldn't even idle. Now im confused i put all the settings back to the way they were before, and tried messing with them with no luck. What is causing this? I was thinking an air leak but can't find one of them, what would work to find an air leak? What i did was spray carb cleaner anywhere i thought it might leak and listen for the engine to rev up, that is what a mechanic buddy of mine told me to do.

#2 Deere Green OFFLINE  

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Posted November 08, 2011 - 11:53 AM

usually the mixture screw on the carb (same one that holds the bowl in place) has a few holes that run through it that may need to be cleaned. you will have to look hard as you would have to use a paperclip to clean them out is how small I am talking the hole is. reason i am thinking this is it is if you have pulled the carb off and cleaned the bowl and float there should not be any other issues why this thing would be starving for air like you are talking. other than this I have had a few Kawi engines that would run rough until I pulled the head off cleaned the carbon build up off and made sure the valves were seating correctly. one or more of these items together cause bad mixture getting to the engine and without the correct mix and air the thing aint gonna run right as you're experiencing.

#3 Jehtro OFFLINE  

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Posted November 08, 2011 - 12:04 PM

Sounds like a vacuum / gasket leak to me,

If you a rubber line on the end of a propane bottle, then move the line around the carb, you can usually find the leak as the engine will smooth out once the leak starts sucking the propane.

#4 JDBrian OFFLINE  

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Posted November 09, 2011 - 05:51 AM

Have you checked the ignition and head gasket. If the carb seems ok then I usually check the other major problem areas. These old engines can have issues in many areas and still run. My 314 was doing that to some extent. It would run with out choke but not well. The head gasket was leaking and the points were out of adjustment. The problem was not in the carb.

#5 MH81 ONLINE  

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Posted November 09, 2011 - 08:06 AM

I'll second the thought that it's getting extra air somewhere. I'd start with the carb gasket(s).

Head gasket is also a good possibility as are a missed port in the carb. If you don't find an air leak, you might try running some gas heavy with a cleaner like Seafoam. After doing that, I have had luck by getting the RPMs up, then putting my hand over the intake for a couple of seconds. Repeat several times and hopefully you'll pull the plug thru.

#6 zr600 OFFLINE  

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Posted November 09, 2011 - 11:30 AM

Is there a right up on how to adjust the points? Maybe they need to just be replaced to. If it has to do with the points why would it run good with the choke on though? The choke has nothing to do witht the points.

#7 lyall ONLINE  

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Posted November 09, 2011 - 06:31 PM

check the throttle shaft for play. if over .010 play you should put in a bushing. bushing is 1/4" id and 7/16"od. I used two bronze bushing washers in my carb and it did make a different. Bronze bushing washers at Ace hardware for around 40 cent a piece and you will 2 -#3x48 screws with lock washer and nuts. cheap fix.

#8 JDBrian OFFLINE  

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Posted November 09, 2011 - 08:00 PM

Is there a right up on how to adjust the points? Maybe they need to just be replaced to. If it has to do with the points why would it run good with the choke on though? The choke has nothing to do witht the points.



If you have a week or poorly timed spark sometimes extra fuel will keep it running. That's my theory anyway. The points are easy to adjust. Download the Kohler K series manual from Kohler's site. You set them to .020 when they are open. If the push rod, cam and points are in good shape the timing will be correct when the gap is .02.
You can usually see oil leakage around the head and cylinder if the head gasket is leaking. If you remove some of the engine covers you can get a good look at the fins. As I said above you should check all this stuff anyway on an old engine that is not running properly. Everything is suspect, particularly if it has been neglected.




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